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12 .\" purpose with or without fee is hereby granted, provided that the above
15 .\" THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
17 .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
21 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
33 PPP is the protocol used for establishing internet links over dial-up
35 links.  The \fIpppd\fR daemon works together with the kernel PPP
37 (called the \fIpeer\fR) and to negotiate Internet Protocol (IP)
38 addresses for each end of the link.  Pppd can also authenticate the
39 peer and/or supply authentication information to the peer.  PPP can be
45 Use the serial port called \fIttyname\fR to communicate with the
47 the string "/dev/" is prepended to \fIttyname\fR to form the
48 name of the device to open.  If no device name is given, or if the
49 name of the terminal
50 connected to the standard input is given, pppd will use that terminal,
51 and will not fork to put itself in the background.  A value for this
56 An option that is a decimal number is taken as the desired baud rate
57 for the serial device.  On systems such as
59 (e.g. Linux, SunOS) only support the commonly-used baud rates.
62 This option sets the Async-Control-Character-Map (ACCM) for this end
63 of the link.  The ACCM is a set of 32 bits, one for each of the
65 indicates that the corresponding control character should not be used
66 in PPP packets sent to this system.  The map is encoded as a
67 hexadecimal number (without a leading 0x) where the least significant
68 bit (00000001) represents character 0 and the most significant bit
70 Pppd will ask the peer to send these characters as a 2-byte
72 If multiple \fIasyncmap\fR options are given, the values are ORed
73 together.  If no \fIasyncmap\fR option is given, the default is zero,
74 so pppd will ask the peer not to escape any control characters.
75 To escape transmitted characters, use the \fIescape\fR option.
78 Require the peer to authenticate itself before allowing network
79 packets to be sent or received.  This option is the default if the
80 system has a default route.  If neither this option nor the
81 \fInoauth\fR option is specified, pppd will only allow the peer to use
82 IP addresses to which the system does not already have a route.
85 Read additional options from the file /etc/ppp/peers/\fIname\fR.  This
87 is not being run by root.  The \fIname\fR string may not begin with /
88 or include .. as a pathname component.  The format of the options file
92 Usually there is something which needs to be done to prepare the link
93 before the PPP protocol can be started; for instance, with a dial-up
94 modem, commands need to be sent to the modem to dial the appropriate
104 Specifies that pppd should set the serial port to use hardware flow
105 control using the RTS and CTS signals in the RS-232 interface.
106 If neither the \fIcrtscts\fR, the
107 \fInocrtscts\fR, the \fIcdtrcts\fR nor the \fInocdtrcts\fR option
108 is given, the hardware flow control setting for the serial port is
112 unidirectional flow control. The serial port will
113 suspend transmission when requested by the modem (via CTS)
114 but will be unable to request the modem to stop sending to the
115 computer. This mode retains the ability to use DTR as
119 Add a default route to the system routing tables, using the peer as
121 This entry is removed when the PPP connection is broken.  This option
122 is privileged if the \fInodefaultroute\fR option has been specified.
125 Execute the command specified by \fIscript\fR, by passing it to a
127 pppd has terminated the link.  This command could, for example, issue
128 commands to the modem to cause it to hang up if hardware modem control
129 signals were not available.  The disconnect script is not run if the
135 (regardless of whether the peer requests them to be escaped with its
136 async control character map).  The characters to be escaped are
138 almost any character can be specified for the \fIescape\fR option,
139 unlike the \fIasyncmap\fR option which only allows control characters
140 to be specified.  The characters which may not be escaped are those
144 Read options from file \fIname\fR (the format is described below).
145 The file must be readable by the user who has invoked pppd.
148 Execute the command specified by \fIscript\fR, by passing it to a shell, to
149 initialize the serial line.  This script would typically use the
150 chat(8) program to configure the modem to enable auto answer.  A value
155 Specifies that pppd should create a UUCP-style lock file for the
156 serial device to ensure exclusive access to the device.  By default,
160 Set the MRU [Maximum Receive Unit] value to \fIn\fR. Pppd
161 will ask the peer to send packets of no more than \fIn\fR bytes.
162 The value of \fIn\fR must be between 128 and 16384; the default is 1500.
166 Note that for the IPv6 protocol, the MRU must be at least 1280.
169 Set the MTU [Maximum Transmit Unit] value to \fIn\fR.  Unless the
171 request that the kernel networking code send data packets of no more
172 than \fIn\fR bytes through the PPP network interface.  Note that for 
173 the IPv6 protocol, the MTU must be at least 1280.
176 Enables the "passive" option in the LCP.  With this option, pppd will
177 attempt to initiate a connection; if no reply is received from the
183 Set the local and/or remote interface IP addresses.  Either one may be
184 omitted.  The IP addresses can be specified with a host name or in
185 decimal dot notation (e.g. 150.234.56.78).  The default local
186 address is the (first) IP address of the system (unless the
188 option is given).  The remote address will be obtained from the peer
192 will not accept a different value from the peer in the IPCP
193 negotiation, unless the \fIipcp\-accept\-local\fR and/or
197 Enable the IPv6CP and IPv6 protocols.
200 Set the local and/or remote 64-bit interface identifier. Either one may be
201 omitted. The identifier must be specified in standard ASCII notation of
202 IPv6 addresses (e.g. ::dead:beef). If the
204 option is given, the local identifier is the local IPv4 address (see above).
206 from the Ethernet MAC address, \fIipv6cp\-use\-persistent\fR option can be
207 used to replace the \fIipv6 <local>,<remote>\fR option. Otherwise the 
213 the idle timer, or cause the link to be brought up in demand-dialling
214 mode.  This option is useful in conjunction with the
216 regularly over the link (for example, routing information packets)
217 which would otherwise prevent the link from ever appearing to be idle.
220 \fBether\fR and \fBarp\fR, are not permitted.  Generally the filter
222 in the expression from being interpreted by the shell. This option
223 is currently only available under Linux, and requires that the kernel
227 packets using the \fBinbound\fR and \fBoutbound\fR qualifiers.
230 Allow peers to use the given IP address or subnet without
231 authenticating themselves.  The parameter is parsed as for each
232 element of the list of allowed IP addresses in the secrets files (see
236 Allow peers to connect from the given telephone number.  A trailing
237 `*' character will match all numbers beginning with the leading part.
240 Request that the peer compress packets that it sends, using the
242 agree to compress packets sent to the peer with a maximum code size of
243 \fInt\fR bits.  If \fInt\fR is not specified, it defaults to the value
244 given for \fInr\fR.  Values in the range 9 to 15 may be used for
248 compression in the corresponding direction.  Use \fInobsdcomp\fR or
253 the flow of data on the serial port.  If neither the \fIcrtscts\fR,
254 the \fInocrtscts\fR, the \fIcdtrcts\fR nor the \fInocdtrcts\fR
255 option is given, the hardware flow control setting for the serial
259 bi-directional flow control. The sacrifice is that this flow
263 If this option is given, pppd will rechallenge the peer every \fIn\fR
267 Set the maximum number of CHAP challenge transmissions to \fIn\fR
271 Set the CHAP restart interval (retransmission timeout for challenges)
276 (such as the command specified with the \fBpty\fR command) to exit
277 before exiting.  At the end of the timeout, pppd will send a SIGTERM
283 Wait for up to \fIn\fR milliseconds after the connect script finishes for
284 a valid PPP packet from the peer.  At the end of this time, or when a
285 valid PPP packet is received from the peer, pppd will commence
286 negotiation by sending its first LCP packet.  The default value is
287 1000 (1 second).  This wait period only applies if the \fBconnect\fR
292 If this option is given, pppd will log the contents of all
293 control packets sent or received in a readable form.  The packets are
300 escaped for both the transmit and the receive direction.
304 pppd will use the default MRU value of 1500 bytes for both the
308 Request that the peer compress packets that it sends, using the
310 agree to compress packets sent to the peer with a maximum window size
312 the value given for \fInr\fR.  Values in the range 9 to 15 may be used
316 compression in the corresponding direction.  Use \fInodeflate\fR or
318 requests Deflate compression in preference to BSD-Compress if the peer
322 Initiate the link only on demand, i.e. when data traffic is present.
323 With this option, the remote IP address may be specified by the user
324 on the command line or in an options file, or if not, pppd will use
325 an arbitrary address in the 10.x.x.x range.  Pppd will initially
326 configure the interface and enable it for IP traffic without
327 connecting to the peer.  When traffic is available, pppd will
328 connect to the peer and perform negotiation, authentication, etc.
330 (i.e., IP packets) across the link.
332 The \fIdemand\fR option implies the \fIpersist\fR option.  If this
333 behaviour is not desired, use the \fInopersist\fR option after the
334 \fIdemand\fR option.  The \fIidle\fR and \fIholdoff\fR
335 options are also useful in conjunction with the \fIdemand\fR option.
338 Append the domain name \fId\fR to the local host name for authentication
339 purposes.  For example, if gethostname() returns the name porsche, but
341 specify \fIdomain Quotron.COM\fR.  Pppd would then use the name
342 \fIporsche.Quotron.COM\fR for looking up secrets in the secrets file,
343 and as the default name to send to the peer when authenticating itself
344 to the peer.  This option is privileged.
347 With the \fBdryrun\fR option, pppd will print out all the option
348 values which have been set and then exit, after parsing the command
349 line and options files and checking the option values, but before
350 initiating the link.  The option values are logged at level info, and
351 also printed to standard output unless the device on standard output
352 is the device that pppd would be using to communicate with the peer.
355 With the \fBdump\fR option, pppd will print out all the option values
356 which have been set.  This option is like the \fBdryrun\fR option
361 When PAM is enabled, the PAM "account" and "session" module stacks
364 regardless of whether the peer name identifies a valid user on the
365 local system, making peers visible in the last(1) log.  This feature
366 is automatically enabled when the pppd \fBlogin\fR option is used.
370 Sets the endpoint discriminator sent by the local machine to the peer
371 during multilink negotiation to \fI<epdisc>\fR.  The default is to use
372 the MAC address of the first ethernet interface on the system, if any,
373 otherwise the IPv4 address corresponding to the hostname, if any,
374 provided it is not in the multicast or locally-assigned IP address
375 ranges, or the localhost address.  The endpoint discriminator can be
376 the string \fBnull\fR or of the form \fItype\fR:\fIvalue\fR, where
377 type is a decimal number or one of the strings \fBlocal\fR, \fBIP\fR,
378 \fBMAC\fR, \fBmagic\fR, or \fBphone\fR.  The value is an IP address in
379 dotted-decimal notation for the \fBIP\fR type, or a string of bytes in
380 hexadecimal, separated by periods or colons for the other types.  For
381 the MAC type, the value may also be the name of an ethernet or similar
386 If this option is given and pppd authenticates the peer with EAP
387 (i.e., is the server), pppd will restart EAP authentication every
388 \fIn\fR seconds.  For EAP SRP\-SHA1, see also the \fBsrp\-interval\fR
392 Set the maximum number of EAP Requests to which pppd will respond (as
396 Set the maximum number of EAP Requests that pppd will issue (as a
400 Set the retransmit timeout for EAP Requests when acting as a server
404 Set the maximum time to wait for the peer to send an EAP Request when
408 When logging the contents of PAP packets, this option causes pppd to
409 exclude the password string from the log.  This is the default.
412 Specifies how many seconds to wait before re-initiating the link after
413 it terminates.  This option only has any effect if the \fIpersist\fR
414 or \fIdemand\fR option is used.  The holdoff period is not applied if
418 Specifies that pppd should disconnect if the link is idle for \fIn\fR
419 seconds.  The link is idle when no data packets (i.e. IP packets) are
421 with the \fIpersist\fR option without the \fIdemand\fR option.
422 If the \fBactive\-filter\fR
423 option is given, data packets which are rejected by the specified
424 activity filter also count as the link being idle.
427 With this option, pppd will accept the peer's idea of our local IP
428 address, even if the local IP address was specified in an option.
431 With this option, pppd will accept the peer's idea of its (remote) IP
432 address, even if the remote IP address was specified in an option.
435 Set the maximum number of IPCP configure-request transmissions to
439 Set the maximum number of IPCP configure-NAKs returned before starting
443 Set the maximum number of IPCP terminate-request transmissions to
447 Set the IPCP restart interval (retransmission timeout) to \fIn\fR
451 Provides an extra parameter to the ip\-up, ip\-pre\-up and ip\-down
453 option is given, the \fIstring\fR supplied is given as the 6th
457 With this option, pppd will accept the peer's idea of our local IPv6
458 interface identifier, even if the local IPv6 interface identifier
462 Set the maximum number of IPv6CP configure-request transmissions to
466 Set the maximum number of IPv6CP configure-NAKs returned before starting
470 Set the maximum number of IPv6CP terminate-request transmissions to
474 Set the IPv6CP restart interval (retransmission timeout) to \fIn\fR
478 Enable the IPXCP and IPX protocols.  This option is presently only
483 Set the IPX network number in the IPXCP configure request frame to
485 valid default.  If this option is not specified, the network number is
486 obtained from the peer.  If the peer does not have the network number,
490 Set the IPX node numbers. The two node numbers are separated from each
491 other with a colon character. The first number \fIn\fR is the local
492 node number. The second number \fIm\fR is the peer's node number. Each
493 node number is a hexadecimal number, at most 10 digits long. The node
494 numbers on the ipx\-network must be unique. There is no valid
495 default. If this option is not specified then the node numbers are
496 obtained from the peer.
499 Set the name of the router. This is a string and is sent to the peer
503 Set the routing protocol to be received by this option. More than one
504 instance of \fIipx\-routing\fR may be specified. The '\fInone\fR'
505 option (0) may be specified as the only instance of ipx\-routing. The
510 Accept the peer's NAK for the node number specified in the ipx\-node
511 option. If a node number was specified, and non-zero, the default is
512 to insist that the value be used. If you include this option then you
513 will permit the peer to override the entry of the node number.
516 Accept the peer's NAK for the network number specified in the
517 ipx\-network option. If a network number was specified, and non-zero, the
518 default is to insist that the value be used. If you include this
519 option then you will permit the peer to override the entry of the node
523 Use the peer's network number specified in the configure request
524 frame. If a node number was specified for the peer and this option was
525 not specified, the peer will be forced to use the value which you have
529 Set the maximum number of IPXCP configure request frames which the
530 system will send to \fIn\fR. The default is 10.
533 Set the maximum number of IPXCP NAK frames which the local system will
534 send before it rejects the options. The default value is 3.
537 Set the maximum number of IPXCP terminate request frames before the
538 local system considers that the peer is not listening to them. The
542 Enable debugging code in the kernel-level PPP driver.  The argument
543 values depend on the specific kernel driver, but in general a value of
545 messages are usually only useful for debugging the kernel driver
546 itself.)  For the Linux 2.2.x kernel driver, the value is a sum of
548 enable general debug messages, 2 to request that the contents of
549 received packets be printed, and 4 to request that the contents of
551 the kernel are logged by syslog(1) to a file as directed in the
557 to 1) if the \fIproxyarp\fR option is used, and will enable the
559 1) in demand mode if the local address changes.
562 If this option is given, pppd will presume the peer to be dead
564 echo\-reply.  If this happens, pppd will terminate the
565 connection.  Use of this option requires a non-zero value for the
567 pppd to terminate after the physical connection has been broken
568 (e.g., the modem has hung up) in situations where no hardware modem
573 the peer every \fIn\fR seconds.  Normally the peer should respond to
575 with the \fIlcp\-echo\-failure\fR option to detect that the peer is no
579 Set the maximum number of LCP configure-request transmissions to
583 Set the maximum number of LCP configure-NAKs returned before starting
587 Set the maximum number of LCP terminate-request transmissions to
591 Set the LCP restart interval (retransmission timeout) to \fIn\fR
595 Sets the logical name of the link to \fIname\fR.  Pppd will create a
598 which instance of pppd is responsible for the link to a given peer
602 Don't use the modem control lines.  With this option, pppd will ignore
603 the state of the CD (Carrier Detect) signal from the modem and will
604 not change the state of the DTR (Data Terminal Ready) signal.  This is
605 the opposite of the \fBmodem\fR option.
610 the log messages to syslog), so this option and the \fBlogfile\fR
611 option are mutually exclusive.  The default is for pppd to send log
612 messages to stdout (file descriptor 1), unless the serial port is
616 Append log messages to the file \fIfilename\fR (as well as sending the
617 log messages to syslog).  The file is opened with the privileges of
621 Use the system password database for authenticating the peer using
622 PAP, and record the user in the system wtmp file.  Note that the peer
623 must have an entry in the /etc/ppp/pap\-secrets file as well as the
624 system password database to be allowed access.  See also the
628 If multilink is enabled and this pppd process is the multilink bundle
629 master, and the link controlled by this pppd process terminates, this
630 pppd process continues to run in order to maintain the bundle.  If the
632 controlling terminal in this situation, even if the \fBnodetach\fR
636 Terminate the connection when it has been available for network
637 traffic for \fIn\fR seconds (i.e. \fIn\fR seconds after the first
642 value of 0 means no limit.  The default value is 10.
645 Use the modem control lines.  This option is the default.  With this
646 option, pppd will wait for the CD (Carrier Detect) signal from the
647 modem to be asserted when opening the serial device (unless a connect
648 script is specified), and it will drop the DTR (Data Terminal Ready)
649 signal briefly when the connection is terminated and before executing
651 control, as for the \fIcrtscts\fR option.  This is the opposite of the
655 Enables the use of PPP multilink; this is an alias for the `multilink'
663 Enables the use of short (12-bit) sequence numbers in multilink
666 enabled (see the multilink option).
669 Sets the Maximum Reconstructed Receive Unit to \fIn\fR.  The MRRU is
671 analogous to the MRU for the individual links.  This option is
673 multilink is enabled (see the multilink option).
678 addresses to the clients.  The first instance of this option specifies
679 the primary DNS address; the second instance (if given) specifies the
681 versions of pppd under the name \fBdns\-addr\fR.)
686 Internet Name Services) server addresses to the clients.  The first
687 instance of this option specifies the primary WINS address; the second
688 instance (if given) specifies the secondary WINS address.
691 Enables the use of the PPP multilink protocol.  If the peer also
693 the local system and the peer.  If there is an existing bundle to the
695 create a new bundle.  See the MULTILINK section below.  This option is
699 Set the name of the local system for authentication purposes to
701 use lines in the secrets files which have \fIname\fR as the second
702 field when looking for a secret to use in authenticating the peer.  In
703 addition, unless overridden with the \fIuser\fR option, \fIname\fR
704 will be used as the name to send to the peer when authenticating the
705 local system to the peer.  (Note that pppd does not append the domain
713 Do not require the peer to authenticate itself.  This option is
718 agree to compress packets using the BSD-Compress scheme.
722 should only be required if the peer is buggy and gets confused by
726 Disable hardware flow control (i.e. RTS/CTS) on the serial port.
727 If neither the \fIcrtscts\fR nor the \fInocrtscts\fR nor the
728 \fIcdtrcts\fR nor the \fInocdtrcts\fR option is given, the hardware
729 flow control setting for the serial port is left unchanged.
736 Disable the \fIdefaultroute\fR option.  The system administrator who
738 can do so by placing this option in the /etc/ppp/options file.
742 compress packets using the Deflate scheme.
745 Don't detach from the controlling terminal.  Without this option, if a
746 serial device other than the terminal on the standard input is
750 Disables pppd from sending an endpoint discriminator to the peer or
751 accepting one from the peer (see the MULTILINK section below).  This
752 option should only be required if the peer is buggy.
756 only be required if the peer is buggy and gets confused by requests
761 only be required if the peer is buggy and gets confused by requests
765 Disables the default behaviour when no local IP address is specified,
766 which is to determine (if possible) the local IP address from the
767 hostname.  With this option, the peer will have to supply the local IP
768 address during IPCP negotiation (unless it specified explicitly on the
772 Disable the IPXCP and IPX protocols.  This option should only be
773 required if the peer is buggy and gets confused by requests from pppd
777 Opposite of the \fIktune\fR option; disables pppd from changing system
781 Opposite of the \fIlock\fR option; specifies that pppd should not
782 create a UUCP-style lock file for the serial device.  This option is
787 cancels the \fBlogfd\fR and \fBlogfile\fR options.
791 detect a looped-back line.  This option should only be needed if the
795 Disables the use of PPP multilink.  This option is currently only
799 Disables MPPE (Microsoft Point to Point Encryption).  This is the default.
808 Disable MPPE stateful mode.  This is the default.
811 Disables the use of short (12-bit) sequence numbers in the PPP
812 multilink protocol, forcing the use of 24-bit sequence numbers.  This
817 Disables the use of PPP multilink.  This option is currently only
821 Disable protocol field compression negotiation in both the receive and
825 Exit once a connection has been made and terminated.  This is the
826 default unless the \fIpersist\fR or \fIdemand\fR option has been
833 Disable the \fIproxyarp\fR option.  The system administrator who
835 do so by placing this option in the /etc/ppp/options file.
838 Allow pppd to operate without having an IP address for the peer.  This
839 option is only available under Linux.  Normally, pppd will request the
840 peer's IP address, and if the peer does not supply it, pppd will use
841 an arbitrary address in the 10.x.x.x subnet.
842 With this option, if the peer does
843 not supply its IP address, pppd will not ask the peer for it, and will
844 not set the destination address of the ppp interface.  In this
845 situation, the ppp interface can be used for routing by creating
846 device routes, but the peer itself cannot be addressed directly for IP
851 will allocate itself a pseudo-tty master/slave pair and use the slave
853 `character shunt' to transfer characters between the pseudo-tty master
856 even if they are not terminal devices.  This option increases the
857 latency and CPU overhead of transferring data over the ppp interface
858 as all of the characters sent and received must flow through the
863 Disable Van Jacobson style TCP/IP header compression in both the
864 transmit and the receive direction.
867 Disable the connection-ID compression option in Van Jacobson style
868 TCP/IP header compression.  With this option, pppd will not omit the
870 ask the peer to do so.
873 Indicates that all secrets in the /etc/ppp/pap\-secrets file which are
874 used for checking the identity of the peer are encrypted, and thus
876 identical to the secret from the /etc/ppp/pap\-secrets file.
879 Set the maximum number of PAP authenticate-request transmissions to
883 Set the PAP restart interval (retransmission timeout) to \fIn\fR
887 Set the maximum time that pppd will wait for the peer to authenticate
893 Packets which are rejected by the filter are silently discarded.  This
899 \fBether\fR and \fBarp\fR, are not permitted.  Generally the filter
901 in the expression from being interpreted by the shell.  Note that it
903 packets using the \fBinbound\fR and \fBoutbound\fR qualifiers. This
904 option is currently only available under Linux, and requires that the
908 Specifies the password to use for authenticating to the peer.  Use
909 of this option is discouraged, as the password is likely to be visible
910 to other users on the system (for example, by using ps(1)).
914 the connection. The \fBmaxfail\fR option still has an effect on
918 Load the shared library object file \fIfilename\fR as a plugin.  This
920 (/), pppd will look in the \fB/usr/lib/pppd/\fIversion\fR directory
921 for the plugin, where
922 \fIversion\fR is the version number of pppd (for example, 2.4.2).
925 Request that the peer compress frames that it sends using Predictor-1
927 if requested.  This option has no effect unless the kernel driver
934 to become root themselves.  Consider it equivalent to putting the
935 members of \fIgroup\-name\fR in the kmem or disk group.
939 with the IP address of the peer and the Ethernet address of this
940 system.  This will have the effect of making the peer appear to other
941 systems to be on the local ethernet.
944 Specifies that the command \fIscript\fR is to be used to communicate
946 pseudo-tty master/slave pair and use the slave as its terminal
947 device.  The \fIscript\fR will be run in a child process with the
949 device name may not be given if this option is used.  (Note: if the
950 \fIrecord\fR option is used in conjunction with the \fIpty\fR option,
954 With this option, pppd will accept all control characters from the
955 peer, including those marked in the receive asyncmap.  Without this
957 This option should only be needed if the peer is buggy.
962 using the user's user-ID and permissions.  This option is implemented
963 using a pseudo-tty and a process to transfer characters between the
964 pseudo-tty and the real serial device, so it will increase the latency
965 and CPU overhead of transferring data over the ppp interface.  The
967 displayed in readable form using the pppdump(8) program.
970 Set the assumed name of the remote system for authentication purposes
974 Set the assumed telephone number of the remote system for authentication
978 With this option, pppd will not agree to authenticate itself to the
982 With this option, pppd will not agree to authenticate itself to the
986 With this option, pppd will not agree to authenticate itself to the
990 With this option, pppd will not agree to authenticate itself to the
994 With this option, pppd will not agree to authenticate itself to the
998 Require the peer to authenticate itself using CHAP [Challenge
1002 Require the use of MPPE (Microsoft Point to Point Encryption).  This
1010 Require the use of MPPE, with 40-bit encryption.
1013 Require the use of MPPE, with 128-bit encryption.
1016 Require the peer to authenticate itself using MS\-CHAP [Microsoft Challenge
1020 Require the peer to authenticate itself using MS\-CHAPv2 [Microsoft Challenge
1024 Require the peer to authenticate itself using EAP [Extensible
1028 Require the peer to authenticate itself using PAP [Password
1033 When set by a privileged source, the variable specified by \fIname\fR
1035 also the \fIunset\fR option and the environment described in
1039 When logging the contents of PAP packets, this option causes pppd to
1040 show the password string in the log message.
1044 connection until a valid LCP packet is received from the peer (as for
1049 the peer (i.e., is the server), then pppd will use the optional
1056 Set the long-term pseudonym-generating secret for the server.  This
1057 value is optional and if set, needs to be known at the server
1059 poll of identical servers).  It is used along with the current date to
1060 generate a key to encrypt and decrypt the client's identity contained
1061 in the pseudonym.
1064 When operating as an EAP SRP\-SHA1 client, attempt to use the pseudonym
1065 stored in ~/.ppp_pseudonym first as the identity, and save in this
1066 file any pseudonym offered by the peer during authentication.
1075 Sets the ppp unit number (for a ppp0 or ppp1 etc interface name) for outbound
1079 Remove a variable from the environment variable for scripts that are
1080 invoked by pppd.  When specified by a privileged source, the variable
1082 source.  See also the \fIset\fR option and the environment described
1087 it has successfully established the ppp connection (to the point where
1088 the first network control protocol, usually the IP control protocol,
1092 Enforce the use of the hostname (with domain name appended, if given)
1093 as the name of the local system for authentication purposes (overrides
1094 the \fIname\fR option).  This option is not normally needed since the
1098 Ask the peer for up to 2 DNS server addresses.  The addresses supplied
1099 by the peer (if any) are passed to the /etc/ppp/ip\-up script in the
1100 environment variables DNS1 and DNS2, and the environment variable
1103 the address(es) supplied by the peer.
1106 Sets the name used for authenticating the local system to the peer to
1110 Sets the number of connection slots to be used by the Van Jacobson
1115 Run the executable or shell command specified by \fIscript\fR before
1116 initiating PPP negotiation, after the connect script (if any) has
1121 Use software flow control (i.e. XON/XOFF) to control the flow of data on
1124 Options can be taken from files as well as the command line.  Pppd
1125 reads options from the files /etc/ppp/options, ~/.ppprc and
1126 /etc/ppp/options.\fIttyname\fR (in that order) before processing the
1127 options on the command line.  (In fact, the command-line options are
1128 scanned to find the terminal name before the options.\fIttyname\fR
1129 file is read.)  In forming the name of the options.\fIttyname\fR file,
1130 the initial /dev/ is removed from the terminal name, and any remaining
1134 whitespace.  Whitespace can be included in a word by enclosing the
1135 word in double-quotes (").  A backslash (\e) quotes the following character.
1136 A hash (#) starts a comment, which continues until the end of the
1137 line.  There is no restriction on using the \fIfile\fR or \fIcall\fR
1143 fear of compromising the security of the server or the network it's
1145 addresses the peer may use, based on its authenticated identity (if
1149 are only accepted in files which are under the control of the system
1153 use a given IP address only if the system does not already have a
1155 permanent connection to the wider internet will normally have a
1157 in order to set up a connection.  On such a system, the \fIauth\fR
1158 option is the default.  On the other hand, a system where the
1159 PPP link is the only connection to the internet will not normally have
1160 a default route, so the peer will be able to use almost any IP address
1165 user running a setuid-root pppd, either on the command line, in the
1166 user's ~/.ppprc file, or in an options file read using the \fIfile\fR
1168 an options file read using the \fIcall\fR option.  If pppd is being
1169 run by the root user, privileged options can be used without
1172 When opening the device, pppd uses either the invoking user's user ID
1173 or the root UID (that is, 0), depending on whether the device name was
1174 specified by the user or the system administrator.  If the device name
1176 options file read using the \fIcall\fR option, pppd uses full root
1177 privileges when opening the device.  Thus, by creating an appropriate
1178 file under /etc/ppp/peers, the system administrator can allow users to
1180 have permission to access.  Otherwise pppd uses the invoking user's
1181 real UID when opening the device.
1183 Authentication is the process whereby one peer convinces the other of
1184 its identity.  This involves the first peer sending its name to the
1186 come from the genuine authorized user of that name.  In such an
1187 exchange, we will call the first peer the "client" and the other the
1188 "server".  The client has a name by which it identifies itself to the
1189 server, and the server also has a name by which it identifies itself
1190 to the client.  Generally the genuine client shares some secret (or
1191 password) with the server, and authenticates itself by proving that it
1192 knows that secret.  Very often, the names used for authentication
1193 correspond to the internet hostnames of the peers, but this is not
1196 At present, pppd supports three authentication protocols: the Password
1199 involves the client sending its name and a cleartext password to the
1200 server to authenticate itself.  In contrast, the server initiates the
1201 CHAP authentication exchange by sending a challenge to the client (the
1202 challenge packet includes the server's name).  The client must respond
1204 the shared secret and the challenge, in order to prove that it knows
1207 and does not require a cleartext password on the server side.
1209 The PPP protocol, being symmetrical, allows both peers to require the
1211 independent authentication exchanges will occur.  The two exchanges
1213 different names could be used in the two exchanges.
1216 requested, and to not require authentication from the peer.  However,
1224 All secrets files have the same format.  The secrets files can
1232 Thus each line in a secrets file has at least 3 fields: the name of
1233 the client, the name of the server, and the secret.  These fields may
1234 be followed by a list of the IP addresses that the specified client
1235 may use when connecting to the specified server.
1237 A secrets file is parsed into words as for a options file, so the
1240 escaped.  Note that case is significant in the client and server names
1241 and in the secret.
1243 If the secret starts with an `@', what follows is assumed to be the
1244 name of a file from which to read the secret.  A "*" as the client or
1245 server name matches any name.  When selecting a secret, pppd takes the
1246 best match, i.e.  the match with the fewest wildcards.
1248 Any following words on the same line are taken to be a list of
1250 the line, or if the first word is "\-", then all IP addresses are
1252 indicates that the specified address is \fInot\fR acceptable.  An
1254 whole subnet, i.e. all addresses which have the same value in the most
1255 significant \fIn\fR bits.  In this form, the address may be followed
1256 by a plus sign ("+") to indicate that one address from the subnet is
1257 authorized, based on the ppp network interface unit number in use.
1258 In this case, the host part of the address will be set to the unit
1263 others.  When pppd is authenticating the peer (checking the peer's
1264 identity), it chooses a secret with the peer's name in the first
1265 field and the name of the local system in the second field.  The
1266 name of the local system defaults to the hostname, with the domain
1267 name appended if the \fIdomain\fR option is used.  This default can be
1268 overridden with the \fIname\fR option, except when the
1269 \fIusehostname\fR option is used.  (For EAP SRP\-SHA1, see the
1271 used in the "secret" field.)
1273 When pppd is choosing a secret to use in authenticating itself to the
1275 itself to the peer.  This name can be specified by the user with the
1276 \fIuser\fR option.  If this option is not used, the name defaults to
1277 the name of the local system, determined as described in the previous
1278 paragraph.  Then pppd looks for a secret with this name in the first
1279 field and the peer's name in the second field.  Pppd will know the
1280 name of the peer if CHAP or EAP authentication is being used, because
1281 the peer will have sent it in the challenge packet.  However, if PAP
1282 is being used, pppd will have to determine the peer's name from the
1283 options specified by the user.  The user can specify the peer's name
1284 directly with the \fIremotename\fR option.  Otherwise, if the remote
1286 name will be used as the peer's name.  Failing that, pppd will use the
1287 null string as the peer's name.
1289 When authenticating the peer with PAP, the supplied password is first
1290 compared with the secret from the secrets file.  If the password
1291 doesn't match the secret, the password is encrypted using crypt() and
1292 checked against the secret again.  Thus secrets for authenticating the
1293 peer can be stored in encrypted form if desired.  If the
1294 \fIpapcrypt\fR option is given, the first (unencrypted) comparison is
1297 Furthermore, if the \fIlogin\fR option was specified, the username and
1298 password are also checked against the system password database.  Thus,
1299 the system administrator can set up the pap\-secrets file to allow PPP
1300 access only to certain users, and to restrict the set of IP addresses
1301 that each user can use.  Typically, when using the \fIlogin\fR option,
1303 password supplied by the peer.  This avoids the need to have the same
1307 other Network Control Protocol) can be started.  If the peer is
1309 terminated the link (by closing LCP).  If IPCP negotiates an
1310 unacceptable IP address for the remote host, IPCP will be closed.  IP
1315 IP addresses, even when the local host generally requires
1316 authentication.  If the peer refuses to authenticate itself when
1318 using the empty string for the username and password.  Thus, by adding
1319 a line to the pap\-secrets file which specifies the empty string for
1324 When IPCP negotiation is completed successfully, pppd will inform the
1325 kernel of the local and remote IP addresses for the ppp interface.
1326 This is sufficient to create a host route to the remote end of the
1327 link, which will enable the peers to exchange IP packets.
1330 Protocol) tables.  In most cases the \fIdefaultroute\fR and/or
1332 further intervention is required.  The /etc/ppp/ip\-up script can be
1335 Sometimes it is desirable to add a default route through the remote
1336 host, as in the case of a machine whose only connection to the
1337 Internet is through the ppp interface.  The \fIdefaultroute\fR option
1339 delete it when the link is terminated.
1343 communicate with the remote host.  The \fIproxyarp\fR option causes
1344 pppd to look for a network interface on the same subnet as the remote
1347 permanent, published ARP entry with the IP address of the remote host
1348 and the hardware address of the network interface found.
1350 When the \fIdemand\fR option is used, the interface IP addresses have
1351 already been set at the point when IPCP comes up.  If pppd has not
1352 been able to negotiate the same addresses that it used to configure
1353 the interface (for example when the peer is an ISP that uses dynamic
1354 IP address assignment), pppd has to change the interface IP addresses
1355 to the negotiated addresses.  This may disrupt existing connections,
1356 and the use of demand dialling with peers that do dynamic IP address
1359 Multilink PPP provides the capability to combine two or more PPP links
1361 single virtual PPP link which has the combined bandwidth of the
1365 Pppd detects that the link it is controlling is connected to the same
1366 peer as another link using the peer's endpoint discriminator and the
1367 authenticated identity of the peer (if it authenticates itself).  The
1371 randomly strings of bytes, or E\-164 phone numbers.  The endpoint
1372 discriminator sent to the peer by pppd can be set using the endpoint
1375 In some circumstances the peer may send no endpoint discriminator or a
1376 non-unique value.  The bundle option adds an extra string which is
1377 added to the peer's endpoint discriminator and authenticated identity
1378 when matching up links to be joined together in a bundle.  The bundle
1379 option can also be used to allow the establishment of multiple bundles
1380 between the local system and the peer.  Pppd uses a TDB database in
1383 Assuming that multilink is enabled and the peer is willing to
1384 negotiate multilink, then when pppd is invoked to bring up the first
1385 link to the peer, it will detect that no other link is connected to
1388 to the peer, it will detect the existing bundle and join its link to
1391 If the first link terminates (for example, because of a hangup or a
1392 received LCP terminate-request) the bundle is not destroyed unless
1393 there are no other links remaining in the bundle.  Rather than
1394 exiting, the first pppd keeps running after its link terminates, until
1395 all the links in the bundle have terminated.  If the first pppd
1396 receives a SIGTERM or SIGINT signal, it will destroy the bundle and
1397 send a SIGHUP to the pppd processes for each of the links in the
1398 bundle.  If the first pppd receives a SIGHUP signal, it will terminate
1399 its link but not the bundle.
1404 The following examples assume that the /etc/ppp/options file contains
1405 the \fIauth\fR option (as in the default /etc/ppp/options file in the
1408 Probably the most common use of pppd is to dial out to an ISP.  This
1413 where the /etc/ppp/peers/isp file is set up by the system
1422 In this example, we are using chat to dial the ISP's modem and go
1423 through any logon sequence required.  The /etc/ppp/chat\-isp file
1424 contains the script used by chat; it could for example contain
1453 See the chat(8) man page for details of chat scripts.
1456 the users already have login accounts, the simplest way to set up the
1457 ppp service is to let the users log in to their accounts and run pppd
1462 To allow a user to use the PPP facilities, you need to allocate an IP
1465 (depending on which authentication method the PPP implementation on
1466 the user's machine supports), so that the user's machine can
1468 "joespc" that is to be allowed to dial in to the machine called
1469 "server" and use the IP address joespc.my.net, you would add an entry
1474 (See srp\-entry(8) for a means to generate the server's entry when
1484 XOFF (^S), using \fIasyncmap a0000\fR.  If the path includes a telnet,
1486 the path includes an rlogin, you will need to use the \fIescape ff\fR
1487 option on the end which is running the rlogin client, since many
1488 rlogin implementations are not transparent; they will remove the
1489 sequence [0xff, 0xff, 0x73, 0x73, followed by any 8 bytes] from the
1493 Messages are sent to the syslog daemon using facility LOG_DAEMON.
1494 (This can be overridden by recompiling pppd with the macro
1495 LOG_PPP defined as the desired facility.)  See the syslog(8)
1496 documentation for details of where the syslog daemon will write the
1497 messages.  On most systems, the syslog daemon uses the
1498 /etc/syslog.conf file to specify the destination(s) for syslog
1501 The \fIdebug\fR option causes the contents of all control packets sent
1503 This can be useful if the PPP negotiation does not succeed or if
1505 If debugging is enabled at compile time, the \fIdebug\fR option also
1509 to the pppd process.  This signal acts as a toggle.
1512 detected, or the reason for the link being terminated.  The values
1516 Pppd has detached, or otherwise the connection was successfully
1517 established and terminated at the peer's request.
1524 An error was detected in processing the options given, such as two
1528 Pppd is not setuid-root and the invoking user is not root.
1531 The kernel does not support PPP, for example, the PPP kernel driver is
1548 The command specified as the argument to the \fIpty\fR option could
1552 The PPP negotiation failed, that is, it didn't reach the point where
1563 The link was established successfully and terminated because the
1570 The link was terminated because the peer is not responding to echo
1574 The link was terminated by the modem hanging up.
1583 We failed to authenticate ourselves to the peer.
1588 Pppd does not wait for the scripts to finish (except for the ip-pre-up
1589 script).  The scripts are
1590 executed as root (with the real and effective user-id set to 0), so
1592 privileged daemons.  Be careful that the contents of these scripts do
1593 not compromise your system's security.  Pppd runs the scripts with
1596 give information about the link.  The environment variables that pppd
1600 The name of the serial tty device being used.
1603 The name of the network interface being used.
1606 The IP address for the local end of the link.  This is only set when
1610 The IP address for the remote end of the link.  This is only set when
1614 The authenticated name of the peer.  This is only set if the peer
1618 The baud rate of the tty device.
1621 The real user-id of the user who invoked pppd.
1624 The username of the real user-id that invoked pppd. This is always set.
1626 For the ip-down and auth-down scripts, pppd also sets the following
1627 variables giving statistics for the connection:
1630 The number of seconds from when the PPP negotiation started until the
1634 The number of bytes sent (at the level of the serial port) during the
1638 The number of bytes received (at the level of the serial port) during
1642 The logical name of the link, set with the \fIlinkname\fR option.
1645 If the peer supplies DNS server addresses, this variable is set to the
1646 first DNS server address supplied (whether or not the usepeerdns
1650 If the peer supplies DNS server addresses, this variable is set to the
1651 second DNS server address supplied (whether or not the usepeerdns
1654 Pppd invokes the following scripts, if they exist.  It is not an error
1658 A program or script which is executed after the remote system
1659 successfully authenticates itself.  It is executed with the parameters
1663 Note that this script is not executed if the peer doesn't authenticate
1664 itself, for example when the \fInoauth\fR option is used.
1667 A program or script which is executed when the link goes down, if
1668 /etc/ppp/auth\-up was previously executed.  It is executed in the same
1669 manner with the same parameters as /etc/ppp/auth\-up.
1672 A program or script which is executed just before the ppp network
1673 interface is brought up.  It is executed with the same parameters as
1674 the ip\-up script (below).  At this point the interface exists and has
1676 add firewall rules before any IP traffic can pass through the
1681 A program or script which is executed when the link is available for
1683 executed with the parameters
1689 A program or script which is executed when the link is no longer
1691 used for undoing the effects of the /etc/ppp/ip\-up and
1693 invoked in the same manner and with the same parameters as the ip\-up
1697 Like /etc/ppp/ip\-up, except that it is executed when the link is available 
1698 for sending and receiving IPv6 packets. It is executed with the parameters
1705 longer be transmitted on the link. It is executed with the same parameters 
1706 as the ipv6\-up script.
1709 A program or script which is executed when the link is available for
1711 executed with the parameters
1718 may be one of the following:
1729 A program or script which is executed when the link is no longer
1731 used for undoing the effects of the /etc/ppp/ipx\-up script.  It is
1732 invoked in the same manner and with the same parameters as the ipx\-up
1741 Process-ID for pppd process for logical link \fIname\fR (see the
1748 pppd instances, the interfaces and devices they are using, IP address
1753 user.  Pppd will log a warning if this is not the case.
1759 this is not the case.
1765 this is not the case.
1768 Saved client-side SRP\-SHA1 pseudonym.  See the \fIsrp\-use\-pseudonym\fR
1779 System default options for the serial port being used, read after
1780 ~/.ppprc.  In forming the \fIttyname\fR part of this
1781 filename, an initial /dev/ is stripped from the port name (if
1782 present), and any slashes in the remaining part are converted to
1787 options, even if pppd was invoked by a user other than root.  The
1789 permit non-privileged users to dial out without requiring the peer to
1802 .I The MD5 Message-Digest Algorithm.
1817 .I The Point-to-Point Protocol (PPP).
1837 .I The SRP Authentication and Key Exchange System
1846 process by sending it a signal from the list below.
1849 These signals cause pppd to terminate the link (by closing LCP),
1850 restore the serial device settings, and exit.  If a connector or
1851 disconnector process is currently running, pppd will send the same
1852 signal to its process group, so as to terminate the connector or
1856 This signal causes pppd to terminate the link, restore the serial
1857 device settings, and close the serial device.  If the \fIpersist\fR or
1858 \fIdemand\fR option has been specified, pppd will try to reopen the
1859 serial device and start another connection (after the holdoff period).
1860 Otherwise pppd will exit.  If this signal is received during the
1861 holdoff period, it causes pppd to end the holdoff period immediately.
1862 If a connector or disconnector process is running, pppd will send the
1866 This signal toggles the state of the \fIdebug\fR option.
1906 Copyright (c) 2002 The Android Open Source Project
1908 The copyright notices contain the following statements.
1911 modification, are permitted provided that the following conditions
1914 1. Redistributions of source code must retain the above copyright
1915    notice, this list of conditions and the following disclaimer.
1917 2. Redistributions in binary form must reproduce the above copyright
1918    notice, this list of conditions and the following disclaimer in
1919    the documentation and/or other materials provided with the
1922 3. The name "Carnegie Mellon University" must not be used to
1939 3b. The name(s) of the authors of this software must not be used to
1943 4. Redistributions of any form whatsoever must retain the following
1964 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
1968 AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
1972 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.