1 .\" manual page [] for pppd 2.3
2 .\" $FreeBSD: src/usr.sbin/pppd/pppd.8,v 1.20.2.4 2003/03/11 22:31:30 trhodes Exp $
3 .\" $DragonFly: src/usr.sbin/pppd/pppd.8,v 1.5 2007/11/23 23:16:37 swildner Exp $
5 .\" SS subsection heading
7 .\" IP indented paragraph
11 pppd \- Point to Point Protocol daemon
23 The Point-to-Point Protocol (PPP) provides a method for transmitting
24 datagrams over serial point-to-point links. PPP
25 is composed of three parts: a method for encapsulating datagrams over
26 serial links, an extensible Link Control Protocol (LCP), and
27 a family of Network Control Protocols (NCP) for establishing
28 and configuring different network-layer protocols.
30 The encapsulation scheme is provided by driver code in the kernel.
31 Pppd provides the basic LCP, authentication support, and an NCP for
32 establishing and configuring the Internet Protocol (IP) (called the IP
33 Control Protocol, IPCP).
34 .SH FREQUENTLY USED OPTIONS
37 Communicate over the named device. The string "/dev/" is prepended if
38 necessary. If no device name is given, or if the name of the terminal
39 connected to the standard input is given, pppd
40 will use that terminal, and will not fork to put itself in the
41 background. This option is privileged if the \fInoauth\fR option is
45 Set the baud rate to <speed> (a decimal number). On systems such as
46 4.4BSD and NetBSD, any speed can be specified, providing that it is
47 supported by the serial device driver. Other systems
48 (e.g. SunOS, Linux) allow only a limited set of speeds.
50 .B active-filter \fIfilter-expression
51 Specifies a packet filter to be applied to data packets to determine
52 which packets are to be regarded as link activity, and therefore reset
53 the idle timer, or cause the link to be brought up in demand-dialling
54 mode. This option is useful in conjunction with the
55 \fBidle\fR option if there are packets being sent or received
56 regularly over the link (for example, routing information packets)
57 which would otherwise prevent the link from ever appearing to be idle.
58 The \fIfilter-expression\fR syntax is as described for tcpdump(1),
59 except that qualifiers which are inappropriate for a PPP link, such as
60 \fBether\fR and \fBarp\fR, are not permitted. Generally the filter
61 expression should be enclosed in single-quotes to prevent whitespace
62 in the expression from being interpreted by the shell.
65 if both the kernel and pppd were compiled with PPP_FILTER defined.
68 Set the async character map to <map>. This map describes which
69 control characters cannot be successfully received over the serial
70 line. Pppd will ask the peer to send these characters as a 2-byte
71 escape sequence. The argument is a 32 bit hex number with each bit
72 representing a character to escape. Bit 0 (00000001) represents the
73 character 0x00; bit 31 (80000000) represents the character 0x1f or ^_.
74 If multiple \fIasyncmap\fR options are given, the values are ORed
75 together. If no \fIasyncmap\fR option is given, no async character
76 map will be negotiated for the receive direction; the peer should then
77 escape \fIall\fR control characters. To escape transmitted
78 characters, use the \fIescape\fR option.
81 Require the peer to authenticate itself before allowing network
82 packets to be sent or received.
85 Read options from the file /etc/ppp/peers/\fIname\fR. This file may
86 contain privileged options, such as \fInoauth\fR, even if pppd
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 Use the executable or shell command specified by \fIscript\fR to set
93 up the serial line. This script would typically use the chat(8)
94 program to dial the modem and start the remote ppp session. This
95 option is privileged if the \fInoauth\fR option is used.
97 .B connect-max-attempts \fI<n>
98 Attempt dial-out connection to remote system no more than specified number
99 of times (default = 1). If the connection is not made, pppd will exit.
100 Requires that \fBpersist\fR has been specified.
103 Use hardware flow control (i.e. RTS/CTS) to control the flow of data
104 on the serial port. If neither the \fIcrtscts\fR nor the
105 \fInocrtscts\fR option is given, the hardware flow control setting
106 for the serial port is left unchanged.
109 Add a default route to the system routing tables, using the peer as
110 the gateway, when IPCP negotiation is successfully completed.
111 This entry is removed when the PPP connection is broken. This option
112 is privileged if the \fInodefaultroute\fR option has been specified.
114 .B disconnect \fIscript
115 Run the executable or shell command specified by \fIscript\fR after
116 pppd has terminated the link. This script could, for example, issue
117 commands to the modem to cause it to hang up if hardware modem control
118 signals were not available. The disconnect script is not run if the
119 modem has already hung up. This option is privileged if the
120 \fInoauth\fR option is used.
122 .B escape \fIxx,yy,...
123 Specifies that certain characters should be escaped on transmission
124 (regardless of whether the peer requests them to be escaped with its
125 async control character map). The characters to be escaped are
126 specified as a list of hex numbers separated by commas. Note that
127 almost any character can be specified for the \fIescape\fR option,
128 unlike the \fIasyncmap\fR option which only allows control characters
129 to be specified. The characters which may not be escaped are those
130 with hex values 0x20 - 0x3f or 0x5e.
133 Read options from file \fIname\fR (the format is described below).
134 The file must be readable by the user who has invoked pppd.
137 Specifies that pppd should create a UUCP-style lock file for the
138 serial device to ensure exclusive access to the device.
141 Set the MRU [Maximum Receive Unit] value to \fIn\fR.
143 will ask the peer to send packets of no more than \fIn\fR bytes. The
144 minimum MRU value is 128. The default MRU value is 1500. A value of
145 296 is recommended for slow links (40 bytes for TCP/IP header + 256
149 Set the MTU [Maximum Transmit Unit] value to \fIn\fR. Unless the
150 peer requests a smaller value via MRU negotiation, pppd will
151 request that the kernel networking code send data packets of no more
152 than \fIn\fR bytes through the PPP network interface.
155 Enables the "passive" option in the LCP. With this option, pppd will
156 attempt to initiate a connection; if no reply is received from the
157 peer, pppd will then just wait passively for a valid LCP packet from
158 the peer, instead of exiting, as it would without this option.
161 .I <local_IP_address>\fB:\fI<remote_IP_address>
162 Set the local and/or remote interface IP addresses. Either one may be
163 omitted. The IP addresses can be specified with a host name or in
164 decimal dot notation (e.g. 150.234.56.78). The default local
165 address is the (first) IP address of the system (unless the
167 option is given). The remote address will be obtained from the peer
168 if not specified in any option. Thus, in simple cases, this option is
169 not required. If a local and/or remote IP address is specified with
171 will not accept a different value from the peer in the IPCP
172 negotiation, unless the \fIipcp-accept-local\fR and/or
173 \fIipcp-accept-remote\fR options are given, respectively.
176 Request that the peer compress packets that it sends, using the
177 BSD-Compress scheme, with a maximum code size of \fInr\fR bits, and
178 agree to compress packets sent to the peer with a maximum code size of
179 \fInt\fR bits. If \fInt\fR is not specified, it defaults to the value
180 given for \fInr\fR. Values in the range 9 to 15 may be used for
181 \fInr\fR and \fInt\fR; larger values give better compression but
182 consume more kernel memory for compression dictionaries.
183 Alternatively, a value of 0 for \fInr\fR or \fInt\fR disables
184 compression in the corresponding direction. Use \fInobsdcomp\fR or
185 \fIbsdcomp 0\fR to disable BSD-Compress compression entirely.
187 .B chap-interval \fIn
188 If this option is given, pppd will rechallenge the peer every \fIn\fR
191 .B chap-max-challenge \fIn
192 Set the maximum number of CHAP challenge transmissions to \fIn\fR
196 Set the CHAP restart interval (retransmission timeout for challenges)
197 to \fIn\fR seconds (default 3).
200 Enables connection debugging facilities.
201 If this option is given, pppd will log the contents of all
202 control packets sent or received in a readable form. The packets are
203 logged through syslog with facility \fIdaemon\fR and level
204 \fIdebug\fR. This information can be directed to a file by setting up
205 /etc/syslog.conf appropriately (see syslog.conf(5)).
208 Disable asyncmap negotiation, forcing all control characters to be
209 escaped for both the transmit and the receive direction.
212 Disable MRU [Maximum Receive Unit] negotiation. With this option,
213 pppd will use the default MRU value of 1500 bytes for both the
214 transmit and receive direction.
217 Request that the peer compress packets that it sends, using the
218 Deflate scheme, with a maximum window size of \fI2**nr\fR bytes, and
219 agree to compress packets sent to the peer with a maximum window size
220 of \fI2**nt\fR bytes. If \fInt\fR is not specified, it defaults to
221 the value given for \fInr\fR. Values in the range 8 to 15 may be used
222 for \fInr\fR and \fInt\fR; larger values give better compression but
223 consume more kernel memory for compression dictionaries.
224 Alternatively, a value of 0 for \fInr\fR or \fInt\fR disables
225 compression in the corresponding direction. Use \fInodeflate\fR or
226 \fIdeflate 0\fR to disable Deflate compression entirely. (Note: pppd
227 requests Deflate compression in preference to BSD-Compress if the peer
231 Initiate the link only on demand, i.e. when data traffic is present.
232 With this option, the remote IP address must be specified by the user
233 on the command line or in an options file. Pppd will initially
234 configure the interface and enable it for IP traffic without
235 connecting to the peer. When traffic is available, pppd will
236 connect to the peer and perform negotiation, authentication, etc.
237 When this is completed, pppd will commence passing data packets
238 (i.e., IP packets) across the link.
240 The \fIdemand\fR option implies the \fIpersist\fR option. If this
241 behaviour is not desired, use the \fInopersist\fR option after the
242 \fIdemand\fR option. The \fIidle\fR and \fIholdoff\fR
243 options are also useful in conjunction with the \fIdemand\fR option.
246 Append the domain name \fId\fR to the local host name for authentication
247 purposes. For example, if gethostname() returns the name porsche, but
248 the fully qualified domain name is porsche.Quotron.COM, you could
249 specify \fIdomain Quotron.COM\fR. Pppd would then use the name
250 \fIporsche.Quotron.COM\fR for looking up secrets in the secrets file,
251 and as the default name to send to the peer when authenticating itself
252 to the peer. This option is privileged.
255 Specifies how many seconds to wait before re-initiating the link after
256 it terminates. This option only has any effect if the \fIpersist\fR
257 or \fIdemand\fR option is used. The holdoff period is not applied if
258 the link was terminated because it was idle.
261 Specifies that pppd should disconnect if the link is idle for \fIn\fR
262 seconds. The link is idle when no data packets (i.e. IP packets) are
263 being sent or received. Note: it is not advisable to use this option
264 with the \fIpersist\fR option without the \fIdemand\fR option.
265 If the \fBactive-filter\fR
266 option is given, data packets which are rejected by the specified
267 activity filter also count as the link being idle.
270 With this option, pppd will accept the peer's idea of our local IP
271 address, even if the local IP address was specified in an option.
273 .B ipcp-accept-remote
274 With this option, pppd will accept the peer's idea of its (remote) IP
275 address, even if the remote IP address was specified in an option.
277 .B ipcp-max-configure \fIn
278 Set the maximum number of IPCP configure-request transmissions to
279 \fIn\fR (default 10).
281 .B ipcp-max-failure \fIn
282 Set the maximum number of IPCP configure-NAKs returned before starting
283 to send configure-Rejects instead to \fIn\fR (default 10).
285 .B ipcp-max-terminate \fIn
286 Set the maximum number of IPCP terminate-request transmissions to
290 Set the IPCP restart interval (retransmission timeout) to \fIn\fR
294 Provides an extra parameter to the ip-up and ip-down scripts. If this
295 option is given, the \fIstring\fR supplied is given as the 6th
296 parameter to those scripts.
299 Enable the IPXCP and IPX protocols. This option is presently only
300 supported under Linux, and only if your kernel has been configured to
304 Set the IPX network number in the IPXCP configure request frame to
305 \fIn\fR, a hexadecimal number (without a leading 0x). There is no
306 valid default. If this option is not specified, the network number is
307 obtained from the peer. If the peer does not have the network number,
308 the IPX protocol will not be started.
310 .B ipx-node \fIn\fB:\fIm
311 Set the IPX node numbers.
312 The two node numbers are separated from each
313 other with a colon character.
314 The first number \fIn\fR is the local
316 The second number \fIm\fR is the peer's node number.
318 node number is a hexadecimal number, at most 10 digits long.
320 numbers on the ipx-network must be unique.
323 If this option is not specified then the node numbers are
324 obtained from the peer.
326 .B ipx-router-name \fI<string>
327 Set the name of the router.
328 This is a string and is sent to the peer
332 Set the routing protocol to be received by this option.
334 instance of \fIipx-routing\fR may be specified.
336 option (0) may be specified as the only instance of ipx-routing.
338 values may be \fI0\fR for \fINONE\fR, \fI2\fR for \fIRIP/SAP\fR, and
339 \fI4\fR for \fINLSP\fR.
341 .B ipxcp-accept-local
342 Accept the peer's NAK for the node number specified in the ipx-node
344 If a node number was specified, and non-zero, the default is
345 to insist that the value be used.
346 If you include this option then you
347 will permit the peer to override the entry of the node number.
349 .B ipxcp-accept-network
350 Accept the peer's NAK for the network number specified in the
352 If a network number was specified, and non-zero, the
353 default is to insist that the value be used.
355 option then you will permit the peer to override the entry of the node
358 .B ipxcp-accept-remote
359 Use the peer's network number specified in the configure request
361 If a node number was specified for the peer and this option was
362 not specified, the peer will be forced to use the value which you have
365 .B ipxcp-max-configure \fIn
366 Set the maximum number of IPXCP configure request frames which the
367 system will send to \fIn\fR.
370 .B ipxcp-max-failure \fIn
371 Set the maximum number of IPXCP NAK frames which the local system will
372 send before it rejects the options.
373 The default value is 3.
375 .B ipxcp-max-terminate \fIn
376 Set the maximum number of IPXCP terminate request frames before the
377 local system considers that the peer is not listening to them.
382 Enable debugging code in the kernel-level PPP driver. The argument
383 \fIn\fR is a number which is the sum of the following values: 1 to
384 enable general debug messages, 2 to request that the contents of
385 received packets be printed, and 4 to request that the contents of
386 transmitted packets be printed. On most systems, messages printed by
387 the kernel are logged by syslog(1) to a file as directed in the
388 /etc/syslog.conf configuration file.
390 .B lcp-echo-failure \fIn
391 If this option is given, pppd will presume the peer to be dead
392 if \fIn\fR LCP echo-requests are sent without receiving a valid LCP
393 echo-reply. If this happens, pppd will terminate the
394 connection. Use of this option requires a non-zero value for the
395 \fIlcp-echo-interval\fR parameter. This option can be used to enable
396 pppd to terminate after the physical connection has been broken
397 (e.g., the modem has hung up) in situations where no hardware modem
398 control lines are available.
400 .B lcp-echo-interval \fIn
401 If this option is given, pppd will send an LCP echo-request frame to
402 the peer every \fIn\fR seconds. Normally the peer should respond to
403 the echo-request by sending an echo-reply. This option can be used
404 with the \fIlcp-echo-failure\fR option to detect that the peer is no
407 .B lcp-max-configure \fIn
408 Set the maximum number of LCP configure-request transmissions to
409 \fIn\fR (default 10).
411 .B lcp-max-failure \fIn
412 Set the maximum number of LCP configure-NAKs returned before starting
413 to send configure-Rejects instead to \fIn\fR (default 10).
415 .B lcp-max-terminate \fIn
416 Set the maximum number of LCP terminate-request transmissions to
420 Set the LCP restart interval (retransmission timeout) to \fIn\fR
424 Don't use the modem control lines. With this option, pppd will ignore
425 the state of the CD (Carrier Detect) signal from the modem and will
426 not change the state of the DTR (Data Terminal Ready) signal.
429 Use the system password database for authenticating the peer using
430 PAP, and record the user in the system wtmp file. Note that the peer
431 must have an entry in the /etc/ppp/pap-secrets file as well as the
432 system password database to be allowed access.
435 Terminate the connection when it has been available for network
436 traffic for \fIn\fR seconds (i.e. \fIn\fR seconds after the first
437 network control protocol comes up).
440 Use the modem control lines. This option is the default. With this
441 option, pppd will wait for the CD (Carrier Detect) signal from the
442 modem to be asserted when opening the serial device (unless a connect
443 script is specified), and it will drop the DTR (Data Terminal Ready)
444 signal briefly when the connection is terminated and before executing
445 the connect script. On Ultrix, this option implies hardware flow
446 control, as for the \fIcrtscts\fR option.
449 If pppd is acting as a server for Microsoft Windows clients, this
450 option allows pppd to supply one or two DNS (Domain Name Server)
451 addresses to the clients. The first instance of this option specifies
452 the primary DNS address; the second instance (if given) specifies the
453 secondary DNS address. (This option was present in some older
454 versions of pppd under the name \fBdns-addr\fR.)
457 If pppd is acting as a server for Microsoft Windows or "Samba"
458 clients, this option allows pppd to supply one or two WINS (Windows
459 Internet Name Services) server addresses to the clients. The first
460 instance of this option specifies the primary WINS address; the second
461 instance (if given) specifies the secondary WINS address.
464 Set the name of the local system for authentication purposes to
465 \fIname\fR. This is a privileged option. With this option, pppd will
466 use lines in the secrets files which have \fIname\fR as the second
467 field when looking for a secret to use in authenticating the peer. In
468 addition, unless overridden with the \fIuser\fR option, \fIname\fR
469 will be used as the name to send to the peer when authenticating the
470 local system to the peer. (Note that pppd does not append the domain
474 Set the interface netmask to \fIn\fR, a 32 bit netmask in "decimal dot"
475 notation (e.g. 255.255.255.0). If this option is given, the value
476 specified is ORed with the default netmask. The default netmask is
477 chosen based on the negotiated remote IP address; it is the
478 appropriate network mask for the class of the remote IP address, ORed
479 with the netmasks for any non point-to-point network interfaces in the
480 system which are on the same network.
483 Disable Address/Control compression in both directions (send and
487 Do not require the peer to authenticate itself. This option is
488 privileged if the \fIauth\fR option is specified in /etc/ppp/options.
491 Disables BSD-Compress compression; \fBpppd\fR will not request or
492 agree to compress packets using the BSD-Compress scheme.
495 Disable CCP (Compression Control Protocol) negotiation. This option
496 should only be required if the peer is buggy and gets confused by
497 requests from pppd for CCP negotiation.
500 Disable hardware flow control (i.e. RTS/CTS) on the serial port. If
501 neither the \fIcrtscts\fR nor the \fInocrtscts\fR option is given,
502 the hardware flow control setting for the serial port is left
506 Disable the \fIdefaultroute\fR option. The system administrator who
507 wishes to prevent users from creating default routes with pppd
508 can do so by placing this option in the /etc/ppp/options file.
511 Disables Deflate compression; pppd will not request or agree to
512 compress packets using the Deflate scheme.
515 Don't detach from the controlling terminal. Without this option, if a
516 serial device other than the terminal on the standard input is
517 specified, pppd will fork to become a background process.
520 Disable IPCP negotiation and IP communication. This option should
521 only be required if the peer is buggy and gets confused by requests
522 from pppd for IPCP negotiation.
525 Disables the default behaviour when no local IP address is specified,
526 which is to determine (if possible) the local IP address from the
527 hostname. With this option, the peer will have to supply the local IP
528 address during IPCP negotiation (unless it specified explicitly on the
529 command line or in an options file).
532 Disable the IPXCP and IPX protocols. This option should only be
533 required if the peer is buggy and gets confused by requests from pppd
534 for IPXCP negotiation.
537 Disable magic number negotiation. With this option, pppd cannot
538 detect a looped-back line. This option should only be needed if the
542 Disable protocol field compression negotiation in both the receive and
543 the transmit direction.
546 Exit once a connection has been made and terminated. This is the
547 default unless the \fIpersist\fR or \fIdemand\fR option has been
551 Do not accept or agree to Predictor-1 compression.
554 Disable the \fIproxyarp\fR option. The system administrator who
555 wishes to prevent users from creating proxy ARP entries with pppd can
556 do so by placing this option in the /etc/ppp/options file.
559 Disable Van Jacobson style TCP/IP header compression in both the
560 transmit and the receive direction.
563 Disable the connection-ID compression option in Van Jacobson style
564 TCP/IP header compression. With this option, pppd will not omit the
565 connection-ID byte from Van Jacobson compressed TCP/IP headers, nor
566 ask the peer to do so.
569 Indicates that all secrets in the /etc/ppp/pap-secrets file which are
570 used for checking the identity of the peer are encrypted, and thus
571 pppd should not accept a password which, before encryption, is
572 identical to the secret from the /etc/ppp/pap-secrets file.
574 .B pap-max-authreq \fIn
575 Set the maximum number of PAP authenticate-request transmissions to
576 \fIn\fR (default 10).
579 Set the PAP restart interval (retransmission timeout) to \fIn\fR
583 Set the maximum time that pppd will wait for the peer to authenticate
584 itself with PAP to \fIn\fR seconds (0 means no limit).
586 .B pass-filter \fIfilter-expression
587 Specifies a packet filter to applied to data packets being sent or
588 received to determine which packets should be allowed to pass.
589 Packets which are rejected by the filter are silently discarded. This
590 option can be used to prevent specific network daemons (such as
591 routed) using up link bandwidth, or to provide a basic firewall
593 The \fIfilter-expression\fR syntax is as described for tcpdump(1),
594 except that qualifiers which are inappropriate for a PPP link, such as
595 \fBether\fR and \fBarp\fR, are not permitted. Generally the filter
596 expression should be enclosed in single-quotes to prevent whitespace
597 in the expression from being interpreted by the shell. Note that it
598 is possible to apply different constraints to incoming and outgoing
599 packets using the \fBinbound\fR and \fBoutbound\fR qualifiers.
601 option is currently only available under NetBSD, and then only if both
602 the kernel and pppd were compiled with PPP_FILTER defined.
605 Do not exit after a connection is terminated; instead try to reopen
609 Request that the peer compress frames that it sends using Predictor-1
610 compression, and agree to compress transmitted frames with Predictor-1
611 if requested. This option has no effect unless the kernel driver
612 supports Predictor-1 compression.
615 Add an entry to this system's ARP [Address Resolution Protocol] table
616 with the IP address of the peer and the Ethernet address of this
617 system. This will have the effect of making the peer appear to other
618 systems to be on the local ethernet.
620 .B remotename \fIname
621 Set the assumed name of the remote system for authentication purposes
625 With this option, pppd will not agree to authenticate itself to the
629 With this option, pppd will not agree to authenticate itself to the
633 Require the peer to authenticate itself using CHAP [Challenge
634 Handshake Authentication Protocol] authentication.
637 Require the peer to authenticate itself using PAP [Password
638 Authentication Protocol] authentication.
641 With this option, pppd will not transmit LCP packets to initiate a
642 connection until a valid LCP packet is received from the peer (as for
643 the `passive' option with ancient versions of pppd).
646 Enforce the use of the hostname (with domain name appended, if given)
647 as the name of the local system for authentication purposes (overrides
648 the \fIname\fR option).
651 Sets the name used for authenticating the local system to the peer to
655 Sets the number of connection slots to be used by the Van Jacobson
656 TCP/IP header compression and decompression code to \fIn\fR, which
657 must be between 2 and 16 (inclusive).
660 Run the executable or shell command specified by \fIscript\fR before
661 initiating PPP negotiation, after the connect script (if any) has
662 completed. This option is privileged if the \fInoauth\fR option is
666 Use software flow control (i.e. XON/XOFF) to control the flow of data on
669 Options can be taken from files as well as the command line. Pppd
670 reads options from the files /etc/ppp/options, ~/.ppprc and
671 /etc/ppp/options.\fIttyname\fR (in that order) before processing the
672 options on the command line. (In fact, the command-line options are
673 scanned to find the terminal name before the options.\fIttyname\fR
674 file is read.) In forming the name of the options.\fIttyname\fR file,
675 the initial /dev/ is removed from the terminal name, and any remaining
676 / characters are replaced with dots.
678 An options file is parsed into a series of words, delimited by
679 whitespace. Whitespace can be included in a word by enclosing the
680 word in double-quotes ("). A backslash (\\) quotes the following character.
681 A hash (#) starts a comment, which continues until the end of the
682 line. There is no restriction on using the \fIfile\fR or \fIcall\fR
683 options within an options file.
686 provides system administrators with sufficient access control that PPP
687 access to a server machine can be provided to legitimate users without
688 fear of compromising the security of the server or the network it's
689 on. In part this is provided by the /etc/ppp/options file, where the
690 administrator can place options to restrict the ways in which pppd can
691 be used, and in part by the PAP and CHAP secrets files, where the
692 administrator can restrict the set of IP addresses which individual
695 The normal way that pppd should be set up is to have the \fIauth\fR
696 option in the /etc/ppp/options file. (This may become the default in
697 later releases.) If users wish to use pppd to dial out to a peer
698 which will refuse to authenticate itself (such as an internet service
699 provider), the system administrator should create an options file
700 under /etc/ppp/peers containing the \fInoauth\fR option, the name of
701 the serial port to use, and the \fIconnect\fR option (if required),
702 plus any other appropriate options. In this way, pppd can be set up
703 to allow non-privileged users to make unauthenticated connections only
706 As indicated above, some security-sensitive options are privileged,
707 which means that they may not be used by an ordinary non-privileged
708 user running a setuid-root pppd, either on the command line, in the
709 user's ~/.ppprc file, or in an options file read using the \fIfile\fR
710 option. Privileged options may be used in /etc/ppp/options file or in
711 an options file read using the \fIcall\fR option. If pppd is being
712 run by the root user, privileged options can be used without
715 Authentication is the process whereby one peer convinces the other of
716 its identity. This involves the first peer sending its name to the
717 other, together with some kind of secret information which could only
718 come from the genuine authorized user of that name. In such an
719 exchange, we will call the first peer the "client" and the other the
720 "server". The client has a name by which it identifies itself to the
721 server, and the server also has a name by which it identifies itself
722 to the client. Generally the genuine client shares some secret (or
723 password) with the server, and authenticates itself by proving that it
724 knows that secret. Very often, the names used for authentication
725 correspond to the internet hostnames of the peers, but this is not
728 At present, pppd supports two authentication protocols: the Password
729 Authentication Protocol (PAP) and the Challenge Handshake
730 Authentication Protocol (CHAP). PAP involves the client sending its
731 name and a cleartext password to the server to authenticate itself.
732 In contrast, the server initiates the CHAP authentication exchange by
733 sending a challenge to the client (the challenge packet includes the
734 server's name). The client must respond with a response which
735 includes its name plus a hash value derived from the shared secret and
736 the challenge, in order to prove that it knows the secret.
738 The PPP protocol, being symmetrical, allows both peers to require the
739 other to authenticate itself. In that case, two separate and
740 independent authentication exchanges will occur. The two exchanges
741 could use different authentication protocols, and in principle,
742 different names could be used in the two exchanges.
744 The default behaviour of pppd is to agree to authenticate if
745 requested, and to not require authentication from the peer. However,
746 pppd will not agree to authenticate itself with a particular protocol
747 if it has no secrets which could be used to do so.
749 Pppd stores secrets for use in authentication in secrets
750 files (/etc/ppp/pap-secrets for PAP, /etc/ppp/chap-secrets for CHAP).
751 Both secrets files have the same format. The secrets files can
752 contain secrets for pppd to use in authenticating itself to other
753 systems, as well as secrets for pppd to use when authenticating other
756 Each line in a secrets file contains one secret. A given secret is
757 specific to a particular combination of client and server - it can
758 only be used by that client to authenticate itself to that server.
759 Thus each line in a secrets file has at least 3 fields: the name of
760 the client, the name of the server, and the secret. These fields may
761 be followed by a list of the IP addresses that the specified client
762 may use when connecting to the specified server.
764 A secrets file is parsed into words as for an options file, so the
765 client name, server name and secrets fields must each be one word,
766 with any embedded spaces or other special characters quoted or
767 escaped. Any following words on the same line are taken to be a list
768 of acceptable IP addresses for that client, or an
769 override for "local:remote" addresses (the same format used on the
770 command line or in the options file) when on a line that contains a
771 specific client name (not a wildcard nor empty).
772 If there are only 3 words
773 on the line, or if the first word is "-", then all IP addresses are
774 disallowed. To allow any address, use "*".
775 A word starting with "!" indicates that the
776 specified address is \fInot\fR acceptable. An address may be followed
777 by "/" and a number \fIn\fR, to indicate a whole subnet, i.e. all
778 addresses which have the same value in the most significant \fIn\fR
779 bits. Note that case is significant in the client and server names
782 If the secret starts with an `@', what follows is assumed to be the
783 name of a file from which to read the secret. A "*" as the client or
784 server name matches any name. When selecting a secret, pppd takes the
785 best match, i.e. the match with the fewest wildcards.
787 Thus a secrets file contains both secrets for use in authenticating
788 other hosts, plus secrets which we use for authenticating ourselves to
789 others. When pppd is authenticating the peer (checking the peer's
790 identity), it chooses a secret with the peer's name in the first
791 field and the name of the local system in the second field. The
792 name of the local system defaults to the hostname, with the domain
793 name appended if the \fIdomain\fR option is used. This default can be
794 overridden with the \fIname\fR option, except when the
795 \fIusehostname\fR option is used.
797 When pppd is choosing a secret to use in authenticating itself to the
798 peer, it first determines what name it is going to use to identify
799 itself to the peer. This name can be specified by the user with the
800 \fIuser\fR option. If this option is not used, the name defaults to
801 the name of the local system, determined as described in the previous
802 paragraph. Then pppd looks for a secret with this name in the first
803 field and the peer's name in the second field. Pppd will know the
804 name of the peer if CHAP authentication is being used, because the
805 peer will have sent it in the challenge packet. However, if PAP is being
806 used, pppd will have to determine the peer's name from the options
807 specified by the user. The user can specify the peer's name directly
808 with the \fIremotename\fR option. Otherwise, if the remote IP address
809 was specified by a name (rather than in numeric form), that name will
810 be used as the peer's name. Failing that, pppd will use the null
811 string as the peer's name.
813 When authenticating the peer with PAP, the supplied password is first
814 compared with the secret from the secrets file. If the password
815 doesn't match the secret, the password is encrypted using crypt() and
816 checked against the secret again. Thus secrets for authenticating the
817 peer can be stored in encrypted form if desired. If the
818 \fIpapcrypt\fR option is given, the first (unencrypted) comparison is
819 omitted, for better security.
821 Furthermore, if the \fIlogin\fR option was specified, the username and
822 password are also checked against the system password database. Thus,
823 the system administrator can set up the pap-secrets file to allow PPP
824 access only to certain users, and to restrict the set of IP addresses
825 that each user can use. Typically, when using the \fIlogin\fR option,
826 the secret in /etc/ppp/pap-secrets would be "", which will match any
827 password supplied by the peer. This avoids the need to have the same
828 secret in two places.
830 Additional checks are performed when the \fBlogin\fR option is used.
831 If the file /etc/ppp/ppp.deny exists, and the user is listed in it,
832 the authentication fails. If the file /etc/ppp/ppp.shells exists and
833 the user's normal login shell is not listed, the authentication fails.
835 Authentication must be satisfactorily completed before IPCP (or any
836 other Network Control Protocol) can be started. If the peer is
837 required to authenticate itself, and fails to do so, pppd will
838 terminated the link (by closing LCP). If IPCP negotiates an
839 unacceptable IP address for the remote host, IPCP will be closed. IP
840 packets can only be sent or received when IPCP is open.
842 In some cases it is desirable to allow some hosts which can't
843 authenticate themselves to connect and use one of a restricted set of
844 IP addresses, even when the local host generally requires
845 authentication. If the peer refuses to authenticate itself when
846 requested, pppd takes that as equivalent to authenticating with PAP
847 using the empty string for the username and password. Thus, by adding
848 a line to the pap-secrets file which specifies the empty string for
849 the client and password, it is possible to allow restricted access to
850 hosts which refuse to authenticate themselves.
853 When IPCP negotiation is completed successfully, pppd will inform the
854 kernel of the local and remote IP addresses for the ppp interface.
855 This is sufficient to create a host route to the remote end of the
856 link, which will enable the peers to exchange IP packets.
857 Communication with other machines generally requires further
858 modification to routing tables and/or ARP (Address Resolution
859 Protocol) tables. In most cases the \fIdefaultroute\fR and/or
860 \fIproxyarp\fR options are sufficient for this, but in some cases
861 further intervention is required. The /etc/ppp/ip-up script can be
864 Sometimes it is desirable to add a default route through the remote
865 host, as in the case of a machine whose only connection to the
866 Internet is through the ppp interface. The \fIdefaultroute\fR option
867 causes pppd to create such a default route when IPCP comes up, and
868 delete it when the link is terminated.
870 In some cases it is desirable to use proxy ARP, for example on a
871 server machine connected to a LAN, in order to allow other hosts to
872 communicate with the remote host. The \fIproxyarp\fR option causes
873 pppd to look for a network interface on the same subnet as the remote
874 host (an interface supporting broadcast and ARP, which is up and not a
875 point-to-point or loopback interface). If found, pppd creates a
876 permanent, published ARP entry with the IP address of the remote host
877 and the hardware address of the network interface found.
879 When the \fIdemand\fR option is used, the interface IP addresses have
880 already been set at the point when IPCP comes up. If pppd has not
881 been able to negotiate the same addresses that it used to configure
882 the interface (for example when the peer is an ISP that uses dynamic
883 IP address assignment), pppd has to change the interface IP addresses
884 to the negotiated addresses. This may disrupt existing connections,
885 and the use of demand dialling with peers that do dynamic IP address
886 assignment is not recommended.
889 The following examples assume that the /etc/ppp/options file contains
890 the \fIauth\fR option (as in the default /etc/ppp/options file in the
893 Probably the most common use of pppd is to dial out to an ISP. This
894 can be done with a command such as
898 where the /etc/ppp/peers/isp file is set up by the system
899 administrator to contain something like this:
903 connect '/usr/sbin/chat -v -f /etc/ppp/chat-isp'
907 In this example, we are using chat to dial the ISP's modem and go
908 through any logon sequence required. The /etc/ppp/chat-isp file
909 contains the script used by chat; it could for example contain
922 ABORT "Username/Password Incorrect"
932 "word:" "\\qmypassword"
938 See the chat(8) man page for details of chat scripts.
940 Pppd can also be used to provide a dial-in ppp service for users. If
941 the users already have login accounts, the simplest way to set up the
942 ppp service is to let the users log in to their accounts and run pppd
943 (installed setuid-root) with a command such as
947 To allow a user to use the PPP facilities, you need to allocate an IP
948 address for that user's machine and create an entry in
949 /etc/ppp/pap-secrets or /etc/ppp/chap-secrets (depending on which
950 authentication method the PPP implementation on the user's machine
951 supports), so that the user's
952 machine can authenticate itself. For example, if Joe has a machine
953 called "joespc" which is to be allowed to dial in to the machine
954 called "server" and use the IP address joespc.my.net, you would add an
955 entry like this to /etc/ppp/pap-secrets or /etc/ppp/chap-secrets:
957 joespc server "joe's secret" joespc.my.net
959 Alternatively, you can create a username called (for example) "ppp",
960 whose login shell is pppd and whose home directory is /etc/ppp.
961 Options to be used when pppd is run this way can be put in
964 If your serial connection is any more complicated than a piece of
965 wire, you may need to arrange for some control characters to be
966 escaped. In particular, it is often useful to escape XON (^Q) and
967 XOFF (^S), using \fIasyncmap a0000\fR. If the path includes a telnet,
968 you probably should escape ^] as well (\fIasyncmap 200a0000\fR). If
969 the path includes an rlogin, you will need to use the \fIescape ff\fR
970 option on the end which is running the rlogin client, since many
971 rlogin implementations are not transparent; they will remove the
972 sequence [0xff, 0xff, 0x73, 0x73, followed by any 8 bytes] from the
976 Messages are sent to the syslog daemon using facility LOG_DAEMON.
977 (This can be overridden by recompiling pppd with the macro
978 LOG_PPP defined as the desired facility.) In order to see the error
979 and debug messages, you will need to edit your /etc/syslog.conf file
980 to direct the messages to the desired output device or file.
982 The \fIdebug\fR option causes the contents of all control packets sent
983 or received to be logged, that is, all LCP, PAP, CHAP or IPCP packets.
984 This can be useful if the PPP negotiation does not succeed or if
985 authentication fails.
986 If debugging is enabled at compile time, the \fIdebug\fR option also
987 causes other debugging messages to be logged.
989 Debugging can also be enabled or disabled by sending a SIGUSR1 signal
990 to the pppd process. This signal acts as a toggle.
992 Pppd invokes scripts at various stages in its processing which can be
993 used to perform site-specific ancillary processing. These scripts are
994 usually shell scripts, but could be executable code files instead.
995 Pppd does not wait for the scripts to finish. The scripts are
996 executed as root (with the real and effective user-id set to 0), so
997 that they can do things such as update routing tables or run
998 privileged daemons. Be careful that the contents of these scripts do
999 not compromise your system's security. Pppd runs the scripts with
1000 standard input, output and error redirected to /dev/null, and with an
1001 environment that is empty except for some environment variables that
1002 give information about the link. The environment variables that pppd
1006 The name of the serial tty device being used.
1009 The name of the network interface being used.
1012 The IP address for the local end of the link. This is only set when
1016 The IP address for the remote end of the link. This is only set when
1020 The authenticated name of the peer. This is only set if the peer
1021 authenticates itself.
1024 The baud rate of the tty device.
1027 The real user-id of the user who invoked pppd.
1029 Pppd invokes the following scripts, if they exist. It is not an error
1030 if they don't exist.
1033 A program or script which is executed after the remote system
1034 successfully authenticates itself. It is executed with the parameters
1036 \fIinterface-name peer-name user-name tty-device speed\fR
1038 Note that this script is not executed if the peer doesn't authenticate
1039 itself, for example when the \fInoauth\fR option is used.
1041 .B /etc/ppp/auth-down
1042 A program or script which is executed when the link goes down, if
1043 /etc/ppp/auth-up was previously executed. It is executed in the same
1044 manner with the same parameters as /etc/ppp/auth-up.
1047 A program or script which is executed when the link is available for
1048 sending and receiving IP packets (that is, IPCP has come up). It is
1049 executed with the parameters
1051 \fIinterface-name tty-device speed local-IP-address
1052 remote-IP-address ipparam\fR
1055 A program or script which is executed when the link is no longer
1056 available for sending and receiving IP packets. This script can be
1057 used for undoing the effects of the /etc/ppp/ip-up script. It is
1058 invoked in the same manner and with the same parameters as the ip-up
1062 A program or script which is executed when the link is available for
1063 sending and receiving IPX packets (that is, IPXCP has come up). It is
1064 executed with the parameters
1066 \fIinterface-name tty-device speed network-number local-IPX-node-address
1067 remote-IPX-node-address local-IPX-routing-protocol remote-IPX-routing-protocol
1068 local-IPX-router-name remote-IPX-router-name ipparam pppd-pid\fR
1070 The local-IPX-routing-protocol and remote-IPX-routing-protocol field
1071 may be one of the following:
1073 NONE to indicate that there is no routing protocol
1075 RIP to indicate that RIP/SAP should be used
1077 NLSP to indicate that Novell NLSP should be used
1079 RIP NLSP to indicate that both RIP/SAP and NLSP should be used
1081 .B /etc/ppp/ipx-down
1082 A program or script which is executed when the link is no longer
1083 available for sending and receiving IPX packets. This script can be
1084 used for undoing the effects of the /etc/ppp/ipx-up script. It is
1085 invoked in the same manner and with the same parameters as the ipx-up
1089 .B /var/run/ppp\fIn\fB.pid \fR(BSD or Linux), \fB/etc/ppp/ppp\fIn\fB.pid \fR(others)
1090 Process-ID for pppd process on ppp interface unit \fIn\fR.
1092 .B /etc/ppp/pap-secrets
1093 Usernames, passwords and IP addresses for PAP authentication. This
1094 file should be owned by root and not readable or writable by any other
1095 user. Pppd will log a warning if this is not the case.
1097 .B /etc/ppp/chap-secrets
1098 Names, secrets and IP addresses for CHAP authentication. As for
1099 /etc/ppp/pap-secrets, this file should be owned by root and not
1100 readable or writable by any other user. Pppd will log a warning if
1101 this is not the case.
1104 System default options for pppd, read before user default options or
1105 command-line options.
1108 User default options, read before /etc/ppp/options.\fIttyname\fR.
1110 .B /etc/ppp/options.\fIttyname
1111 System default options for the serial port being used, read after
1112 ~/.ppprc. In forming the \fIttyname\fR part of this
1113 filename, an initial /dev/ is stripped from the port name (if
1114 present), and any slashes in the remaining part are converted to
1118 A directory containing options files which may contain privileged
1119 options, even if pppd was invoked by a user other than root. The
1120 system administrator can create options files in this directory to
1121 permit non-privileged users to dial out without requiring the peer to
1122 authenticate, but only to certain trusted peers.
1124 .B /etc/ppp/ppp.deny
1125 Lists users who may not use the system password PAP authentication.
1127 .B /etc/ppp/ppp.shells
1128 Lists user shells which are approved for system password PAP authentication
1131 .B /usr/share/examples/pppd/
1132 Sample pppd configuration files.
1139 \fICompressing TCP/IP headers for low-speed serial links.\fR
1144 .I The MD5 Message-Digest Algorithm.
1149 .I PPP Internet Protocol Control Protocol (IPCP).
1153 Lloyd, B.; Simpson, W.A.
1154 .I PPP authentication protocols.
1159 .I The Point\-to\-Point Protocol (PPP).
1164 .I PPP in HDLC-like Framing.
1167 The following signals have the specified effect when sent to pppd.
1170 These signals cause pppd to terminate the link (by closing LCP),
1171 restore the serial device settings, and exit.
1174 This signal causes pppd to terminate the link, restore the serial
1175 device settings, and close the serial device. If the \fIpersist\fR or
1176 \fIdemand\fR option has been specified, pppd will try to reopen the
1177 serial device and start another connection (after the holdoff period).
1178 Otherwise pppd will exit. If this signal is received during the
1179 holdoff period, it causes pppd to end the holdoff period immediately.
1182 This signal toggles the state of the \fIdebug\fR option.
1185 This signal causes pppd to renegotiate compression. This can be
1186 useful to re-enable compression after it has been disabled as a result
1187 of a fatal decompression error. (Fatal decompression errors generally
1188 indicate a bug in one or other implementation.)
1191 Paul Mackerras (Paul.Mackerras@cs.anu.edu.au), based on earlier work by
lentferj's projects / dragonfly.git / blob