PPPD(8)                                                   PPPD(8)

     NAME
          pppd - Point-to-Point Protocol Daemon

     SYNOPSIS
          pppd [ options ]

     DESCRIPTION
          PPP is the protocol used for establishing internet links
          over dial-up modems, DSL connections, and many other types
          of point-to-point links.  The pppd daemon works together
          with the kernel PPP driver to establish and maintain a PPP
          link with another system (called the peer) and to negotiate
          Internet Protocol (IP) addresses for each end of the link.
          Pppd can also authenticate the peer and/or supply authenti-
          cation information to the peer.  PPP can be used with other
          network protocols besides IP, but such use is becoming
          increasingly rare.

     FREQUENTLY USED OPTIONS
          ttyname
               Use the serial port called ttyname to communicate with
               the peer.  If ttyname does not begin with a slash (/),
               the string "/dev/" is prepended to ttyname to form the
               name of the device to open.  If no device name is
               given, or if the name of the terminal connected to the
               standard input is given, pppd will use that terminal,
               and will not fork to put itself in the background.  A
               value for this option from a privileged source cannot
               be overridden by a non-privileged user.

          speed
               An option that is a decimal number is taken as the
               desired baud rate for the serial device.  On systems
               such as 4.4BSD and NetBSD, any speed can be specified.
               Other systems (e.g. Linux, SunOS) only support the
               commonly-used baud rates.

          asyncmap map
               This option sets the Async-Control-Character-Map (ACCM)
               for this end of the link.  The ACCM is a set of 32
               bits, one for each of the ASCII control characters with
               values from 0 to 31, where a 1 bit indicates that the
               corresponding control character should not be used in
               PPP packets sent to this system.  The map is encoded as
               a hexadecimal number (without a leading 0x) where the
               least significant bit (00000001) represents character 0
               and the most significant bit (80000000) represents
               character 31.  Pppd will ask the peer to send these
               characters as a 2-byte escape sequence.  If multiple
               asyncmap options are given, the values are ORed

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     PPPD(8)                                                   PPPD(8)

               together.  If no asyncmap option is given, the default
               is zero, so pppd will ask the peer not to escape any
               control characters.  To escape transmitted characters,
               use the escape option.

          auth Require the peer to authenticate itself before allowing
               network packets to be sent or received.  This option is
               the default if the system has a default route.  If nei-
               ther this option nor the noauth option is specified,
               pppd will only allow the peer to use IP addresses to
               which the system does not already have a route.

          call name
               Read additional options from the file
               /etc/ppp/peers/name.  This file may contain privileged
               options, such as noauth, even if pppd is not being run
               by root.  The name string may not begin with / or
               include .. as a pathname component.  The format of the
               options file is described below.

          connect script
               Usually there is something which needs to be done to
               prepare the link before the PPP protocol can be
               started; for instance, with a dial-up modem, commands
               need to be sent to the modem to dial the appropriate
               phone number.  This option specifies an command for
               pppd to execute (by passing it to a shell) before
               attempting to start PPP negotiation.  The chat (8) pro-
               gram is often useful here, as it provides a way to send
               arbitrary strings to a modem and respond to received
               characters.  A value for this option from a privileged
               source cannot be overridden by a non-privileged user.

          crtscts
               Specifies that pppd should set the serial port to use
               hardware flow control using the RTS and CTS signals in
               the RS-232 interface.  If neither the crtscts, the
               nocrtscts, the cdtrcts nor the nocdtrcts option is
               given, the hardware flow control setting for the serial
               port is left unchanged.  Some serial ports (such as
               Macintosh serial ports) lack a true RTS output. Such
               serial ports use this mode to implement unidirectional
               flow control. The serial port will suspend transmission
               when requested by the modem (via CTS) but will be
               unable to request the modem to stop sending to the com-
               puter. This mode retains the ability to use DTR as a
               modem control line.

          defaultroute
               Add a default route to the system routing tables, using
               the peer as the gateway, when IPCP negotiation is suc-
               cessfully completed.  This entry is removed when the

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     PPPD(8)                                                   PPPD(8)

               PPP connection is broken.  This option is privileged if
               the nodefaultroute option has been specified.

          defaultroute-metric
               Define the metric of the defaultroute and only add it
               if there is no other default route with the same met-
               ric.  With the default value of -1, the route is only
               added if there is no default route at all.

          defaultroute6
               Add a default IPv6 route to the system routing tables,
               using the peer as the gateway, when IPv6CP negotiation
               is successfully completed.  This entry is removed when
               the PPP connection is broken.  This option is privi-
               leged if the nodefaultroute6 option has been specified.

          replacedefaultroute
               This option is a flag to the defaultroute option. If
               defaultroute is set and this flag is also set, pppd
               replaces an existing default route with the new default
               route.  This option is privileged.

          disconnect script
               Execute the command specified by script, by passing it
               to a shell, after pppd has terminated the link.  This
               command could, for example, issue commands to the modem
               to cause it to hang up if hardware modem control sig-
               nals were not available.  The disconnect script is not
               run if the modem has already hung up.  A value for this
               option from a privileged source cannot be overridden by
               a non-privileged user.

          escape xx,yy,...
               Specifies that certain characters should be escaped on
               transmission (regardless of whether the peer requests
               them to be escaped with its async control character
               map).  The characters to be escaped are specified as a
               list of hex numbers separated by commas.  Note that
               almost any character can be specified for the escape
               option, unlike the asyncmap option which only allows
               control characters to be specified.  The characters
               which may not be escaped are those with hex values 0x20
               - 0x3f or 0x5e.

          file name
               Read options from file name (the format is described
               below).  The file must be readable by the user who has
               invoked pppd.

          init script
               Execute the command specified by script, by passing it
               to a shell, to initialize the serial line.  This script

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     PPPD(8)                                                   PPPD(8)

               would typically use the chat(8) program to configure
               the modem to enable auto answer.  A value for this
               option from a privileged source cannot be overridden by
               a non-privileged user.

          lock Specifies that pppd should create a UUCP-style lock
               file for the serial device to ensure exclusive access
               to the device.  By default, pppd will not create a lock
               file.

          mru n
               Set the MRU [Maximum Receive Unit] value to n. Pppd
               will ask the peer to send packets of no more than n
               bytes.  The value of n must be between 128 and 16384;
               the default is 1500.  A value of 296 works well on very
               slow links (40 bytes for TCP/IP header + 256 bytes of
               data).  Note that for the IPv6 protocol, the MRU must
               be at least 1280.

          mtu n
               Set the MTU [Maximum Transmit Unit] value to n.  Unless
               the peer requests a smaller value via MRU negotiation,
               pppd will request that the kernel networking code send
               data packets of no more than n bytes through the PPP
               network interface.  Note that for the IPv6 protocol,
               the MTU must be at least 1280.

          passive
               Enables the "passive" option in the LCP.  With this
               option, pppd will attempt to initiate a connection; if
               no reply is received from the peer, pppd will then just
               wait passively for a valid LCP packet from the peer,
               instead of exiting, as it would without this option.

     OPTIONS
          <local_IP_address>:<remote_IP_address>
               Set the local and/or remote interface IP addresses.
               Either one may be omitted.  The IP addresses can be
               specified with a host name or in decimal dot notation
               (e.g. 150.234.56.78).  The default local address is the
               (first) IP address of the system (unless the noipde-
               fault option is given).  The remote address will be
               obtained from the peer if not specified in any option.
               Thus, in simple cases, this option is not required.  If
               a local and/or remote IP address is specified with this
               option, pppd will not accept a different value from the
               peer in the IPCP negotiation, unless the
               ipcp-accept-local and/or ipcp-accept-remote options are
               given, respectively.

          +ipv6
               Enable the IPv6CP and IPv6 protocols.

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     PPPD(8)                                                   PPPD(8)

          ipv6 <local_interface_identifier>,<remote_interface_identifier>
               Set the local and/or remote 64-bit interface identi-
               fier. Either one may be omitted. The identifier must be
               specified in standard ASCII notation of IPv6 addresses
               (e.g. ::dead:beef). If the ipv6cp-use-ipaddr option is
               given, the local identifier is the local IPv4 address
               (see above).  On systems which supports a unique per-
               sistent id, such as EUI-48 derived from the Ethernet
               MAC address, ipv6cp-use-persistent option can be used
               to replace the ipv6 <local>,<remote> option. Otherwise
               the identifier is randomized.

          active-filter filter-expression
               Specifies a packet filter to be applied to data packets
               to determine which packets are to be regarded as link
               activity, and therefore reset the idle timer, or cause
               the link to be brought up in demand-dialling mode.
               This option is useful in conjunction with the idle
               option if there are packets being sent or received reg-
               ularly over the link (for example, routing information
               packets) which would otherwise prevent the link from
               ever appearing to be idle.  The filter-expression syn-
               tax is as described for tcpdump(1), except that quali-
               fiers which are inappropriate for a PPP link, such as
               ether and arp, are not permitted.  Generally the filter
               expression should be enclosed in single-quotes to pre-
               vent whitespace in the expression from being inter-
               preted by the shell. This option is currently only
               available under Linux, and requires that the kernel was
               configured to include PPP filtering support
               (CONFIG_PPP_FILTER).  Note that it is possible to apply
               different constraints to incoming and outgoing packets
               using the inbound and outbound qualifiers.

          allow-ip address(es)
               Allow peers to use the given IP address or subnet with-
               out authenticating themselves.  The parameter is parsed
               as for each element of the list of allowed IP addresses
               in the secrets files (see the AUTHENTICATION section
               below).

          allow-number number
               Allow peers to connect from the given telephone number.
               A trailing `*' character will match all numbers begin-
               ning with the leading part.

          bsdcomp nr,nt
               Request that the peer compress packets that it sends,
               using the BSD-Compress scheme, with a maximum code size
               of nr bits, and agree to compress packets sent to the
               peer with a maximum code size of nt bits.  If nt is not
               specified, it defaults to the value given for nr.

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     PPPD(8)                                                   PPPD(8)

               Values in the range 9 to 15 may be used for nr and nt;
               larger values give better compression but consume more
               kernel memory for compression dictionaries.  Alterna-
               tively, a value of 0 for nr or nt disables compression
               in the corresponding direction.  Use nobsdcomp or bsd-
               comp 0 to disable BSD-Compress compression entirely.

          ca ca-file
               (EAP-TLS) Use the file ca-file as the X.509 Certificate
               Authority (CA) file (in PEM format), needed for setting
               up an EAP-TLS connection.  This option is used on the
               client-side in conjunction with the cert and key
               options.

          cdtrcts
               Use a non-standard hardware flow control (i.e. DTR/CTS)
               to control the flow of data on the serial port.  If
               neither the crtscts, the nocrtscts, the cdtrcts nor the
               nocdtrcts option is given, the hardware flow control
               setting for the serial port is left unchanged.  Some
               serial ports (such as Macintosh serial ports) lack a
               true RTS output. Such serial ports use this mode to
               implement true bi-directional flow control. The sacri-
               fice is that this flow control mode does not permit
               using DTR as a modem control line.

          cert certfile
               (EAP-TLS) Use the file certfile as the X.509 certifi-
               cate (in PEM format), needed for setting up an EAP-TLS
               connection. This option is used on the client-side in
               conjunction with the ca and key options.

          chap-interval n
               If this option is given, pppd will rechallenge the peer
               every n seconds.

          chap-max-challenge n
               Set the maximum number of CHAP challenge transmissions
               to n (default 10).

          chap-restart n
               Set the CHAP restart interval (retransmission timeout
               for challenges) to n seconds (default 3).

          chap-timeout n
               Set timeout for CHAP authentication by peer to n sec-
               onds (default 60).

          chapms-strip-domain
               Some Windows 9x/ME clients might be transmitting the MS
               domain before the username in the provided client name.
               This option enables stripping the domain from the

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     PPPD(8)                                                   PPPD(8)

               client name on the server side before matching it
               against the secret file.

          child-timeout n
               When exiting, wait for up to n seconds for any child
               processes (such as the command specified with the pty
               command) to exit before exiting.  At the end of the
               timeout, pppd will send a SIGTERM signal to any remain-
               ing child processes and exit.  A value of 0 means no
               timeout, that is, pppd will wait until all child pro-
               cesses have exited.

          connect-delay n
               Wait for up to n milliseconds after the connect script
               finishes for a valid PPP packet from the peer.  At the
               end of this time, or when a valid PPP packet is
               received from the peer, pppd will commence negotiation
               by sending its first LCP packet.  The default value is
               1000 (1 second).  This wait period only applies if the
               connect or pty option is used.

          crl filename
               (EAP-TLS) Use the file filename as the Certificate
               Revocation List to check for the validity of the peer's
               certificate. This option is not mandatory for setting
               up an EAP-TLS connection. Also see the crl-dir option.

          crl-dir directory
               (EAP-TLS) Use the directory directory to scan for CRL
               files in has format ($hash.r0) to check for the valid-
               ity of the peer's certificate.  This option is not
               mandatory for setting up an EAP-TLS connection.  Also
               see the crl option.

          debug
               Enables connection debugging facilities.  If this
               option is given, pppd will log the contents of all con-
               trol packets sent or received in a readable form.  The
               packets are logged through syslog with facility daemon
               and level debug.  This information can be directed to a
               file by setting up /etc/syslog.conf appropriately (see
               syslog.conf(5)).

          default-asyncmap
               Disable asyncmap negotiation, forcing all control char-
               acters to be escaped for both the transmit and the
               receive direction.

          default-mru
               Disable MRU [Maximum Receive Unit] negotiation.  With
               this option, pppd will use the default MRU value of
               1500 bytes for both the transmit and receive direction.

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     PPPD(8)                                                   PPPD(8)

          deflate nr,nt
               Request that the peer compress packets that it sends,
               using the Deflate scheme, with a maximum window size of
               2**nr bytes, and agree to compress packets sent to the
               peer with a maximum window size of 2**nt bytes.  If nt
               is not specified, it defaults to the value given for
               nr.  Values in the range 9 to 15 may be used for nr and
               nt; larger values give better compression but consume
               more kernel memory for compression dictionaries.
               Alternatively, a value of 0 for nr or nt disables com-
               pression in the corresponding direction.  Use nodeflate
               or deflate 0 to disable Deflate compression entirely.
               (Note: pppd requests Deflate compression in preference
               to BSD-Compress if the peer can do either.)

          demand
               Initiate the link only on demand, i.e. when data traf-
               fic is present.  With this option, the remote IP
               address may be specified by the user on the command
               line or in an options file, or if not, pppd will use an
               arbitrary address in the 10.x.x.x range.  Pppd will
               initially configure the interface and enable it for IP
               traffic without connecting to the peer.  When traffic
               is available, pppd will connect to the peer and perform
               negotiation, authentication, etc.  When this is com-
               pleted, pppd will commence passing data packets (i.e.,
               IP packets) across the link.

               The demand option implies the persist option.  If this
               behaviour is not desired, use the nopersist option
               after the demand option.  The idle and holdoff options
               are also useful in conjunction with the demand option.

          domain d
               Append the domain name d to the local host name for
               authentication purposes.  For example, if gethostname()
               returns the name porsche, but the fully qualified
               domain name is porsche.Quotron.COM, you could specify
               domain Quotron.COM.  Pppd would then use the name
               porsche.Quotron.COM for looking up secrets in the
               secrets file, and as the default name to send to the
               peer when authenticating itself to the peer.  This
               option is privileged.

          dryrun
               With the dryrun option, pppd will print out all the
               option values which have been set and then exit, after
               parsing the command line and options files and checking
               the option values, but before initiating the link.  The
               option values are logged at level info, and also
               printed to standard output unless the device on stan-
               dard output is the device that pppd would be using to

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     PPPD(8)                                                   PPPD(8)

               communicate with the peer.

          dump With the dump option, pppd will print out all the
               option values which have been set.  This option is like
               the dryrun option except that pppd proceeds as normal
               rather than exiting.

          enable-session
               Enables session accounting via PAM or wtwp/wtmpx, as
               appropriate.  When PAM is enabled, the PAM "account"
               and "session" module stacks determine behavior, and are
               enabled for all PPP authentication protocols.  When PAM
               is disabled, wtmp/wtmpx entries are recorded regardless
               of whether the peer name identifies a valid user on the
               local system, making peers visible in the last(1) log.
               This feature is automatically enabled when the pppd
               login option is used.  Session accounting is disabled
               by default.

          endpoint <epdisc>
               Sets the endpoint discriminator sent by the local
               machine to the peer during multilink negotiation to
               <epdisc>.  The default is to use the MAC address of the
               first ethernet interface on the system, if any, other-
               wise the IPv4 address corresponding to the hostname, if
               any, provided it is not in the multicast or locally-
               assigned IP address ranges, or the localhost address.
               The endpoint discriminator can be the string null or of
               the form type:value, where type is a decimal number or
               one of the strings local, IP, MAC, magic, or phone.
               The value is an IP address in dotted-decimal notation
               for the IP type, or a string of bytes in hexadecimal,
               separated by periods or colons for the other types.
               For the MAC type, the value may also be the name of an
               ethernet or similar network interface.  This option is
               currently only available under Linux.

          eap-interval n
               If this option is given and pppd authenticates the peer
               with EAP (i.e., is the server), pppd will restart EAP
               authentication every n seconds.  For EAP SRP-SHA1, see
               also the srp-interval option, which enables lightweight
               rechallenge.

          eap-max-rreq n
               Set the maximum number of EAP Requests to which pppd
               will respond (as a client) without hearing EAP Success
               or Failure.  (Default is 20.)

          eap-max-sreq n
               Set the maximum number of EAP Requests that pppd will
               issue (as a server) while attempting authentication.

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     PPPD(8)                                                   PPPD(8)

               (Default is 10.)

          eap-restart n
               Set the retransmit timeout for EAP Requests when acting
               as a server (authenticator).  (Default is 3 seconds.)

          eap-timeout n
               Set the maximum time to wait for the peer to send an
               EAP Request when acting as a client (authenticatee).
               (Default is 20 seconds.)

          hide-password
               When logging the contents of PAP packets, this option
               causes pppd to exclude the password string from the
               log.  This is the default.

          holdoff n
               Specifies how many seconds to wait before re-initiating
               the link after it terminates.  This option only has any
               effect if the persist or demand option is used.  The
               holdoff period is not applied if the link was termi-
               nated because it was idle.

          idle n
               Specifies that pppd should disconnect if the link is
               idle for n seconds.  The link is idle when no data
               packets (i.e. IP packets) are being sent or received.
               Note: it is not advisable to use this option with the
               persist option without the demand option.  If the
               active-filter option is given, data packets which are
               rejected by the specified activity filter also count as
               the link being idle.

          ipcp-accept-local
               With this option, pppd will accept the peer's idea of
               our local IP address, even if the local IP address was
               specified in an option.

          ipcp-accept-remote
               With this option, pppd will accept the peer's idea of
               its (remote) IP address, even if the remote IP address
               was specified in an option.

          ipcp-max-configure n
               Set the maximum number of IPCP configure-request trans-
               missions to n (default 10).

          ipcp-max-failure n
               Set the maximum number of IPCP configure-NAKs returned
               before starting to send configure-Rejects instead to n
               (default 10).

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     PPPD(8)                                                   PPPD(8)

          ipcp-max-terminate n
               Set the maximum number of IPCP terminate-request trans-
               missions to n (default 3).

          ipcp-restart n
               Set the IPCP restart interval (retransmission timeout)
               to n seconds (default 3).

          ipparam string
               Provides an extra parameter to the ip-up, ip-pre-up and
               ip-down scripts.  If this option is given, the string
               supplied is given as the 6th parameter to those
               scripts.

          ipv6cp-accept-local
               With this option, pppd will accept the peer's idea of
               our local IPv6 interface identifier, even if the local
               IPv6 interface identifier was specified in an option.

          ipv6cp-accept-remote
               With this option, pppd will accept the peer's idea of
               its (remote) IPv6 interface identifier, even if the
               remote IPv6 interface identifier was specified in an
               option.

          ipv6cp-max-configure n
               Set the maximum number of IPv6CP configure-request
               transmissions to n (default 10).

          ipv6cp-max-failure n
               Set the maximum number of IPv6CP configure-NAKs
               returned before starting to send configure-Rejects
               instead to n (default 10).

          ipv6cp-max-terminate n
               Set the maximum number of IPv6CP terminate-request
               transmissions to n (default 3).

          ipv6cp-restart n
               Set the IPv6CP restart interval (retransmission time-
               out) to n seconds (default 3).

          ipx  Enable the IPXCP and IPX protocols.  This option is
               presently only supported under Linux, and only if your
               kernel has been configured to include IPX support.

          ipx-network n
               Set the IPX network number in the IPXCP configure
               request frame to n, a hexadecimal number (without a
               leading 0x).  There is no valid default.  If this
               option is not specified, the network number is obtained
               from the peer.  If the peer does not have the network

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     PPPD(8)                                                   PPPD(8)

               number, the IPX protocol will not be started.

          ipx-node n:m
               Set the IPX node numbers. The two node numbers are sep-
               arated from each other with a colon character. The
               first number n is the local node number. The second
               number m is the peer's node number. Each node number is
               a hexadecimal number, at most 10 digits long. The node
               numbers on the ipx-network must be unique. There is no
               valid default. If this option is not specified then the
               node numbers are obtained from the peer.

          ipx-router-name <string>
               Set the name of the router. This is a string and is
               sent to the peer as information data.

          ipx-routing n
               Set the routing protocol to be received by this option.
               More than one instance of ipx-routing may be specified.
               The 'none' option (0) may be specified as the only
               instance of ipx-routing. The values may be 0 for NONE,
               2 for RIP/SAP, and 4 for NLSP.

          ipxcp-accept-local
               Accept the peer's NAK for the node number specified in
               the ipx-node option. If a node number was specified,
               and non-zero, the default is to insist that the value
               be used. If you include this option then you will per-
               mit the peer to override the entry of the node number.

          ipxcp-accept-network
               Accept the peer's NAK for the network number specified
               in the ipx-network option. If a network number was
               specified, and non-zero, the default is to insist that
               the value be used. If you include this option then you
               will permit the peer to override the entry of the node
               number.

          ipxcp-accept-remote
               Use the peer's network number specified in the config-
               ure request frame. If a node number was specified for
               the peer and this option was not specified, the peer
               will be forced to use the value which you have speci-
               fied.

          ipxcp-max-configure n
               Set the maximum number of IPXCP configure request
               frames which the system will send to n. The default is
               10.

          ipxcp-max-failure n
               Set the maximum number of IPXCP NAK frames which the

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     PPPD(8)                                                   PPPD(8)

               local system will send before it rejects the options.
               The default value is 3.

          ipxcp-max-terminate n
               Set the maximum number of IPXCP terminate request
               frames before the local system considers that the peer
               is not listening to them. The default value is 3.

          kdebug n
               Enable debugging code in the kernel-level PPP driver.
               The argument values depend on the specific kernel
               driver, but in general a value of 1 will enable general
               kernel debug messages.  (Note that these messages are
               usually only useful for debugging the kernel driver
               itself.)  For the Linux 2.2.x kernel driver, the value
               is a sum of bits: 1 to enable general debug messages, 2
               to request that the contents of received packets be
               printed, and 4 to request that the contents of trans-
               mitted packets be printed.  On most systems, messages
               printed by the kernel are logged by syslog(1) to a file
               as directed in the /etc/syslog.conf configuration file.

          key keyfile
               (EAP-TLS) Use the file keyfile as the private key file
               (in PEM format), needed for setting up an EAP-TLS con-
               nection. This option is used on the client-side in con-
               junction with the ca and cert options.

          ktune
               Enables pppd to alter kernel settings as appropriate.
               Under Linux, pppd will enable IP forwarding (i.e. set
               /proc/sys/net/ipv4/ip_forward to 1) if the proxyarp
               option is used, and will enable the dynamic IP address
               option (i.e. set /proc/sys/net/ipv4/ip_dynaddr to 1) in
               demand mode if the local address changes.

          lcp-echo-adaptive
               If this option is used with the lcp-echo-failure option
               then pppd will send LCP echo-request frames only if no
               traffic was received from the peer since the last
               echo-request was sent.

          lcp-echo-failure n
               If this option is given, pppd will presume the peer to
               be dead if n LCP echo-requests are sent without receiv-
               ing a valid LCP echo-reply.  If this happens, pppd will
               terminate the connection.  Use of this option requires
               a non-zero value for the lcp-echo-interval parameter.
               This option can be used to enable pppd to terminate
               after the physical connection has been broken (e.g.,
               the modem has hung up) in situations where no hardware
               modem control lines are available.

     Page 13                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          lcp-echo-interval n
               If this option is given, pppd will send an LCP
               echo-request frame to the peer every n seconds.  Nor-
               mally the peer should respond to the echo-request by
               sending an echo-reply.  This option can be used with
               the lcp-echo-failure option to detect that the peer is
               no longer connected.

          lcp-max-configure n
               Set the maximum number of LCP configure-request trans-
               missions to n (default 10).

          lcp-max-failure n
               Set the maximum number of LCP configure-NAKs returned
               before starting to send configure-Rejects instead to n
               (default 10).

          lcp-max-terminate n
               Set the maximum number of LCP terminate-request trans-
               missions to n (default 3).

          lcp-restart n
               Set the LCP restart interval (retransmission timeout)
               to n seconds (default 3).

          linkname name
               Sets the logical name of the link to name.  Pppd will
               create a file named ppp-name.pid in /var/run (or
               /etc/ppp on some systems) containing its process ID.
               This can be useful in determining which instance of
               pppd is responsible for the link to a given peer sys-
               tem.  This is a privileged option.

          local
               Don't use the modem control lines.  With this option,
               pppd will ignore the state of the CD (Carrier Detect)
               signal from the modem and will not change the state of
               the DTR (Data Terminal Ready) signal.  This is the
               opposite of the modem option.

          logfd n
               Send log messages to file descriptor n.  Pppd will send
               log messages to at most one file or file descriptor (as
               well as sending the log messages to syslog), so this
               option and the logfile option are mutually exclusive.
               The default is for pppd to send log messages to stdout
               (file descriptor 1), unless the serial port is already
               open on stdout.

          logfile filename
               Append log messages to the file filename (as well as
               sending the log messages to syslog).  The file is

     Page 14                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

               opened with the privileges of the user who invoked
               pppd, in append mode.

          login
               Use the system password database for authenticating the
               peer using PAP, and record the user in the system wtmp
               file.  Note that the peer must have an entry in the
               /etc/ppp/pap-secrets file as well as the system pass-
               word database to be allowed access.  See also the
               enable-session option.

          master_detach
               If multilink is enabled and this pppd process is the
               multilink bundle master, and the link controlled by
               this pppd process terminates, this pppd process contin-
               ues to run in order to maintain the bundle.  If the
               master_detach option has been given, pppd will detach
               from its controlling terminal in this situation, even
               if the nodetach option has been given.

          maxconnect n
               Terminate the connection when it has been available for
               network traffic for n seconds (i.e. n seconds after the
               first network control protocol comes up).

          maxfail n
               Terminate after n consecutive failed connection
               attempts.  A value of 0 means no limit.  The default
               value is 10.

          modem
               Use the modem control lines.  This option is the
               default.  With this option, pppd will wait for the CD
               (Carrier Detect) signal from the modem to be asserted
               when opening the serial device (unless a connect script
               is specified), and it will drop the DTR (Data Terminal
               Ready) signal briefly when the connection is terminated
               and before executing the connect script.  On Ultrix,
               this option implies hardware flow control, as for the
               crtscts option.  This is the opposite of the local
               option.

          mp   Enables the use of PPP multilink; this is an alias for
               the `multilink' option.  This option is currently only
               available under Linux.

          mppe-stateful
               Allow MPPE to use stateful mode.  Stateless mode is
               still attempted first.  The default is to disallow
               stateful mode.

          mpshortseq

     Page 15                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

               Enables the use of short (12-bit) sequence numbers in
               multilink headers, as opposed to 24-bit sequence num-
               bers.  This option is only available under Linux, and
               only has any effect if multilink is enabled (see the
               multilink option).

          mrru n
               Sets the Maximum Reconstructed Receive Unit to n.  The
               MRRU is the maximum size for a received packet on a
               multilink bundle, and is analogous to the MRU for the
               individual links.  This option is currently only avail-
               able under Linux, and only has any effect if multilink
               is enabled (see the multilink option).

          ms-dns <addr>
               If pppd is acting as a server for Microsoft Windows
               clients, this option allows pppd to supply one or two
               DNS (Domain Name Server) addresses to the clients.  The
               first instance of this option specifies the primary DNS
               address; the second instance (if given) specifies the
               secondary DNS address.  (This option was present in
               some older versions of pppd under the name dns-addr.)

          ms-wins <addr>
               If pppd is acting as a server for Microsoft Windows or
               "Samba" clients, this option allows pppd to supply one
               or two WINS (Windows Internet Name Services) server
               addresses to the clients.  The first instance of this
               option specifies the primary WINS address; the second
               instance (if given) specifies the secondary WINS
               address.

          multilink
               Enables the use of the PPP multilink protocol.  If the
               peer also supports multilink, then this link can become
               part of a bundle between the local system and the peer.
               If there is an existing bundle to the peer, pppd will
               join this link to that bundle, otherwise pppd will cre-
               ate a new bundle.  See the MULTILINK section below.
               This option is currently only available under Linux.

          name name
               Set the name of the local system for authentication
               purposes to name.  This is a privileged option.  With
               this option, pppd will use lines in the secrets files
               which have name as the second field when looking for a
               secret to use in authenticating the peer.  In addition,
               unless overridden with the user option, name will be
               used as the name to send to the peer when authenticat-
               ing the local system to the peer.  (Note that pppd does
               not append the domain name to name.)

     Page 16                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          noaccomp
               Disable Address/Control compression in both directions
               (send and receive).

          need-peer-eap
               (EAP-TLS) Require the peer to verify our authentication
               credentials.

          noauth
               Do not require the peer to authenticate itself.  This
               option is privileged.

          nobsdcomp
               Disables BSD-Compress compression; pppd will not
               request or agree to compress packets using the BSD-
               Compress scheme.

          noccp
               Disable CCP (Compression Control Protocol) negotiation.
               This option should only be required if the peer is
               buggy and gets confused by requests from pppd for CCP
               negotiation.

          nocrtscts
               Disable hardware flow control (i.e. RTS/CTS) on the
               serial port.  If neither the crtscts nor the nocrtscts
               nor the cdtrcts nor the nocdtrcts option is given, the
               hardware flow control setting for the serial port is
               left unchanged.

          nocdtrcts
               This option is a synonym for nocrtscts. Either of these
               options will disable both forms of hardware flow con-
               trol.

          nodefaultroute
               Disable the defaultroute option.  The system adminis-
               trator who wishes to prevent users from adding a
               default route with pppd can do so by placing this
               option in the /etc/ppp/options file.

          noreplacedefaultroute
               Disable the replacedefaultroute option. This allows to
               disable a replacedefaultroute option set previously in
               the configuration.

          nodefaultroute6
               Disable the defaultroute6 option.  The system adminis-
               trator who wishes to prevent users from adding a
               default route with pppd can do so by placing this
               option in the /etc/ppp/options file.

     Page 17                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          nodeflate
               Disables Deflate compression; pppd will not request or
               agree to compress packets using the Deflate scheme.

          nodetach
               Don't detach from the controlling terminal.  Without
               this option, if a serial device other than the terminal
               on the standard input is specified, pppd will fork to
               become a background process.

          noendpoint
               Disables pppd from sending an endpoint discriminator to
               the peer or accepting one from the peer (see the MULTI-
               LINK section below).  This option should only be
               required if the peer is buggy.

          noip Disable IPCP negotiation and IP communication.  This
               option should only be required if the peer is buggy and
               gets confused by requests from pppd for IPCP negotia-
               tion.

          noipv6
               Disable IPv6CP negotiation and IPv6 communication. This
               option should only be required if the peer is buggy and
               gets confused by requests from pppd for IPv6CP negotia-
               tion.

          noipdefault
               Disables the default behaviour when no local IP address
               is specified, which is to determine (if possible) the
               local IP address from the hostname.  With this option,
               the peer will have to supply the local IP address dur-
               ing IPCP negotiation (unless it specified explicitly on
               the command line or in an options file).

          noipx
               Disable the IPXCP and IPX protocols.  This option
               should only be required if the peer is buggy and gets
               confused by requests from pppd for IPXCP negotiation.

          noktune
               Opposite of the ktune option; disables pppd from chang-
               ing system settings.

          nolock
               Opposite of the lock option; specifies that pppd should
               not create a UUCP-style lock file for the serial
               device.  This option is privileged.

          nolog
               Do not send log messages to a file or file descriptor.
               This option cancels the logfd and logfile options.

     Page 18                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          nomagic
               Disable magic number negotiation.  With this option,
               pppd cannot detect a looped-back line.  This option
               should only be needed if the peer is buggy.

          nomp Disables the use of PPP multilink.  This option is cur-
               rently only available under Linux.

          nomppe
               Disables MPPE (Microsoft Point to Point Encryption).
               This is the default.

          nomppe-40
               Disable 40-bit encryption with MPPE.

          nomppe-128
               Disable 128-bit encryption with MPPE.

          nomppe-stateful
               Disable MPPE stateful mode.  This is the default.

          nompshortseq
               Disables the use of short (12-bit) sequence numbers in
               the PPP multilink protocol, forcing the use of 24-bit
               sequence numbers.  This option is currently only avail-
               able under Linux, and only has any effect if multilink
               is enabled.

          nomultilink
               Disables the use of PPP multilink.  This option is cur-
               rently only available under Linux.

          nopcomp
               Disable protocol field compression negotiation in both
               the receive and the transmit direction.

          nopersist
               Exit once a connection has been made and terminated.
               This is the default unless the persist or demand option
               has been specified.

          nopredictor1
               Do not accept or agree to Predictor-1 compression.

          noproxyarp
               Disable the proxyarp option.  The system administrator
               who wishes to prevent users from creating proxy ARP
               entries with pppd can do so by placing this option in
               the /etc/ppp/options file.

          noremoteip
               Allow pppd to operate without having an IP address for

     Page 19                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

               the peer.  This option is only available under Linux.
               Normally, pppd will request the peer's IP address, and
               if the peer does not supply it, pppd will use an arbi-
               trary address in the 10.x.x.x subnet.  With this
               option, if the peer does not supply its IP address,
               pppd will not ask the peer for it, and will not set the
               destination address of the ppp interface.  In this sit-
               uation, the ppp interface can be used for routing by
               creating device routes, but the peer itself cannot be
               addressed directly for IP traffic.

          notty
               Normally, pppd requires a terminal device.  With this
               option, pppd will allocate itself a pseudo-tty
               master/slave pair and use the slave as its terminal
               device.  Pppd will create a child process to act as a
               `character shunt' to transfer characters between the
               pseudo-tty master and its standard input and output.
               Thus pppd will transmit characters on its standard out-
               put and receive characters on its standard input even
               if they are not terminal devices.  This option
               increases the latency and CPU overhead of transferring
               data over the ppp interface as all of the characters
               sent and received must flow through the character shunt
               process.  An explicit device name may not be given if
               this option is used.

          novj Disable Van Jacobson style TCP/IP header compression in
               both the transmit and the receive direction.

          novjccomp
               Disable the connection-ID compression option in Van
               Jacobson style TCP/IP header compression.  With this
               option, pppd will not omit the connection-ID byte from
               Van Jacobson compressed TCP/IP headers, nor ask the
               peer to do so.

          papcrypt
               Indicates that all secrets in the /etc/ppp/pap-secrets
               file which are used for checking the identity of the
               peer are encrypted, and thus pppd should not accept a
               password which, before encryption, is identical to the
               secret from the /etc/ppp/pap-secrets file.

          pap-max-authreq n
               Set the maximum number of PAP authenticate-request
               transmissions to n (default 10).

          pap-restart n
               Set the PAP restart interval (retransmission timeout)
               to n seconds (default 3).

     Page 20                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          pap-timeout n
               Set the maximum time that pppd will wait for the peer
               to authenticate itself with PAP to n seconds (0 means
               no limit).

          pass-filter filter-expression
               Specifies a packet filter to applied to data packets
               being sent or received to determine which packets
               should be allowed to pass.  Packets which are rejected
               by the filter are silently discarded.  This option can
               be used to prevent specific network daemons (such as
               routed) using up link bandwidth, or to provide a very
               basic firewall capability.  The filter-expression syn-
               tax is as described for tcpdump(1), except that quali-
               fiers which are inappropriate for a PPP link, such as
               ether and arp, are not permitted.  Generally the filter
               expression should be enclosed in single-quotes to pre-
               vent whitespace in the expression from being inter-
               preted by the shell.  Note that it is possible to apply
               different constraints to incoming and outgoing packets
               using the inbound and outbound qualifiers. This option
               is currently only available under Linux, and requires
               that the kernel was configured to include PPP filtering
               support (CONFIG_PPP_FILTER).

          password password-string
               Specifies the password to use for authenticating to the
               peer.  Use of this option is discouraged, as the pass-
               word is likely to be visible to other users on the sys-
               tem (for example, by using ps(1)).

          persist
               Do not exit after a connection is terminated; instead
               try to reopen the connection. The maxfail option still
               has an effect on persistent connections.

          plugin filename
               Load the shared library object file filename as a plu-
               gin.  This is a privileged option.  If filename does
               not contain a slash (/), pppd will look in the
               /usr/lib/pppd/version directory for the plugin, where
               version is the version number of pppd (for example,
               2.4.2).

          predictor1
               Request that the peer compress frames that it sends
               using Predictor-1 compression, and agree to compress
               transmitted frames with Predictor-1 if requested.  This
               option has no effect unless the kernel driver supports
               Predictor-1 compression.

          privgroup group-name

     Page 21                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

               Allows members of group group-name to use privileged
               options.  This is a privileged option.  Use of this
               option requires care as there is no guarantee that mem-
               bers of group-name cannot use pppd to become root them-
               selves.  Consider it equivalent to putting the members
               of group-name in the kmem or disk group.

          proxyarp
               Add an entry to this system's ARP [Address Resolution
               Protocol] table with the IP address of the peer and the
               Ethernet address of this system.  This will have the
               effect of making the peer appear to other systems to be
               on the local ethernet.

          pty script
               Specifies that the command script is to be used to com-
               municate rather than a specific terminal device.  Pppd
               will allocate itself a pseudo-tty master/slave pair and
               use the slave as its terminal device.  The script will
               be run in a child process with the pseudo-tty master as
               its standard input and output.  An explicit device name
               may not be given if this option is used.  (Note: if the
               record option is used in conjunction with the pty
               option, the child process will have pipes on its stan-
               dard input and output.)

          receive-all
               With this option, pppd will accept all control charac-
               ters from the peer, including those marked in the
               receive asyncmap.  Without this option, pppd will dis-
               card those characters as specified in RFC1662.  This
               option should only be needed if the peer is buggy.

          record filename
               Specifies that pppd should record all characters sent
               and received to a file named filename.  This file is
               opened in append mode, using the user's user-ID and
               permissions.  This option is implemented using a
               pseudo-tty and a process to transfer characters between
               the pseudo-tty and the real serial device, so it will
               increase the latency and CPU overhead of transferring
               data over the ppp interface.  The characters are stored
               in a tagged format with timestamps, which can be dis-
               played in readable form using the pppdump(8) program.

          remotename name
               Set the assumed name of the remote system for authenti-
               cation purposes to name.

          remotenumber number
               Set the assumed telephone number of the remote system
               for authentication purposes to number.

     Page 22                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          refuse-chap
               With this option, pppd will not agree to authenticate
               itself to the peer using CHAP.

          refuse-mschap
               With this option, pppd will not agree to authenticate
               itself to the peer using MS-CHAP.

          refuse-mschap-v2
               With this option, pppd will not agree to authenticate
               itself to the peer using MS-CHAPv2.

          refuse-eap
               With this option, pppd will not agree to authenticate
               itself to the peer using EAP.

          refuse-pap
               With this option, pppd will not agree to authenticate
               itself to the peer using PAP.

          require-chap
               Require the peer to authenticate itself using CHAP
               [Challenge Handshake Authentication Protocol] authenti-
               cation.

          require-mppe
               Require the use of MPPE (Microsoft Point to Point
               Encryption).  This option disables all other compres-
               sion types.  This option enables both 40-bit and 128-
               bit encryption.  In order for MPPE to successfully come
               up, you must have authenticated with either MS-CHAP or
               MS-CHAPv2.  This option is presently only supported
               under Linux, and only if your kernel has been config-
               ured to include MPPE support.

          require-mppe-40
               Require the use of MPPE, with 40-bit encryption.

          require-mppe-128
               Require the use of MPPE, with 128-bit encryption.

          require-mschap
               Require the peer to authenticate itself using MS-CHAP
               [Microsoft Challenge Handshake Authentication Protocol]
               authentication.

          require-mschap-v2
               Require the peer to authenticate itself using MS-CHAPv2
               [Microsoft Challenge Handshake Authentication Protocol,
               Version 2] authentication.

          require-eap

     Page 23                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

               Require the peer to authenticate itself using EAP
               [Extensible Authentication Protocol] authentication.

          require-pap
               Require the peer to authenticate itself using PAP
               [Password Authentication Protocol] authentication.

          set name=value
               Set an environment variable for scripts that are
               invoked by pppd.  When set by a privileged source, the
               variable specified by name cannot be changed by options
               contained in an unprivileged source.  See also the
               unset option and the environment described in SCRIPTS.

          show-password
               When logging the contents of PAP packets, this option
               causes pppd to show the password string in the log mes-
               sage.

          silent
               With this option, pppd will not transmit LCP packets to
               initiate a connection until a valid LCP packet is
               received from the peer (as for the `passive' option
               with ancient versions of pppd).

          srp-interval n
               If this parameter is given and pppd uses EAP SRP-SHA1
               to authenticate the peer (i.e., is the server), then
               pppd will use the optional lightweight SRP rechallenge
               mechanism at intervals of n seconds.  This option is
               faster than eap-interval reauthentication because it
               uses a hash-based mechanism and does not derive a new
               session key.

          srp-pn-secret string
               Set the long-term pseudonym-generating secret for the
               server.  This value is optional and if set, needs to be
               known at the server (authenticator) side only, and
               should be different for each server (or poll of identi-
               cal servers).  It is used along with the current date
               to generate a key to encrypt and decrypt the client's
               identity contained in the pseudonym.

          srp-use-pseudonym
               When operating as an EAP SRP-SHA1 client, attempt to
               use the pseudonym stored in ~/.ppp_pseudonym first as
               the identity, and save in this file any pseudonym
               offered by the peer during authentication.

          stop-bits n
               Set the number of stop bits for the serial port. Valid
               values are 1 or 2.  The default value is 1.

     Page 24                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          sync Use synchronous HDLC serial encoding instead of asyn-
               chronous.  The device used by pppd with this option
               must have sync support.  Currently supports Microgate
               SyncLink adapters under Linux and FreeBSD 2.2.8 and
               later.

          unit num
               Sets the ppp unit number (for a ppp0 or ppp1 etc inter-
               face name) for outbound connections.  If the unit is
               already in use a dynamically allocated number will be
               used.

          ifname string
               Set the ppp interface name for outbound connections.
               If the interface name is already in use, or if the name
               cannot be used for any other reason, pppd will termi-
               nate.

          unset name
               Remove a variable from the environment variable for
               scripts that are invoked by pppd.  When specified by a
               privileged source, the variable name cannot be set by
               options contained in an unprivileged source.  See also
               the set option and the environment described in
               SCRIPTS.

          updetach
               With this option, pppd will detach from its controlling
               terminal once it has successfully established the ppp
               connection (to the point where the first network con-
               trol protocol, usually the IP control protocol, has
               come up).

          up_sdnotify
               Use this option to run pppd in systemd service units of
               Type=notify (up_sdnotify implies nodetach).  When
               up_sdnotify is enabled, pppd will notify systemd once
               it has successfully established the ppp connection (to
               the point where the first network control protocl, usu-
               ally the IP control protocol, has come up). This option
               is only availble when pppd is compiled with systemd
               support.

          usehostname
               Enforce the use of the hostname (with domain name
               appended, if given) as the name of the local system for
               authentication purposes (overrides the name option).
               This option is not normally needed since the name
               option is privileged.

          usepeerdns
               Ask the peer for up to 2 DNS server addresses.  The

     Page 25                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

               addresses supplied by the peer (if any) are passed to
               the /etc/ppp/ip-up script in the environment variables
               DNS1 and DNS2, and the environment variable USEPEERDNS
               will be set to 1.  In addition, pppd will create an
               /etc/ppp/resolv.conf file containing one or two name-
               server lines with the address(es) supplied by the peer.

          user name
               Sets the name used for authenticating the local system
               to the peer to name.

          vj-max-slots n
               Sets the number of connection slots to be used by the
               Van Jacobson TCP/IP header compression and decompres-
               sion code to n, which must be between 2 and 16 (inclu-
               sive).

          welcome script
               Run the executable or shell command specified by script
               before initiating PPP negotiation, after the connect
               script (if any) has completed.  A value for this option
               from a privileged source cannot be overridden by a
               non-privileged user.

          xonxoff
               Use software flow control (i.e. XON/XOFF) to control
               the flow of data on the serial port.

     PPPOE OPTIONS
          To establish PPP link over Ethernet (PPPoE) it is needed to
          load pppd's plugin pppoe.so and then specify option nic-
          interface instead of modem options ttyname and speed.  Rec-
          ognized pppd's PPPoE options are:

          nic-interface
               Use the ethernet device interface to communicate with
               the peer.  For example, establishing PPPoE link on eth0
               interface is done by specifying ppp'd option nic-eth0.
               Prefix nic- for this option may be avoided if interface
               name is unambiguous and does not look like any other
               pppd's option.

          pppoe-service name
               Connect to specified PPPoE service name. For backward
               compatibility also rp_pppoe_service option name is sup-
               ported.

          pppoe-ac name
               Connect to specified PPPoE access concentrator name.
               For backward compatibility also rp_pppoe_ac option name
               is supported.

     Page 26                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          pppoe-sess sessid:macaddr
               Attach to existing PPPoE session. For backward compati-
               bility also rp_pppoe_sess option name is supported.

          pppoe-verbose n
               Be verbose about discovered access concentrators. For
               backward compatibility also rp_pppoe_verbose option
               name is supported.

          pppoe-mac macaddr
               Connect to specified MAC address.

          pppoe-host-uniq string
               Set the PPPoE Host-Uniq tag to the supplied hex string.
               By default PPPoE Host-Uniq tag is set to the pppd's
               process PID.  For backward compatibility this option
               may be specified without pppoe- prefix.

          pppoe-padi-timeout n
               Initial timeout for discovery packets in seconds
               (default 5).

          pppoe-padi-attempts n
               Number of discovery attempts (default 3).

     OPTIONS FILES
          Options can be taken from files as well as the command line.
          Pppd reads options from the files /etc/ppp/options, ~/.ppprc
          and /etc/ppp/options.ttyname (in that order) before process-
          ing the options on the command line.  (In fact, the
          command-line options are scanned to find the terminal name
          before the options.ttyname file is read.)  In forming the
          name of the options.ttyname file, the initial /dev/ is
          removed from the terminal name, and any remaining / charac-
          ters are replaced with dots.

          An options file is parsed into a series of words, delimited
          by whitespace.  Whitespace can be included in a word by
          enclosing the word in double-quotes (").  A backslash (\)
          quotes the following character.  A hash (#) starts a com-
          ment, which continues until the end of the line.  There is
          no restriction on using the file or call options within an
          options file.

     SECURITY
          pppd provides system administrators with sufficient access
          control that PPP access to a server machine can be provided
          to legitimate users without fear of compromising the secu-
          rity of the server or the network it's on.  This control is
          provided through restrictions on which IP addresses the peer
          may use, based on its authenticated identity (if any), and
          through restrictions on which options a non-privileged user

     Page 27                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          may use.  Several of pppd's options are privileged, in par-
          ticular those which permit potentially insecure configura-
          tions; these options are only accepted in files which are
          under the control of the system administrator, or if pppd is
          being run by root.

          The default behaviour of pppd is to allow an unauthenticated
          peer to use a given IP address only if the system does not
          already have a route to that IP address.  For example, a
          system with a permanent connection to the wider internet
          will normally have a default route, and thus all peers will
          have to authenticate themselves in order to set up a connec-
          tion.  On such a system, the auth option is the default.  On
          the other hand, a system where the PPP link is the only con-
          nection to the internet will not normally have a default
          route, so the peer will be able to use almost any IP address
          without authenticating itself.

          As indicated above, some security-sensitive options are
          privileged, which means that they may not be used by an
          ordinary non-privileged user running a setuid-root pppd,
          either on the command line, in the user's ~/.ppprc file, or
          in an options file read using the file option.  Privileged
          options may be used in /etc/ppp/options file or in an
          options file read using the call option.  If pppd is being
          run by the root user, privileged options can be used without
          restriction.

          When opening the device, pppd uses either the invoking
          user's user ID or the root UID (that is, 0), depending on
          whether the device name was specified by the user or the
          system administrator.  If the device name comes from a priv-
          ileged source, that is, /etc/ppp/options or an options file
          read using the call option, pppd uses full root privileges
          when opening the device.  Thus, by creating an appropriate
          file under /etc/ppp/peers, the system administrator can
          allow users to establish a ppp connection via a device which
          they would not normally have permission to access.  Other-
          wise pppd uses the invoking user's real UID when opening the
          device.

     AUTHENTICATION
          Authentication is the process whereby one peer convinces the
          other of its identity.  This involves the first peer sending
          its name to the other, together with some kind of secret
          information which could only come from the genuine autho-
          rized user of that name.  In such an exchange, we will call
          the first peer the "client" and the other the "server".  The
          client has a name by which it identifies itself to the
          server, and the server also has a name by which it identi-
          fies itself to the client.  Generally the genuine client
          shares some secret (or password) with the server, and

     Page 28                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          authenticates itself by proving that it knows that secret.
          Very often, the names used for authentication correspond to
          the internet hostnames of the peers, but this is not essen-
          tial.

          At present, pppd supports three authentication protocols:
          the Password Authentication Protocol (PAP), Challenge Hand-
          shake Authentication Protocol (CHAP), and Extensible Authen-
          tication Protocol (EAP).  PAP involves the client sending
          its name and a cleartext password to the server to authenti-
          cate itself.  In contrast, the server initiates the CHAP
          authentication exchange by sending a challenge to the client
          (the challenge packet includes the server's name).  The
          client must respond with a response which includes its name
          plus a hash value derived from the shared secret and the
          challenge, in order to prove that it knows the secret.  EAP
          supports CHAP-style authentication, and also includes the
          SRP-SHA1 mechanism, which is resistant to dictionary-based
          attacks and does not require a cleartext password on the
          server side.

          The PPP protocol, being symmetrical, allows both peers to
          require the other to authenticate itself.  In that case, two
          separate and independent authentication exchanges will
          occur.  The two exchanges could use different authentication
          protocols, and in principle, different names could be used
          in the two exchanges.

          The default behaviour of pppd is to agree to authenticate if
          requested, and to not require authentication from the peer.
          However, pppd will not agree to authenticate itself with a
          particular protocol if it has no secrets which could be used
          to do so.

          Pppd stores secrets for use in authentication in secrets
          files (/etc/ppp/pap-secrets for PAP, /etc/ppp/chap-secrets
          for CHAP, MS-CHAP, MS-CHAPv2, and EAP MD5-Challenge, and
          /etc/ppp/srp-secrets for EAP SRP-SHA1).  All secrets files
          have the same format.  The secrets files can contain secrets
          for pppd to use in authenticating itself to other systems,
          as well as secrets for pppd to use when authenticating other
          systems to itself.

          Each line in a secrets file contains one secret.  A given
          secret is specific to a particular combination of client and
          server - it can only be used by that client to authenticate
          itself to that server.  Thus each line in a secrets file has
          at least 3 fields: the name of the client, the name of the
          server, and the secret.  These fields may be followed by a
          list of the IP addresses that the specified client may use
          when connecting to the specified server.

     Page 29                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          A secrets file is parsed into words as for a options file,
          so the client name, server name and secrets fields must each
          be one word, with any embedded spaces or other special char-
          acters quoted or escaped.  Note that case is significant in
          the client and server names and in the secret.

          If the secret starts with an `@', what follows is assumed to
          be the name of a file from which to read the secret.  A "*"
          as the client or server name matches any name.  When select-
          ing a secret, pppd takes the best match, i.e.  the match
          with the fewest wildcards.

          Any following words on the same line are taken to be a list
          of acceptable IP addresses for that client.  If there are
          only 3 words on the line, or if the first word is "-", then
          all IP addresses are disallowed.  To allow any address, use
          "*".  A word starting with "!"  indicates that the specified
          address is not acceptable.  An address may be followed by
          "/" and a number n, to indicate a whole subnet, i.e. all
          addresses which have the same value in the most significant
          n bits.  In this form, the address may be followed by a plus
          sign ("+") to indicate that one address from the subnet is
          authorized, based on the ppp network interface unit number
          in use.  In this case, the host part of the address will be
          set to the unit number plus one.

          Thus a secrets file contains both secrets for use in authen-
          ticating other hosts, plus secrets which we use for authen-
          ticating ourselves to others.  When pppd is authenticating
          the peer (checking the peer's identity), it chooses a secret
          with the peer's name in the first field and the name of the
          local system in the second field.  The name of the local
          system defaults to the hostname, with the domain name
          appended if the domain option is used.  This default can be
          overridden with the name option, except when the usehostname
          option is used.  (For EAP SRP-SHA1, see the srp-entry(8)
          utility for generating proper validator entries to be used
          in the "secret" field.)

          When pppd is choosing a secret to use in authenticating
          itself to the peer, it first determines what name it is
          going to use to identify itself to the peer.  This name can
          be specified by the user with the user option.  If this
          option is not used, the name defaults to the name of the
          local system, determined as described in the previous para-
          graph.  Then pppd looks for a secret with this name in the
          first field and the peer's name in the second field.  Pppd
          will know the name of the peer if CHAP or EAP authentication
          is being used, because the peer will have sent it in the
          challenge packet.  However, if PAP is being used, pppd will
          have to determine the peer's name from the options specified
          by the user.  The user can specify the peer's name directly

     Page 30                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          with the remotename option.  Otherwise, if the remote IP
          address was specified by a name (rather than in numeric
          form), that name will be used as the peer's name.  Failing
          that, pppd will use the null string as the peer's name.

          When authenticating the peer with PAP, the supplied password
          is first compared with the secret from the secrets file.  If
          the password doesn't match the secret, the password is
          encrypted using crypt() and checked against the secret
          again.  Thus secrets for authenticating the peer can be
          stored in encrypted form if desired.  If the papcrypt option
          is given, the first (unencrypted) comparison is omitted, for
          better security.

          Furthermore, if the login option was specified, the username
          and password are also checked against the system password
          database.  Thus, the system administrator can set up the
          pap-secrets file to allow PPP access only to certain users,
          and to restrict the set of IP addresses that each user can
          use.  Typically, when using the login option, the secret in
          /etc/ppp/pap-secrets would be "", which will match any pass-
          word supplied by the peer.  This avoids the need to have the
          same secret in two places.

          Authentication must be satisfactorily completed before IPCP
          (or any other Network Control Protocol) can be started.  If
          the peer is required to authenticate itself, and fails to do
          so, pppd will terminated the link (by closing LCP).  If IPCP
          negotiates an unacceptable IP address for the remote host,
          IPCP will be closed.  IP packets can only be sent or
          received when IPCP is open.

          In some cases it is desirable to allow some hosts which
          can't authenticate themselves to connect and use one of a
          restricted set of IP addresses, even when the local host
          generally requires authentication.  If the peer refuses to
          authenticate itself when requested, pppd takes that as
          equivalent to authenticating with PAP using the empty string
          for the username and password.  Thus, by adding a line to
          the pap-secrets file which specifies the empty string for
          the client and password, it is possible to allow restricted
          access to hosts which refuse to authenticate themselves.

     ROUTING
          When IPCP negotiation is completed successfully, pppd will
          inform the kernel of the local and remote IP addresses for
          the ppp interface.  This is sufficient to create a host
          route to the remote end of the link, which will enable the
          peers to exchange IP packets.  Communication with other
          machines generally requires further modification to routing
          tables and/or ARP (Address Resolution Protocol) tables.  In
          most cases the defaultroute and/or proxyarp options are

     Page 31                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          sufficient for this, but in some cases further intervention
          is required.  The /etc/ppp/ip-up script can be used for
          this.

          Sometimes it is desirable to add a default route through the
          remote host, as in the case of a machine whose only connec-
          tion to the Internet is through the ppp interface.  The
          defaultroute option causes pppd to create such a default
          route when IPCP comes up, and delete it when the link is
          terminated.

          In some cases it is desirable to use proxy ARP, for example
          on a server machine connected to a LAN, in order to allow
          other hosts to communicate with the remote host.  The prox-
          yarp option causes pppd to look for a network interface on
          the same subnet as the remote host (an interface supporting
          broadcast and ARP, which is up and not a point-to-point or
          loopback interface).  If found, pppd creates a permanent,
          published ARP entry with the IP address of the remote host
          and the hardware address of the network interface found.

          When the demand option is used, the interface IP addresses
          have already been set at the point when IPCP comes up.  If
          pppd has not been able to negotiate the same addresses that
          it used to configure the interface (for example when the
          peer is an ISP that uses dynamic IP address assignment),
          pppd has to change the interface IP addresses to the negoti-
          ated addresses.  This may disrupt existing connections, and
          the use of demand dialling with peers that do dynamic IP
          address assignment is not recommended.

     MULTILINK
          Multilink PPP provides the capability to combine two or more
          PPP links between a pair of machines into a single `bundle',
          which appears as a single virtual PPP link which has the
          combined bandwidth of the individual links.  Currently, mul-
          tilink PPP is only supported under Linux.

          Pppd detects that the link it is controlling is connected to
          the same peer as another link using the peer's endpoint dis-
          criminator and the authenticated identity of the peer (if it
          authenticates itself).  The endpoint discriminator is a
          block of data which is hopefully unique for each peer.  Sev-
          eral types of data can be used, including locally-assigned
          strings of bytes, IP addresses, MAC addresses, randomly
          strings of bytes, or E-164 phone numbers.  The endpoint dis-
          criminator sent to the peer by pppd can be set using the
          endpoint option.

          In some circumstances the peer may send no endpoint discrim-
          inator or a non-unique value.  The bundle option adds an
          extra string which is added to the peer's endpoint

     Page 32                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          discriminator and authenticated identity when matching up
          links to be joined together in a bundle.  The bundle option
          can also be used to allow the establishment of multiple bun-
          dles between the local system and the peer.  Pppd uses a TDB
          database in /var/run/pppd2.tdb to match up links.

          Assuming that multilink is enabled and the peer is willing
          to negotiate multilink, then when pppd is invoked to bring
          up the first link to the peer, it will detect that no other
          link is connected to the peer and create a new bundle, that
          is, another ppp network interface unit.  When another pppd
          is invoked to bring up another link to the peer, it will
          detect the existing bundle and join its link to it.

          If the first link terminates (for example, because of a
          hangup or a received LCP terminate-request) the bundle is
          not destroyed unless there are no other links remaining in
          the bundle.  Rather than exiting, the first pppd keeps run-
          ning after its link terminates, until all the links in the
          bundle have terminated.  If the first pppd receives a
          SIGTERM or SIGINT signal, it will destroy the bundle and
          send a SIGHUP to the pppd processes for each of the links in
          the bundle.  If the first pppd receives a SIGHUP signal, it
          will terminate its link but not the bundle.

          Note: demand mode is not currently supported with multilink.

     EXAMPLES
          The following examples assume that the /etc/ppp/options file
          contains the auth option (as in the default /etc/ppp/options
          file in the ppp distribution).

          Probably the most common use of pppd is to dial out to an
          ISP.  This can be done with a command such as

               pppd call isp

          where the /etc/ppp/peers/isp file is set up by the system
          administrator to contain something like this:

               ttyS0 19200 crtscts
               connect '/usr/sbin/chat -v -f /etc/ppp/chat-isp'
               noauth

          In this example, we are using chat to dial the ISP's modem
          and go through any logon sequence required.  The
          /etc/ppp/chat-isp file contains the script used by chat; it
          could for example contain something like this:

               ABORT "NO CARRIER"
               ABORT "NO DIALTONE"
               ABORT "ERROR"

     Page 33                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

               ABORT "NO ANSWER"
               ABORT "BUSY"
               ABORT "Username/Password Incorrect"
               "" "at"
               OK "at&d0&c1"
               OK "atdt2468135"
               "name:" "^Umyuserid"
               "word:" "\qmypassword"
               "ispts" "\q^Uppp"
               "~-^Uppp-~"

          See the chat(8) man page for details of chat scripts.

          Pppd can also be used to provide a dial-in ppp service for
          users.  If the users already have login accounts, the sim-
          plest way to set up the ppp service is to let the users log
          in to their accounts and run pppd (installed setuid-root)
          with a command such as

               pppd proxyarp

          To allow a user to use the PPP facilities, you need to allo-
          cate an IP address for that user's machine and create an
          entry in /etc/ppp/pap-secrets, /etc/ppp/chap-secrets, or
          /etc/ppp/srp-secrets (depending on which authentication
          method the PPP implementation on the user's machine sup-
          ports), so that the user's machine can authenticate itself.
          For example, if Joe has a machine called "joespc" that is to
          be allowed to dial in to the machine called "server" and use
          the IP address joespc.my.net, you would add an entry like
          this to /etc/ppp/pap-secrets or /etc/ppp/chap-secrets:

               joespc    server    "joe's secret" joespc.my.net

          (See srp-entry(8) for a means to generate the server's entry
          when SRP-SHA1 is in use.)  Alternatively, you can create a
          username called (for example) "ppp", whose login shell is
          pppd and whose home directory is /etc/ppp.  Options to be
          used when pppd is run this way can be put in
          /etc/ppp/.ppprc.

          If your serial connection is any more complicated than a
          piece of wire, you may need to arrange for some control
          characters to be escaped.  In particular, it is often useful
          to escape XON (^Q) and XOFF (^S), using asyncmap a0000.  If
          the path includes a telnet, you probably should escape ^] as
          well (asyncmap 200a0000).  If the path includes an rlogin,
          you will need to use the escape ff option on the end which
          is running the rlogin client, since many rlogin implementa-
          tions are not transparent; they will remove the sequence
          [0xff, 0xff, 0x73, 0x73, followed by any 8 bytes] from the
          stream.

     Page 34                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

     DIAGNOSTICS
          Messages are sent to the syslog daemon using facility
          LOG_DAEMON.  (This can be overridden by recompiling pppd
          with the macro LOG_PPP defined as the desired facility.)
          See the syslog(8) documentation for details of where the
          syslog daemon will write the messages.  On most systems, the
          syslog daemon uses the /etc/syslog.conf file to specify the
          destination(s) for syslog messages.  You may need to edit
          that file to suit.

          The debug option causes the contents of all control packets
          sent or received to be logged, that is, all LCP, PAP, CHAP,
          EAP, or IPCP packets.  This can be useful if the PPP negoti-
          ation does not succeed or if authentication fails.  If
          debugging is enabled at compile time, the debug option also
          causes other debugging messages to be logged.

          Debugging can also be enabled or disabled by sending a
          SIGUSR1 signal to the pppd process.  This signal acts as a
          toggle.

     EXIT STATUS
          The exit status of pppd is set to indicate whether any error
          was detected, or the reason for the link being terminated.
          The values used are:

          0    Pppd has detached, or otherwise the connection was suc-
               cessfully established and terminated at the peer's
               request.

          1    An immediately fatal error of some kind occurred, such
               as an essential system call failing, or running out of
               virtual memory.

          2    An error was detected in processing the options given,
               such as two mutually exclusive options being used.

          3    Pppd is not setuid-root and the invoking user is not
               root.

          4    The kernel does not support PPP, for example, the PPP
               kernel driver is not included or cannot be loaded.

          5    Pppd terminated because it was sent a SIGINT, SIGTERM
               or SIGHUP signal.

          6    The serial port could not be locked.

          7    The serial port could not be opened.

          8    The connect script failed (returned a non-zero exit
               status).

     Page 35                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          9    The command specified as the argument to the pty option
               could not be run.

          10   The PPP negotiation failed, that is, it didn't reach
               the point where at least one network protocol (e.g. IP)
               was running.

          11   The peer system failed (or refused) to authenticate
               itself.

          12   The link was established successfully and terminated
               because it was idle.

          13   The link was established successfully and terminated
               because the connect time limit was reached.

          14   Callback was negotiated and an incoming call should
               arrive shortly.

          15   The link was terminated because the peer is not
               responding to echo requests.

          16   The link was terminated by the modem hanging up.

          17   The PPP negotiation failed because serial loopback was
               detected.

          18   The init script failed (returned a non-zero exit sta-
               tus).

          19   We failed to authenticate ourselves to the peer.

     SCRIPTS
          Pppd invokes scripts at various stages in its processing
          which can be used to perform site-specific ancillary pro-
          cessing.  These scripts are usually shell scripts, but could
          be executable code files instead.  Pppd does not wait for
          the scripts to finish (except for the ip-pre-up script).
          The scripts are executed as root (with the real and effec-
          tive user-id set to 0), so that they can do things such as
          update routing tables or run privileged daemons.  Be careful
          that the contents of these scripts do not compromise your
          system's security.  Pppd runs the scripts with standard
          input, output and error redirected to /dev/null, and with an
          environment that is empty except for some environment vari-
          ables that give information about the link.  The environment
          variables that pppd sets are:

          DEVICE
               The name of the serial tty device being used.

          IFNAME

     Page 36                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

               The name of the network interface being used.

          IPLOCAL
               The IP address for the local end of the link.  This is
               only set when IPCP has come up.

          IPREMOTE
               The IP address for the remote end of the link.  This is
               only set when IPCP has come up.

          PEERNAME
               The authenticated name of the peer.  This is only set
               if the peer authenticates itself.

          SPEED
               The baud rate of the tty device.

          ORIG_UID
               The real user-id of the user who invoked pppd.

          PPPLOGNAME
               The username of the real user-id that invoked pppd.
               This is always set.

          For the ip-down and auth-down scripts, pppd also sets the
          following variables giving statistics for the connection:

          CONNECT_TIME
               The number of seconds from when the PPP negotiation
               started until the connection was terminated.

          BYTES_SENT
               The number of bytes sent (at the level of the serial
               port) during the connection.

          BYTES_RCVD
               The number of bytes received (at the level of the
               serial port) during the connection.

          LINKNAME
               The logical name of the link, set with the linkname
               option.

          CALL_FILE
               The value of the call option.

          DNS1 If the peer supplies DNS server addresses, this vari-
               able is set to the first DNS server address supplied
               (whether or not the usepeerdns option was given).

          DNS2 If the peer supplies DNS server addresses, this vari-
               able is set to the second DNS server address supplied

     Page 37                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

               (whether or not the usepeerdns option was given).

          Pppd invokes the following scripts, if they exist.  It is
          not an error if they don't exist.

          /etc/ppp/auth-up
               A program or script which is executed after the remote
               system successfully authenticates itself.  It is exe-
               cuted with the parameters

               interface-name peer-name user-name tty-device speed

               Note that this script is not executed if the peer
               doesn't authenticate itself, for example when the
               noauth option is used.

          /etc/ppp/auth-down
               A program or script which is executed when the link
               goes down, if /etc/ppp/auth-up was previously executed.
               It is executed in the same manner with the same parame-
               ters as /etc/ppp/auth-up.

          /etc/ppp/ip-pre-up
               A program or script which is executed just before the
               ppp network interface is brought up.  It is executed
               with the same parameters as the ip-up script (below).
               At this point the interface exists and has IP addresses
               assigned but is still down.  This can be used to add
               firewall rules before any IP traffic can pass through
               the interface.  Pppd will wait for this script to fin-
               ish before bringing the interface up, so this script
               should run quickly.

          /etc/ppp/ip-up
               A program or script which is executed when the link is
               available for sending and receiving IP packets (that
               is, IPCP has come up).  It is executed with the parame-
               ters

               interface-name tty-device speed local-IP-address
               remote-IP-address ipparam

          /etc/ppp/ip-down
               A program or script which is executed when the link is
               no longer available for sending and receiving IP pack-
               ets.  This script can be used for undoing the effects
               of the /etc/ppp/ip-up and /etc/ppp/ip-pre-up scripts.
               It is invoked in the same manner and with the same
               parameters as the ip-up script.

          /etc/ppp/ipv6-up
               Like /etc/ppp/ip-up, except that it is executed when

     Page 38                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

               the link is available for sending and receiving IPv6
               packets. It is executed with the parameters

               interface-name tty-device speed
               local-link-local-address remote-link-local-address
               ipparam

          /etc/ppp/ipv6-down
               Similar to /etc/ppp/ip-down, but it is executed when
               IPv6 packets can no longer be transmitted on the link.
               It is executed with the same parameters as the ipv6-up
               script.

          /etc/ppp/ipx-up
               A program or script which is executed when the link is
               available for sending and receiving IPX packets (that
               is, IPXCP has come up).  It is executed with the param-
               eters

               interface-name tty-device speed network-number
               local-IPX-node-address remote-IPX-node-address
               local-IPX-routing-protocol remote-IPX-routing-protocol
               local-IPX-router-name remote-IPX-router-name ipparam
               pppd-pid

               The local-IPX-routing-protocol and
               remote-IPX-routing-protocol field may be one of the
               following:

               NONE      to indicate that there is no routing protocol
               RIP       to indicate that RIP/SAP should be used
               NLSP      to indicate that Novell NLSP should be used
               RIP NLSP  to indicate that both RIP/SAP and NLSP should
               be used

          /etc/ppp/ipx-down
               A program or script which is executed when the link is
               no longer available for sending and receiving IPX pack-
               ets.  This script can be used for undoing the effects
               of the /etc/ppp/ipx-up script.  It is invoked in the
               same manner and with the same parameters as the ipx-up
               script.

     FILES
          /var/run/pppn.pid (BSD or Linux), /etc/ppp/pppn.pid (others)
               Process-ID for pppd process on ppp interface unit n.

          /var/run/ppp-name.pid (BSD or Linux),
               /etc/ppp/ppp-name.pid (others) Process-ID for pppd pro-
               cess for logical link name (see the linkname option).

          /var/run/pppd2.tdb

     Page 39                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

               Database containing information about pppd processes,
               interfaces and links, used for matching links to bun-
               dles in multilink operation.  May be examined by exter-
               nal programs to obtain information about running pppd
               instances, the interfaces and devices they are using,
               IP address assignments, etc.  /etc/ppp/pap-secrets
               Usernames, passwords and IP addresses for PAP authenti-
               cation.  This file should be owned by root and not
               readable or writable by any other user.  Pppd will log
               a warning if this is not the case.

          /etc/ppp/chap-secrets
               Names, secrets and IP addresses for
               CHAP/MS-CHAP/MS-CHAPv2 authentication.  As for
               /etc/ppp/pap-secrets, this file should be owned by root
               and not readable or writable by any other user.  Pppd
               will log a warning if this is not the case.

          /etc/ppp/srp-secrets
               Names, secrets, and IP addresses for EAP authentica-
               tion.  As for /etc/ppp/pap-secrets, this file should be
               owned by root and not readable or writable by any other
               user.  Pppd will log a warning if this is not the case.

          ~/.ppp_pseudonym
               Saved client-side SRP-SHA1 pseudonym.  See the
               srp-use-pseudonym option for details.

          /etc/ppp/options
               System default options for pppd, read before user
               default options or command-line options.

          ~/.ppprc
               User default options, read before
               /etc/ppp/options.ttyname.

          /etc/ppp/options.ttyname
               System default options for the serial port being used,
               read after ~/.ppprc.  In forming the ttyname part of
               this filename, an initial /dev/ is stripped from the
               port name (if present), and any slashes in the remain-
               ing part are converted to dots.

          /etc/ppp/peers
               A directory containing options files which may contain
               privileged options, even if pppd was invoked by a user
               other than root.  The system administrator can create
               options files in this directory to permit non-
               privileged users to dial out without requiring the peer
               to authenticate, but only to certain trusted peers.

     SEE ALSO

     Page 40                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          chat(8), pppstats(8)

          RFC1144
               Jacobson, V.  Compressing TCP/IP headers for low-speed
               serial links.  February 1990.

          RFC1321
               Rivest, R.  The MD5 Message-Digest Algorithm. April
               1992.

          RFC1332
               McGregor, G.  PPP Internet Protocol Control Protocol
               (IPCP).  May 1992.

          RFC1334
               Lloyd, B.; Simpson, W.A.  PPP authentication protocols.
               October 1992.

          RFC1661
               Simpson, W.A.  The Point-to-Point Protocol (PPP). July
               1994.

          RFC1662
               Simpson, W.A.  PPP in HDLC-like Framing. July 1994.

          RFC1990
               Sklower, K.; et al., The PPP Multilink Protocol (MP).
               August 1996.

          RFC2284
               Blunk, L.; Vollbrecht, J., PPP Extensible
               Authentication Protocol (EAP). March 1998.

          RFC2472
               Haskin, D.  IP Version 6 over PPP December 1998.

          RFC2945
               Wu, T., The SRP Authentication and Key Exchange Septem-
               ber 2000.

          draft-ietf-pppext-eap-srp-03.txt
               Carlson, J.; et al., EAP SRP-SHA1 Authentication
               Protocol. July 2001.

     NOTES
          Some limited degree of control can be exercised over a run-
          ning pppd process by sending it a signal from the list
          below.

          SIGINT, SIGTERM
               These signals cause pppd to terminate the link (by
               closing LCP), restore the serial device settings, and

     Page 41                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

               exit.  If a connector or disconnector process is cur-
               rently running, pppd will send the same signal to its
               process group, so as to terminate the connector or dis-
               connector process.

          SIGHUP
               This signal causes pppd to terminate the link, restore
               the serial device settings, and close the serial
               device.  If the persist or demand option has been spec-
               ified, pppd will try to reopen the serial device and
               start another connection (after the holdoff period).
               Otherwise pppd will exit.  If this signal is received
               during the holdoff period, it causes pppd to end the
               holdoff period immediately.  If a connector or discon-
               nector process is running, pppd will send the same sig-
               nal to its process group.

          SIGUSR1
               This signal toggles the state of the debug option.

          SIGUSR2
               This signal causes pppd to renegotiate compression.
               This can be useful to re-enable compression after it
               has been disabled as a result of a fatal decompression
               error.  (Fatal decompression errors generally indicate
               a bug in one or other implementation.)

     AUTHORS
          Paul Mackerras (paulus@samba.org), based on earlier work by
          Drew Perkins, Brad Clements, Karl Fox, Greg Christy, and
          Brad Parker.

     COPYRIGHT
          Pppd is copyrighted and made available under conditions
          which provide that it may be copied and used in source or
          binary forms provided that the conditions listed below are
          met.  Portions of pppd are covered by the following copy-
          right notices:

          Copyright (c) 1984-2000 Carnegie Mellon University. All
          rights reserved.
          Copyright (c) 1993-2004 Paul Mackerras. All rights reserved.
          Copyright (c) 1995 Pedro Roque Marques.  All rights
          reserved.
          Copyright (c) 1995 Eric Rosenquist.  All rights reserved.
          Copyright (c) 1999 Tommi Komulainen.  All rights reserved.
          Copyright (C) Andrew Tridgell 1999
          Copyright (c) 2000 by Sun Microsystems, Inc.  All rights
          reserved.
          Copyright (c) 2001 by Sun Microsystems, Inc.  All rights

     Page 42                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

          reserved.
          Copyright (c) 2002 Google, Inc.  All rights reserved.

          The copyright notices contain the following statements.

          Redistribution and use in source and binary forms, with or
          without modification, are permitted provided that the fol-
          lowing conditions are met:

          1. Redistributions of source code must retain the above
          copyright
             notice, this list of conditions and the following dis-
          claimer.

          2. Redistributions in binary form must reproduce the above
          copyright
             notice, this list of conditions and the following dis-
          claimer in
             the documentation and/or other materials provided with
          the
             distribution.

          3. The name "Carnegie Mellon University" must not be used to
             endorse or promote products derived from this software
          without
             prior written permission. For permission or any legal
             details, please contact
               Office of Technology Transfer
               Carnegie Mellon University
               5000 Forbes Avenue
               Pittsburgh, PA  15213-3890
               (412) 268-4387, fax: (412) 268-7395
               tech-transfer@andrew.cmu.edu

          3b. The name(s) of the authors of this software must not be
          used to
             endorse or promote products derived from this software
          without
             prior written permission.

          4. Redistributions of any form whatsoever must retain the
          following
             acknowledgements:
             "This product includes software developed by Computing
          Services
              at Carnegie Mellon University
          (http://www.cmu.edu/computing/)."
             "This product includes software developed by Paul Macker-
          ras
              <paulus@samba.org>".
             "This product includes software developed by Pedro Roque
          Marques

     Page 43                      Plan 9             (printed 5/24/22)

     PPPD(8)                                                   PPPD(8)

              <pedro_m@yahoo.com>".
             "This product includes software developed by Tommi Komu-
          lainen
              <Tommi.Komulainen@iki.fi>".

          CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH
          REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
          MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL CARNEGIE MEL-
          LON UNIVERSITY BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSE-
          QUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
          LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CON-
          TRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
          OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFT-
          WARE.

          THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH
          REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
          MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL THE AUTHORS
          BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES
          OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA
          OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
          OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH
          THE USE OR PERFORMANCE OF THIS SOFTWARE.

     Page 44                      Plan 9             (printed 5/24/22)