Generally use NULL instead of explicitly casting 0 to some pointer type (part2).
[dragonfly.git] / usr.sbin / pppd / pppd.8
1.\" manual page [] for pppd 2.3
2.\" $FreeBSD: src/usr.sbin/pppd/pppd.8,v 2003/03/11 22:31:30 trhodes Exp $
cabeba47 3.\" $DragonFly: src/usr.sbin/pppd/pppd.8,v 1.5 2007/11/23 23:16:37 swildner Exp $
4.\" SH section heading
5.\" SS subsection heading
6.\" LP paragraph
7.\" IP indented paragraph
8.\" TP hanging label
11pppd \- Point to Point Protocol daemon
13.B pppd
15.I tty_name
16] [
17.I speed
18] [
19.I options
23The Point-to-Point Protocol (PPP) provides a method for transmitting
24datagrams over serial point-to-point links. PPP
25is composed of three parts: a method for encapsulating datagrams over
26serial links, an extensible Link Control Protocol (LCP), and
27a family of Network Control Protocols (NCP) for establishing
28and configuring different network-layer protocols.
30The encapsulation scheme is provided by driver code in the kernel.
31Pppd provides the basic LCP, authentication support, and an NCP for
32establishing and configuring the Internet Protocol (IP) (called the IP
33Control Protocol, IPCP).
36.I <tty_name>
37Communicate over the named device. The string "/dev/" is prepended if
38necessary. If no device name is given, or if the name of the terminal
39connected to the standard input is given, pppd
40will use that terminal, and will not fork to put itself in the
41background. This option is privileged if the \fInoauth\fR option is
44.I <speed>
45Set the baud rate to <speed> (a decimal number). On systems such as
464.4BSD and NetBSD, any speed can be specified, providing that it is
47supported 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
51Specifies a packet filter to be applied to data packets to determine
52which packets are to be regarded as link activity, and therefore reset
53the idle timer, or cause the link to be brought up in demand-dialling
54mode. This option is useful in conjunction with the
55\fBidle\fR option if there are packets being sent or received
56regularly over the link (for example, routing information packets)
57which would otherwise prevent the link from ever appearing to be idle.
58The \fIfilter-expression\fR syntax is as described for tcpdump(1),
59except that qualifiers which are inappropriate for a PPP link, such as
60\fBether\fR and \fBarp\fR, are not permitted. Generally the filter
61expression should be enclosed in single-quotes to prevent whitespace
62in the expression from being interpreted by the shell.
63This option
64only available
65if both the kernel and pppd were compiled with PPP_FILTER defined.
67.B asyncmap \fI<map>
68Set the async character map to <map>. This map describes which
69control characters cannot be successfully received over the serial
70line. Pppd will ask the peer to send these characters as a 2-byte
71escape sequence. The argument is a 32 bit hex number with each bit
72representing a character to escape. Bit 0 (00000001) represents the
73character 0x00; bit 31 (80000000) represents the character 0x1f or ^_.
74If multiple \fIasyncmap\fR options are given, the values are ORed
75together. If no \fIasyncmap\fR option is given, no async character
76map will be negotiated for the receive direction; the peer should then
77escape \fIall\fR control characters. To escape transmitted
78characters, use the \fIescape\fR option.
80.B auth
81Require the peer to authenticate itself before allowing network
82packets to be sent or received.
84.B call \fIname
85Read options from the file /etc/ppp/peers/\fIname\fR. This file may
86contain privileged options, such as \fInoauth\fR, even if pppd
87is not being run by root. The \fIname\fR string may not begin with /
88or include .. as a pathname component. The format of the options file
89is described below.
91.B connect \fIscript
92Use the executable or shell command specified by \fIscript\fR to set
93up the serial line. This script would typically use the chat(8)
94program to dial the modem and start the remote ppp session. This
95option is privileged if the \fInoauth\fR option is used.
97.B connect-max-attempts \fI<n>
98Attempt dial-out connection to remote system no more than specified number
99of times (default = 1). If the connection is not made, pppd will exit.
100Requires that \fBpersist\fR has been specified.
102.B crtscts
103Use hardware flow control (i.e. RTS/CTS) to control the flow of data
104on the serial port. If neither the \fIcrtscts\fR nor the
105\fInocrtscts\fR option is given, the hardware flow control setting
106for the serial port is left unchanged.
108.B defaultroute
109Add a default route to the system routing tables, using the peer as
110the gateway, when IPCP negotiation is successfully completed.
111This entry is removed when the PPP connection is broken. This option
112is privileged if the \fInodefaultroute\fR option has been specified.
114.B disconnect \fIscript
115Run the executable or shell command specified by \fIscript\fR after
116pppd has terminated the link. This script could, for example, issue
117commands to the modem to cause it to hang up if hardware modem control
118signals were not available. The disconnect script is not run if the
119modem has already hung up. This option is privileged if the
120\fInoauth\fR option is used.
122.B escape \fIxx,yy,...
123Specifies that certain characters should be escaped on transmission
124(regardless of whether the peer requests them to be escaped with its
125async control character map). The characters to be escaped are
126specified as a list of hex numbers separated by commas. Note that
127almost any character can be specified for the \fIescape\fR option,
128unlike the \fIasyncmap\fR option which only allows control characters
129to be specified. The characters which may not be escaped are those
130with hex values 0x20 - 0x3f or 0x5e.
132.B file \fIname
133Read options from file \fIname\fR (the format is described below).
134The file must be readable by the user who has invoked pppd.
136.B lock
137Specifies that pppd should create a UUCP-style lock file for the
138serial device to ensure exclusive access to the device.
140.B mru \fIn
141Set the MRU [Maximum Receive Unit] value to \fIn\fR.
143will ask the peer to send packets of no more than \fIn\fR bytes. The
144minimum MRU value is 128. The default MRU value is 1500. A value of
145296 is recommended for slow links (40 bytes for TCP/IP header + 256
146bytes of data).
148.B mtu \fIn
149Set the MTU [Maximum Transmit Unit] value to \fIn\fR. Unless the
150peer requests a smaller value via MRU negotiation, pppd will
151request that the kernel networking code send data packets of no more
152than \fIn\fR bytes through the PPP network interface.
154.B passive
155Enables the "passive" option in the LCP. With this option, pppd will
156attempt to initiate a connection; if no reply is received from the
157peer, pppd will then just wait passively for a valid LCP packet from
158the peer, instead of exiting, as it would without this option.
161.I <local_IP_address>\fB:\fI<remote_IP_address>
162Set the local and/or remote interface IP addresses. Either one may be
163omitted. The IP addresses can be specified with a host name or in
164decimal dot notation (e.g. The default local
165address is the (first) IP address of the system (unless the
167option is given). The remote address will be obtained from the peer
168if not specified in any option. Thus, in simple cases, this option is
169not required. If a local and/or remote IP address is specified with
170this option, pppd
171will not accept a different value from the peer in the IPCP
172negotiation, unless the \fIipcp-accept-local\fR and/or
173\fIipcp-accept-remote\fR options are given, respectively.
175.B bsdcomp \fInr,nt
176Request that the peer compress packets that it sends, using the
177BSD-Compress scheme, with a maximum code size of \fInr\fR bits, and
178agree 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
180given 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
182consume more kernel memory for compression dictionaries.
183Alternatively, a value of 0 for \fInr\fR or \fInt\fR disables
184compression in the corresponding direction. Use \fInobsdcomp\fR or
185\fIbsdcomp 0\fR to disable BSD-Compress compression entirely.
187.B chap-interval \fIn
188If this option is given, pppd will rechallenge the peer every \fIn\fR
191.B chap-max-challenge \fIn
192Set the maximum number of CHAP challenge transmissions to \fIn\fR
193(default 10).
195.B chap-restart \fIn
196Set the CHAP restart interval (retransmission timeout for challenges)
197to \fIn\fR seconds (default 3).
199.B debug
200Enables connection debugging facilities.
201If this option is given, pppd will log the contents of all
202control packets sent or received in a readable form. The packets are
203logged 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)).
207.B default-asyncmap
208Disable asyncmap negotiation, forcing all control characters to be
209escaped for both the transmit and the receive direction.
211.B default-mru
212Disable MRU [Maximum Receive Unit] negotiation. With this option,
213pppd will use the default MRU value of 1500 bytes for both the
214transmit and receive direction.
216.B deflate \fInr,nt
217Request that the peer compress packets that it sends, using the
218Deflate scheme, with a maximum window size of \fI2**nr\fR bytes, and
219agree to compress packets sent to the peer with a maximum window size
220of \fI2**nt\fR bytes. If \fInt\fR is not specified, it defaults to
221the value given for \fInr\fR. Values in the range 8 to 15 may be used
222for \fInr\fR and \fInt\fR; larger values give better compression but
223consume more kernel memory for compression dictionaries.
224Alternatively, a value of 0 for \fInr\fR or \fInt\fR disables
225compression in the corresponding direction. Use \fInodeflate\fR or
226\fIdeflate 0\fR to disable Deflate compression entirely. (Note: pppd
227requests Deflate compression in preference to BSD-Compress if the peer
228can do either.)
230.B demand
231Initiate the link only on demand, i.e. when data traffic is present.
232With this option, the remote IP address must be specified by the user
233on the command line or in an options file. Pppd will initially
234configure the interface and enable it for IP traffic without
235connecting to the peer. When traffic is available, pppd will
236connect to the peer and perform negotiation, authentication, etc.
237When this is completed, pppd will commence passing data packets
238(i.e., IP packets) across the link.
240The \fIdemand\fR option implies the \fIpersist\fR option. If this
241behaviour is not desired, use the \fInopersist\fR option after the
242\fIdemand\fR option. The \fIidle\fR and \fIholdoff\fR
3f5e28f4 243options are also useful in conjunction with the \fIdemand\fR option.
245.B domain \fId
246Append the domain name \fId\fR to the local host name for authentication
247purposes. For example, if gethostname() returns the name porsche, but
248the fully qualified domain name is porsche.Quotron.COM, you could
249specify \fIdomain Quotron.COM\fR. Pppd would then use the name
250\fIporsche.Quotron.COM\fR for looking up secrets in the secrets file,
251and as the default name to send to the peer when authenticating itself
252to the peer. This option is privileged.
254.B holdoff \fIn
255Specifies how many seconds to wait before re-initiating the link after
256it terminates. This option only has any effect if the \fIpersist\fR
257or \fIdemand\fR option is used. The holdoff period is not applied if
258the link was terminated because it was idle.
260.B idle \fIn
261Specifies that pppd should disconnect if the link is idle for \fIn\fR
262seconds. The link is idle when no data packets (i.e. IP packets) are
263being sent or received. Note: it is not advisable to use this option
264with the \fIpersist\fR option without the \fIdemand\fR option.
265If the \fBactive-filter\fR
266option is given, data packets which are rejected by the specified
267activity filter also count as the link being idle.
269.B ipcp-accept-local
270With this option, pppd will accept the peer's idea of our local IP
271address, even if the local IP address was specified in an option.
273.B ipcp-accept-remote
274With this option, pppd will accept the peer's idea of its (remote) IP
275address, even if the remote IP address was specified in an option.
277.B ipcp-max-configure \fIn
278Set the maximum number of IPCP configure-request transmissions to
279\fIn\fR (default 10).
281.B ipcp-max-failure \fIn
282Set the maximum number of IPCP configure-NAKs returned before starting
283to send configure-Rejects instead to \fIn\fR (default 10).
285.B ipcp-max-terminate \fIn
286Set the maximum number of IPCP terminate-request transmissions to
287\fIn\fR (default 3).
289.B ipcp-restart \fIn
290Set the IPCP restart interval (retransmission timeout) to \fIn\fR
291seconds (default 3).
293.B ipparam \fIstring
294Provides an extra parameter to the ip-up and ip-down scripts. If this
295option is given, the \fIstring\fR supplied is given as the 6th
296parameter to those scripts.
298.B ipx
299Enable the IPXCP and IPX protocols. This option is presently only
300supported under Linux, and only if your kernel has been configured to
301include IPX support.
303.B ipx-network \fIn
304Set the IPX network number in the IPXCP configure request frame to
305\fIn\fR, a hexadecimal number (without a leading 0x). There is no
306valid default. If this option is not specified, the network number is
307obtained from the peer. If the peer does not have the network number,
308the IPX protocol will not be started.
310.B ipx-node \fIn\fB:\fIm
311Set the IPX node numbers.
312The two node numbers are separated from each
313other with a colon character.
314The first number \fIn\fR is the local
315node number.
316The second number \fIm\fR is the peer's node number.
318node number is a hexadecimal number, at most 10 digits long.
319The node
320numbers on the ipx-network must be unique.
321There is no valid
323If this option is not specified then the node numbers are
324obtained from the peer.
326.B ipx-router-name \fI<string>
327Set the name of the router.
328This is a string and is sent to the peer
329as information data.
331.B ipx-routing \fIn
332Set the routing protocol to be received by this option.
333More than one
334instance of \fIipx-routing\fR may be specified.
335The '\fInone\fR'
336option (0) may be specified as the only instance of ipx-routing.
338values 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
342Accept the peer's NAK for the node number specified in the ipx-node
344If a node number was specified, and non-zero, the default is
345to insist that the value be used.
346If you include this option then you
347will permit the peer to override the entry of the node number.
349.B ipxcp-accept-network
350Accept the peer's NAK for the network number specified in the
351ipx-network option.
352If a network number was specified, and non-zero, the
353default is to insist that the value be used.
354If you include this
355option then you will permit the peer to override the entry of the node
358.B ipxcp-accept-remote
359Use the peer's network number specified in the configure request
361If a node number was specified for the peer and this option was
362not specified, the peer will be forced to use the value which you have
365.B ipxcp-max-configure \fIn
366Set the maximum number of IPXCP configure request frames which the
367system will send to \fIn\fR.
368The default is 10.
370.B ipxcp-max-failure \fIn
371Set the maximum number of IPXCP NAK frames which the local system will
372send before it rejects the options.
373The default value is 3.
375.B ipxcp-max-terminate \fIn
3f5e28f4 376Set the maximum number of IPXCP terminate request frames before the
377local system considers that the peer is not listening to them.
379default value is 3.
381.B kdebug \fIn
382Enable 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
384enable general debug messages, 2 to request that the contents of
385received packets be printed, and 4 to request that the contents of
386transmitted packets be printed. On most systems, messages printed by
387the 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
391If this option is given, pppd will presume the peer to be dead
392if \fIn\fR LCP echo-requests are sent without receiving a valid LCP
393echo-reply. If this happens, pppd will terminate the
394connection. Use of this option requires a non-zero value for the
395\fIlcp-echo-interval\fR parameter. This option can be used to enable
396pppd to terminate after the physical connection has been broken
397(e.g., the modem has hung up) in situations where no hardware modem
398control lines are available.
400.B lcp-echo-interval \fIn
401If this option is given, pppd will send an LCP echo-request frame to
402the peer every \fIn\fR seconds. Normally the peer should respond to
403the echo-request by sending an echo-reply. This option can be used
404with the \fIlcp-echo-failure\fR option to detect that the peer is no
405longer connected.
407.B lcp-max-configure \fIn
408Set the maximum number of LCP configure-request transmissions to
409\fIn\fR (default 10).
411.B lcp-max-failure \fIn
412Set the maximum number of LCP configure-NAKs returned before starting
413to send configure-Rejects instead to \fIn\fR (default 10).
415.B lcp-max-terminate \fIn
416Set the maximum number of LCP terminate-request transmissions to
417\fIn\fR (default 3).
419.B lcp-restart \fIn
420Set the LCP restart interval (retransmission timeout) to \fIn\fR
421seconds (default 3).
423.B local
424Don't use the modem control lines. With this option, pppd will ignore
425the state of the CD (Carrier Detect) signal from the modem and will
426not change the state of the DTR (Data Terminal Ready) signal.
428.B login
429Use the system password database for authenticating the peer using
430PAP, and record the user in the system wtmp file. Note that the peer
431must have an entry in the /etc/ppp/pap-secrets file as well as the
432system password database to be allowed access.
434.B maxconnect \fIn
435Terminate the connection when it has been available for network
436traffic for \fIn\fR seconds (i.e. \fIn\fR seconds after the first
437network control protocol comes up).
439.B modem
440Use the modem control lines. This option is the default. With this
441option, pppd will wait for the CD (Carrier Detect) signal from the
442modem to be asserted when opening the serial device (unless a connect
443script is specified), and it will drop the DTR (Data Terminal Ready)
444signal briefly when the connection is terminated and before executing
445the connect script. On Ultrix, this option implies hardware flow
446control, as for the \fIcrtscts\fR option.
448.B ms-dns \fI<addr>
449If pppd is acting as a server for Microsoft Windows clients, this
450option allows pppd to supply one or two DNS (Domain Name Server)
451addresses to the clients. The first instance of this option specifies
452the primary DNS address; the second instance (if given) specifies the
453secondary DNS address. (This option was present in some older
454versions of pppd under the name \fBdns-addr\fR.)
456.B ms-wins \fI<addr>
457If pppd is acting as a server for Microsoft Windows or "Samba"
458clients, this option allows pppd to supply one or two WINS (Windows
459Internet Name Services) server addresses to the clients. The first
460instance of this option specifies the primary WINS address; the second
461instance (if given) specifies the secondary WINS address.
463.B name \fIname
464Set the name of the local system for authentication purposes to
465\fIname\fR. This is a privileged option. With this option, pppd will
466use lines in the secrets files which have \fIname\fR as the second
467field when looking for a secret to use in authenticating the peer. In
468addition, unless overridden with the \fIuser\fR option, \fIname\fR
469will be used as the name to send to the peer when authenticating the
470local system to the peer. (Note that pppd does not append the domain
471name to \fIname\fR.)
473.B netmask \fIn
474Set the interface netmask to \fIn\fR, a 32 bit netmask in "decimal dot"
475notation (e.g. If this option is given, the value
476specified is ORed with the default netmask. The default netmask is
477chosen based on the negotiated remote IP address; it is the
478appropriate network mask for the class of the remote IP address, ORed
479with the netmasks for any non point-to-point network interfaces in the
480system which are on the same network.
482.B noaccomp
483Disable Address/Control compression in both directions (send and
486.B noauth
487Do not require the peer to authenticate itself. This option is
488privileged if the \fIauth\fR option is specified in /etc/ppp/options.
490.B nobsdcomp
491Disables BSD-Compress compression; \fBpppd\fR will not request or
492agree to compress packets using the BSD-Compress scheme.
494.B noccp
495Disable CCP (Compression Control Protocol) negotiation. This option
496should only be required if the peer is buggy and gets confused by
497requests from pppd for CCP negotiation.
499.B nocrtscts
500Disable hardware flow control (i.e. RTS/CTS) on the serial port. If
501neither the \fIcrtscts\fR nor the \fInocrtscts\fR option is given,
502the hardware flow control setting for the serial port is left
505.B nodefaultroute
506Disable the \fIdefaultroute\fR option. The system administrator who
507wishes to prevent users from creating default routes with pppd
508can do so by placing this option in the /etc/ppp/options file.
510.B nodeflate
511Disables Deflate compression; pppd will not request or agree to
512compress packets using the Deflate scheme.
514.B nodetach
515Don't detach from the controlling terminal. Without this option, if a
516serial device other than the terminal on the standard input is
517specified, pppd will fork to become a background process.
519.B noip
520Disable IPCP negotiation and IP communication. This option should
521only be required if the peer is buggy and gets confused by requests
522from pppd for IPCP negotiation.
524.B noipdefault
525Disables the default behaviour when no local IP address is specified,
526which is to determine (if possible) the local IP address from the
527hostname. With this option, the peer will have to supply the local IP
528address during IPCP negotiation (unless it specified explicitly on the
529command line or in an options file).
531.B noipx
532Disable the IPXCP and IPX protocols. This option should only be
533required if the peer is buggy and gets confused by requests from pppd
534for IPXCP negotiation.
536.B nomagic
537Disable magic number negotiation. With this option, pppd cannot
538detect a looped-back line. This option should only be needed if the
539peer is buggy.
541.B nopcomp
542Disable protocol field compression negotiation in both the receive and
543the transmit direction.
545.B nopersist
546Exit once a connection has been made and terminated. This is the
547default unless the \fIpersist\fR or \fIdemand\fR option has been
550.B nopredictor1
551Do not accept or agree to Predictor-1 compression.
553.B noproxyarp
554Disable the \fIproxyarp\fR option. The system administrator who
555wishes to prevent users from creating proxy ARP entries with pppd can
556do so by placing this option in the /etc/ppp/options file.
558.B novj
559Disable Van Jacobson style TCP/IP header compression in both the
560transmit and the receive direction.
562.B novjccomp
563Disable the connection-ID compression option in Van Jacobson style
564TCP/IP header compression. With this option, pppd will not omit the
565connection-ID byte from Van Jacobson compressed TCP/IP headers, nor
566ask the peer to do so.
568.B papcrypt
569Indicates that all secrets in the /etc/ppp/pap-secrets file which are
570used for checking the identity of the peer are encrypted, and thus
571pppd should not accept a password which, before encryption, is
572identical to the secret from the /etc/ppp/pap-secrets file.
574.B pap-max-authreq \fIn
575Set the maximum number of PAP authenticate-request transmissions to
576\fIn\fR (default 10).
578.B pap-restart \fIn
579Set the PAP restart interval (retransmission timeout) to \fIn\fR
580seconds (default 3).
582.B pap-timeout \fIn
583Set the maximum time that pppd will wait for the peer to authenticate
584itself with PAP to \fIn\fR seconds (0 means no limit).
586.B pass-filter \fIfilter-expression
587Specifies a packet filter to applied to data packets being sent or
588received to determine which packets should be allowed to pass.
589Packets which are rejected by the filter are silently discarded. This
590option can be used to prevent specific network daemons (such as
591routed) using up link bandwidth, or to provide a basic firewall
593The \fIfilter-expression\fR syntax is as described for tcpdump(1),
594except that qualifiers which are inappropriate for a PPP link, such as
595\fBether\fR and \fBarp\fR, are not permitted. Generally the filter
596expression should be enclosed in single-quotes to prevent whitespace
597in the expression from being interpreted by the shell. Note that it
598is possible to apply different constraints to incoming and outgoing
599packets using the \fBinbound\fR and \fBoutbound\fR qualifiers.
601option is currently only available under NetBSD, and then only if both
602the kernel and pppd were compiled with PPP_FILTER defined.
604.B persist
605Do not exit after a connection is terminated; instead try to reopen
606the connection.
608.B predictor1
609Request that the peer compress frames that it sends using Predictor-1
610compression, and agree to compress transmitted frames with Predictor-1
611if requested. This option has no effect unless the kernel driver
612supports Predictor-1 compression.
614.B proxyarp
615Add an entry to this system's ARP [Address Resolution Protocol] table
616with the IP address of the peer and the Ethernet address of this
617system. This will have the effect of making the peer appear to other
618systems to be on the local ethernet.
620.B remotename \fIname
621Set the assumed name of the remote system for authentication purposes
622to \fIname\fR.
624.B refuse-chap
625With this option, pppd will not agree to authenticate itself to the
626peer using CHAP.
628.B refuse-pap
629With this option, pppd will not agree to authenticate itself to the
630peer using PAP.
632.B require-chap
633Require the peer to authenticate itself using CHAP [Challenge
634Handshake Authentication Protocol] authentication.
636.B require-pap
637Require the peer to authenticate itself using PAP [Password
638Authentication Protocol] authentication.
640.B silent
641With this option, pppd will not transmit LCP packets to initiate a
642connection until a valid LCP packet is received from the peer (as for
643the `passive' option with ancient versions of pppd).
645.B usehostname
646Enforce the use of the hostname (with domain name appended, if given)
647as the name of the local system for authentication purposes (overrides
648the \fIname\fR option).
650.B user \fIname
651Sets the name used for authenticating the local system to the peer to
654.B vj-max-slots \fIn
655Sets the number of connection slots to be used by the Van Jacobson
656TCP/IP header compression and decompression code to \fIn\fR, which
657must be between 2 and 16 (inclusive).
659.B welcome \fIscript
660Run the executable or shell command specified by \fIscript\fR before
661initiating PPP negotiation, after the connect script (if any) has
662completed. This option is privileged if the \fInoauth\fR option is
665.B xonxoff
666Use software flow control (i.e. XON/XOFF) to control the flow of data on
667the serial port.
669Options can be taken from files as well as the command line. Pppd
670reads options from the files /etc/ppp/options, ~/.ppprc and
671/etc/ppp/options.\fIttyname\fR (in that order) before processing the
672options on the command line. (In fact, the command-line options are
673scanned to find the terminal name before the options.\fIttyname\fR
674file is read.) In forming the name of the options.\fIttyname\fR file,
675the initial /dev/ is removed from the terminal name, and any remaining
676/ characters are replaced with dots.
678An options file is parsed into a series of words, delimited by
679whitespace. Whitespace can be included in a word by enclosing the
680word in double-quotes ("). A backslash (\\) quotes the following character.
681A hash (#) starts a comment, which continues until the end of the
682line. There is no restriction on using the \fIfile\fR or \fIcall\fR
683options within an options file.
685.I pppd
686provides system administrators with sufficient access control that PPP
687access to a server machine can be provided to legitimate users without
688fear of compromising the security of the server or the network it's
689on. In part this is provided by the /etc/ppp/options file, where the
690administrator can place options to restrict the ways in which pppd can
691be used, and in part by the PAP and CHAP secrets files, where the
692administrator can restrict the set of IP addresses which individual
693users may use.
695The normal way that pppd should be set up is to have the \fIauth\fR
696option in the /etc/ppp/options file. (This may become the default in
697later releases.) If users wish to use pppd to dial out to a peer
698which will refuse to authenticate itself (such as an internet service
699provider), the system administrator should create an options file
700under /etc/ppp/peers containing the \fInoauth\fR option, the name of
701the serial port to use, and the \fIconnect\fR option (if required),
702plus any other appropriate options. In this way, pppd can be set up
703to allow non-privileged users to make unauthenticated connections only
704to trusted peers.
706As indicated above, some security-sensitive options are privileged,
707which means that they may not be used by an ordinary non-privileged
708user running a setuid-root pppd, either on the command line, in the
709user's ~/.ppprc file, or in an options file read using the \fIfile\fR
710option. Privileged options may be used in /etc/ppp/options file or in
711an options file read using the \fIcall\fR option. If pppd is being
712run by the root user, privileged options can be used without
715Authentication is the process whereby one peer convinces the other of
716its identity. This involves the first peer sending its name to the
717other, together with some kind of secret information which could only
718come from the genuine authorized user of that name. In such an
719exchange, 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
721server, and the server also has a name by which it identifies itself
722to the client. Generally the genuine client shares some secret (or
723password) with the server, and authenticates itself by proving that it
724knows that secret. Very often, the names used for authentication
725correspond to the internet hostnames of the peers, but this is not
728At present, pppd supports two authentication protocols: the Password
729Authentication Protocol (PAP) and the Challenge Handshake
730Authentication Protocol (CHAP). PAP involves the client sending its
731name and a cleartext password to the server to authenticate itself.
732In contrast, the server initiates the CHAP authentication exchange by
733sending a challenge to the client (the challenge packet includes the
734server's name). The client must respond with a response which
735includes its name plus a hash value derived from the shared secret and
736the challenge, in order to prove that it knows the secret.
738The PPP protocol, being symmetrical, allows both peers to require the
739other to authenticate itself. In that case, two separate and
740independent authentication exchanges will occur. The two exchanges
741could use different authentication protocols, and in principle,
742different names could be used in the two exchanges.
744The default behaviour of pppd is to agree to authenticate if
745requested, and to not require authentication from the peer. However,
746pppd will not agree to authenticate itself with a particular protocol
747if it has no secrets which could be used to do so.
749Pppd stores secrets for use in authentication in secrets
750files (/etc/ppp/pap-secrets for PAP, /etc/ppp/chap-secrets for CHAP).
751Both secrets files have the same format. The secrets files can
752contain secrets for pppd to use in authenticating itself to other
753systems, as well as secrets for pppd to use when authenticating other
754systems to itself.
756Each line in a secrets file contains one secret. A given secret is
757specific to a particular combination of client and server - it can
758only be used by that client to authenticate itself to that server.
759Thus each line in a secrets file has at least 3 fields: the name of
760the client, the name of the server, and the secret. These fields may
761be followed by a list of the IP addresses that the specified client
762may use when connecting to the specified server.
764A secrets file is parsed into words as for an options file, so the
765client name, server name and secrets fields must each be one word,
766with any embedded spaces or other special characters quoted or
767escaped. Any following words on the same line are taken to be a list
768of acceptable IP addresses for that client, or an
769override for "local:remote" addresses (the same format used on the
770command line or in the options file) when on a line that contains a
771specific client name (not a wildcard nor empty).
772If there are only 3 words
773on the line, or if the first word is "-", then all IP addresses are
774disallowed. To allow any address, use "*".
775A word starting with "!" indicates that the
776specified address is \fInot\fR acceptable. An address may be followed
777by "/" and a number \fIn\fR, to indicate a whole subnet, i.e. all
778addresses which have the same value in the most significant \fIn\fR
779bits. Note that case is significant in the client and server names
780and in the secret.
782If the secret starts with an `@', what follows is assumed to be the
783name of a file from which to read the secret. A "*" as the client or
784server name matches any name. When selecting a secret, pppd takes the
785best match, i.e. the match with the fewest wildcards.
787Thus a secrets file contains both secrets for use in authenticating
788other hosts, plus secrets which we use for authenticating ourselves to
789others. When pppd is authenticating the peer (checking the peer's
790identity), it chooses a secret with the peer's name in the first
791field and the name of the local system in the second field. The
792name of the local system defaults to the hostname, with the domain
793name appended if the \fIdomain\fR option is used. This default can be
794overridden with the \fIname\fR option, except when the
795\fIusehostname\fR option is used.
797When pppd is choosing a secret to use in authenticating itself to the
798peer, it first determines what name it is going to use to identify
799itself 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
801the name of the local system, determined as described in the previous
802paragraph. Then pppd looks for a secret with this name in the first
803field and the peer's name in the second field. Pppd will know the
804name of the peer if CHAP authentication is being used, because the
805peer will have sent it in the challenge packet. However, if PAP is being
806used, pppd will have to determine the peer's name from the options
807specified by the user. The user can specify the peer's name directly
808with the \fIremotename\fR option. Otherwise, if the remote IP address
809was specified by a name (rather than in numeric form), that name will
810be used as the peer's name. Failing that, pppd will use the null
811string as the peer's name.
813When authenticating the peer with PAP, the supplied password is first
814compared with the secret from the secrets file. If the password
815doesn't match the secret, the password is encrypted using crypt() and
816checked against the secret again. Thus secrets for authenticating the
817peer can be stored in encrypted form if desired. If the
818\fIpapcrypt\fR option is given, the first (unencrypted) comparison is
819omitted, for better security.
821Furthermore, if the \fIlogin\fR option was specified, the username and
822password are also checked against the system password database. Thus,
823the system administrator can set up the pap-secrets file to allow PPP
824access only to certain users, and to restrict the set of IP addresses
825that each user can use. Typically, when using the \fIlogin\fR option,
826the secret in /etc/ppp/pap-secrets would be "", which will match any
827password supplied by the peer. This avoids the need to have the same
828secret in two places.
830Additional checks are performed when the \fBlogin\fR option is used.
831If the file /etc/ppp/ppp.deny exists, and the user is listed in it,
832the authentication fails. If the file /etc/ppp/ppp.shells exists and
833the user's normal login shell is not listed, the authentication fails.
835Authentication must be satisfactorily completed before IPCP (or any
836other Network Control Protocol) can be started. If the peer is
837required to authenticate itself, and fails to do so, pppd will
838terminated the link (by closing LCP). If IPCP negotiates an
839unacceptable IP address for the remote host, IPCP will be closed. IP
840packets can only be sent or received when IPCP is open.
842In some cases it is desirable to allow some hosts which can't
843authenticate themselves to connect and use one of a restricted set of
844IP addresses, even when the local host generally requires
845authentication. If the peer refuses to authenticate itself when
846requested, pppd takes that as equivalent to authenticating with PAP
847using the empty string for the username and password. Thus, by adding
848a line to the pap-secrets file which specifies the empty string for
849the client and password, it is possible to allow restricted access to
850hosts which refuse to authenticate themselves.
853When IPCP negotiation is completed successfully, pppd will inform the
854kernel of the local and remote IP addresses for the ppp interface.
855This is sufficient to create a host route to the remote end of the
856link, which will enable the peers to exchange IP packets.
857Communication with other machines generally requires further
858modification to routing tables and/or ARP (Address Resolution
859Protocol) tables. In most cases the \fIdefaultroute\fR and/or
860\fIproxyarp\fR options are sufficient for this, but in some cases
861further intervention is required. The /etc/ppp/ip-up script can be
862used for this.
864Sometimes it is desirable to add a default route through the remote
865host, as in the case of a machine whose only connection to the
866Internet is through the ppp interface. The \fIdefaultroute\fR option
867causes pppd to create such a default route when IPCP comes up, and
868delete it when the link is terminated.
870In some cases it is desirable to use proxy ARP, for example on a
871server machine connected to a LAN, in order to allow other hosts to
872communicate with the remote host. The \fIproxyarp\fR option causes
873pppd to look for a network interface on the same subnet as the remote
874host (an interface supporting broadcast and ARP, which is up and not a
875point-to-point or loopback interface). If found, pppd creates a
876permanent, published ARP entry with the IP address of the remote host
877and the hardware address of the network interface found.
879When the \fIdemand\fR option is used, the interface IP addresses have
880already been set at the point when IPCP comes up. If pppd has not
881been able to negotiate the same addresses that it used to configure
882the interface (for example when the peer is an ISP that uses dynamic
883IP address assignment), pppd has to change the interface IP addresses
884to the negotiated addresses. This may disrupt existing connections,
885and the use of demand dialling with peers that do dynamic IP address
886assignment is not recommended.
889The following examples assume that the /etc/ppp/options file contains
890the \fIauth\fR option (as in the default /etc/ppp/options file in the
891ppp distribution).
893Probably the most common use of pppd is to dial out to an ISP. This
894can be done with a command such as
896pppd call isp
898where the /etc/ppp/peers/isp file is set up by the system
899administrator to contain something like this:
901ttyS0 19200 crtscts
903connect '/usr/sbin/chat -v -f /etc/ppp/chat-isp'
907In this example, we are using chat to dial the ISP's modem and go
908through any logon sequence required. The /etc/ppp/chat-isp file
909contains the script used by chat; it could for example contain
910something like this:
922ABORT "Username/Password Incorrect"
924"" "at"
926OK "at&d0&c1"
928OK "atdt2468135"
930"name:" "^Umyuserid"
932"word:" "\\qmypassword"
934"ispts" "\\q^Uppp"
938See the chat(8) man page for details of chat scripts.
940Pppd can also be used to provide a dial-in ppp service for users. If
941the users already have login accounts, the simplest way to set up the
942ppp service is to let the users log in to their accounts and run pppd
943(installed setuid-root) with a command such as
945pppd proxyarp
947To allow a user to use the PPP facilities, you need to allocate an IP
948address for that user's machine and create an entry in
949/etc/ppp/pap-secrets or /etc/ppp/chap-secrets (depending on which
950authentication method the PPP implementation on the user's machine
951supports), so that the user's
952machine can authenticate itself. For example, if Joe has a machine
953called "joespc" which is to be allowed to dial in to the machine
954called "server" and use the IP address, you would add an
955entry like this to /etc/ppp/pap-secrets or /etc/ppp/chap-secrets:
957joespc server "joe's secret"
959Alternatively, you can create a username called (for example) "ppp",
960whose login shell is pppd and whose home directory is /etc/ppp.
961Options to be used when pppd is run this way can be put in
964If your serial connection is any more complicated than a piece of
965wire, you may need to arrange for some control characters to be
966escaped. In particular, it is often useful to escape XON (^Q) and
967XOFF (^S), using \fIasyncmap a0000\fR. If the path includes a telnet,
968you probably should escape ^] as well (\fIasyncmap 200a0000\fR). If
969the path includes an rlogin, you will need to use the \fIescape ff\fR
970option on the end which is running the rlogin client, since many
971rlogin implementations are not transparent; they will remove the
972sequence [0xff, 0xff, 0x73, 0x73, followed by any 8 bytes] from the
976Messages are sent to the syslog daemon using facility LOG_DAEMON.
56be8454 977(This can be overridden by recompiling pppd with the macro
978LOG_PPP defined as the desired facility.) In order to see the error
979and debug messages, you will need to edit your /etc/syslog.conf file
980to direct the messages to the desired output device or file.
982The \fIdebug\fR option causes the contents of all control packets sent
983or received to be logged, that is, all LCP, PAP, CHAP or IPCP packets.
984This can be useful if the PPP negotiation does not succeed or if
985authentication fails.
986If debugging is enabled at compile time, the \fIdebug\fR option also
987causes other debugging messages to be logged.
989Debugging can also be enabled or disabled by sending a SIGUSR1 signal
990to the pppd process. This signal acts as a toggle.
992Pppd invokes scripts at various stages in its processing which can be
993used to perform site-specific ancillary processing. These scripts are
994usually shell scripts, but could be executable code files instead.
995Pppd does not wait for the scripts to finish. The scripts are
996executed as root (with the real and effective user-id set to 0), so
997that they can do things such as update routing tables or run
998privileged daemons. Be careful that the contents of these scripts do
999not compromise your system's security. Pppd runs the scripts with
1000standard input, output and error redirected to /dev/null, and with an
1001environment that is empty except for some environment variables that
1002give information about the link. The environment variables that pppd
1003sets are:
1006The name of the serial tty device being used.
1009The name of the network interface being used.
1012The IP address for the local end of the link. This is only set when
1013IPCP has come up.
1016The IP address for the remote end of the link. This is only set when
1017IPCP has come up.
1020The authenticated name of the peer. This is only set if the peer
1021authenticates itself.
1023.B SPEED
1024The baud rate of the tty device.
1026.B UID
1027The real user-id of the user who invoked pppd.
1029Pppd invokes the following scripts, if they exist. It is not an error
1030if they don't exist.
1032.B /etc/ppp/auth-up
1033A program or script which is executed after the remote system
1034successfully authenticates itself. It is executed with the parameters
1036\fIinterface-name peer-name user-name tty-device speed\fR
1038Note that this script is not executed if the peer doesn't authenticate
1039itself, for example when the \fInoauth\fR option is used.
1041.B /etc/ppp/auth-down
1042A 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
1044manner with the same parameters as /etc/ppp/auth-up.
1046.B /etc/ppp/ip-up
1047A program or script which is executed when the link is available for
1048sending and receiving IP packets (that is, IPCP has come up). It is
1049executed with the parameters
1051\fIinterface-name tty-device speed local-IP-address
1052remote-IP-address ipparam\fR
1054.B /etc/ppp/ip-down
1055A program or script which is executed when the link is no longer
1056available for sending and receiving IP packets. This script can be
1057used for undoing the effects of the /etc/ppp/ip-up script. It is
1058invoked in the same manner and with the same parameters as the ip-up
1061.B /etc/ppp/ipx-up
1062A program or script which is executed when the link is available for
1063sending and receiving IPX packets (that is, IPXCP has come up). It is
1064executed with the parameters
1066\fIinterface-name tty-device speed network-number local-IPX-node-address
1067remote-IPX-node-address local-IPX-routing-protocol remote-IPX-routing-protocol
1068local-IPX-router-name remote-IPX-router-name ipparam pppd-pid\fR
1070The local-IPX-routing-protocol and remote-IPX-routing-protocol field
1071may be one of the following:
1073NONE to indicate that there is no routing protocol
1075RIP to indicate that RIP/SAP should be used
1077NLSP to indicate that Novell NLSP should be used
1079RIP NLSP to indicate that both RIP/SAP and NLSP should be used
1081.B /etc/ppp/ipx-down
1082A program or script which is executed when the link is no longer
1083available for sending and receiving IPX packets. This script can be
1084used for undoing the effects of the /etc/ppp/ipx-up script. It is
1085invoked in the same manner and with the same parameters as the ipx-up
1089.B /var/run/ppp\fIn\ \fR(BSD or Linux), \fB/etc/ppp/ppp\fIn\ \fR(others)
1090Process-ID for pppd process on ppp interface unit \fIn\fR.
1092.B /etc/ppp/pap-secrets
1093Usernames, passwords and IP addresses for PAP authentication. This
1094file should be owned by root and not readable or writable by any other
1095user. Pppd will log a warning if this is not the case.
1097.B /etc/ppp/chap-secrets
1098Names, secrets and IP addresses for CHAP authentication. As for
1099/etc/ppp/pap-secrets, this file should be owned by root and not
1100readable or writable by any other user. Pppd will log a warning if
1101this is not the case.
1103.B /etc/ppp/options
1104System default options for pppd, read before user default options or
1105command-line options.
1107.B ~/.ppprc
1108User default options, read before /etc/ppp/options.\fIttyname\fR.
1110.B /etc/ppp/options.\fIttyname
1111System default options for the serial port being used, read after
1112~/.ppprc. In forming the \fIttyname\fR part of this
1113filename, an initial /dev/ is stripped from the port name (if
1114present), and any slashes in the remaining part are converted to
1117.B /etc/ppp/peers
1118A directory containing options files which may contain privileged
1119options, even if pppd was invoked by a user other than root. The
1120system administrator can create options files in this directory to
1121permit non-privileged users to dial out without requiring the peer to
1122authenticate, but only to certain trusted peers.
1124.B /etc/ppp/ppp.deny
1125Lists users who may not use the system password PAP authentication.
1127.B /etc/ppp/ppp.shells
1128Lists user shells which are approved for system password PAP authentication
1131.B /usr/share/examples/pppd/
1132Sample pppd configuration files.
1134.IR chat(8),
1135.IR ppp(8)
cabeba47 1137.B RFC 1144
1138Jacobson, V.
1139\fICompressing TCP/IP headers for low-speed serial links.\fR
1140February 1990.
cabeba47 1142.B RFC 1321
1143Rivest, R.
1144.I The MD5 Message-Digest Algorithm.
1145April 1992.
cabeba47 1147.B RFC 1332
1148McGregor, G.
1149.I PPP Internet Protocol Control Protocol (IPCP).
1150May 1992.
cabeba47 1152.B RFC 1334
1153Lloyd, B.; Simpson, W.A.
1154.I PPP authentication protocols.
1155October 1992.
cabeba47 1157.B RFC 1661
1158Simpson, W.A.
1159.I The Point\-to\-Point Protocol (PPP).
1160July 1994.
cabeba47 1162.B RFC 1662
1163Simpson, W.A.
1164.I PPP in HDLC-like Framing.
1165July 1994.
1167The following signals have the specified effect when sent to pppd.
1170These signals cause pppd to terminate the link (by closing LCP),
1171restore the serial device settings, and exit.
1174This signal causes pppd to terminate the link, restore the serial
1175device settings, and close the serial device. If the \fIpersist\fR or
1176\fIdemand\fR option has been specified, pppd will try to reopen the
1177serial device and start another connection (after the holdoff period).
1178Otherwise pppd will exit. If this signal is received during the
1179holdoff period, it causes pppd to end the holdoff period immediately.
1181.B SIGUSR1
1182This signal toggles the state of the \fIdebug\fR option.
1184.B SIGUSR2
1185This signal causes pppd to renegotiate compression. This can be
1186useful to re-enable compression after it has been disabled as a result
1187of a fatal decompression error. (Fatal decompression errors generally
1188indicate a bug in one or other implementation.)
1191Paul Mackerras (, based on earlier work by
1192Drew Perkins,
1193Brad Clements,
1194Karl Fox,
1195Greg Christy,
1197Brad Parker.