NetBSD/usr.sbin/pppd/pppd.8

.\" manual page [] for pppd 2.0
.\" $Id: pppd.8,v 1.5 1994/02/22 00:12:04 paulus Exp $
.\" SH section heading
.\" SS subsection heading
.\" LP paragraph
.\" IP indented paragraph
.\" TP hanging label
.TH PPPD 8
.SH NAME
pppd \- Point to Point Protocol daemon
.SH SYNOPSIS
.B pppd
[
.I options
] [
.I tty_name
] [
.I speed
]
.SH DESCRIPTION
.LP
The Point-to-Point Protocol (PPP) provides a method for transmitting
datagrams over serial point-to-point links.  PPP
is composed of three parts: a method for encapsulating datagrams over
serial links, an extensible Link Control Protocol (LCP), and
a family of Network Control Protocols (NCP) for establishing
and configuring different network-layer protocols.
.LP
The encapsulation scheme is provided by driver code in the kernel.
.B pppd
provides the basic LCP, authentication support, and an
NCP for establishing and configuring the Internet Protocol (IP)
(called the IP Control Protocol, IPCP).
.SH FREQUENTLY USED OPTIONS
.TP
.I <tty_name>
Communicate over the named device.  The string "/dev/"
is prepended if necessary.  If no device name is given,
.I pppd
will use the controlling terminal, and will not fork to put itself in
the background.
.TP
.I <speed>
Set the baud rate to <speed>.  On systems such as 4.4BSD and NetBSD,
any speed can be specified.  Other systems (e.g. SunOS) allow only a
limited set of speeds.
.TP
.B asyncmap \fI<map>
Set the async character map to <map>.
This map describes which control characters cannot be successfully
received over the serial line.
.I pppd
will ask the peer to send these characters as a 2-byte "escape" sequence.
The argument is a 32 bit hex number
with each bit representing a character to escape. 
Bit 0 (00000001) represents the character 0x00;
bit 31 (80000000) represents the character 0x1f or ^_.
The default asyncmap is 0.  If multiple \fBasyncmap\fR options are
given, the values are ORed together.
.TP
.B auth
Require the peer to authenticate itself before allowing network
packets to be sent or received.
.TP
.B connect \fI<p>
Use the executable or shell command specified by <p> to set up the
serial line.  This script would typically use the "chat" program to
dial the modem and start the remote ppp session.
.TP
.B crtscts
Use hardware flow control (i.e. RTS/CTS) to control the flow of data on
the serial port.
.TP
.B defaultroute
Add a default route to the system routing tables, using the peer as
the gateway, when IPCP negotiation is successfully completed.
This entry is removed when the PPP connection is broken.
.TP
.B file \fI<f>
Read options from file <f> (the format is described below).
.TP
.B mru \fI<n>
Set the MRU [Maximum Receive Unit] value to <n> for negotiation.
.I pppd
will ask the peer to send packets of no more than <n> bytes.
 The minimum MRU value is 128. 
The default MRU value is 1500.  A value of 296 is recommended for slow
links (40 bytes for TCP/IP header + 256 bytes of data).
.TP
.B netmask \fI<n>
Set the interface netmask to <n>, a 32 bit netmask in "decimal dot" notation
(e.g. 255.255.255.0).
.TP
.B passive
Enables the "passive" option in the LCP.  With this option,
.I pppd
will attempt to initiate a connection; if no reply is received from
the peer,
.I pppd
will then just wait passively for a valid LCP packet from the peer
(instead of exiting, as it does without this option).
.TP
.B silent
With this option,
.I pppd
will not transmit LCP packets to initiate a connection until a valid
LCP packet is received from the peer (as for the "passive" option with
old versions of \fIpppd\fR).
.SH OPTIONS
.TP
.I <local_IP_address>\fB:\fI<remote_IP_address>
Set the local and/or remote interface IP addresses.  Either one may be
omitted.  The IP addresses can be specified with a host name or in
decimal dot notation (e.g. 150.234.56.78).  The default local
address is the (first) IP address of the system (unless the
.B noipdefault
option is given).  The remote address will be obtained from the peer
if not specified in any option.  Thus, in simple cases, this option is
not required.
If a local and/or remote IP address is specified with this option,
.I pppd
will not accept a different value from the peer in the IPCP
negotiation, unless the
.B ipcp-accept-local
and/or
.B ipcp-accept-remote
options are given, respectively.
.TP
.B -all
Don't request or allow negotiation of any options for LCP and IPCP (use
default values).
.TP
.B -ac
Disable Address/Control compression negotiation (use default, i.e.
disabled).
.TP
.B -am
Disable asyncmap negotiation (use default, i.e. 0xffffffff).
.TP
.B -as \fI<n>
Same as
.B asyncmap \fI<n>
.TP
.B -d
Increase debugging level.
.TP
.B -detach
Don't fork to become a background process (otherwise
.I pppd
will do so if a serial device is specified).
.TP
.B -ip
Disable IP address negotiation (with this option, the remote IP
address must be specified with an option on the command line or in an
options file).
.TP
.B -mn
Disable magic number negotiation.  With this option,
.I pppd
cannot detect a looped-back line.
.TP
.B -mru
Disable MRU [Maximum Receive Unit] negotiation (use default, i.e. 1500).
.TP
.B -p
Same as the
.B passive
option.
.TP
.B -pc
Disable protocol field compression negotiation (use default, i.e. disabled).
.TP
.B +ua \fI<p>
Agree to authenticate using PAP [Password Authentication Protocol] if
requested by the peer, and
use the data in file <p> for the user and password to send to the
peer. The file contains the remote user name, followed by a newline,
followed by the remote password, followed by a newline.  This option
is obsolescent.
.TP
.B +pap
Require the peer to authenticate itself using PAP.
.TP
.B -pap
Don't agree to authenticate using PAP.
.TP
.B +chap
Require the peer to authenticate itself using CHAP [Cryptographic
Handshake Authentication Protocol] authentication.
.TP
.B -chap
Don't agree to authenticate using CHAP.
.TP
.B -vj
Disable negotiation of Van Jacobson style IP header compression (use
default, i.e. no compression).
.TP
.B debug
Increase debugging level (same as
.B -d
).
.TP
.B domain \fI<d>
Append the domain name <d> to the local host name for authentication
purposes.  For example, if gethostname() returns the name porsche, but the
fully qualified domain name is porsche.Quotron.COM, you would use the
domain option to set the domain name to Quotron.COM.
.TP
.B modem
Use the modem control lines.  (This option is not fully implemented.)
.TP
.B local
Don't use the modem control lines.
.TP
.B name \fI<n>
Set the name of the local system for authentication purposes to <n>.
.TP
.B user \fI<u>
Set the user name to use for authenticating this machine with the peer
using PAP to <u>.
.TP
.B usehostname
Enforce the use of the hostname as the name of the local system for
authentication purposes (overrides the
.B name
option).
.TP
.B remotename \fI<n>
Set the assumed name of the remote system for authentication purposes
to <n>.
.TP
.B proxyarp
Add an entry to this system's ARP [Address Resolution Protocol] table
with the IP address of the peer and the Ethernet address of this
system.
.TP
.B login
Use the system password database for authenticating the peer using
PAP.
.TP
.B noipdefault
Disables the default behaviour when no local IP address is specified,
which is to determine (if possible) the local IP address from the
hostname.  With this option, the peer will have to supply the local IP
address during IPCP negotiation (unless it specified explicitly on the
command line or in an options file).
.TP
.B lcp-restart \fI<n>
Set the LCP restart interval (retransmission timeout) to <n> seconds
(default 3).
.TP
.B lcp-max-terminate \fI<n>
Set the maximum number of LCP terminate-request transmissions to <n>
(default 3).
.TP
.B lcp-max-configure \fI<n>
Set the maximum number of LCP configure-request transmissions to <n>
(default 10).
.TP
.B lcp-max-failure \fI<n>
Set the maximum number of LCP configure-NAKs returned before starting
to send configure-Rejects instead to <n> (default 10).
.TP
.B ipcp-restart \fI<n>
Set the IPCP restart interval (retransmission timeout) to <n> seconds
(default 3).
.TP
.B ipcp-max-terminate \fI<n>
Set the maximum number of IPCP terminate-request transmissions to <n>
(default 3).
.TP
.B ipcp-max-configure \fI<n>
Set the maximum number of IPCP configure-request transmissions to <n>
(default 10).
.TP
.B ipcp-max-failure \fI<n>
Set the maximum number of IPCP configure-NAKs returned before starting
to send configure-Rejects instead to <n> (default 10).
.TP
.B pap-restart \fI<n>
Set the PAP restart interval (retransmission timeout) to <n> seconds
(default 3).
.TP
.B pap-max-authreq \fI<n>
Set the maximum number of PAP authenticate-request transmissions to
<n> (default 10).
.TP
.B chap-restart \fI<n>
Set the CHAP restart interval (retransmission timeout for challenges)
to <n> seconds (default 3).
.TP
.B chap-max-challenge \fI<n>
Set the maximum number of CHAP challenge transmissions to <n> (default
10).
.TP
.B chap-interval \fI<n>
If this option is given,
.I pppd
will rechallenge the peer every <n> seconds.
.TP
.B ipcp-accept-local
With this option,
.I pppd
will accept the peer's idea of our local IP address, even if the
local IP address was specified in an option.
.TP
.B ipcp-accept-remote
With this option,
.I pppd
will accept the peer's idea of its (remote) IP address, even if the
remote IP address was specified in an option.
.SH OPTIONS FILES
Options can be taken from files as well as the command line.  
.I pppd
reads options from the files /etc/ppp/options and $HOME/.ppprc before
looking at the command line.  An options file is parsed into a series
of words, delimited by whitespace.  Whitespace can be included in a
word by enclosing the word in quotes (").  A backslash (\\) quotes the
following character.  A hash (#) starts a comment, which continues
until the end of the line.
.SH AUTHENTICATION
.I pppd
provides system administrators with sufficient access control that PPP
access to a server machine can be provided to legitimate users without
fear of compromising the security of the server or the network it's
on.  In part this is provided by the /etc/ppp/options file, where the
administrator can place options to require authentication whenever
.I pppd
is run, and in part by the PAP and CHAP secrets files, where the
administrator can restrict the set of IP addresses which individual
users may use.
.LP
The default behaviour of
.I pppd
is to agree to authenticate if requested, and to not
require authentication from the peer.  However, 
.I pppd
will not agree to
authenticate itself with a particular protocol if it has no secrets
which could be used to do so.
.LP
Authentication is based on secrets, which are selected from secrets
files (/etc/ppp/pap-secrets for PAP, /etc/ppp/chap-secrets for CHAP).
Both secrets files have the same format, and both can store secrets
for several combinations of server (authenticating peer) and client
(peer being authenticated).  Note that
.I pppd
can be both a server
and client, and that different protocols can be used in the two
directions if desired.
.LP
A secrets file is parsed into words as for a options file.  A secret
is specified by a line containing at least 3 words, in the order
client, server, secret.  Any following words on the same line are
taken to be a list of acceptable IP addresses for that client.  If
there are only 3 words on the line, it is assumed that any IP address
is OK; to disallow all IP addresses, use "-".  If the secret starts
with an `@', what follows is assumed to be the name of a file from
which to read the secret.  A "*" as the client or server name matches
any name.  When selecting a secret, \fIpppd\fR takes the best match, i.e.
the match with the fewest wildcards.
.LP
Thus a secrets file contains both secrets for use in authenticating
other hosts, plus secrets which we use for authenticating ourselves to
others.  Which secret to use is chosen based on the names of the host
(the `local name') and its peer (the `remote name').  The local name
is set as follows:
.TP 3
if the \fBusehostname\fR option is given,
then the local name is the hostname of this machine
(with the domain appended, if given)
.TP 3
else if the \fBname\fR option is given,
then use the argument of the first \fBname\fR option seen
.TP 3
else if the local IP address is specified with a hostname,
then use that name
.TP 3
else use the hostname of this machine (with the domain appended, if given)
.LP
When authenticating ourselves using PAP, there is also a `username'
which is the local name by default, but can be set with the \fBuser\fR
option or the \fB+ua\fR option.
.LP
The remote name is set as follows:
.TP 3
if the \fBremotename\fR option is given,
then use the argument of the last \fBremotename\fR option seen
.TP 3
else if the remote IP address is specified with a hostname,
then use that host name
.TP 3
else the remote name is the null string "".
.LP
Secrets are selected from the PAP secrets file as follows:
.TP 2
*
For authenticating the peer, look for a secret with client ==
username specified in the PAP authenticate-request, and server ==
local name.
.TP 2
*
For authenticating ourselves to the peer, look for a secret with
client == our username, server == remote name.
.LP
When authenticating the peer with PAP, a secret of "" matches any
password supplied by the peer.  If the password doesn't match the
secret, the password is encrypted using crypt() and checked against
the secret again; thus secrets for authenticating the peer can be
stored in encrypted form.  If the \fBlogin\fR option was specified, the
username and password are also checked against the system password
database.  Thus, the system administrator can set up the pap-secrets
file to allow PPP access only to certain users, and to restrict the
set of IP addresses that each user can use.
.LP
Secrets are selected from the CHAP secrets file as follows:
.TP 2
*
For authenticating the peer, look for a secret with client == name
specified in the CHAP-Response message, and server == local name.
.TP 2
*
For authenticating ourselves to the peer, look for a secret with
client == local name, and server == name specified in the
CHAP-Challenge message.
.LP
Authentication must be satisfactorily completed before IPCP (or any
other Network Control Protocol) can be started.  If authentication
fails, \fIpppd\fR will terminated the link (by closing LCP).  If IPCP
negotiates an unacceptable IP address for the remote host, IPCP will
be closed.  IP packets can only be sent or received when IPCP is open.
.SH ROUTING
.LP
When IPCP negotiation is completed successfully,
.I pppd
will inform the kernel of the local and remote IP addresses for the
ppp interface.  This is sufficient to create a
host route to the remote end of the link, which will enable the peers
to exchange IP packets.  Communication with other machines generally
requires further modification to routing tables and/or ARP (Address
Resolution Protocol) tables.  In some cases this will be done
automatically through the actions of the \fIrouted\fR or \fIgated\fR
daemons, but in most cases some further intervention is required.
.LP
Sometimes it is desirable
to add a default route through the remote host, as in the case of a
machine whose only connection to the Internet is through the ppp
interface.  The \fBdefaultroute\fR option causes \fIpppd\fR to create such a
default route when IPCP comes up, and delete it when the link is
terminated.
.LP
In some cases it is desirable to use proxy ARP, for example on a
server machine connected to a LAN, in order to allow other hosts to
communicate with the remote host.  The \fBproxyarp\fR option causes \fIpppd\fR
to look for a network interface on the same subnet as the remote host
(an interface supporting broadcast and ARP, which is up and not a
point-to-point or loopback interface).  If found, \fIpppd\fR creates a
permanent, published ARP entry with the IP address of the remote host
and the hardware address of the network interface found.
.SH EXAMPLES
.LP
In the simplest case, you can connect the serial ports of two machines
and issue a command like
.IP
pppd /dev/ttya 9600 passive
.LP
to each machine, assuming there is no \fIgetty\fR running on the
serial ports.  If one machine has a \fIgetty\fR running, you can use
\fIkermit\fR or \fItip\fR on the other machine to log in to the first
machine and issue a command like
.IP
pppd passive
.LP
Then exit from the communications program (making sure the connection
isn't dropped), and issue a command like
.IP
pppd /dev/ttya 9600
.LP
The process of logging in to the other machine and starting \fIpppd\fR
can be automated by using the \fBconnect\fR option to run \fIchat\fR,
for example:
.IP
pppd /dev/ttya 38400 connect 'chat "" "" "login:" "username"
"Password:" "password" "% " "exec pppd passive"'
.LP
If your serial connection is any more complicated than a piece of
wire, you may need to arrange for some control characters to be
escaped.  In particular, it is often useful to escape XON (^Q) and
XOFF (^S), using \fBasyncmap a0000\fR.  If the path includes a telnet,
you probably should escape ^] as well (\fBasyncmap 200a0000\fR).
Don't use an rlogin in the path - many implementations are not
transparent; they will remove the sequence [0xff, 0xff, 0x73, 0x73,
followed by any 8 bytes] from the stream.
.SH DIAGNOSTICS
.LP
Messages are sent to the syslog daemon using facility
LOG_DAEMON unless
.I pppd
has been compiled with debugging code.  In this case the logging
facility used will be LOG_LOCAL2 in order to allow separation of the debug
output from the other daemons using the  LOG_DAEMON facility.  You can
override this by defining the macro LOG_PPP to the desired facility
and recompiling.  In order to see the error and debug messages, you
will need to edit your /etc/syslog.conf file to direct the messages to
the desired output device or file.
.LP
If enabled at compile time, debugging printout can be enabled by
setting the -d or debug flag on the command line, or by sending a
SIGUSR1 to the
.I pppd
process.
Debugging may be disabled by sending a SIGUSR2 to the
.I pppd
process.
.SH FILES
.TP
.B /var/run/ppp\fIn\fB.pid \fR(BSD), \fB/etc/ppp/ppp\fIn\fB.pid \fR(SunOS)
Process-ID for \fIpppd\fR process on ppp interface unit \fIn\fR.
.TP
.B /etc/ppp/pap-secrets
Usernames, passwords and IP addresses for PAP authentication.
.TP
.B /etc/ppp/chap-secrets
Names, secrets and IP addresses for CHAP authentication.
.TP
.B /etc/ppp/options
System default options for
.I pppd,
read before user default options or command-line options.
.TP
.B $HOME/.ppprc
User default options, read before command-line options.
.SH SEE ALSO
.TP
.B RFC1144
Jacobson, V.
.I Compressing TCP/IP headers for low-speed serial links.
1990 February.
.TP
.B RFC1321
Rivest, R.
.I The MD5 Message-Digest Algorithm.
1992 April.
.TP
.B RFC1331
Simpson, W.A.
.I Point\-to\-Point Protocol (PPP) for the transmission of multi\-protocol
.I datagrams over point\-to\-point links.
1992 May.
.TP
.B RFC1332
McGregor, G.
.I PPP Internet Protocol Control Protocol (IPCP).
1992 May.
.TP
.B RFC1334
Lloyd, B.; Simpson, W.A.
.I PPP authentication protocols.
1992 October.
.SH NOTES
The following signals have the specified effect when sent to the
.I pppd
process.
.TP
.B SIGINT, SIGTERM
These signals cause \fIpppd\fR to terminate the link (by closing LCP),
restore the serial device settings, and exit.
.TP
.B SIGHUP
Indicates that the physical layer has been disconnected.  \fIpppd\fR
will attempt to restore the serial device settings (this may produce
error messages on Suns), and then exit.
.SH BUGS
The use of the modem control lines and the effects of the \fBmodem\fR
and \fBlocal\fR options are not well defined.
.SH AUTHORS
Drew Perkins,
Brad Clements,
Karl Fox,
Greg Christy,
Brad Parker (brad@fcr.com),
Paul Mackerras (paulus@cs.anu.edu.au)