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PPP(8) FreeBSD System Manager's Manual PPP(8)

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[править] NAME

    ppp -- Point to Point Protocol (a.k.a. user-ppp)

[править] SYNOPSIS

    ppp [-mode] [-nat] [-quiet] [-unitN] [system ...]

[править] DESCRIPTION

    This is a user process PPP software package.  Sometimes, PPP is imple-
    mented as a part of the kernel (e.g., as managed by pppd) and it is thus
    somewhat hard to debug and/or modify its behaviour.  However, in this
    implementation PPP is done as a user process with the help of the tunnel
    device driver (tun).
    The -nat flag does the equivalent of a ``nat enable yes, enabling ppp's
    network address translation features.  This allows ppp to act as a NAT or
    masquerading engine for all machines on an internal LAN.  Refer to
    libalias(3) for details on the technical side of the NAT engine.  Refer
    to the NETWORK ADDRESS TRANSLATION (PACKET ALIASING) section of this man-
    ual page for details on how to configure NAT in ppp.
    The -quiet flag tells ppp to be silent at startup rather than displaying
    the mode and interface to standard output.
    The -unit flag tells ppp to only attempt to open /dev/tunN.  Normally,
    ppp will start with a value of 0 for N, and keep trying to open a tunnel
    device by incrementing the value of N by one each time until it succeeds.
    If it fails three times in a row because the device file is missing, it
    gives up.
    The following modes are understood by ppp:
       -auto
            ppp opens the tun interface, configures it then goes into the
            background.  The link is not brought up until outgoing data is
            detected on the tun interface at which point ppp attempts to
            bring up the link.  Packets received (including the first one)
            while ppp is trying to bring the link up will remain queued for a
            default of 2 minutes.  See the ``set choked command below.
            In -auto mode, at least one ``system must be given on the com-
            mand line (see below) and a ``set ifaddr must be done in the
            system profile that specifies a peer IP address to use when con-
            figuring the interface.  Something like ``10.0.0.1/0 is usually
            appropriate.  See the ``pmdemand system in
            /usr/share/examples/ppp/ppp.conf.sample for an example.
       -background
            Here, ppp attempts to establish a connection with the peer imme-
            diately.  If it succeeds, ppp goes into the background and the
            parent process returns an exit code of 0.  If it fails, ppp exits
            with a non-zero result.
       -foreground
            In foreground mode, ppp attempts to establish a connection with
            the peer immediately, but never becomes a daemon.  The link is
            created in background mode.  This is useful if you wish to con-
            trol ppp's invocation from another process.
       -direct
            This is used for communicating over an already established con-
            nection, usually when receiving incoming connections accepted by
            getty(8).  ppp ignores the ``set device line and uses descrip-
            tor 0 as the link.  ppp will also ignore any configured chat
            scripts unless the ``force-scripts option has been enabled.
            If callback is configured, ppp will use the ``set device infor-
            mation when dialing back.
            When run in -direct mode, ppp will behave slightly differently if
            descriptor 0 was created by pipe(2).  As pipes are not bi-direc-
            tional, ppp will redirect all writes to descriptor 1 (standard
            output), leaving only reads acting on descriptor 0.  No special
            action is taken if descriptor 0 was created by socketpair(2).
       -dedicated
            This option is designed for machines connected with a dedicated
            wire.  ppp will always keep the device open and will ignore any
            configured chat scripts unless the ``force-scripts option has
            been enabled.
       -ddial
            This mode is equivalent to -auto mode except that ppp will bring
            the link back up any time it is dropped for any reason.
       -interactive
            This is a no-op, and gives the same behaviour as if none of the
            above modes have been specified.  ppp loads any sections speci-
            fied on the command line then provides an interactive prompt.
    One or more configuration entries or systems (as specified in
    /etc/ppp/ppp.conf) may also be specified on the command line.  ppp will
    read the ``default system from /etc/ppp/ppp.conf at startup, followed
    by each of the systems specified on the command line.

Major Features

    Provides an interactive user interface.  Using its command mode, the user
    can easily enter commands to establish the connection with the remote
    end, check the status of connection and close the connection.  All func-
    tions can also be optionally password protected for security.
    Supports both manual and automatic dialing.  Interactive mode has a
    ``term command which enables you to talk to the device directly.  When
    you are connected to the remote peer and it starts to talk PPP, ppp
    detects it and switches to packet mode automatically.  Once you have
    determined the proper sequence for connecting with the remote host, you
    can write a chat script to define the necessary dialing and login proce-
    dure for later convenience.
    Supports on-demand dialup capability.  By using -auto mode, ppp will act
    as a daemon and wait for a packet to be sent over the PPP link.  When
    this happens, the daemon automatically dials and establishes the connec-
    tion.  In almost the same manner -ddial mode (direct-dial mode) also
    automatically dials and establishes the connection.  However, it differs
    in that it will dial the remote site any time it detects the link is
    down, even if there are no packets to be sent.  This mode is useful for
    full-time connections where we worry less about line charges and more
    about being connected full time.  A third -dedicated mode is also avail-
    able.  This mode is targeted at a dedicated link between two machines.
    ppp will never voluntarily quit from dedicated mode - you must send it
    the ``quit all command via its diagnostic socket.  A SIGHUP will force
    an LCP renegotiation, and a SIGTERM will force it to exit.
    Supports client callback.  ppp can use either the standard LCP callback
    protocol or the Microsoft CallBack Control Protocol
    (ftp://ftp.microsoft.com/developr/rfc/cbcp.txt).
    Supports NAT or packet aliasing.  Packet aliasing (a.k.a. IP masquerad-
    ing) allows computers on a private, unregistered network to access the
    Internet.  The PPP host acts as a masquerading gateway.  IP addresses as
    well as TCP and UDP port numbers are NAT'd for outgoing packets and de-
    NAT'd for returning packets.
    Supports background PPP connections.  In background mode, if ppp success-
    fully establishes the connection, it will become a daemon.  Otherwise, it
    will exit with an error.  This allows the setup of scripts that wish to
    execute certain commands only if the connection is successfully estab-
    lished.
    Supports server-side PPP connections.  In direct mode, ppp acts as server
    which accepts incoming PPP connections on stdin/stdout.
    Supports PAP and CHAP (rfc 1994, 2433 and 2759) authentication.  With PAP
    or CHAP, it is possible to skip the Unix style login(1) procedure, and
    use the PPP protocol for authentication instead.  If the peer requests
    Microsoft CHAP authentication and ppp is compiled with DES support, an
    appropriate MD4/DES response will be made.
    Supports RADIUS (rfc 2138 & 2548) authentication.  An extension to PAP
    and CHAP, Remote Access Dial In User Service allows authentication infor-
    mation to be stored in a central or distributed database along with vari-
    ous per-user framed connection characteristics.  If libradius(3) is
    available at compile time, ppp will use it to make RADIUS requests when
    configured to do so.
    Supports Proxy Arp.  ppp can be configured to make one or more proxy arp
    entries on behalf of the peer.  This allows routing from the peer to the
    LAN without configuring each machine on that LAN.
    Supports packet filtering.  User can define four kinds of filters: the in
    filter for incoming packets, the out filter for outgoing packets, the
    dial filter to define a dialing trigger packet and the alive filter for
    keeping a connection alive with the trigger packet.
    Tunnel driver supports bpf.  The user can use tcpdump(1) to check the
    packet flow over the PPP link.
    Supports PPP over TCP and PPP over UDP.  If a device name is specified as
    host:port[/tcp|udp], ppp will open a TCP or UDP connection for transport-
    ing data rather than using a conventional serial device.  UDP connections
    force ppp into synchronous mode.
    Supports PPP over Ethernet (rfc 2516).  If ppp is given a device specifi-
    cation of the format PPPoE:iface[:provider] and if netgraph(4) is avail-
    able, ppp will attempt talk PPP over Ethernet to provider using the iface
    network interface.
    On systems that do not support netgraph(4), an external program such as
    pppoed(8) may be used.
    Supports IETF draft Predictor-1 (rfc 1978) and DEFLATE (rfc 1979)
    compression.  ppp supports not only VJ-compression but also Predictor-1
    and DEFLATE compression.  Normally, a modem has built-in compression
    (e.g., v42.bis) and the system may receive higher data rates from it as a
    result of such compression.  While this is generally a good thing in most
    other situations, this higher speed data imposes a penalty on the system
    by increasing the number of serial interrupts the system has to process
    in talking to the modem and also increases latency.  Unlike VJ-compres-
    sion, Predictor-1 and DEFLATE compression pre-compresses all network
    traffic flowing through the link, thus reducing overheads to a minimum.
    Supports Microsoft's IPCP extensions (rfc 1877).  Name Server Addresses
    and NetBIOS Name Server Addresses can be negotiated with clients using
    the Microsoft PPP stack (i.e., Win95, WinNT)
    Supports Multi-link PPP (rfc 1990)  It is possible to configure ppp to
    open more than one physical connection to the peer, combining the band-
    width of all links for better throughput.
    Supports MPPE (draft-ietf-pppext-mppe)  MPPE is Microsoft Point to Point
    Encryption scheme.  It is possible to configure ppp to participate in
    Microsoft's Windows VPN.  For now, ppp can only get encryption keys from
    CHAP 81 authentication.  ppp must be compiled with DES for MPPE to oper-
    ate.
    Supports IPV6CP (rfc 2023).  An IPv6 connection can be made in addition
    to or instead of the normal IPv4 connection.

[править] PERMISSIONS

    ppp is installed as user root and group network, with permissions 04554.
    By default, ppp will not run if the invoking user id is not zero.  This
    may be overridden by using the ``allow users command in
    /etc/ppp/ppp.conf.  When running as a normal user, ppp switches to user
    id 0 in order to alter the system routing table, set up system lock files
    and read the ppp configuration files.  All external commands (executed
    via the "shell" or "!bg" commands) are executed as the user id that
    invoked ppp.  Refer to the `ID0' logging facility if you are interested
    in what exactly is done as user id zero.

[править] GETTING STARTED

    When you first run ppp you may need to deal with some initial configura-
    tion details.
    o   Make sure that your system has a group named ``network in the
        /etc/group file and that the group contains the names of all users
        expected to use ppp.  Refer to the group(5) manual page for details.
        Each of these users must also be given access using the ``allow
        users command in /etc/ppp/ppp.conf.
    o   Create a log file.  ppp uses syslog(3) to log information.  A common
        log file name is /var/log/ppp.log.  To make output go to this file,
        put the following lines in the /etc/syslog.conf file:
              !ppp
              *.*<TAB>/var/log/ppp.log
        It is possible to have more than one PPP log file by creating a link
        to the ppp executable:
              # cd /usr/sbin
              # ln ppp ppp0
        and using
              !ppp0
              *.*<TAB>/var/log/ppp0.log
        in /etc/syslog.conf.  Do not forget to send a HUP signal to
        syslogd(8) after altering /etc/syslog.conf.
    o   Although not strictly relevant to ppp's operation, you should config-
        ure your resolver so that it works correctly.  This can be done by
        configuring a local DNS (using named(8)) or by adding the correct
        `nameserver' lines to the file /etc/resolv.conf.  Refer to the
        resolv.conf(5) manual page for details.
        Alternatively, if the peer supports it, ppp can be configured to ask
        the peer for the nameserver address(es) and to update
        /etc/resolv.conf automatically.  Refer to the ``enable dns and
        ``resolv commands below for details.

[править] MANUAL DIALING

    In the following examples, we assume that your machine name is awfulhak.
    when you invoke ppp (see PERMISSIONS above) with no arguments, you are
    presented with a prompt:
          ppp ON awfulhak>
    The `ON' part of your prompt should always be in upper case.  If it is in
    lower case, it means that you must supply a password using the ``passwd
    command.  This only ever happens if you connect to a running version of
    ppp and have not authenticated yourself using the correct password.
    You can start by specifying the device name and speed:
          ppp ON awfulhak> set device /dev/cuad0
          ppp ON awfulhak> set speed 38400
    Normally, hardware flow control (CTS/RTS) is used.  However, under cer-
    tain circumstances (as may happen when you are connected directly to cer-
    tain PPP-capable terminal servers), this may result in ppp hanging as
    soon as it tries to write data to your communications link as it is wait-
    ing for the CTS (clear to send) signal - which will never come.  Thus, if
    you have a direct line and cannot seem to make a connection, try turning
    CTS/RTS off with ``set ctsrts off.  If you need to do this, check the
    ``set accmap description below too - you will probably need to ``set
    accmap 000a0000.
    Usually, parity is set to ``none, and this is ppp's default.  Parity is
    a rather archaic error checking mechanism that is no longer used because
    modern modems do their own error checking, and most link-layer protocols
    (that is what ppp is) use much more reliable checking mechanisms.  Parity
    has a relatively huge overhead (a 12.5% increase in traffic) and as a
    result, it is always disabled (set to ``none) when PPP is opened.  How-
    ever, some ISPs (Internet Service Providers) may use specific parity set-
    tings at connection time (before PPP is opened).  Notably, Compuserve
    insist on even parity when logging in:
          ppp ON awfulhak> set parity even
    You can now see what your current device settings look like:
          ppp ON awfulhak> show physical
          Name: deflink
           State:           closed
           Device:          N/A
           Link Type:       interactive
           Connect Count:   0
           Queued Packets:  0
           Phone Number:    N/A
          Defaults:
           Device List:     /dev/cuad0
           Characteristics: 38400bps, cs8, even parity, CTS/RTS on
          Connect time: 0 secs
          0 octets in, 0 octets out
          Overall 0 bytes/sec
          ppp ON awfulhak>
    The term command can now be used to talk directly to the device:
          ppp ON awfulhak> term
          at
          OK
          atdt123456
          CONNECT
          login: myispusername
          Password: myisppassword
          Protocol: ppp
    When the peer starts to talk in PPP, ppp detects this automatically and
    returns to command mode.
          ppp ON awfulhak>               # No link has been established
          Ppp ON awfulhak>               # We've connected & finished LCP
          PPp ON awfulhak>               # We've authenticated
          PPP ON awfulhak>               # We've agreed IP numbers
    If it does not, it is probable that the peer is waiting for your end to
    start negotiating.  To force ppp to start sending PPP configuration pack-
    ets to the peer, use the ``~p command to drop out of terminal mode and
    enter packet mode.
    If you never even receive a login prompt, it is quite likely that the
    peer wants to use PAP or CHAP authentication instead of using Unix-style
    login/password authentication.  To set things up properly, drop back to
    the prompt and set your authentication name and key, then reconnect:
          ~.
          ppp ON awfulhak> set authname myispusername
          ppp ON awfulhak> set authkey myisppassword
          ppp ON awfulhak> term
          at
          OK
          atdt123456
          CONNECT
    You may need to tell ppp to initiate negotiations with the peer here too:
          ~p
          ppp ON awfulhak>               # No link has been established
          Ppp ON awfulhak>               # We've connected & finished LCP
          PPp ON awfulhak>               # We've authenticated
          PPP ON awfulhak>               # We've agreed IP numbers
    You are now connected!  Note that `PPP' in the prompt has changed to cap-
    ital letters to indicate that you have a peer connection.  If only some
    of the three Ps go uppercase, wait until either everything is uppercase
    or lowercase.  If they revert to lowercase, it means that ppp could not
    successfully negotiate with the peer.  A good first step for trou-
    bleshooting at this point would be to
          ppp ON awfulhak> set log local phase lcp ipcp
    and try again.  Refer to the ``set log command description below for
    further details.  If things fail at this point, it is quite important
    that you turn logging on and try again.  It is also important that you
    note any prompt changes and report them to anyone trying to help you.
    When the link is established, the show command can be used to see how
    things are going:
          PPP ON awfulhak> show physical
          * Modem related information is shown here *
          PPP ON awfulhak> show ccp
          * CCP (compression) related information is shown here *
          PPP ON awfulhak> show lcp
          * LCP (line control) related information is shown here *
          PPP ON awfulhak> show ipcp
          * IPCP (IP) related information is shown here *
          PPP ON awfulhak> show ipv6cp
          * IPV6CP (IPv6) related information is shown here *
          PPP ON awfulhak> show link
          * Link (high level) related information is shown here *
          PPP ON awfulhak> show bundle
          * Logical (high level) connection related information is shown here *
    At this point, your machine has a host route to the peer.  This means
    that you can only make a connection with the host on the other side of
    the link.  If you want to add a default route entry (telling your machine
    to send all packets without another routing entry to the other side of
    the PPP link), enter the following command:
          PPP ON awfulhak> add default HISADDR
    The string `HISADDR' represents the IP address of the connected peer.  If
    the ``add command fails due to an existing route, you can overwrite the
    existing route using:
          PPP ON awfulhak> add! default HISADDR
    This command can also be executed before actually making the connection.
    If a new IP address is negotiated at connection time, ppp will update
    your default route accordingly.
    You can now use your network applications (ping, telnet, ftp, etc.)  in
    other windows or terminals on your machine.  If you wish to reuse the
    current terminal, you can put ppp into the background using your standard
    shell suspend and background commands (usually ``^Z followed by
    ``bg).
    Refer to the PPP COMMAND LIST section for details on all available com-
    mands.

[править] AUTOMATIC DIALING

    To use automatic dialing, you must prepare some Dial and Login chat
    scripts.  See the example definitions in
    /usr/share/examples/ppp/ppp.conf.sample (the format of /etc/ppp/ppp.conf
    is pretty simple).  Each line contains one comment, inclusion, label or
    command:
    o   A line starting with a (``#) character is treated as a comment
        line.  Leading whitespace are ignored when identifying comment lines.
    o   An inclusion is a line beginning with the word `!include'.  It must
        have one argument - the file to include.  You may wish to ``!include
        ~/.ppp.conf for compatibility with older versions of ppp.
    o   A label name starts in the first column and is followed by a colon
        (``:).
    o   A command line must contain a space or tab in the first column.
    o   A string starting with the ``$ character is substituted with the
        value of the environment variable by the same name.  Likewise, a
        string starting with the ``~ character is substituted with the full
        path to the home directory of the user account by the same name, and
        the ``~ character by itself is substituted with the full path to
        the home directory of the current user.  If you want to include a
        literal ``$ or ``~ character in a command or argument, enclose
        them in double quotes, e.g.,
              set password "pa$ss~word"
    The /etc/ppp/ppp.conf file should consist of at least a ``default sec-
    tion.  This section is always executed.  It should also contain one or
    more sections, named according to their purpose, for example, ``MyISP
    would represent your ISP, and ``ppp-in would represent an incoming ppp
    configuration.  You can now specify the destination label name when you
    invoke ppp.  Commands associated with the ``default label are executed,
    followed by those associated with the destination label provided.  When
    ppp is started with no arguments, the ``default section is still exe-
    cuted.  The load command can be used to manually load a section from the
    /etc/ppp/ppp.conf file:
          ppp ON awfulhak> load MyISP
    Note, no action is taken by ppp after a section is loaded, whether it is
    the result of passing a label on the command line or using the ``load
    command.  Only the commands specified for that label in the configuration
    file are executed.  However, when invoking ppp with the -background,
    -ddial, or -dedicated switches, the link mode tells ppp to establish a
    connection.  Refer to the ``set mode command below for further details.
    Once the connection is made, the `ppp' portion of the prompt will change
    to `PPP':
          # ppp MyISP
          ...
          ppp ON awfulhak> dial
          Ppp ON awfulhak>
          PPp ON awfulhak>
          PPP ON awfulhak>
    The Ppp prompt indicates that ppp has entered the authentication phase.
    The PPp prompt indicates that ppp has entered the network phase.  The PPP
    prompt indicates that ppp has successfully negotiated a network layer
    protocol and is in a usable state.
    If the /etc/ppp/ppp.linkup file is available, its contents are executed
    when the PPP connection is established.  See the provided ``pmdemand
    example in /usr/share/examples/ppp/ppp.conf.sample which runs a script in
    the background after the connection is established (refer to the
    ``shell and ``bg commands below for a description of possible substi-
    tution strings).  Similarly, when a connection is closed, the contents of
    the /etc/ppp/ppp.linkdown file are executed.  Both of these files have
    the same format as /etc/ppp/ppp.conf.
    In previous versions of ppp, it was necessary to re-add routes such as
    the default route in the ppp.linkup file.  ppp supports `sticky routes',
    where all routes that contain the HISADDR, MYADDR, HISADDR6 or MYADDR6
    literals will automatically be updated when the values of these variables
    change.

[править] BACKGROUND DIALING

    If you want to establish a connection using ppp non-interactively (such
    as from a crontab(5) entry or an at(1) job) you should use the
    -background option.  When -background is specified, ppp attempts to
    establish the connection immediately.  If multiple phone numbers are
    specified, each phone number will be tried once.  If the attempt fails,
    ppp exits immediately with a non-zero exit code.  If it succeeds, then
    ppp becomes a daemon, and returns an exit status of zero to its caller.
    The daemon exits automatically if the connection is dropped by the remote
    system, or it receives a TERM signal.

[править] DIAL ON DEMAND

    Demand dialing is enabled with the -auto or -ddial options.  You must
    also specify the destination label in /etc/ppp/ppp.conf to use.  It must
    contain the ``set ifaddr command to define the remote peers IP address.
    (refer to /usr/share/examples/ppp/ppp.conf.sample)
          # ppp -auto pmdemand
    When -auto or -ddial is specified, ppp runs as a daemon but you can still
    configure or examine its configuration by using the ``set server com-
    mand in /etc/ppp/ppp.conf, (for example, ``set server +3000 mypasswd)
    and connecting to the diagnostic port as follows:
          # pppctl 3000   (assuming tun0)
          Password:
          PPP ON awfulhak> show who
          tcp (127.0.0.1:1028) *
    The ``show who command lists users that are currently connected to ppp
    itself.  If the diagnostic socket is closed or changed to a different
    socket, all connections are immediately dropped.
    In -auto mode, when an outgoing packet is detected, ppp will perform the
    dialing action (chat script) and try to connect with the peer.  In -ddial
    mode, the dialing action is performed any time the line is found to be
    down.  If the connect fails, the default behaviour is to wait 30 seconds
    and then attempt to connect when another outgoing packet is detected.
    This behaviour can be changed using the ``set redial command:
    set redial secs[+inc[-max]][.next] [attempts]
    secs      is the number of seconds to wait before attempting to connect
              again.  If the argument is the literal string `random', the
              delay period is a random value between 1 and 30 seconds inclu-
              sive.
    inc       is the number of seconds that secs should be incremented each
              time a new dial attempt is made.  The timeout reverts to secs
              only after a successful connection is established.  The default
              value for inc is zero.
    max       is the maximum number of times ppp should increment secs.  The
              default value for max is 10.
    next      is the number of seconds to wait before attempting to dial the
              next number in a list of numbers (see the ``set phone com-
              mand).  The default is 3 seconds.  Again, if the argument is
              the literal string `random', the delay period is a random value
              between 1 and 30 seconds.
    attempts  is the maximum number of times to try to connect for each out-
              going packet that triggers a dial.  The previous value is
              unchanged if this parameter is omitted.  If a value of zero is
              specified for attempts, ppp will keep trying until a connection
              is made.
    So, for example:
          set redial 10.3 4
    will attempt to connect 4 times for each outgoing packet that causes a
    dial attempt with a 3 second delay between each number and a 10 second
    delay after all numbers have been tried.  If multiple phone numbers are
    specified, the total number of attempts is still 4 (it does not attempt
    each number 4 times).
    Alternatively,
          set redial 10+10-5.3 20
    tells ppp to attempt to connect 20 times.  After the first attempt, ppp
    pauses for 10 seconds.  After the next attempt it pauses for 20 seconds
    and so on until after the sixth attempt it pauses for 1 minute.  The next
    14 pauses will also have a duration of one minute.  If ppp connects, dis-
    connects and fails to connect again, the timeout starts again at 10 sec-
    onds.
    Modifying the dial delay is very useful when running ppp in -auto mode on
    both ends of the link.  If each end has the same timeout, both ends wind
    up calling each other at the same time if the link drops and both ends
    have packets queued.  At some locations, the serial link may not be reli-
    able, and carrier may be lost at inappropriate times.  It is possible to
    have ppp redial should carrier be unexpectedly lost during a session.
          set reconnect timeout ntries
    This command tells ppp to re-establish the connection ntries times on
    loss of carrier with a pause of timeout seconds before each try.  For
    example,
          set reconnect 3 5
    tells ppp that on an unexpected loss of carrier, it should wait 3 seconds
    before attempting to reconnect.  This may happen up to 5 times before ppp
    gives up.  The default value of ntries is zero (no reconnect).  Care
    should be taken with this option.  If the local timeout is slightly
    longer than the remote timeout, the reconnect feature will always be
    triggered (up to the given number of times) after the remote side times
    out and hangs up.  NOTE: In this context, losing too many LQRs consti-
    tutes a loss of carrier and will trigger a reconnect.  If the -background
    flag is specified, all phone numbers are dialed at most once until a con-
    nection is made.  The next number redial period specified with the ``set
    redial command is honoured, as is the reconnect tries value.  If your
    redial value is less than the number of phone numbers specified, not all
    the specified numbers will be tried.  To terminate the program, type
          PPP ON awfulhak> close
          ppp ON awfulhak> quit all
    A simple ``quit command will terminate the pppctl(8) or telnet(1) con-
    nection but not the ppp program itself.  You must use ``quit all to
    terminate ppp as well.

[править] RECEIVING INCOMING PPP CONNECTIONS (Method 1)

    To handle an incoming PPP connection request, follow these steps:
    1.   Make sure the modem and (optionally) /etc/rc.serial is configured
         correctly.
         o   Use Hardware Handshake (CTS/RTS) for flow control.
         o   Modem should be set to NO echo back (ATE0) and NO results string
             (ATQ1).
    2.   Edit /etc/ttys to enable a getty(8) on the port where the modem is
         attached.  For example:
               ttyd1 "/usr/libexec/getty std.38400" dialup on secure
         Do not forget to send a HUP signal to the init(8) process to start
         the getty(8):
               # kill -HUP 1
         It is usually also necessary to train your modem to the same DTR
         speed as the getty:
               # ppp
               ppp ON awfulhak> set device /dev/cuad1
               ppp ON awfulhak> set speed 38400
               ppp ON awfulhak> term
               deflink: Entering terminal mode on /dev/cuad1
               Type `~?' for help
               at
               OK
               at
               OK
               atz
               OK
               at
               OK
               ~.
               ppp ON awfulhak> quit
    3.   Create a /usr/local/bin/ppplogin file with the following contents:
               #! /bin/sh
               exec /usr/sbin/ppp -direct incoming
         Direct mode (-direct) lets ppp work with stdin and stdout.  You can
         also use pppctl(8) to connect to a configured diagnostic port, in
         the same manner as with client-side ppp.
         Here, the incoming section must be set up in /etc/ppp/ppp.conf.
         Make sure that the incoming section contains the ``allow users
         command as appropriate.
    4.   Prepare an account for the incoming user.
         ppp:xxxx:66:66:PPP Login User:/home/ppp:/usr/local/bin/ppplogin
         Refer to the manual entries for adduser(8) and vipw(8) for details.
    5.   Support for IPCP Domain Name Server and NetBIOS Name Server negotia-
         tion can be enabled using the ``accept dns and ``set nbns com-
         mands.  Refer to their descriptions below.

[править] RECEIVING INCOMING PPP CONNECTIONS (Method 2)

    This method differs in that we use ppp to authenticate the connection
    rather than login(1):
    1.   Configure your default section in /etc/gettytab with automatic ppp
         recognition by specifying the ``pp capability:
         default:\
                 :pp=/usr/local/bin/ppplogin:\
                 .....
    2.   Configure your serial device(s), enable a getty(8) and create
         /usr/local/bin/ppplogin as in the first three steps for method 1
         above.
    3.   Add either ``enable chap or ``enable pap (or both) to
         /etc/ppp/ppp.conf under the `incoming' label (or whatever label
         ppplogin uses).
    4.   Create an entry in /etc/ppp/ppp.secret for each incoming user:
         Pfred<TAB>xxxx
         Pgeorge<TAB>yyyy
    Now, as soon as getty(8) detects a ppp connection (by recognising the
    HDLC frame headers), it runs ``/usr/local/bin/ppplogin.
    It is VITAL that either PAP or CHAP are enabled as above.  If they are
    not, you are allowing anybody to establish a ppp session with your
    machine without a password, opening yourself up to all sorts of potential
    attacks.

[править] AUTHENTICATING INCOMING CONNECTIONS

    Normally, the receiver of a connection requires that the peer authenti-
    cates itself.  This may be done using login(1), but alternatively, you
    can use PAP or CHAP.  CHAP is the more secure of the two, but some
    clients may not support it.  Once you decide which you wish to use, add
    the command `enable chap' or `enable pap' to the relevant section of
    ppp.conf.
    You must then configure the /etc/ppp/ppp.secret file.  This file contains
    one line per possible client, each line containing up to five fields:
    name key [hisaddr [label [callback-number]]]
    The name and key specify the client username and password.  If key is
    ``* and PAP is being used, ppp will look up the password database
    (passwd(5)) when authenticating.  If the client does not offer a suitable
    response based on any name/key combination in ppp.secret, authentication
    fails.
    If authentication is successful, hisaddr (if specified) is used when
    negotiating IP numbers.  See the ``set ifaddr command for details.
    If authentication is successful and label is specified, the current sys-
    tem label is changed to match the given label.  This will change the sub-
    sequent parsing of the ppp.linkup and ppp.linkdown files.
    If authentication is successful and callback-number is specified and
    ``set callback has been used in ppp.conf, the client will be called
    back on the given number.  If CBCP is being used, callback-number may
    also contain a list of numbers or a ``*, as if passed to the ``set
    cbcp command.  The value will be used in ppp's subsequent CBCP phase.

[править] PPP OVER TCP and UDP (a.k.a Tunnelling)

    Instead of running ppp over a serial link, it is possible to use a TCP
    connection instead by specifying the host, port and protocol as the
    device:
          set device ui-gate:6669/tcp
    Instead of opening a serial device, ppp will open a TCP connection to the
    given machine on the given socket.  It should be noted however that ppp
    does not use the telnet protocol and will be unable to negotiate with a
    telnet server.  You should set up a port for receiving this PPP connec-
    tion on the receiving machine (ui-gate).  This is done by first updating
    /etc/services to name the service:
          ppp-in 6669/tcp # Incoming PPP connections over TCP
    and updating /etc/inetd.conf to tell inetd(8) how to deal with incoming
    connections on that port:
          ppp-in stream tcp nowait root /usr/sbin/ppp ppp -direct ppp-in
    Do not forget to send a HUP signal to inetd(8) after you have updated
    /etc/inetd.conf.  Here, we use a label named ``ppp-in.  The entry in
    /etc/ppp/ppp.conf on ui-gate (the receiver) should contain the following:
          ppp-in:
           set timeout 0
           set ifaddr 10.0.4.1 10.0.4.2
    and the entry in /etc/ppp/ppp.linkup should contain:
          ppp-in:
           add 10.0.1.0/24 HISADDR
    It is necessary to put the ``add command in ppp.linkup to ensure that
    the route is only added after ppp has negotiated and assigned addresses
    to its interface.
    You may also want to enable PAP or CHAP for security.  To enable PAP, add
    the following line:
           enable PAP
    You will also need to create the following entry in /etc/ppp/ppp.secret:
          MyAuthName MyAuthPasswd
    If MyAuthPasswd is a ``*, the password is looked up in the passwd(5)
    database.
    The entry in /etc/ppp/ppp.conf on awfulhak (the initiator) should contain
    the following:
          ui-gate:
           set escape 0xff
           set device ui-gate:ppp-in/tcp
           set dial
           set timeout 30
           set log Phase Chat Connect hdlc LCP IPCP IPV6CP CCP tun
           set ifaddr 10.0.4.2 10.0.4.1
    with the route setup in /etc/ppp/ppp.linkup:
          ui-gate:
           add 10.0.2.0/24 HISADDR
    Again, if you are enabling PAP, you will also need this in the
    /etc/ppp/ppp.conf profile:
           set authname MyAuthName
           set authkey MyAuthKey
    We are assigning the address of 10.0.4.1 to ui-gate, and the address
    10.0.4.2 to awfulhak.  To open the connection, just type
          awfulhak # ppp -background ui-gate
    The result will be an additional "route" on awfulhak to the 10.0.2.0/24
    network via the TCP connection, and an additional "route" on ui-gate to
    the 10.0.1.0/24 network.  The networks are effectively bridged - the
    underlying TCP connection may be across a public network (such as the
    Internet), and the PPP traffic is conceptually encapsulated (although not
    packet by packet) inside the TCP stream between the two gateways.
    The major disadvantage of this mechanism is that there are two "guaran-
    teed delivery" mechanisms in place - the underlying TCP stream and what-
    ever protocol is used over the PPP link - probably TCP again.  If packets
    are lost, both levels will get in each others way trying to negotiate
    sending of the missing packet.
    To avoid this overhead, it is also possible to do all this using UDP
    instead of TCP as the transport by simply changing the protocol from
    "tcp" to "udp".  When using UDP as a transport, ppp will operate in syn-
    chronous mode.  This is another gain as the incoming data does not have
    to be rearranged into packets.
    Care should be taken when adding a default route through a tunneled setup
    like this.  It is quite common for the default route (added in
    /etc/ppp/ppp.linkup) to end up routing the link's TCP connection through
    the tunnel, effectively garrotting the connection.  To avoid this, make
    sure you add a static route for the benefit of the link:
          ui-gate:
           set escape 0xff
           set device ui-gate:ppp-in/tcp
           add ui-gate x.x.x.x
           .....
    where ``x.x.x.x is the IP number that your route to ``ui-gate would
    normally use.
    When routing your connection accross a public network such as the Inter-
    net, it is preferable to encrypt the data.  This can be done with the
    help of the MPPE protocol, although currently this means that you will
    not be able to also compress the traffic as MPPE is implemented as a com-
    pression layer (thank Microsoft for this).  To enable MPPE encryption,
    add the following lines to /etc/ppp/ppp.conf on the server:
            enable MSCHAPv2
            disable deflate pred1
            deny deflate pred1
    ensuring that you have put the requisite entry in /etc/ppp/ppp.secret
    (MSCHAPv2 is challenge based, so passwd(5) cannot be used)
    MSCHAPv2 and MPPE are accepted by default, so the client end should work
    without any additional changes (although ensure you have ``set authname
    and ``set authkey in your profile).

[править] NETWORK ADDRESS TRANSLATION (PACKET ALIASING)

    The -nat command line option enables network address translation (a.k.a.
    packet aliasing).  This allows the ppp host to act as a masquerading
    gateway for other computers over a local area network.  Outgoing IP pack-
    ets are NAT'd so that they appear to come from the ppp host, and incoming
    packets are de-NAT'd so that they are routed to the correct machine on
    the local area network.  NAT allows computers on private, unregistered
    subnets to have Internet access, although they are invisible from the
    outside world.  In general, correct ppp operation should first be veri-
    fied with network address translation disabled.  Then, the -nat option
    should be switched on, and network applications (web browser, telnet(1),
    ftp(1), ping(8), traceroute(8)) should be checked on the ppp host.
    Finally, the same or similar applications should be checked on other com-
    puters in the LAN.  If network applications work correctly on the ppp
    host, but not on other machines in the LAN, then the masquerading soft-
    ware is working properly, but the host is either not forwarding or possi-
    bly receiving IP packets.  Check that IP forwarding is enabled in
    /etc/rc.conf and that other machines have designated the ppp host as the
    gateway for the LAN.

[править] PACKET FILTERING

    This implementation supports packet filtering.  There are four kinds of
    filters: the in filter, the out filter, the dial filter and the alive
    filter.  Here are the basics:
    o   A filter definition has the following syntax:
        set filter name rule-no action [!] [[host] src_addr[/width]
        [dst_addr[/width]]] [proto [src cmp port] [dst cmp port] [estab]
        [syn] [finrst] [timeout secs]]
        1.   Name should be one of `in', `out', `dial' or `alive'.
        2.   Rule-no is a numeric value between `0' and `39' specifying the
             rule number.  Rules are specified in numeric order according to
             rule-no, but only if rule `0' is defined.
        3.   Action may be specified as `permit' or `deny', in which case, if
             a given packet matches the rule, the associated action is taken
             immediately.  Action can also be specified as `clear' to clear
             the action associated with that particular rule, or as a new
             rule number greater than the current rule.  In this case, if a
             given packet matches the current rule, the packet will next be
             matched against the new rule number (rather than the next rule
             number).
             The action may optionally be followed with an exclamation mark
             (``!), telling ppp to reverse the sense of the following
             match.
        4.   [src_addr[/width]] and [dst_addr[/width]] are the source and
             destination IP number specifications.  If [/width] is specified,
             it gives the number of relevant netmask bits, allowing the spec-
             ification of an address range.
             Either src_addr or dst_addr may be given the values MYADDR,
             HISADDR, MYADDR6 or HISADDR6 (refer to the description of the
             ``bg command for a description of these values).  When these
             values are used, the filters will be updated any time the values
             change.  This is similar to the behaviour of the ``add command
             below.
        5.   Proto may be any protocol from protocols(5).
        6.   Cmp is one of `lt', `eq' or `gt', meaning less-than, equal and
             greater-than respectively.  Port can be specified as a numeric
             port or by service name from /etc/services.
        7.   The `estab', `syn', and `finrst' flags are only allowed when
             proto is set to `tcp', and represent the TH_ACK, TH_SYN and
             TH_FIN or TH_RST TCP flags respectively.
        8.   The timeout value adjusts the current idle timeout to at least
             secs seconds.  If a timeout is given in the alive filter as well
             as in the in/out filter, the in/out value is used.  If no time-
             out is given, the default timeout (set using set timeout and
             defaulting to 180 seconds) is used.
    o   Each filter can hold up to 40 rules, starting from rule 0.  The
        entire rule set is not effective until rule 0 is defined, i.e., the
        default is to allow everything through.
    o   If no rule in a defined set of rules matches a packet, that packet
        will be discarded (blocked).  If there are no rules in a given fil-
        ter, the packet will be permitted.
    o   It is possible to filter based on the payload of UDP frames where
        those frames contain a PROTO_IP PPP frame header.  See the
        filter-decapsulation option below for further details.
    o   Use ``set filter name -1 to flush all rules.
    See /usr/share/examples/ppp/ppp.conf.sample.

[править] SETTING THE IDLE TIMER

    To check/set the idle timer, use the ``show bundle and ``set timeout
    commands:
          ppp ON awfulhak> set timeout 600
    The timeout period is measured in seconds, the default value for which is
    180 seconds (or 3 min).  To disable the idle timer function, use the com-
    mand
          ppp ON awfulhak> set timeout 0
    In -ddial and -dedicated modes, the idle timeout is ignored.  In -auto
    mode, when the idle timeout causes the PPP session to be closed, the ppp
    program itself remains running.  Another trigger packet will cause it to
    attempt to re-establish the link.

[править] PREDICTOR-1 and DEFLATE COMPRESSION

    ppp supports both Predictor type 1 and deflate compression.  By default,
    ppp will attempt to use (or be willing to accept) both compression proto-
    cols when the peer agrees (or requests them).  The deflate protocol is
    preferred by ppp.  Refer to the ``disable and ``deny commands if you
    wish to disable this functionality.
    It is possible to use a different compression algorithm in each direction
    by using only one of ``disable deflate and ``deny deflate (assuming
    that the peer supports both algorithms).
    By default, when negotiating DEFLATE, ppp will use a window size of 15.
    Refer to the ``set deflate command if you wish to change this behav-
    iour.
    A special algorithm called DEFLATE24 is also available, and is disabled
    and denied by default.  This is exactly the same as DEFLATE except that
    it uses CCP ID 24 to negotiate.  This allows ppp to successfully negoti-
    ate DEFLATE with pppd version 2.3.*.

[править] CONTROLLING IP ADDRESS

    For IPv4, ppp uses IPCP to negotiate IP addresses.  Each side of the con-
    nection specifies the IP address that it is willing to use, and if the
    requested IP address is acceptable then ppp returns an ACK to the
    requester.  Otherwise, ppp returns NAK to suggest that the peer use a
    different IP address.  When both sides of the connection agree to accept
    the received request (and send an ACK), IPCP is set to the open state and
    a network level connection is established.  To control this IPCP behav-
    iour, this implementation has the ``set ifaddr command for defining the
    local and remote IP address:
          set ifaddr [src_addr[/nn] [dst_addr[/nn] [netmask [trigger_addr]]]]
    where, `src_addr' is the IP address that the local side is willing to
    use, `dst_addr' is the IP address which the remote side should use and
    `netmask' is the netmask that should be used.  `Src_addr' defaults to the
    current hostname(1), `dst_addr' defaults to 0.0.0.0, and `netmask'
    defaults to whatever mask is appropriate for `src_addr'.  It is only pos-
    sible to make `netmask' smaller than the default.  The usual value is
    255.255.255.255, as most kernels ignore the netmask of a POINTOPOINT
    interface.
    Some incorrect PPP implementations require that the peer negotiates a
    specific IP address instead of `src_addr'.  If this is the case,
    `trigger_addr' may be used to specify this IP number.  This will not
    affect the routing table unless the other side agrees with this proposed
    number.
          set ifaddr 192.244.177.38 192.244.177.2 255.255.255.255 0.0.0.0
    The above specification means:
    o   I will first suggest that my IP address should be 0.0.0.0, but I will
        only accept an address of 192.244.177.38.
    o   I strongly insist that the peer uses 192.244.177.2 as his own address
        and will not permit the use of any IP address but 192.244.177.2.
        When the peer requests another IP address, I will always suggest that
        it uses 192.244.177.2.
    o   The routing table entry will have a netmask of 0xffffffff.
    This is all fine when each side has a pre-determined IP address, however
    it is often the case that one side is acting as a server which controls
    all IP addresses and the other side should go along with it.  In order to
    allow more flexible behaviour, the ``set ifaddr command allows the user
    to specify IP addresses more loosely:
          set ifaddr 192.244.177.38/24 192.244.177.2/20
    A number followed by a slash (``/) represents the number of bits sig-
    nificant in the IP address.  The above example means:
    o   I would like to use 192.244.177.38 as my address if it is possible,
        but I will also accept any IP address between 192.244.177.0 and
        192.244.177.255.
    o   I would like to make him use 192.244.177.2 as his own address, but I
        will also permit him to use any IP address between 192.244.176.0 and
        192.244.191.255.
    o   As you may have already noticed, 192.244.177.2 is equivalent to say-
        ing 192.244.177.2/32.
    o   As an exception, 0 is equivalent to 0.0.0.0/0, meaning that I have no
        preferred IP address and will obey the remote peers selection.  When
        using zero, no routing table entries will be made until a connection
        is established.
    o   192.244.177.2/0 means that I will accept/permit any IP address but I
        will suggest that 192.244.177.2 be used first.
    When negotiating IPv6 addresses, no control is given to the user.  IPV6CP
    negotiation is fully automatic.

[править] CONNECTING WITH YOUR INTERNET SERVICE PROVIDER

    The following steps should be taken when connecting to your ISP:
    1.   Describe your providers phone number(s) in the dial script using the
         ``set phone command.  This command allows you to set multiple
         phone numbers for dialing and redialing separated by either a pipe
         (``|) or a colon (``:):
               set phone telno[|backupnumber]...[:nextnumber]...
         Numbers after the first in a pipe-separated list are only used if
         the previous number was used in a failed dial or login script.  Num-
         bers separated by a colon are used sequentially, irrespective of
         what happened as a result of using the previous number.  For exam-
         ple:
               set phone "1234567|2345678:3456789|4567890"
         Here, the 1234567 number is attempted.  If the dial or login script
         fails, the 2345678 number is used next time, but *only* if the dial
         or login script fails.  On the dial after this, the 3456789 number
         is used.  The 4567890 number is only used if the dial or login
         script using the 3456789 fails.  If the login script of the 2345678
         number fails, the next number is still the 3456789 number.  As many
         pipes and colons can be used as are necessary (although a given site
         would usually prefer to use either the pipe or the colon, but not
         both).  The next number redial timeout is used between all numbers.
         When the end of the list is reached, the normal redial period is
         used before starting at the beginning again.  The selected phone
         number is substituted for the \\T string in the ``set dial command
         (see below).
    2.   Set up your redial requirements using ``set redial.  For example,
         if you have a bad telephone line or your provider is usually engaged
         (not so common these days), you may want to specify the following:
               set redial 10 4
         This says that up to 4 phone calls should be attempted with a pause
         of 10 seconds before dialing the first number again.
    3.   Describe your login procedure using the ``set dial and ``set
         login commands.  The ``set dial command is used to talk to your
         modem and establish a link with your ISP, for example:
               set dial "ABORT BUSY ABORT NO\\sCARRIER TIMEOUT 4 \"\" \
                 ATZ OK-ATZ-OK ATDT\\T TIMEOUT 60 CONNECT"
         This modem "chat" string means:
         o   Abort if the string "BUSY" or "NO CARRIER" are received.
         o   Set the timeout to 4 seconds.
         o   Expect nothing.
         o   Send ATZ.
         o   Expect OK.  If that is not received within the 4 second timeout,
             send ATZ and expect OK.
         o   Send ATDTxxxxxxx where xxxxxxx is the next number in the phone
             list from above.
         o   Set the timeout to 60.
         o   Wait for the CONNECT string.
         Once the connection is established, the login script is executed.
         This script is written in the same style as the dial script, but
         care should be taken to avoid having your password logged:
               set authkey MySecret
               set login "TIMEOUT 15 login:-\\r-login: awfulhak \
                 word: \\P ocol: PPP HELLO"
         This login "chat" string means:
         o   Set the timeout to 15 seconds.
         o   Expect "login:".  If it is not received, send a carriage return
             and expect "login:" again.
         o   Send "awfulhak"
         o   Expect "word:" (the tail end of a "Password:" prompt).
         o   Send whatever our current authkey value is set to.
         o   Expect "ocol:" (the tail end of a "Protocol:" prompt).
         o   Send "PPP".
         o   Expect "HELLO".
         The ``set authkey command is logged specially.  When command or
         chat logging is enabled, the actual password is not logged;
         `********' is logged instead.
         Login scripts vary greatly between ISPs.  If you are setting one up
         for the first time, ENABLE CHAT LOGGING so that you can see if your
         script is behaving as you expect.
    4.   Use ``set device and ``set speed to specify your serial line and
         speed, for example:
               set device /dev/cuad0
               set speed 115200
         Cuad0 is the first serial port on FreeBSD.  If you are running ppp
         on OpenBSD, cua00 is the first.  A speed of 115200 should be speci-
         fied if you have a modem capable of bit rates of 28800 or more.  In
         general, the serial speed should be about four times the modem
         speed.
    5.   Use the ``set ifaddr command to define the IP address.
         o   If you know what IP address your provider uses, then use it as
             the remote address (dst_addr), otherwise choose something like
             10.0.0.2/0 (see below).
         o   If your provider has assigned a particular IP address to you,
             then use it as your address (src_addr).
         o   If your provider assigns your address dynamically, choose a
             suitably unobtrusive and unspecific IP number as your address.
             10.0.0.1/0 would be appropriate.  The bit after the / specifies
             how many bits of the address you consider to be important, so if
             you wanted to insist on something in the class C network
             1.2.3.0, you could specify 1.2.3.1/24.
         o   If you find that your ISP accepts the first IP number that you
             suggest, specify third and forth arguments of ``0.0.0.0.  This
             will force your ISP to assign a number.  (The third argument
             will be ignored as it is less restrictive than the default mask
             for your `src_addr').
         An example for a connection where you do not know your IP number or
         your ISPs IP number would be:
               set ifaddr 10.0.0.1/0 10.0.0.2/0 0.0.0.0 0.0.0.0
    6.   In most cases, your ISP will also be your default router.  If this
         is the case, add the line
               add default HISADDR
         to /etc/ppp/ppp.conf (or to /etc/ppp/ppp.linkup for setups that do
         not use -auto mode).
         This tells ppp to add a default route to whatever the peer address
         is (10.0.0.2 in this example).  This route is `sticky', meaning that
         should the value of HISADDR change, the route will be updated
         accordingly.
    7.   If your provider requests that you use PAP/CHAP authentication meth-
         ods, add the next lines to your /etc/ppp/ppp.conf file:
               set authname MyName
               set authkey MyPassword
         Both are accepted by default, so ppp will provide whatever your ISP
         requires.
         It should be noted that a login script is rarely (if ever) required
         when PAP or CHAP are in use.
    8.   Ask your ISP to authenticate your nameserver address(es) with the
         line
               enable dns
         Do NOT do this if you are running a local DNS unless you also either
         use ``resolv readonly or have ``resolv restore in
         /etc/ppp/ppp.linkdown, as ppp will simply circumvent its use by
         entering some nameserver lines in /etc/resolv.conf.
    Please refer to /usr/share/examples/ppp/ppp.conf.sample and
    /usr/share/examples/ppp/ppp.linkup.sample for some real examples.  The
    pmdemand label should be appropriate for most ISPs.

[править] LOGGING FACILITY

    ppp is able to generate the following log info either via syslog(3) or
    directly to the screen:
       All        Enable all logging facilities.  This generates a lot of
                  log.  The most common use of 'all' is as a basis, where you
                  remove some facilities after enabling 'all' ('debug' and
                  'timer' are usually best disabled.)
       Async      Dump async level packet in hex.
       CBCP       Generate CBCP (CallBack Control Protocol) logs.
       CCP        Generate a CCP packet trace.
       Chat       Generate `dial', `login', `logout' and `hangup' chat script
                  trace logs.
       Command    Log commands executed either from the command line or any
                  of the configuration files.
       Connect    Log Chat lines containing the string "CONNECT".
       Debug      Log debug information.
       DNS        Log DNS QUERY packets.
       Filter     Log packets permitted by the dial filter and denied by any
                  filter.
       HDLC       Dump HDLC packet in hex.
       ID0        Log all function calls specifically made as user id 0.
       IPCP       Generate an IPCP packet trace.
       LCP        Generate an LCP packet trace.
       LQM        Generate LQR reports.
       Phase      Phase transition log output.
       Physical   Dump physical level packet in hex.
       Radius     Dump RADIUS information.  RADIUS information resulting from
                  the link coming up or down is logged at ``Phase level
                  unless ``Radius logging is enabled.  This log level is
                  most useful for monitoring RADIUS alive information.
       Sync       Dump sync level packet in hex.
       TCP/IP     Dump all TCP/IP packets.
       Timer      Log timer manipulation.
       TUN        Include the tun device on each log line.
       Warning    Output to the terminal device.  If there is currently no
                  terminal, output is sent to the log file using syslogs
                  LOG_WARNING.
       Error      Output to both the terminal device and the log file using
                  syslogs LOG_ERROR.
       Alert      Output to the log file using LOG_ALERT.
    The ``set log command allows you to set the logging output level.  Mul-
    tiple levels can be specified on a single command line.  The default is
    equivalent to ``set log Phase.
    It is also possible to log directly to the screen.  The syntax is the
    same except that the word ``local should immediately follow ``set
    log.  The default is ``set log local (i.e., only the un-maskable
    warning, error and alert output).
    If The first argument to ``set log [local] begins with a `+' or a `-'
    character, the current log levels are not cleared, for example:
          PPP ON awfulhak> set log phase
          PPP ON awfulhak> show log
          Log:   Phase Warning Error Alert
          Local: Warning Error Alert
          PPP ON awfulhak> set log +tcp/ip -warning
          PPP ON awfulhak> set log local +command
          PPP ON awfulhak> show log
          Log:   Phase TCP/IP Warning Error Alert
          Local: Command Warning Error Alert
    Log messages of level Warning, Error and Alert are not controllable using
    ``set log [local].
    The Warning level is special in that it will not be logged if it can be
    displayed locally.

[править] SIGNAL HANDLING

    ppp deals with the following signals:
    INT   Receipt of this signal causes the termination of the current con-
          nection (if any).  This will cause ppp to exit unless it is in
          -auto or -ddial mode.
    HUP, TERM & QUIT
          These signals tell ppp to exit.
    USR1  This signal, tells ppp to re-open any existing server socket, drop-
          ping all existing diagnostic connections.  Sockets that could not
          previously be opened will be retried.
    USR2  This signal, tells ppp to close any existing server socket, drop-
          ping all existing diagnostic connections.  SIGUSR1 can still be
          used to re-open the socket.

[править] MULTI-LINK PPP

    If you wish to use more than one physical link to connect to a PPP peer,
    that peer must also understand the MULTI-LINK PPP protocol.  Refer to RFC 1990 for specification details.
    The peer is identified using a combination of his ``endpoint
    discriminator and his ``authentication id.  Either or both of these
    may be specified.  It is recommended that at least one is specified, oth-
    erwise there is no way of ensuring that all links are actually connected
    to the same peer program, and some confusing lock-ups may result.
    Locally, these identification variables are specified using the ``set
    enddisc and ``set authname commands.  The `authname' (and `authkey')
    must be agreed in advance with the peer.
    Multi-link capabilities are enabled using the ``set mrru command (set
    maximum reconstructed receive unit).  Once multi-link is enabled, ppp
    will attempt to negotiate a multi-link connection with the peer.
    By default, only one `link' is available (called `deflink').  To create
    more links, the ``clone command is used.  This command will clone
    existing links, where all characteristics are the same except:
    1.   The new link has its own name as specified on the ``clone command
         line.
    2.   The new link is an `interactive' link.  Its mode may subsequently be
         changed using the ``set mode command.
    3.   The new link is in a `closed' state.
    A summary of all available links can be seen using the ``show links
    command.
    Once a new link has been created, command usage varies.  All link spe-
    cific commands must be prefixed with the ``link name command, specify-
    ing on which link the command is to be applied.  When only a single link
    is available, ppp is smart enough not to require the ``link name pre-
    fix.
    Some commands can still be used without specifying a link - resulting in
    an operation at the `bundle' level.  For example, once two or more links
    are available, the command ``show ccp will show CCP configuration and
    statistics at the multi-link level, and ``link deflink show ccp will
    show the same information at the ``deflink link level.
    Armed with this information, the following configuration might be used:
          mp:
           set timeout 0
           set log phase chat
           set device /dev/cuad0 /dev/cuad1 /dev/cuad2
           set phone "123456789"
           set dial "ABORT BUSY ABORT NO\sCARRIER TIMEOUT 5 \"\" ATZ \
                     OK-AT-OK \\dATDT\\T TIMEOUT 45 CONNECT"
           set login
           set ifaddr 10.0.0.1/0 10.0.0.2/0 0.0.0.0 0.0.0.0
           set authname ppp
           set authkey ppppassword
           set mrru 1500
           clone 1,2,3            # Create 3 new links - duplicates of the default
           link deflink remove    # Delete the default link (called ``deflink)
    Note how all cloning is done at the end of the configuration.  Usually,
    the link will be configured first, then cloned.  If you wish all links to
    be up all the time, you can add the following line to the end of your
    configuration.
            link 1,2,3 set mode ddial
    If you want the links to dial on demand, this command could be used:
            link * set mode auto
    Links may be tied to specific names by removing the ``set device line
    above, and specifying the following after the ``clone command:
           link 1 set device /dev/cuad0
           link 2 set device /dev/cuad1
           link 3 set device /dev/cuad2
    Use the ``help command to see which commands require context (using the
    ``link command), which have optional context and which should not have
    any context.
    When ppp has negotiated MULTI-LINK mode with the peer, it creates a local
    domain socket in the /var/run directory.  This socket is used to pass
    link information (including the actual link file descriptor) between dif-
    ferent ppp invocations.  This facilitates ppp's ability to be run from a
    getty(8) or directly from /etc/gettydefs (using the `pp=' capability),
    without needing to have initial control of the serial line.  Once ppp
    negotiates multi-link mode, it will pass its open link to any already
    running process.  If there is no already running process, ppp will act as
    the master, creating the socket and listening for new connections.

[править] PPP COMMAND LIST

    This section lists the available commands and their effect.  They are
    usable either from an interactive ppp session, from a configuration file
    or from a pppctl(8) or telnet(1) session.
    accept|deny|enable|disable option....
        These directives tell ppp how to negotiate the initial connection
        with the peer.  Each ``option has a default of either accept or
        deny and enable or disable.  ``Accept means that the option will be
        ACK'd if the peer asks for it.  ``Deny means that the option will
        be NAK'd if the peer asks for it.  ``Enable means that the option
        will be requested by us.  ``Disable means that the option will not
        be requested by us.
        ``Option may be one of the following:
        acfcomp
            Default: Enabled and Accepted.  ACFComp stands for Address and
            Control Field Compression.  Non LCP packets will usually have an
            address field of 0xff (the All-Stations address) and a control
            field of 0x03 (the Unnumbered Information command).  If this
            option is negotiated, these two bytes are simply not sent, thus
            minimising traffic.
            See rfc1662 for details.
        chap[05]
            Default: Disabled and Accepted.  CHAP stands for Challenge Hand-
            shake Authentication Protocol.  Only one of CHAP and PAP (below)
            may be negotiated.  With CHAP, the authenticator sends a "chal-
            lenge" message to its peer.  The peer uses a one-way hash func-
            tion to encrypt the challenge and sends the result back.  The
            authenticator does the same, and compares the results.  The
            advantage of this mechanism is that no passwords are sent across
            the connection.  A challenge is made when the connection is first
            made.  Subsequent challenges may occur.  If you want to have your
            peer authenticate itself, you must ``enable chap.  in
            /etc/ppp/ppp.conf, and have an entry in /etc/ppp/ppp.secret for
            the peer.
            When using CHAP as the client, you need only specify ``AuthName
            and ``AuthKey in /etc/ppp/ppp.conf.  CHAP is accepted by
            default.  Some PPP implementations use "MS-CHAP" rather than MD5
            when encrypting the challenge.  MS-CHAP is a combination of MD4
            and DES.  If ppp was built on a machine with DES libraries avail-
            able, it will respond to MS-CHAP authentication requests, but
            will never request them.
        deflate
            Default: Enabled and Accepted.  This option decides if deflate
            compression will be used by the Compression Control Protocol
            (CCP).  This is the same algorithm as used by the gzip(1) pro-
            gram.  Note: There is a problem negotiating deflate capabilities
            with pppd - a PPP implementation available under many operating
            systems.  pppd (version 2.3.1) incorrectly attempts to negotiate
            deflate compression using type 24 as the CCP configuration type
            rather than type 26 as specified in rfc1979.  Type 24 is actually
            specified as ``PPP Magna-link Variable Resource Compression in
            rfc1975!  ppp is capable of negotiating with pppd, but only if
            ``deflate24 is enabled and accepted.
        deflate24
            Default: Disabled and Denied.  This is a variance of the deflate
            option, allowing negotiation with the pppd program.  Refer to the
            deflate section above for details.  It is disabled by default as
            it violates rfc1975.
        dns
            Default: Disabled and Denied.  This option allows DNS negotia-
            tion.
            If ``enabled, ppp will request that the peer confirms the
            entries in /etc/resolv.conf.  If the peer NAKs our request (sug-
            gesting new IP numbers), /etc/resolv.conf is updated and another
            request is sent to confirm the new entries.
            If ``accepted, ppp will answer any DNS queries requested by the
            peer rather than rejecting them.  The answer is taken from
            /etc/resolv.conf unless the ``set dns command is used as an
            override.
        enddisc
            Default: Enabled and Accepted.  This option allows control over
            whether we negotiate an endpoint discriminator.  We only send our
            discriminator if ``set enddisc is used and enddisc is enabled.
            We reject the peers discriminator if enddisc is denied.
        LANMan|chap80lm
            Default: Disabled and Accepted.  The use of this authentication
            protocol is discouraged as it partially violates the authentica-
            tion protocol by implementing two different mechanisms (LANMan &
            NT) under the guise of a single CHAP type (0x80).  ``LANMan
            uses a simple DES encryption mechanism and is the least secure of
            the CHAP alternatives (although is still more secure than PAP).
            Refer to the ``MSChap description below for more details.
        lqr
            Default: Disabled and Accepted.  This option decides if Link
            Quality Requests will be sent or accepted.  LQR is a protocol
            that allows ppp to determine that the link is down without rely-
            ing on the modems carrier detect.  When LQR is enabled, ppp sends
            the QUALPROTO option (see ``set lqrperiod below) as part of the
            LCP request.  If the peer agrees, both sides will exchange LQR
            packets at the agreed frequency, allowing detailed link quality
            monitoring by enabling LQM logging.  If the peer does not agree,
            and if the ``echo option is enabled, ppp will send LCP ECHO
            requests instead.  These packets pass no information of interest,
            but they MUST be replied to by the peer.
            Whether using LQR or LCP ECHO, ppp will abruptly drop the connec-
            tion if 5 unacknowledged packets have been sent rather than send-
            ing a 6th.  A message is logged at the PHASE level, and any
            appropriate ``reconnect values are honoured as if the peer were
            responsible for dropping the connection.
            Refer to the ``enable echo command description for differences
            in behaviour prior to ppp version 3.4.2.
        mppe
            Default: Enabled and Accepted.  This is Microsoft Point to Point
            Encryption scheme.  MPPE key size can be 40-, 56- and 128-bits.
            Refer to ``set mppe command.
        MSChapV2|chap81
            Default: Disabled and Accepted.  It is very similar to standard
            CHAP (type 0x05) except that it issues challenges of a fixed 16
            bytes in length and uses a combination of MD4, SHA-1 and DES to
            encrypt the challenge rather than using the standard MD5 mecha-
            nism.
        MSChap|chap80nt
            Default: Disabled and Accepted.  The use of this authentication
            protocol is discouraged as it partially violates the authentica-
            tion protocol by implementing two different mechanisms (LANMan &
            NT) under the guise of a single CHAP type (0x80).  It is very
            similar to standard CHAP (type 0x05) except that it issues chal-
            lenges of a fixed 8 bytes in length and uses a combination of MD4
            and DES to encrypt the challenge rather than using the standard
            MD5 mechanism.  CHAP type 0x80 for LANMan is also supported - see
            ``enable LANMan for details.
            Because both ``LANMan and ``NT use CHAP type 0x80, when act-
            ing as authenticator with both ``enabled, ppp will rechallenge
            the peer up to three times if it responds using the wrong one of
            the two protocols.  This gives the peer a chance to attempt using
            both protocols.
            Conversely, when ppp acts as the authenticatee with both proto-
            cols ``accepted, the protocols are used alternately in response
            to challenges.
            Note: If only LANMan is enabled, pppd (version 2.3.5) misbehaves
            when acting as authenticatee.  It provides both the NT and the
            LANMan answers, but also suggests that only the NT answer should
            be used.
        pap
            Default: Disabled and Accepted.  PAP stands for Password Authen-
            tication Protocol.  Only one of PAP and CHAP (above) may be nego-
            tiated.  With PAP, the ID and Password are sent repeatedly to the
            peer until authentication is acknowledged or the connection is
            terminated.  This is a rather poor security mechanism.  It is
            only performed when the connection is first established.  If you
            want to have your peer authenticate itself, you must ``enable
            pap.  in /etc/ppp/ppp.conf, and have an entry in
            /etc/ppp/ppp.secret for the peer (although see the ``passwdauth
            and ``set radius options below).
            When using PAP as the client, you need only specify ``AuthName
            and ``AuthKey in /etc/ppp/ppp.conf.  PAP is accepted by
            default.
        pred1
            Default: Enabled and Accepted.  This option decides if Predictor
            1 compression will be used by the Compression Control Protocol
            (CCP).
        protocomp
            Default: Enabled and Accepted.  This option is used to negotiate
            PFC (Protocol Field Compression), a mechanism where the protocol
            field number is reduced to one octet rather than two.
        shortseq
            Default: Enabled and Accepted.  This option determines if ppp
            will request and accept requests for short (12 bit) sequence num-
            bers when negotiating multi-link mode.  This is only applicable
            if our MRRU is set (thus enabling multi-link).
        vjcomp
            Default: Enabled and Accepted.  This option determines if Van
            Jacobson header compression will be used.
        The following options are not actually negotiated with the peer.
        Therefore, accepting or denying them makes no sense.
        echo
            Default: Disabled.  When this option is enabled, ppp will send
            LCP ECHO requests to the peer at the frequency defined by
            ``echoperiod.  Note, LQR requests will supersede LCP ECHO
            requests if enabled and negotiated.  See ``set lqrperiod below
            for details.
            Prior to ppp version 3.4.2, ``echo was considered enabled if
            lqr was enabled and negotiated, otherwise it was considered dis-
            abled.  For the same behaviour, it is now necessary to ``enable
            lqr echo rather than just ``enable lqr.
        filter-decapsulation
            Default: Disabled.  When this option is enabled, ppp will examine
            UDP frames to see if they actually contain a PPP frame as their
            payload.  If this is the case, all filters will operate on the
            payload rather than the actual packet.
            This is useful if you want to send PPPoUDP traffic over a PPP
            link, but want that link to do smart things with the real data
            rather than the UDP wrapper.
            The UDP frame payload must not be compressed in any way, other-
            wise ppp will not be able to interpret it.  It is therefore rec-
            ommended that you disable vj pred1 deflate and deny vj pred1
            deflate in the configuration for the ppp invocation with the udp
            link.
        force-scripts
            Default: Disabled.  Forces execution of the configured chat
            scripts in direct and dedicated modes.
        idcheck
            Default: Enabled.  When ppp exchanges low-level LCP, CCP and IPCP
            configuration traffic, the Identifier field of any replies is
            expected to be the same as that of the request.  By default, ppp
            drops any reply packets that do not contain the expected identi-
            fier field, reporting the fact at the respective log level.  If
            idcheck is disabled, ppp will ignore the identifier field.
        iface-alias
            Default: Enabled if -nat is specified.  This option simply tells
            ppp to add new interface addresses to the interface rather than
            replacing them.  The option can only be enabled if network
            address translation is enabled (``nat enable yes).
            With this option enabled, ppp will pass traffic for old interface
            addresses through the NAT engine (see libalias(3)), resulting in
            the ability (in -auto mode) to properly connect the process that
            caused the PPP link to come up in the first place.
            Disabling NAT with ``nat enable no will also disable
            `iface-alias'.
        ipcp
            Default: Enabled.  This option allows ppp to attempt to negotiate
            IP control protocol capabilities and if successful to exchange IP
            datagrams with the peer.
        ipv6cp
            Default: Enabled.  This option allows ppp to attempt to negotiate
            IPv6 control protocol capabilities and if successful to exchange
            IPv6 datagrams with the peer.
        keep-session
            Default: Disabled.  When ppp runs as a Multi-link server, a dif-
            ferent ppp instance initially receives each connection.  After
            determining that the link belongs to an already existing bundle
            (controlled by another ppp invocation), ppp will transfer the
            link to that process.
            If the link is a tty device or if this option is enabled, ppp
            will not exit, but will change its process name to ``session
            owner and wait for the controlling ppp to finish with the link
            and deliver a signal back to the idle process.  This prevents the
            confusion that results from ppp's parent considering the link
            resource available again.
            For tty devices that have entries in /etc/ttys, this is necessary
            to prevent another getty(8) from being started, and for program
            links such as sshd(8), it prevents sshd(8) from exiting due to
            the death of its child.  As ppp cannot determine its parents
            requirements (except for the tty case), this option must be
            enabled manually depending on the circumstances.
        loopback
            Default: Enabled.  When loopback is enabled, ppp will automati-
            cally loop back packets being sent out with a destination address
            equal to that of the PPP interface.  If disabled, ppp will send
            the packet, probably resulting in an ICMP redirect from the other
            end.  It is convenient to have this option enabled when the
            interface is also the default route as it avoids the necessity of
            a loopback route.
        NAS-IP-Address
            Default: Enabled.  This option controls whether ppp sends the
            ``NAS-IP-Address attribute to the RADIUS server when RADIUS is
            in use (see ``set radius).
            Note, at least one of ``NAS-IP-Address and ``NAS-Identifier
            must be enabled.
            Versions of ppp prior to version 3.4.1 did not send the
            ``NAS-IP-Address attribute as it was reported to break the
            Radiator RADIUS server.  As the latest rfc (2865) no longer hints
            that only one of ``NAS-IP-Address and ``NAS-Identifier should
            be sent (as rfc 2138 did), ppp now sends both and leaves it up to
            the administrator that chooses to use bad RADIUS implementations
            to ``disable NAS-IP-Address.
        NAS-Identifier
            Default: Enabled.  This option controls whether ppp sends the
            ``NAS-Identifier attribute to the RADIUS server when RADIUS is
            in use (see ``set radius).
            Note, at least one of ``NAS-IP-Address and ``NAS-Identifier
            must be enabled.
        passwdauth
            Default: Disabled.  Enabling this option will tell the PAP
            authentication code to use the password database (see passwd(5))
            to authenticate the caller if they cannot be found in the
            /etc/ppp/ppp.secret file.  /etc/ppp/ppp.secret is always checked
            first.  If you wish to use passwords from passwd(5), but also to
            specify an IP number or label for a given client, use ``* as
            the client password in /etc/ppp/ppp.secret.
        proxy
            Default: Disabled.  Enabling this option will tell ppp to proxy
            ARP for the peer.  This means that ppp will make an entry in the
            ARP table using HISADDR and the MAC address of the local network
            in which HISADDR appears.  This allows other machines connecteed
            to the LAN to talk to the peer as if the peer itself was con-
            nected to the LAN.  The proxy entry cannot be made unless HISADDR
            is an address from a LAN.
        proxyall
            Default: Disabled.  Enabling this will tell ppp to add proxy arp
            entries for every IP address in all class C or smaller subnets
            routed via the tun interface.
            Proxy arp entries are only made for sticky routes that are added
            using the ``add command.  No proxy arp entries are made for the
            interface address itself (as created by the ``set ifaddr com-
            mand).
        sroutes
            Default: Enabled.  When the ``add command is used with the
            HISADDR, MYADDR, HISADDR6 or MYADDR6 values, entries are stored
            in the `sticky route' list.  Each time these variables change,
            this list is re-applied to the routing table.
            Disabling this option will prevent the re-application of sticky
            routes, although the `stick route' list will still be maintained.
        [tcp]mssfixup
            Default: Enabled.  This option tells ppp to adjust TCP SYN pack-
            ets so that the maximum receive segment size is not greater than
            the amount allowed by the interface MTU.
        throughput
            Default: Enabled.  This option tells ppp to gather throughput
            statistics.  Input and output is sampled over a rolling 5 second
            window, and current, best and total figures are retained.  This
            data is output when the relevant PPP layer shuts down, and is
            also available using the ``show command.  Throughput statistics
            are available at the ``IPCP and ``physical levels.
        utmp
            Default: Enabled.  Normally, when a user is authenticated using
            PAP or CHAP, and when ppp is running in -direct mode, an entry is
            made in the utmp and wtmp files for that user.  Disabling this
            option will tell ppp not to make any utmp or wtmp entries.  This
            is usually only necessary if you require the user to both login
            and authenticate themselves.
    add[!] dest[/nn] [mask] [gateway]
        Dest is the destination IP address.  The netmask is specified either
        as a number of bits with /nn or as an IP number using mask.  0 0 or
        simply 0 with no mask refers to the default route.  It is also possi-
        ble to use the literal name `default' instead of 0.  Gateway is the
        next hop gateway to get to the given dest machine/network.  Refer to
        the route(8) command for further details.
        It is possible to use the symbolic names `MYADDR', `HISADDR',
        `MYADDR6' or `HISADDR6' as the destination, and `HISADDR' or
        `HISADDR6' as the gateway.  `MYADDR' is replaced with the interface
        IP address, `HISADDR' is replaced with the interface IP destination
        (peer) address, `MYADDR6' is replaced with the interface IPv6
        address, and `HISADDR6' is replaced with the interface IPv6 destina-
        tion address,
        If the add! command is used (note the trailing ``!), then if the
        route already exists, it will be updated as with the `route change'
        command (see route(8) for further details).
        Routes that contain the ``HISADDR, ``MYADDR, ``HISADDR6,
        ``MYADDR6, ``DNS0, or ``DNS1 constants are considered `sticky'.
        They are stored in a list (use ``show ncp to see the list), and
        each time the value of one of these variables changes, the appropri-
        ate routing table entries are updated.  This facility may be disabled
        using ``disable sroutes.
    allow command [args]
        This command controls access to ppp and its configuration files.  It
        is possible to allow user-level access, depending on the configura-
        tion file label and on the mode that ppp is being run in.  For exam-
        ple, you may wish to configure ppp so that only user `fred' may
        access label `fredlabel' in -background mode.
        User id 0 is immune to these commands.
        allow user[s] logname...
            By default, only user id 0 is allowed access to ppp.  If this
            command is used, all of the listed users are allowed access to
            the section in which the ``allow users command is found.  The
            `default' section is always checked first (even though it is only
            ever automatically loaded at startup).  ``allow users commands
            are cumulative in a given section, but users allowed in any given
            section override users allowed in the default section, so it is
            possible to allow users access to everything except a given label
            by specifying default users in the `default' section, and then
            specifying a new user list for that label.
            If user `*' is specified, access is allowed to all users.
        allow mode[s] mode...
            By default, access using any ppp mode is possible.  If this com-
            mand is used, it restricts the access modes allowed to load the
            label under which this command is specified.  Again, as with the
            ``allow users command, each ``allow modes command overrides
            any previous settings, and the `default' section is always
            checked first.
            Possible modes are: `interactive', `auto', `direct', `dedicated',
            `ddial', `background' and `*'.
            When running in multi-link mode, a section can be loaded if it
            allows any of the currently existing line modes.
    nat command [args]
        This command allows the control of the network address translation
        (also known as masquerading or IP aliasing) facilities that are built
        into ppp.  NAT is done on the external interface only, and is
        unlikely to make sense if used with the -direct flag.
        If nat is enabled on your system (it may be omitted at compile time),
        the following commands are possible:
        nat enable yes|no
            This command either switches network address translation on or
            turns it off.  The -nat command line flag is synonymous with
            ``nat enable yes.
        nat addr [addr_local addr_alias]
            This command allows data for addr_alias to be redirected to
            addr_local.  It is useful if you own a small number of real IP
            numbers that you wish to map to specific machines behind your
            gateway.
        nat deny_incoming yes|no
            If set to yes, this command will refuse all incoming packets
            where an aliasing link does not already exist.  Refer to the
            CONCEPTUAL BACKGROUND section of libalias(3) for a description of
            what an ``aliasing link is.
            It should be noted under what circumstances an aliasing link is
            created by libalias(3).  It may be necessary to further protect
            your network from outside connections using the ``set filter or
            ``nat target commands.
        nat help|?
            This command gives a summary of available nat commands.
        nat log yes|no
            This option causes various NAT statistics and information to be
            logged to the file /var/log/alias.log.
        nat port proto targetIP:targetPort[-targetPort] aliasPort[-aliasPort]
            [remoteIP:remotePort[-remotePort]]
            This command causes incoming proto connections to aliasPort to be
            redirected to targetPort on targetIP.  proto is either ``tcp or
            ``udp.
            A range of port numbers may be specified as shown above.  The
            ranges must be of the same size.
            If remoteIP is specified, only data coming from that IP number is
            redirected.  remotePort must either be ``0 (indicating any
            source port) or a range of ports the same size as the other
            ranges.
            This option is useful if you wish to run things like Internet
            phone on machines behind your gateway, but is limited in that
            connections to only one interior machine per source machine and
            target port are possible.
        nat proto proto localIP [publicIP [remoteIP]]
            This command tells ppp to redirect packets of protocol type proto
            (see protocols(5)) to the internal address localIP.
            If publicIP is specified, only packets destined for that address
            are matched, otherwise the default alias address is used.
            If remoteIP is specified, only packets matching that source
            address are matched,
            This command is useful for redirecting tunnel endpoints to an
            internal machine, for example:
                  nat proto ipencap 10.0.0.1
        nat proxy cmd arg...
            This command tells ppp to proxy certain connections, redirecting
            them to a given server.  Refer to the description of
            PacketAliasProxyRule() in libalias(3) for details of the avail-
            able commands.
        nat punch_fw [base count]
            This command tells ppp to punch holes in the firewall for FTP or
            IRC DCC connections.  This is done dynamically by installing
            termporary firewall rules which allow a particular connection
            (and only that connection) to go through the firewall.  The rules
            are removed once the corresponding connection terminates.
            A maximum of count rules starting from rule number base will be
            used for punching firewall holes.  The range will be cleared when
            the ``nat punch_fw command is run.
            If no arguments are given, firewall punching is disabled.
        nat skinny_port [port]
            This command tells ppp which TCP port is used by the Skinny Sta-
            tion protocol.  Skinny is used by Cisco IP phones to communicate
            with Cisco Call Managers to setup voice over IP calls.  The typi-
            cal port used by Skinny is 2000.
            If no argument is given, skinny aliasing is disabled.
        nat same_ports yes|no
            When enabled, this command will tell the network address transla-
            tion engine to attempt to avoid changing the port number on out-
            going packets.  This is useful if you want to support protocols
            such as RPC and LPD which require connections to come from a well
            known port.
        nat target [address]
            Set the given target address or clear it if no address is given.
            The target address is used by libalias to specify how to NAT
            incoming packets by default.  If a target address is not set or
            if ``default is given, packets are not altered and are allowed
            to route to the internal network.
            The target address may be set to ``MYADDR, in which case
            libalias will redirect all packets to the interface address.
        nat use_sockets yes|no
            When enabled, this option tells the network address translation
            engine to create a socket so that it can guarantee a correct
            incoming ftp data or IRC connection.
        nat unregistered_only yes|no
            Only alter outgoing packets with an unregistered source address.
            According to RFC 1918, unregistered source addresses are
            10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16.
        These commands are also discussed in the file README.nat which comes
        with the source distribution.
    [!]bg command
        The given command is executed in the background with the following
        words replaced:
        AUTHNAME         This is replaced with the local authname value.  See
                         the ``set authname command below.
        COMPILATIONDATE  In previous software revisions, this was replaced
                         with the date on which ppp was compiled.  This is no
                         longer supported as it breaks the ability to recom-
                         pile the same code to produce an exact duplicate of
                         a previous compilation.
        DNS0 & DNS1      These are replaced with the primary and secondary
                         nameserver IP numbers.  If nameservers are negoti-
                         ated by IPCP, the values of these macros will
                         change.
        ENDDISC          This is replaced with the local endpoint discrimina-
                         tor value.  See the ``set enddisc command below.
        HISADDR          This is replaced with the peers IP number.
        HISADDR6         This is replaced with the peers IPv6 number.
        INTERFACE        This is replaced with the name of the interface that
                         is in use.
        IPOCTETSIN       This is replaced with the number of IP bytes
                         received since the connection was established.
        IPOCTETSOUT      This is replaced with the number of IP bytes sent
                         since the connection was established.
        IPPACKETSIN      This is replaced with the number of IP packets
                         received since the connection was established.
        IPPACKETSOUT     This is replaced with the number of IP packets sent
                         since the connection was established.
        IPV6OCTETSIN     This is replaced with the number of IPv6 bytes
                         received since the connection was established.
        IPV6OCTETSOUT    This is replaced with the number of IPv6 bytes sent
                         since the connection was established.
        IPV6PACKETSIN    This is replaced with the number of IPv6 packets
                         received since the connection was established.
        IPV6PACKETSOUT   This is replaced with the number of IPv6 packets
                         sent since the connection was established.
        LABEL            This is replaced with the last label name used.  A
                         label may be specified on the ppp command line, via
                         the ``load or ``dial commands and in the
                         ppp.secret file.
        MYADDR           This is replaced with the IP number assigned to the
                         local interface.
        MYADDR6          This is replaced with the IPv6 number assigned to
                         the local interface.
        OCTETSIN         This is replaced with the number of bytes received
                         since the connection was established.
        OCTETSOUT        This is replaced with the number of bytes sent since
                         the connection was established.
        PACKETSIN        This is replaced with the number of packets received
                         since the connection was established.
        PACKETSOUT       This is replaced with the number of packets sent
                         since the connection was established.
        PEER_ENDDISC     This is replaced with the value of the peers end-
                         point discriminator.
        PROCESSID        This is replaced with the current process id.
        SOCKNAME         This is replaced with the name of the diagnostic
                         socket.
        UPTIME           This is replaced with the bundle uptime in HH:MM:SS
                         format.
        USER             This is replaced with the username that has been
                         authenticated with PAP or CHAP.  Normally, this
                         variable is assigned only in -direct mode.  This
                         value is available irrespective of whether utmp log-
                         ging is enabled.
        VERSION          This is replaced with the current version number of
                         ppp.
        These substitutions are also done by the ``set proctitle, ``ident
        and ``log commands.
        If you wish to pause ppp while the command executes, use the
        ``shell command instead.
    clear physical|ipcp|ipv6 [current|overall|peak...]
        Clear the specified throughput values at either the ``physical,
        ``ipcp or ``ipv6cp level.  If ``physical is specified, context
        must be given (see the ``link command below).  If no second argu-
        ment is given, all values are cleared.
    clone name[,name]...
        Clone the specified link, creating one or more new links according to
        the name argument(s).  This command must be used from the ``link
        command below unless you have only got a single link (in which case
        that link becomes the default).  Links may be removed using the
        ``remove command below.
        The default link name is ``deflink.
    close [lcp|ccp[!]]
        If no arguments are given, the relevant protocol layers will be
        brought down and the link will be closed.  If ``lcp is specified,
        the LCP layer is brought down, but ppp will not bring the link
        offline.  It is subsequently possible to use ``term (see below) to
        talk to the peer machine if, for example, something like ``slirp is
        being used.  If ``ccp is specified, only the relevant compression
        layer is closed.  If the ``! is used, the compression layer will
        remain in the closed state, otherwise it will re-enter the STOPPED
        state, waiting for the peer to initiate further CCP negotiation.  In
        any event, this command does not disconnect the user from ppp or exit
        ppp.  See the ``quit command below.
    delete[!] dest
        This command deletes the route with the given dest IP address.  If
        dest is specified as `ALL', all non-direct entries in the routing ta-
        ble for the current interface, and all `sticky route' entries are
        deleted.  If dest is specified as `default', the default route is
        deleted.
        If the delete! command is used (note the trailing ``!), ppp will
        not complain if the route does not already exist.
    dial|call [label]...
        This command is the equivalent of ``load label followed by
        ``open, and is provided for backwards compatibility.
    down [lcp|ccp]
        Bring the relevant layer down ungracefully, as if the underlying
        layer had become unavailable.  It is not considered polite to use
        this command on a Finite State Machine that is in the OPEN state.  If
        no arguments are supplied, the entire link is closed (or if no con-
        text is given, all links are terminated).  If `lcp' is specified, the
        LCP layer is terminated but the device is not brought offline and the
        link is not closed.  If `ccp' is specified, only the relevant com-
        pression layer(s) are terminated.
    help|? [command]
        Show a list of available commands.  If command is specified, show the
        usage string for that command.
    ident [text...]
        Identify the link to the peer using text.  If text is empty, link
        identification is disabled.  It is possible to use any of the words
        described for the bg command above.  Refer to the sendident command
        for details of when ppp identifies itself to the peer.
    iface command [args]
        This command is used to control the interface used by ppp.  Command
        may be one of the following:
        iface add[!] addr[/bits] [peer]
        iface add[!] addr mask peer
            Add the given addr mask peer combination to the interface.
            Instead of specifying mask, /bits can be used (with no space
            between it and addr).  If the given address already exists, the
            command fails unless the ``! is used - in which case the previ-
            ous interface address entry is overwritten with the new one,
            allowing a change of netmask or peer address.
            If only addr is specified, bits defaults to ``32 and peer
            defaults to ``255.255.255.255.  This address (the broadcast
            address) is the only duplicate peer address that ppp allows.
        iface clear [INET | INET6]
            If this command is used while ppp is in the OPENED state or while
            in -auto mode, all addresses except for the NCP negotiated
            address are deleted from the interface.  If ppp is not in the
            OPENED state and is not in -auto mode, all interface addresses
            are deleted.
            If the INET or INET6 arguments are used, only addresses for that
            address family are cleared.
        iface delete[!]|rm[!] addr
            This command deletes the given addr from the interface.  If the
            ``! is used, no error is given if the address is not currently
            assigned to the interface (and no deletion takes place).
        iface name name
            Renames the interface to name.
        iface description description
            Sets the interface description to description.  Useful if you
            have many interfaces on your system.
        iface show
            Shows the current state and current addresses for the interface.
            It is much the same as running ``ifconfig INTERFACE.
        iface help [sub-command]
            This command, when invoked without sub-command, will show a list
            of possible ``iface sub-commands and a brief synopsis for each.
            When invoked with sub-command, only the synopsis for the given
            sub-command is shown.
    [data]link name[,name]... command [args]
        This command may prefix any other command if the user wishes to spec-
        ify which link the command should affect.  This is only applicable
        after multiple links have been created in Multi-link mode using the
        ``clone command.
        Name specifies the name of an existing link.  If name is a comma sep-
        arated list, command is executed on each link.  If name is ``*,
        command is executed on all links.
    load [label]...
        Load the given label(s) from the ppp.conf file.  If label is not
        given, the default label is used.
        Unless the label section uses the ``set mode, ``open or ``dial
        commands, ppp will not attempt to make an immediate connection.
    log word...
        Send the given word(s) to the log file with the prefix ``LOG:.
        Word substitutions are done as explained under the ``!bg command
        above.
    open [lcp|ccp|ipcp]
        This is the opposite of the ``close command.  All closed links are
        immediately brought up apart from second and subsequent demand-dial
        links - these will come up based on the ``set autoload command that
        has been used.
        If the ``lcp argument is used while the LCP layer is already open,
        LCP will be renegotiated.  This allows various LCP options to be
        changed, after which ``open lcp can be used to put them into
        effect.  After renegotiating LCP, any agreed authentication will also
        take place.
        If the ``ccp argument is used, the relevant compression layer is
        opened.  Again, if it is already open, it will be renegotiated.
        If the ``ipcp argument is used, the link will be brought up as nor-
        mal, but if IPCP is already open, it will be renegotiated and the
        network interface will be reconfigured.
        It is probably not good practice to re-open the PPP state machines
        like this as it is possible that the peer will not behave correctly.
        It is however useful as a way of forcing the CCP or VJ dictionaries
        to be reset.
    passwd pass
        Specify the password required for access to the full ppp command set.
        This password is required when connecting to the diagnostic port (see
        the ``set server command).  Pass is specified on the ``set server
        command line.  The value of pass is not logged when command logging
        is active, instead, the literal string `********' is logged.
    quit|bye [all]
        If ``quit is executed from the controlling connection or from a
        command file, ppp will exit after closing all connections.  Other-
        wise, if the user is connected to a diagnostic socket, the connection
        is simply dropped.
        If the all argument is given, ppp will exit despite the source of the
        command after closing all existing connections.
    remove|rm
        This command removes the given link.  It is only really useful in
        multi-link mode.  A link must be in the CLOSED state before it is
        removed.
    rename|mv name
        This command renames the given link to name.  It will fail if name is
        already used by another link.
        The default link name is `deflink'.  Renaming it to `modem', `cuad0'
        or `USR' may make the log file more readable.
    resolv command
        This command controls ppp's manipulation of the resolv.conf(5) file.
        When ppp starts up, it loads the contents of this file into memory
        and retains this image for future use.  command is one of the follow-
        ing:
        readonly  Treat /etc/resolv.conf as read only.  If ``dns is
                  enabled, ppp will still attempt to negotiate nameservers
                  with the peer, making the results available via the DNS0
                  and DNS1 macros.  This is the opposite of the ``resolv
                  writable command.
        reload    Reload /etc/resolv.conf into memory.  This may be necessary
                  if for example a DHCP client overwrote /etc/resolv.conf.
        restore   Replace /etc/resolv.conf with the version originally read
                  at startup or with the last ``resolv reload command.
                  This is sometimes a useful command to put in the
                  /etc/ppp/ppp.linkdown file.
        rewrite   Rewrite the /etc/resolv.conf file.  This command will work
                  even if the ``resolv readonly command has been used.  It
                  may be useful as a command in the /etc/ppp/ppp.linkup file
                  if you wish to defer updating /etc/resolv.conf until after
                  other commands have finished.
        writable  Allow ppp to update /etc/resolv.conf if ``dns is enabled
                  and ppp successfully negotiates a DNS.  This is the oppo-
                  site of the ``resolv readonly command.
    save
        This option is not (yet) implemented.
    sendident
        This command tells ppp to identify itself to the peer.  The link must
        be in LCP state or higher.  If no identity has been set (via the
        ident command), sendident will fail.
        When an identity has been set, ppp will automatically identify itself
        when it sends or receives a configure reject, when negotiation fails
        or when LCP reaches the opened state.
        Received identification packets are logged to the LCP log (see set
        log for details) and are never responded to.
    set[up] var value
        This option allows the setting of any of the following variables:
        set accmap hex-value
            ACCMap stands for Asynchronous Control Character Map.  This is
            always negotiated with the peer, and defaults to a value of
            00000000 in hex.  This protocol is required to defeat hardware
            that depends on passing certain characters from end to end (such
            as XON/XOFF etc).
            For the XON/XOFF scenario, use ``set accmap 000a0000.
        set [auth]key value
            This sets the authentication key (or password) used in client
            mode PAP or CHAP negotiation to the given value.  It also speci-
            fies the password to be used in the dial or login scripts in
            place of the `\P' sequence, preventing the actual password from
            being logged.  If command or chat logging is in effect, value is
            logged as `********' for security reasons.
            If the first character of value is an exclamation mark (``!),
            ppp treats the remainder of the string as a program that must be
            executed to determine the ``authname and ``authkey values.
            If the ``! is doubled up (to ``!!), it is treated as a single
            literal ``!, otherwise, ignoring the ``!, value is parsed as
            a program to execute in the same was as the ``!bg command
            above, substituting special names in the same manner.  Once exe-
            cuted, ppp will feed the program three lines of input, each ter-
            minated by a newline character:
            o   The host name as sent in the CHAP challenge.
            o   The challenge string as sent in the CHAP challenge.
            o   The locally defined ``authname.
            Two lines of output are expected:
            o   The ``authname to be sent with the CHAP response.
            o   The ``authkey, which is encrypted with the challenge and
                request id, the answer being sent in the CHAP response
                packet.
            When configuring ppp in this manner, it is expected that the host
            challenge is a series of ASCII digits or characters.  An encryp-
            tion device or Secure ID card is usually required to calculate
            the secret appropriate for the given challenge.
        set authname id
            This sets the authentication id used in client mode PAP or CHAP
            negotiation.
            If used in -direct mode with CHAP enabled, id is used in the ini-
            tial authentication challenge and should normally be set to the
            local machine name.
        set autoload min-percent max-percent period
            These settings apply only in multi-link mode and default to zero,
            zero and five respectively.  When more than one demand-dial (also
            known as -auto) mode link is available, only the first link is
            made active when ppp first reads data from the tun device.  The
            next demand-dial link will be opened only when the current bundle
            throughput is at least max-percent percent of the total bundle
            bandwidth for period seconds.  When the current bundle throughput
            decreases to min-percent percent or less of the total bundle
            bandwidth for period seconds, a demand-dial link will be brought
            down as long as it is not the last active link.
            Bundle throughput is measured as the maximum of inbound and out-
            bound traffic.
            The default values cause demand-dial links to simply come up one
            at a time.
            Certain devices cannot determine their physical bandwidth, so it
            is sometimes necessary to use the ``set bandwidth command
            (described below) to make ``set autoload work correctly.
        set bandwidth value
            This command sets the connection bandwidth in bits per second.
            value must be greater than zero.  It is currently only used by
            the ``set autoload command above.
        set callback option...
            If no arguments are given, callback is disabled, otherwise, ppp
            will request (or in -direct mode, will accept) one of the given
            options.  In client mode, if an option is NAK'd ppp will request
            a different option, until no options remain at which point ppp
            will terminate negotiations (unless ``none is one of the speci-
            fied option).  In server mode, ppp will accept any of the given
            protocols - but the client must request one of them.  If you wish
            callback to be optional, you must include none as an option.
            The options are as follows (in this order of preference):
            auth    The callee is expected to decide the callback number
                    based on authentication.  If ppp is the callee, the num-
                    ber should be specified as the fifth field of the peers
                    entry in /etc/ppp/ppp.secret.
            cbcp    Microsoft's callback control protocol is used.  See ``set
                    cbcp below.
                    If you wish to negotiate cbcp in client mode but also
                    wish to allow the server to request no callback at CBCP
                    negotiation time, you must specify both cbcp and none as
                    callback options.
            E.164 *|number[,number]...
                    The caller specifies the number.  If ppp is the callee,
                    number should be either a comma separated list of allow-
                    able numbers or a ``*, meaning any number is permitted.
                    If ppp is the caller, only a single number should be
                    specified.
                    Note, this option is very unsafe when used with a ``*
                    as a malicious caller can tell ppp to call any (possibly
                    international) number without first authenticating them-
                    selves.
            none    If the peer does not wish to do callback at all, ppp will
                    accept the fact and continue without callback rather than
                    terminating the connection.  This is required (in addi-
                    tion to one or more other callback options) if you wish
                    callback to be optional.
        set cbcp [*|number[,number...] [delay [retry]]]
            If no arguments are given, CBCP (Microsoft's CallBack Control
            Protocol) is disabled - ie, configuring CBCP in the ``set
            callback command will result in ppp requesting no callback in
            the CBCP phase.  Otherwise, ppp attempts to use the given phone
            number(s).
            In server mode (-direct), ppp will insist that the client uses
            one of these numbers, unless ``* is used in which case the
            client is expected to specify the number.
            In client mode, ppp will attempt to use one of the given numbers
            (whichever it finds to be agreeable with the peer), or if ``*
            is specified, ppp will expect the peer to specify the number.
        set cd [off|seconds[!]]
            Normally, ppp checks for the existence of carrier depending on
            the type of device that has been opened:
               Terminal Devices
                    Carrier is checked one second after the login script is
                    complete.  If it is not set, ppp assumes that this is
                    because the device does not support carrier (which is
                    true for most ``laplink NULL-modem cables), logs the
                    fact and stops checking for carrier.
                    As ptys do not support the TIOCMGET ioctl, the tty device
                    will switch all carrier detection off when it detects
                    that the device is a pty.
               PPPoE (netgraph) Devices
                    Carrier is checked once per second for 5 seconds.  If it
                    is not set after the fifth second, the connection attempt
                    is considered to have failed and the device is closed.
                    Carrier is always required for PPPoE devices.
            All other device types do not support carrier.  Setting a carrier
            value will result in a warning when the device is opened.
            Some modems take more than one second after connecting to assert
            the carrier signal.  If this delay is not increased, this will
            result in ppp's inability to detect when the link is dropped, as
            ppp assumes that the device is not asserting carrier.
            The ``set cd command overrides the default carrier behaviour.
            seconds specifies the maximum number of seconds that ppp should
            wait after the dial script has finished before deciding if car-
            rier is available or not.
            If ``off is specified, ppp will not check for carrier on the
            device, otherwise ppp will not proceed to the login script until
            either carrier is detected or until seconds has elapsed, at which
            point ppp assumes that the device will not set carrier.
            If no arguments are given, carrier settings will go back to their
            default values.
            If seconds is followed immediately by an exclamation mark
            (``!), ppp will require carrier.  If carrier is not detected
            after seconds seconds, the link will be disconnected.
        set choked [timeout]
            This sets the number of seconds that ppp will keep a choked out-
            put queue before dropping all pending output packets.  If timeout
            is less than or equal to zero or if timeout is not specified, it
            is set to the default value of 120 seconds.
            A choked output queue occurs when ppp has read a certain number
            of packets from the local network for transmission, but cannot
            send the data due to link failure (the peer is busy etc.).  ppp
            will not read packets indefinitely.  Instead, it reads up to 30
            packets (or 30 + nlinks * 2 packets in multi-link mode), then
            stops reading the network interface until either timeout seconds
            have passed or at least one packet has been sent.
            If timeout seconds pass, all pending output packets are dropped.
        set ctsrts|crtscts on|off
            This sets hardware flow control.  Hardware flow control is on by
            default.
        set deflate out-winsize [in-winsize]
            This sets the DEFLATE algorithms default outgoing and incoming
            window sizes.  Both out-winsize and in-winsize must be values
            between 8 and 15.  If in-winsize is specified, ppp will insist
            that this window size is used and will not accept any other val-
            ues from the peer.
        set dns [primary [secondary]]
            This command specifies DNS overrides for the ``accept dns com-
            mand.  Refer to the ``accept command description above for
            details.  This command does not affect the IP numbers requested
            using ``enable dns.
        set device|line value...
            This sets the device(s) to which ppp will talk to the given
            ``value.
            All serial device names are expected to begin with /dev/.  Serial
            devices are usually called cuaXX.
            If ``value does not begin with /dev/, it must either begin with
            an exclamation mark (``!), be of the format
            PPPoE:iface[:provider] (on netgraph(4) enabled systems), or be of
            the format host:port[/tcp|udp].
            If it begins with an exclamation mark, the rest of the device
            name is treated as a program name, and that program is executed
            when the device is opened.  Standard input, output and error are
            fed back to ppp and are read and written as if they were a regu-
            lar device.
            If a PPPoE:iface[:provider] specification is given, ppp will
            attempt to create a PPP over Ethernet connection using the given
            iface interface by using netgraph(4).  If netgraph(4) is not
            available, ppp will attempt to load it using kldload(2).  If this
            fails, an external program must be used such as the pppoed(8)
            program available under OpenBSD.  The given provider is passed as
            the service name in the PPPoE Discovery Initiation (PADI) packet.
            If no provider is given, an empty value will be used.
            When a PPPoE connection is established, ppp will place the name
            of the Access Concentrator in the environment variable ACNAME.
            Refer to netgraph(4) and ng_pppoe(4) for further details.
            If a host:port[/tcp|udp] specification is given, ppp will attempt
            to connect to the given host on the given port.  If a ``/tcp or
            ``/udp suffix is not provided, the default is ``/tcp.  Refer
            to the section on PPP OVER TCP and UDP above for further details.
            If multiple ``values are specified, ppp will attempt to open
            each one in turn until it succeeds or runs out of devices.
        set dial chat-script
            This specifies the chat script that will be used to dial the
            other side.  See also the ``set login command below.  Refer to
            chat(8) and to the example configuration files for details of the
            chat script format.  It is possible to specify some special
            `values' in your chat script as follows:
            \c  When used as the last character in a `send' string, this
                indicates that a newline should not be appended.
            \d  When the chat script encounters this sequence, it delays two
                seconds.
            \p  When the chat script encounters this sequence, it delays for
                one quarter of a second.
            \n  This is replaced with a newline character.
            \r  This is replaced with a carriage return character.
            \s  This is replaced with a space character.
            \t  This is replaced with a tab character.
            \T  This is replaced by the current phone number (see ``set
                phone below).
            \P  This is replaced by the current authkey value (see ``set
                authkey above).
            \U  This is replaced by the current authname value (see ``set
                authname above).
            Note that two parsers will examine these escape sequences, so in
            order to have the `chat parser' see the escape character, it is
            necessary to escape it from the `command parser'.  This means
            that in practice you should use two escapes, for example:
                  set dial "... ATDT\\T CONNECT"
            It is also possible to execute external commands from the chat
            script.  To do this, the first character of the expect or send
            string is an exclamation mark (``!).  If a literal exclamation
            mark is required, double it up to ``!! and it will be treated
            as a single literal ``!.  When the command is executed, stan-
            dard input and standard output are directed to the open device
            (see the ``set device command), and standard error is read by
            ppp and substituted as the expect or send string.  If ppp is run-
            ning in interactive mode, file descriptor 3 is attached to
            /dev/tty.
            For example (wrapped for readability):
                  set login "TIMEOUT 5 \"\" \"\" login:--login: ppp \
                  word: ppp \"!sh \\-c \\\"echo \\-n label: >&2\\\"\" \
                  \"!/bin/echo in\" HELLO"
            would result in the following chat sequence (output using the
            `set log local chat' command before dialing):
                  Dial attempt 1 of 1
                  dial OK!
                  Chat: Expecting:
                  Chat: Sending:
                  Chat: Expecting: login:--login:
                  Chat: Wait for (5): login:
                  Chat: Sending: ppp
                  Chat: Expecting: word:
                  Chat: Wait for (5): word:
                  Chat: Sending: ppp
                  Chat: Expecting: !sh \-c "echo \-n label: >&2"
                  Chat: Exec: sh -c "echo -n label: >&2"
                  Chat: Wait for (5): !sh \-c "echo \-n label: >&2" --> label:
                  Chat: Exec: /bin/echo in
                  Chat: Sending:
                  Chat: Expecting: HELLO
                  Chat: Wait for (5): HELLO
                  login OK!
            Note (again) the use of the escape character, allowing many lev-
            els of nesting.  Here, there are four parsers at work.  The first
            parses the original line, reading it as three arguments.  The
            second parses the third argument, reading it as 11 arguments.  At
            this point, it is important that the ``- signs are escaped,
            otherwise this parser will see them as constituting an expect-
            send-expect sequence.  When the ``! character is seen, the exe-
            cution parser reads the first command as three arguments, and
            then sh(1) itself expands the argument after the -c.  As we wish
            to send the output back to the modem, in the first example we re-
            direct our output to file descriptor 2 (stderr) so that ppp
            itself sends and logs it, and in the second example, we just out-
            put to stdout, which is attached directly to the modem.
            This, of course means that it is possible to execute an entirely
            external ``chat command rather than using the internal one.
            See chat(8) for a good alternative.
            The external command that is executed is subjected to the same
            special word expansions as the ``!bg command.
        set enddisc [label|IP|MAC|magic|psn value]
            This command sets our local endpoint discriminator.  If set prior
            to LCP negotiation, and if no ``disable enddisc command has
            been used, ppp will send the information to the peer using the
            LCP endpoint discriminator option.  The following discriminators
            may be set:
            label   The current label is used.
            IP      Our local IP number is used.  As LCP is negotiated prior
                    to IPCP, it is possible that the IPCP layer will subse-
                    quently change this value.  If it does, the endpoint dis-
                    criminator stays at the old value unless manually reset.
            MAC     This is similar to the IP option above, except that the
                    MAC address associated with the local IP number is used.
                    If the local IP number is not resident on any Ethernet
                    interface, the command will fail.
                    As the local IP number defaults to whatever the machine
                    host name is, ``set enddisc mac is usually done prior
                    to any ``set ifaddr commands.
            magic   A 20 digit random number is used.  Care should be taken
                    when using magic numbers as restarting ppp or creating a
                    link using a different ppp invocation will also use a
                    different magic number and will therefore not be recog-
                    nised by the peer as belonging to the same bundle.  This
                    makes it unsuitable for -direct connections.
            psn value
                    The given value is used.  Value should be set to an abso-
                    lute public switched network number with the country code
                    first.
            If no arguments are given, the endpoint discriminator is reset.
        set escape value...
            This option is similar to the ``set accmap option above.  It
            allows the user to specify a set of characters that will be
            `escaped' as they travel across the link.
        set filter dial|alive|in|out rule-no permit|deny|clear|rule-no [!]
            [[host] src_addr[/width] [dst_addr[/width]]] [proto [src lt|eq|gt
            port] [dst lt|eq|gt port] [estab] [syn] [finrst] [timeout secs]]
            ppp supports four filter sets.  The alive filter specifies pack-
            ets that keep the connection alive - resetting the idle timer.
            The dial filter specifies packets that cause ppp to dial when in
            -auto mode.  The in filter specifies packets that are allowed to
            travel into the machine and the out filter specifies packets that
            are allowed out of the machine.
            Filtering is done prior to any IP alterations that might be done
            by the NAT engine on outgoing packets and after any IP alter-
            ations that might be done by the NAT engine on incoming packets.
            By default all empty filter sets allow all packets to pass.
            Rules are processed in order according to rule-no (unless skipped
            by specifying a rule number as the action).  Up to 40 rules may
            be given for each set.  If a packet does not match any of the
            rules in a given set, it is discarded.  In the case of in and out
            filters, this means that the packet is dropped.  In the case of
            alive filters it means that the packet will not reset the idle
            timer (even if the in/out filter has a ``timeout value) and in
            the case of dial filters it means that the packet will not trig-
            ger a dial.  A packet failing to trigger a dial will be dropped
            rather than queued.  Refer to the section on PACKET FILTERING
            above for further details.
        set hangup chat-script
            This specifies the chat script that will be used to reset the
            device before it is closed.  It should not normally be necessary,
            but can be used for devices that fail to reset themselves prop-
            erly on close.
        set help|? [command]
            This command gives a summary of available set commands, or if
            command is specified, the command usage is shown.
        set ifaddr [myaddr[/nn] [hisaddr[/nn] [netmask [triggeraddr]]]]
            This command specifies the IP addresses that will be used during
            IPCP negotiation.  Addresses are specified using the format
                  a.b.c.d/nn
            Where ``a.b.c.d is the preferred IP, but nn specifies how many
            bits of the address we will insist on.  If /nn is omitted, it
            defaults to ``/32 unless the IP address is 0.0.0.0 in which
            case it defaults to ``/0.
            If you wish to assign a dynamic IP number to the peer, hisaddr
            may also be specified as a range of IP numbers in the format
                  IP[-IP][,IP[-IP]]...
            for example:
                  set ifaddr 10.0.0.1 10.0.1.2-10.0.1.10,10.0.1.20
            will only negotiate ``10.0.0.1 as the local IP number, but may
            assign any of the given 10 IP numbers to the peer.  If the peer
            requests one of these numbers, and that number is not already in
            use, ppp will grant the peers request.  This is useful if the
            peer wants to re-establish a link using the same IP number as was
            previously allocated (thus maintaining any existing tcp or udp
            connections).
            If the peer requests an IP number that is either outside of this
            range or is already in use, ppp will suggest a random unused IP
            number from the range.
            If triggeraddr is specified, it is used in place of myaddr in the
            initial IPCP negotiation.  However, only an address in the myaddr
            range will be accepted.  This is useful when negotiating with
            some PPP implementations that will not assign an IP number unless
            their peer requests ``0.0.0.0.
            It should be noted that in -auto mode, ppp will configure the
            interface immediately upon reading the ``set ifaddr line in the
            config file.  In any other mode, these values are just used for
            IPCP negotiations, and the interface is not configured until the
            IPCP layer is up.
            Note that the HISADDR argument may be overridden by the third
            field in the ppp.secret file once the client has authenticated
            itself (if PAP or CHAP are ``enabled).  Refer to the
            AUTHENTICATING INCOMING CONNECTIONS section for details.
            In all cases, if the interface is already configured, ppp will
            try to maintain the interface IP numbers so that any existing
            bound sockets will remain valid.
        set ifqueue packets
            Set the maximum number of packets that ppp will read from the
            tunnel interface while data cannot be sent to any of the avail-
            able links.  This queue limit is necessary to flow control outgo-
            ing data as the tunnel interface is likely to be far faster than
            the combined links available to ppp.
            If packets is set to a value less than the number of links, ppp
            will read up to that value regardless.  This prevents any possi-
            ble latency problems.
            The default value for packets is ``30.
        set ccpretry|ccpretries [timeout [reqtries [trmtries]]]
        set chapretry|chapretries [timeout [reqtries]]
        set ipcpretry|ipcpretries [timeout [reqtries [trmtries]]]
        set ipv6cpretry|ipv6cpretries [timeout [reqtries [trmtries]]]
        set lcpretry|lcpretries [timeout [reqtries [trmtries]]]
        set papretry|papretries [timeout [reqtries]]
            These commands set the number of seconds that ppp will wait
            before resending Finite State Machine (FSM) Request packets.  The
            default timeout for all FSMs is 3 seconds (which should suffice
            in most cases).
            If reqtries is specified, it tells ppp how many configuration
            request attempts it should make while receiving no reply from the
            peer before giving up.  The default is 5 attempts for CCP, LCP
            and IPCP and 3 attempts for PAP and CHAP.
            If trmtries is specified, it tells ppp how many terminate
            requests should be sent before giving up waiting for the peers
            response.  The default is 3 attempts.  Authentication protocols
            are not terminated and it is therefore invalid to specify
            trmtries for PAP or CHAP.
            In order to avoid negotiations with the peer that will never con-
            verge, ppp will only send at most 3 times the configured number
            of reqtries in any given negotiation session before giving up and
            closing that layer.
        set log [local] [+|-]value...
            This command allows the adjustment of the current log level.
            Refer to the Logging Facility section for further details.
        set login chat-script
            This chat-script compliments the dial-script.  If both are speci-
            fied, the login script will be executed after the dial script.
            Escape sequences available in the dial script are also available
            here.
        set logout chat-script
            This specifies the chat script that will be used to logout before
            the hangup script is called.  It should not normally be neces-
            sary.
        set lqrperiod|echoperiod frequency
            This command sets the frequency in seconds at which LQR or LCP
            ECHO packets are sent.  The default is 30 seconds.  You must also
            use the ``enable lqr and/or ``enable echo commands if you
            wish to send LQR or LCP ECHO requests to the peer.
        set mode interactive|auto|ddial|background
            This command allows you to change the `mode' of the specified
            link.  This is normally only useful in multi-link mode, but may
            also be used in uni-link mode.
            It is not possible to change a link that is `direct' or
            `dedicated'.
            Note: If you issue the command ``set mode auto, and have net-
            work address translation enabled, it may be useful to ``enable
            iface-alias afterwards.  This will allow ppp to do the neces-
            sary address translations to enable the process that triggers the
            connection to connect once the link is up despite the peer
            assigning us a new (dynamic) IP address.
        set mppe [40|56|128|* [stateless|stateful|*]]
            This option selects the encryption parameters used when negotia-
            tion MPPE.  MPPE can be disabled entirely with the ``disable
            mppe command.  If no arguments are given, ppp will attempt to
            negotiate a stateful link with a 128 bit key, but will agree to
            whatever the peer requests (including no encryption at all).
            If any arguments are given, ppp will insist on using MPPE and
            will close the link if it is rejected by the peer (Note; this be-
            haviour can be overridden by a configured RADIUS server).
            The first argument specifies the number of bits that ppp should
            insist on during negotiations and the second specifies whether
            ppp should insist on stateful or stateless mode.  In stateless
            mode, the encryption dictionary is re-initialised with every
            packet according to an encryption key that is changed with every
            packet.  In stateful mode, the encryption dictionary is re-ini-
            tialised every 256 packets or after the loss of any data and the
            key is changed every 256 packets.  Stateless mode is less effi-
            cient but is better for unreliable transport layers.
        set mrru [value]
            Setting this option enables Multi-link PPP negotiations, also
            known as Multi-link Protocol or MP.  There is no default MRRU
            (Maximum Reconstructed Receive Unit) value.  If no argument is
            given, multi-link mode is disabled.
        set mru [max[imum]] [value]
            The default MRU (Maximum Receive Unit) is 1500.  If it is
            increased, the other side *may* increase its MTU.  In theory
            there is no point in decreasing the MRU to below the default as
            the PPP protocol says implementations *must* be able to accept
            packets of at least 1500 octets.
            If the ``maximum keyword is used, ppp will refuse to negotiate
            a higher value.  The maximum MRU can be set to 2048 at most.
            Setting a maximum of less than 1500 violates the PPP rfc, but may
            sometimes be necessary.  For example, PPPoE imposes a maximum of
            1492 due to hardware limitations.
            If no argument is given, 1500 is assumed.  A value must be given
            when ``maximum is specified.
        set mtu [max[imum]] [value]
            The default MTU is 1500.  At negotiation time, ppp will accept
            whatever MRU the peer requests (assuming it is not less than 296
            bytes or greater than the assigned maximum).  If the MTU is set,
            ppp will not accept MRU values less than value.  When negotia-
            tions are complete, the MTU is used when writing to the inter-
            face, even if the peer requested a higher value MRU.  This can be
            useful for limiting your packet size (giving better bandwidth
            sharing at the expense of more header data).
            If the ``maximum keyword is used, ppp will refuse to negotiate
            a higher value.  The maximum MTU can be set to 2048 at most.
            Note, it is necessary to use the ``maximum keyword to limit the
            MTU when using PPPoE.
            If no value is given, 1500, or whatever the peer asks for is
            used.  A value must be given when ``maximum is specified.
        set nbns [x.x.x.x [y.y.y.y]]
            This option allows the setting of the Microsoft NetBIOS name
            server values to be returned at the peers request.  If no values
            are given, ppp will reject any such requests.
        set openmode active|passive [delay]
            By default, openmode is always active with a one second delay.
            That is, ppp will always initiate LCP/IPCP/CCP negotiation one
            second after the line comes up.  If you want to wait for the peer
            to initiate negotiations, you can use the value passive.  If you
            want to initiate negotiations immediately or after more than one
            second, the appropriate delay may be specified here in seconds.
        set parity odd|even|none|mark
            This allows the line parity to be set.  The default value is
            none.
        set phone telno[|backupnumber]...[:nextnumber]...
            This allows the specification of the phone number to be used in
            place of the \\T string in the dial and login chat scripts.  Mul-
            tiple phone numbers may be given separated either by a pipe
            (``|) or a colon (``:).
            Numbers after the pipe are only dialed if the dial or login
            script for the previous number failed.
            Numbers after the colon are tried sequentially, irrespective of
            the reason the line was dropped.
            If multiple numbers are given, ppp will dial them according to
            these rules until a connection is made, retrying the maximum num-
            ber of times specified by ``set redial below.  In -background
            mode, each number is attempted at most once.
        set pppoe [standard|3Com]
            This option configures the underlying ng_pppoe(4) node to either
            standard RFC2516 PPPoE or proprietary 3Com mode.  If not set the
            system default will be used.
        set [proc]title [value]
            The current process title as displayed by ps(1) is changed
            according to value.  If value is not specified, the original
            process title is restored.  All the word replacements done by the
            shell commands (see the ``bg command above) are done here too.
            Note, if USER is required in the process title, the ``set
            proctitle command must appear in ppp.linkup, as it is not known
            when the commands in ppp.conf are executed.
        set radius [config-file]
            This command enables RADIUS support (if it is compiled in).
            config-file refers to the radius client configuration file as
            described in radius.conf(5).  If PAP, CHAP, MSCHAP or MSCHAPv2
            are ``enabled, ppp behaves as a Network Access Server and uses
            the configured RADIUS server to authenticate rather than authen-
            ticating from the ppp.secret file or from the passwd database.
            If none of PAP, CHAP, MSCHAP or MSCHAPv2 are enabled, ``set
            radius will do nothing.
            ppp uses the following attributes from the RADIUS reply:
               RAD_FRAMED_IP_ADDRESS
                    The peer IP address is set to the given value.
               RAD_FRAMED_IP_NETMASK
                    The tun interface netmask is set to the given value.
               RAD_FRAMED_MTU
                    If the given MTU is less than the peers MRU as agreed
                    during LCP negotiation, *and* it is less that any config-
                    ured MTU (see the ``set mru command), the tun interface
                    MTU is set to the given value.
               RAD_FRAMED_COMPRESSION
                    If the received compression type is ``1, ppp will
                    request VJ compression during IPCP negotiations despite
                    any ``disable vj configuration command.
               RAD_FILTER_ID
                    If this attribute is supplied, ppp will attempt to use it
                    as an additional label to load from the ppp.linkup and
                    ppp.linkdown files.  The load will be attempted before
                    (and in addition to) the normal label search.  If the
                    label does not exist, no action is taken and ppp proceeds
                    to the normal load using the current label.
               RAD_FRAMED_ROUTE
                    The received string is expected to be in the format
                    dest[/bits] gw [metrics].  Any specified metrics are
                    ignored.  MYADDR and HISADDR are understood as valid val-
                    ues for dest and gw, ``default can be used for dest to
                    sepcify the default route, and ``0.0.0.0 is understood
                    to be the same as ``default for dest and HISADDR for
                    gw.
                    For example, a returned value of ``1.2.3.4/24 0.0.0.0 1 2
                    -1 3 400 would result in a routing table entry to the
                    1.2.3.0/24 network via HISADDR and a returned value of
                    ``0.0.0.0 0.0.0.0 or ``default HISADDR would result
                    in a default route to HISADDR.
                    All RADIUS routes are applied after any sticky routes are
                    applied, making RADIUS routes override configured routes.
                    This also applies for RADIUS routes that do not include
                    the MYADDR or HISADDR keywords.
               RAD_FRAMED_IPV6_PREFIX
                    If this attribute is supplied, the value is substituted
                    for IPV6PREFIX in a command.  You may pass it to an upper
                    layer protocol such as DHCPv6 for delegating an IPv6 pre-
                    fix to a peer.
               RAD_FRAMED_IPV6_ROUTE
                    The received string is expected to be in the format
                    dest[/bits] gw [metrics].  Any specified metrics are
                    ignored.  MYADDR6 and HISADDR6 are understood as valid
                    values for dest and gw, ``default can be used for dest
                    to sepcify the default route, and ``:: is understood to
                    be the same as ``default for dest and HISADDR6 for gw.
                    For example, a returned value of ``3ffe:505:abcd::/48
                    :: would result in a routing table entry to the
                    3ffe:505:abcd::/48 network via HISADDR6 and a returned
                    value of ``:: :: or ``default HISADDR6 would result
                    in a default route to HISADDR6.
                    All RADIUS IPv6 routes are applied after any sticky
                    routes are applied, making RADIUS IPv6 routes override
                    configured routes.  This also applies for RADIUS IPv6
                    routes that do not include the MYADDR6 or HISADDR6 key-
                    words.
               RAD_SESSION_TIMEOUT
                    If supplied, the client connection is closed after the
                    given number of seconds.
               RAD_REPLY_MESSAGE
                    If supplied, this message is passed back to the peer as
                    the authentication SUCCESS text.
               RAD_MICROSOFT_MS_CHAP_ERROR
                    If this RAD_VENDOR_MICROSOFT vendor specific attribute is
                    supplied, it is passed back to the peer as the authenti-
                    cation FAILURE text.
               RAD_MICROSOFT_MS_CHAP2_SUCCESS
                    If this RAD_VENDOR_MICROSOFT vendor specific attribute is
                    supplied and if MS-CHAPv2 authentication is being used,
                    it is passed back to the peer as the authentication SUC-
                    CESS text.
               RAD_MICROSOFT_MS_MPPE_ENCRYPTION_POLICY
                    If this RAD_VENDOR_MICROSOFT vendor specific attribute is
                    supplied and has a value of 2 (Required), ppp will insist
                    that MPPE encryption is used (even if no ``set mppe
                    configuration command has been given with arguments).  If
                    it is supplied with a value of 1 (Allowed), encryption is
                    made optional (despite any ``set mppe configuration
                    commands with arguments).
               RAD_MICROSOFT_MS_MPPE_ENCRYPTION_TYPES
                    If this RAD_VENDOR_MICROSOFT vendor specific attribute is
                    supplied, bits 1 and 2 are examined.  If either or both
                    are set, 40 bit and/or 128 bit (respectively) encryption
                    options are set, overriding any given first argument to
                    the ``set mppe command.  Note, it is not currently pos-
                    sible for the RADIUS server to specify 56 bit encryption.
               RAD_MICROSOFT_MS_MPPE_RECV_KEY
                    If this RAD_VENDOR_MICROSOFT vendor specific attribute is
                    supplied, it is value is used as the master key for
                    decryption of incoming data.  When clients are authenti-
                    cated using MSCHAPv2, the RADIUS server MUST provide this
                    attribute if inbound MPPE is to function.
               RAD_MICROSOFT_MS_MPPE_SEND_KEY
                    If this RAD_VENDOR_MICROSOFT vendor specific attribute is
                    supplied, it is value is used as the master key for
                    encryption of outgoing data.  When clients are authenti-
                    cated using MSCHAPv2, the RADIUS server MUST provide this
                    attribute if outbound MPPE is to function.
            Values received from the RADIUS server may be viewed using ``show
            bundle.
        set rad_alive timeout
            When RADIUS is configured, setting ``rad_alive to a non-zero
            timeout value will tell ppp to sent RADIUS accounting information
            to the RADIUS server every timeout seconds.
        set rad_port_id option
            When RADIUS is configured, setting the ``rad_port_id value
            allows to specify what should be sent to the RADIUS server as
            NAS-Port-Id.  The options are as follows:
            pid     PID of the corresponding tunnel.
            tunnum  tun(4) interface number.
            ifnum   index of the interface as returned by if_nametoindex(3).
            default
                    keeps the default behavior.
        set reconnect timeout ntries
            Should the line drop unexpectedly (due to loss of CD or LQR fail-
            ure), a connection will be re-established after the given
            timeout.  The line will be re-connected at most ntries times.
            Ntries defaults to zero.  A value of random for timeout will
            result in a variable pause, somewhere between 1 and 30 seconds.
        set recvpipe [value]
            This sets the routing table RECVPIPE value.  The optimum value is
            just over twice the MTU value.  If value is unspecified or zero,
            the default kernel controlled value is used.
        set redial secs[+inc[-max]][.next] [attempts]
            ppp can be instructed to attempt to redial attempts times.  If
            more than one phone number is specified (see ``set phone
            above), a pause of next is taken before dialing each number.  A
            pause of secs is taken before starting at the first number again.
            A literal value of ``random may be used here in place of secs
            and next, causing a random delay of between 1 and 30 seconds.
            If inc is specified, its value is added onto secs each time ppp
            tries a new number.  secs will only be incremented at most max
            times.  max defaults to 10.
            Note, the secs delay will be effective, even after attempts has
            been exceeded, so an immediate manual dial may appear to have
            done nothing.  If an immediate dial is required, a ``! should
            immediately follow the ``open keyword.  See the ``open
            description above for further details.
        set sendpipe [value]
            This sets the routing table SENDPIPE value.  The optimum value is
            just over twice the MTU value.  If value is unspecified or zero,
            the default kernel controlled value is used.
        set server|socket TcpPort|LocalName|none|open|closed [password
            [mask]]
            This command tells ppp to listen on the given socket or
            `diagnostic port' for incoming command connections.
            The word ``none instructs ppp to close any existing socket and
            clear the socket configuration.  The word ``open instructs ppp
            to attempt to re-open the port.  The word ``closed instructs
            ppp to close the open port.
            If you wish to specify a local domain socket, LocalName must be
            specified as an absolute file name, otherwise it is assumed to be
            the name or number of a TCP port.  You may specify the octal
            umask to be used with a local domain socket.  Refer to umask(2)
            for umask details.  Refer to services(5) for details of how to
            translate TCP port names.
            You must also specify the password that must be entered by the
            client (using the ``passwd variable above) when connecting to
            this socket.  If the password is specified as an empty string, no
            password is required for connecting clients.
            When specifying a local domain socket, the first ``%d sequence
            found in the socket name will be replaced with the current inter-
            face unit number.  This is useful when you wish to use the same
            profile for more than one connection.
            In a similar manner TCP sockets may be prefixed with the ``+
            character, in which case the current interface unit number is
            added to the port number.
            When using ppp with a server socket, the pppctl(8) command is the
            preferred mechanism of communications.  Currently, telnet(1) can
            also be used, but link encryption may be implemented in the
            future, so telnet(1) should be avoided.
            Note; SIGUSR1 and SIGUSR2 interact with the diagnostic socket.
        set speed value
            This sets the speed of the serial device.  If speed is specified
            as ``sync, ppp treats the device as a synchronous device.
            Certain device types will know whether they should be specified
            as synchronous or asynchronous.  These devices will override
            incorrect settings and log a warning to this effect.
        set stopped [LCPseconds [CCPseconds]]
            If this option is set, ppp will time out after the given FSM
            (Finite State Machine) has been in the stopped state for the
            given number of ``seconds.  This option may be useful if the
            peer sends a terminate request, but never actually closes the
            connection despite our sending a terminate acknowledgement.  This
            is also useful if you wish to ``set openmode passive and time
            out if the peer does not send a Configure Request within the
            given time.  Use ``set log +lcp +ccp to make ppp log the appro-
            priate state transitions.
            The default value is zero, where ppp does not time out in the
            stopped state.
            This value should not be set to less than the openmode delay (see
            ``set openmode above).
        set timeout idleseconds [mintimeout]
            This command allows the setting of the idle timer.  Refer to the
            section titled SETTING THE IDLE TIMER for further details.
            If mintimeout is specified, ppp will never idle out before the
            link has been up for at least that number of seconds.
        set urgent [tcp|udp|none] [[+|-]port] ...
            This command controls the ports that ppp prioritizes when trans-
            mitting data.  The default priority TCP ports are ports 21 (ftp
            control), 22 (ssh), 23 (telnet), 513 (login), 514 (shell), 543
            (klogin) and 544 (kshell).  There are no priority UDP ports by
            default.  See services(5) for details.
            If neither ``tcp or ``udp are specified, ``tcp is assumed.
            If no ports are given, the priority port lists are cleared
            (although if ``tcp or ``udp is specified, only that list is
            cleared).  If the first port argument is prefixed with a plus
            (``+) or a minus (``-), the current list is adjusted, other-
            wise the list is reassigned.  ports prefixed with a plus or not
            prefixed at all are added to the list and ports prefixed with a
            minus are removed from the list.
            If ``none is specified, all priority port lists are disabled
            and even IPTOS_LOWDELAY packets are not prioritised.
        set vj slotcomp on|off
            This command tells ppp whether it should attempt to negotiate VJ
            slot compression.  By default, slot compression is turned on.
        set vj slots nslots
            This command sets the initial number of slots that ppp will try
            to negotiate with the peer when VJ compression is enabled (see
            the `enable' command above).  It defaults to a value of 16.
            Nslots must be between 4 and 16 inclusive.
    shell|! [command]
        If command is not specified a shell is invoked according to the SHELL
        environment variable.  Otherwise, the given command is executed.
        Word replacement is done in the same way as for the ``!bg command
        as described above.
        Use of the ! character requires a following space as with any of the
        other commands.  You should note that this command is executed in the
        foreground; ppp will not continue running until this process has
        exited.  Use the bg command if you wish processing to happen in the
        background.
    show var
        This command allows the user to examine the following:
        show bundle
            Show the current bundle settings.
        show ccp
            Show the current CCP compression statistics.
        show compress
            Show the current VJ compression statistics.
        show escape
            Show the current escape characters.
        show filter [name]
            List the current rules for the given filter.  If name is not
            specified, all filters are shown.
        show hdlc
            Show the current HDLC statistics.
        show help|?
            Give a summary of available show commands.
        show iface
            Show the current interface information (the same as ``iface
            show).
        show ipcp
            Show the current IPCP statistics.
        show layers
            Show the protocol layers currently in use.
        show lcp
            Show the current LCP statistics.
        show [data]link
            Show high level link information.
        show links
            Show a list of available logical links.
        show log
            Show the current log values.
        show mem
            Show current memory statistics.
        show ncp
            Show the current NCP statistics.
        show physical
            Show low level link information.
        show mp
            Show Multi-link information.
        show proto
            Show current protocol totals.
        show route
            Show the current routing tables.
        show stopped
            Show the current stopped timeouts.
        show timer
            Show the active alarm timers.
        show version
            Show the current version number of ppp.
    term
        Go into terminal mode.  Characters typed at the keyboard are sent to
        the device.  Characters read from the device are displayed on the
        screen.  When a remote PPP peer is detected, ppp automatically
        enables Packet Mode and goes back into command mode.

[править] MORE DETAILS

    o   Read the example configuration files.  They are a good source of
        information.
    o   Use ``help, ``nat ?, ``enable ?, ``set ? and ``show ? to
        get online information about what is available.
    o   The following URLs contain useful information:
        o   http://www.FreeBSD.org/doc/en_US.ISO8859-1/books/faq/ppp.html
        o   http://www.FreeBSD.org/doc/handbook/userppp.html

[править] FILES

    ppp refers to four files: ppp.conf, ppp.linkup, ppp.linkdown and
    ppp.secret.  These files are placed in the /etc/ppp directory.
    /etc/ppp/ppp.conf
        System default configuration file.
    /etc/ppp/ppp.secret
        An authorisation file for each system.
    /etc/ppp/ppp.linkup
        A file to check when ppp establishes a network level connection.
    /etc/ppp/ppp.linkdown
        A file to check when ppp closes a network level connection.
    /var/log/ppp.log
        Logging and debugging information file.  Note, this name is specified
        in /etc/syslog.conf.  See syslog.conf(5) for further details.
    /var/spool/lock/LCK..*
        tty port locking file.  Refer to uucplock(3) for further details.
    /var/run/tunN.pid
        The process id (pid) of the ppp program connected to the tunN device,
        where `N' is the number of the device.
    /var/run/ttyXX.if
        The tun interface used by this port.  Again, this file is only cre-
        ated in -background, -auto and -ddial modes.
    /etc/services
        Get port number if port number is using service name.
    /var/run/ppp-authname-class-value
        In multi-link mode, local domain sockets are created using the peer
        authentication name (`authname'), the peer endpoint discriminator
        class (`class') and the peer endpoint discriminator value (`value').
        As the endpoint discriminator value may be a binary value, it is
        turned to HEX to determine the actual file name.
        This socket is used to pass links between different instances of ppp.

[править] SEE ALSO

at(1), ftp(1), gzip(1), hostname(1), login(1), tcpdump(1), telnet(1), kldload(2), pipe(2), socketpair(2), libalias(3), libradius(3), syslog(3), uucplock(3), netgraph(4), ng_pppoe(4), crontab(5), group(5), passwd(5), protocols(5), radius.conf(5), resolv.conf(5), syslog.conf(5), adduser(8), chat(8), getty(8), inetd(8), init(8), named(8), ping(8), pppctl(8), pppoed(8), route(8), sshd(8), syslogd(8), traceroute(8), vipw(8)

[править] HISTORY

    This program was originally written by Toshiharu OHNO <tony-o@iij.ad.jp>,
    and was submitted to FreeBSD 2.0.5 by Atsushi Murai <amurai@spec.co.jp>.
    It was substantially modified during 1997 by Brian Somers
    <brian@Awfulhak.org>, and was ported to OpenBSD in November that year
    (just after the 2.2 release).
    Most of the code was rewritten by Brian Somers in early 1998 when multi-
    link ppp support was added.

FreeBSD 9.0 August 25, 2009 FreeBSD 9.0

Источник — «http://xgu.ru/wiki/man/orig/ppp»