.\" manual page [] for ipppd 2.0
.\" $Id: ipppd.man.in,v 1.11 2003/07/01 09:03:45 keil Exp $
.\" CHECKIN $Date: 2003/07/01 09:03:45 $
.\" SH section heading
.\" SS subsection heading
.\" LP paragraph
.\" IP indented paragraph
.\" TP hanging label
.TH IPPPD 8 "2003/07/01" isdn4k-utils-3.27 "Linux System Administration"
.SH NAME
ipppd \- (ISDN) Point to Point Protocol daemon
.SH SYNOPSIS
.B /usr/bin/ipppd
[
.I options
] [
.I device
]
.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.
.I ipppd
provides the basic LCP, authentication support, and an
NCP for establishing and configuring the Internet Protocol (IP)
(called the IP Control Protocol, IPCP).
.SH NOTES for (ISDN) IPPPD
This special (ISDN) PPP daemon is a modified version of pppd 
and provides synchronous PPP for ISDN connections.
.PP
If you need asynchronous PPP over ISDN lines use pppd
instead with the ISDN character devices, see
.BR ttyI (4).
.PP
The 
.I ipppd 
can handle multiple devices. This is necessary to
link several connections together to one bundle.
.I ipppd 
should be started once. It opens the devices
and waits for connections. 
If the connections is closed
.I ipppd
reopens the device automatically (the device, that's it ... not the link
to the remote).
So you shouldn't kill the ipppd to close a link. Instead, trigger
a hangup on the netdevice layer  by 'isdnctrl hangup <device>'.
.PP
The facility to configure the daemon via file
/etc/ppp/ioptions.<devname> is disabled. 
The 'file' option or the command line may be used for individual
configuration.
.PP
Do not set the permissions of the program to 'setuid to root 
on execution'. Call the daemon as root instead.
No common user should have the need to call the daemon!
.SH OPTIONS
.TP
.I <device>
Communicate over the named device.  The string "/dev/"
is prepended if necessary.  If no device name is given,
or if the name of the controlling terminal is given,
.I ipppd
will use the controlling terminal, and will not fork to put itself in
the background.
.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 ipppd
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 active-filter \fIfilter-expression
Specifies a packet filter to be applied to data packets to determine
which packets are to be regarded as link activity, and therefore reset
the idle timer, or cause the link to be brought up in demand-dialling
mode. This option is useful in conjunction with the
\fBidle\fR option if there are packets being sent or received
regularly over the link (for example, routing information packets)
which would otherwise prevent the link from ever appearing to be idle.
The \fIfilter-expression\fR syntax is as described for tcpdump(1),
except that qualifiers which are inappropriate for a PPP link, such as
\fBether\fR and \fBarp\fR, are not permitted. Generally the filter
expression should be enclosed in single-quotes to prevent whitespace
in the expression from being interpreted by the shell. This option
is currently only available if both the kernel and ipppd were compiled
with IPPP_FILTER defined.
.TP
.B -ac
Disable Address/Control compression negotiation (use default, i.e.
address/control field compression disabled).
.TP
.B -all
Don't request or allow negotiation of any options for LCP and IPCP (use
default values).
.TP
.B auth
Require the peer to authenticate itself before allowing network
packets to be sent or received.
.TP
.B bsdcomp \fInr,nt
Request that the peer compress packets that it sends, using the
BSD-Compress scheme, with a maximum code size of \fInr\fR bits, and
agree to compress packets sent to the peer with a maximum code size of
\fInt\fR bits.  If \fInt\fR is not specified, it defaults to the value
given for \fInr\fR.  Values in the range 9 to 15 may be used for
\fInr\fR and \fInt\fR; larger values give better compression but
consume more kernel memory for compression dictionaries.
Alternatively, a value of 0 for \fInr\fR or \fInt\fR disables
compression in the corresponding direction.
.TP
.B \-bsdcomp
Disables compression; \fIipppd\fR will not request or agree to compress
packets using the BSD-Compress scheme.
.TP
.B callback \fI<string>
Request the peer to call back at the location given in
<string>. Ususally this is a phone number, but it may be interpreted
differently (or ignored) depending on the \fBcallback-type\fR option.
If <string> is the empty string, \fIipppd\fR automatically tries to
negotiate a callback type that does not need a location to be specified.
.TP
.B callback-delay \fI<n>
Callback delay for CBCP in seconds. If callback is negotiated using
CBCP, request that the peer waits at least <n> seconds before calling
back. Ignored if callback is negotiated as specified in RFC
1570. Legal range is 0..255, default is 5.
.TP
.B callback-cbcp
Enable callback negotiation via CBCB (default).
.TP
.B -callback-cbcp
Disable callback negotiation via CBCB.
.TP
.B no-callback-cbcp
Disable callback negotiation via CBCB.
.TP
.B callback-cbcp-preferred
If both CBCP and RFC 1570 style callback negotiation is enabled, CBCP
is preferred (default)
.TP
.B callback-rfc1570-preferred
If both CBCP and RFC 1570 style callback negotiation is enabled, RFC
1570 style is preferred.
.TP
.B callback-rfc1570
Enable RFC 1570 style callback negotiation (default).
.TP
.B -callback-rfc1570
Disable RFC 1570 style callback negotiation.
.TP
.B no-callback-rfc1570
Disable RFC 1570 style callback negotiation (default).
.TP
.B callback-type \fI<n>
Specifies how to interpret the location identifier given as
parameter of the \fBcallback\fR option. Legal values are 0..4. A value 
of 0 means that only callback types should be negotiated that need no 
extra location id. No location id is sent to the peer in this case.
For RFC 1570 style callback negotiation, the values 1..4
indicate how the peer should interpret the location identifier:
1 - id is a system specific dial string,  2 - id is used for database
lookup by the peer, 3 - id is a phone number, and 4 id is a name. For
CBCP callback negotiation, the location id is always interpreted as a
phone number.
.TP
.B -ccp
Necessary for a few netblazers on the remote side.
.TP
.B noccp
same as
.B -ccp
.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 chap-interval \fI<n>
If this option is given,
.I ipppd
will rechallenge the peer every <n> seconds.
.TP
.B chap-max-challenge \fI<n>
Set the maximum number of CHAP challenge 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 debug
Increase debugging level (same as \fB\-d\fR).
If this option is given, \fIipppd\fR will log the contents of all
control packets sent or received in a readable form.  The packets are
logged through syslog with facility \fIdaemon\fR and level
\fIdebug\fR.  This information can be directed to a file by setting up
/etc/syslog.conf appropriately (see syslog.conf(5)).
.TP
.B -d
Increase debugging level (same as the \fBdebug\fR option).
.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 \-defaultroute
Disable the \fBdefaultroute\fR option.  The system administrator who
wishes to prevent users from creating default routes with \fIipppd\fR
can do so by placing this option in the /etc/ppp/ioptions file.
.TP
.B deldefaultroute
Replace default route if it already exists. Together with the option 
\fBdefaultroute\fR, this will replace any existing default route by a new
one through this ipppd's interface when it comes up.
.TP 
.B -detach
Don't fork to become a background process (otherwise
.I ipppd
will do so if a serial device other than its controlling terminal is
specified).
.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 file \fI<f>
Read options from file <f> (the format is described below).
.TP
.B -ip
Disable IP address negotiation.  If this option is used, the remote IP
address must be specified with an option on the command line or in an
options file.
.TP
.B +ip-protocol
Enable the IPCP and IP protocols. This is the default condition. This
option is only needed if the default setting is -ip-protocol.
.TP
.B -ip-protocol
Disable the IPCP and IP protocols. This should only be used if you
know that you are using a client which only understands IPX and you
don't want to confuse the client with the IPCP protocol.
.TP
.B +ipx-protocol
Enable the IPXCP and IPX protocols. This is the default condition if
your kernel supports IPX. This option is only needed if the default
setting is -ipx-protocol. If your kernel does not support IPX then this
option will have no effect.
.TP
.B -ipx-protocol
Disable the IPXCP and IPX protocols. This should only be used if you
know that you are using a client which only understands IP and you
don't want to confuse the client with the IPXCP protocol.
.TP
.B ipcp-accept-local
With this option,
.I ipppd
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 ipppd
will accept the peer's idea of its (remote) IP address, even if the
remote IP address was specified in an option.
.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 ipcp-max-terminate \fI<n>
Set the maximum number of IPCP terminate-request transmissions to <n>
(default 3).
.TP
.B ipcp-restart \fI<n>
Set the IPCP restart interval (retransmission timeout) to <n> seconds
(default 3).
.TP
.B ipparam \fIstring
Provides an extra parameter to the ip-up and ip-down scripts.  If this
option is given, the \fIstring\fR supplied is given as the 6th
parameter to those scripts.
.TP
.B ipx-network \fI<n>
Set the IPX network number in the IPXCP configure request frame to
<n>. There is no valid default. If this option is not specified then
the network number is obtained from the peer. If the peer does not
have the network number, the IPX protocol will not be started. This is
a hexadecimal number and is entered without any leading sequence such
as 0x. It is related to the \fIipxcp-accept-network\fR option.
.TP
.B ipx-node \fI<n>:<m>
Set the IPX node numbers. The two node numbers are separated from each
other with a colon character. The first number <n> is the local node
number. The second number <m> is the peer's node number. Each node number
is a hexadecimal number, to the maximum of ten significant digits. The
node numbers on the ipx-network must be unique. There is no valid
default. If this option is not specified then the node number is
obtained from the peer. This option is a related to the
\fIipxcp-accept-local\fR and \fIipxcp-accept-remote\fR options.
.TP
.B ipx-router-name \fI<string>
Set the name of the router. This is a string and is sent to the peer
as information data.
.TP
.B ipx-routing \fI<n>
Set the routing protocol to be received by this option. Use a
comma-serperated list if you want to specify more than one 
protocol.
The '\fInone\fR'
option (0) may be specified as the only instance of ipx-routing. The
values may be \fI0\fR for \fINONE\fR, \fI2\fR for \fIRIP/SAP\fR, and
\fI4\fR for \fINLSP\fR.
.TP
.B ipxcp-accept-local
Accept the peer's NAK for the node number specified in the ipx-node
option. If a node number was specified, and non-zero, the default is
to insist that the value be used. If you include this option then you
will permit the peer to override the entry of the node number.
.TP
.B ipxcp-accept-network
Accept the peer's NAK for the network number specified in the
ipx-network option. If a network number was specified, and non-zero, the
default is to insist that the value be used. If you include this
option then you will permit the peer to override the entry of the node
number.
.TP
.B ipxcp-accept-remote
Use the peer's network number specified in the configure request
frame. If a node number was specified for the peer and this option was
not specified, the peer will be forced to use the value which you have
specified.
.TP
.B ipxcp-max-configure \fI<n>
Set the maximum number of IPXCP configure request frames which the
system will send to <n>. The default is 10.
.TP
.B ipxcp-max-failure \fI<n>
Set the maximum number of IPXCP NAK frames which the local system will
send before it rejects the options. The default value is 3.
.TP
.B ipxcp-max-terminate \fI<n>
Set the maximum nuber of IPXCP terminate request frames before the
local system considers that the peer is not listening to them. The
default value is 3.
.TP
.B kdebug \fIn
Enable debugging code in the kernel-level PPP driver.  The argument
\fIn\fR is a number which is the sum of the following values: 1 to
enable general debug messages, 2 to request that the contents of
received packets be printed, and 4 to request that the contents of
transmitted packets be printed.
.TP
.B lcp-echo-failure \fI<n>
If this option is given, \fIipppd\fR will presume the peer to be dead
if \fIn\fR LCP echo-requests are sent without receiving a valid LCP
echo-reply.  If this happens, \fIipppd\fR will terminate the
connection.  Use of this option requires a non-zero value for the
\fBlcp-echo-interval\fR parameter.  This option can be used to enable
\fIipppd\fR to terminate after the physical connection has been broken
(e.g., the line hung up) in situations where no hardware modem
control lines are available.
.TP
.B lcp-echo-interval \fI<n>
If this option is given, \fIipppd\fR will send an LCP echo-request
frame to the peer every \fIn\fR seconds.  With Linux, the
echo-request is sent when no packets have been received from the peer
for \fIn\fR seconds.  Normally the peer should respond to the
echo-request by sending an echo-reply.  This option can be used with
the \fBlcp-echo-failure\fR option to detect that the peer is no longer
connected.
.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 lcp-max-terminate \fI<n>
Set the maximum number of LCP terminate-request transmissions to <n>
(default 3).
.TP
.B lcp-restart \fI<n>
Set the LCP restart interval (retransmission timeout) to <n> seconds
(default 3).
.TP
.B lock
Specifies that \fIipppd\fR should create a UUCP-style lock file for the
serial device to ensure exclusive access to the device.
.TP
.B login
Use the system password database for authenticating the peer using
PAP, and record the user in the system wtmp file.
.TP
.B -mn
Disable magic number negotiation.  With this option,
.I ipppd
cannot detect a looped-back line.
.TP
.B +mp
enables MPPP negotiation
.TP
.B mru \fI<n>
Set the MRU [Maximum Receive Unit] value to <n> for negotiation.
.I ipppd
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 -mru
Disable MRU [Maximum Receive Unit] negotiation.  With this option,
\fIipppd\fR will use the default MRU value of 1500 bytes.
.TP
.B ms-dns \fI<n>
This option sets the IP address or addresses for the Domain Name
Server. It is used by Microsoft Windows clients. The primary DNS
address is specified by the first instance of the ms-dns option. The
secondary is specified by the second instance.
.TP
.B ms-get-dns
Implements the client side of RFC1877.  If \fIipppd\fR is acting as a client
to a server that implements RFC1877 such as one intended to be used
with Microsoft Windows clients, this option allows \fIipppd\fR to obtain one
or two DNS (Domain Name Server) addresses from the server.  It does
not do anything with these addresses except put them in the
environment (MS_DNS1 MS_DNS2) that is passed to scripts.  For
compatibility with the async pppd, DNS1 DNS2 environment variables are
also set. A sample resolv.conf is created in /etc/ppp/resolv.conf.
The /etc/ppp/ip-up script should use this information to perform
whatever adjustment is necessary.  Note: RFC1877 is a horrible protocol
layering violation, the correct approach would be to use DHCP after
the IPCP phase.
.TP
.B ms-get-wins
As ms-get-dns but for WINS (Windows Internet Name Services) server
addresses. Environment variables are MS_WINS1 and MS_WINS2.
.TP
.B mtu \fI<n>
Set the MTU [Maximum Transmit Unit] value to \fI<n>\fR.  Unless the
peer requests a smaller value via MRU negotiation, \fIipppd\fR will
request that the kernel networking code send data packets of no more
than \fIn\fR bytes through the PPP network interface. 
.TP
.B name \fI<n>
Set the name of the local system for authentication purposes to <n>.
.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).  If this option is given, the value
specified is ORed with the default netmask.  The default netmask is
chosen based on the negotiated remote IP address; it is the
appropriate network mask for the class of the remote IP address, ORed
with the netmasks for any non point-to-point network interfaces in the
system which are on the same network.
.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 passive
Enables the "passive" option in the LCP.  With this option,
.I ipppd
will attempt to initiate a connection; if no reply is received from
the peer,
.I ipppd
will then just wait passively for a valid LCP packet from the peer
(instead of exiting, as it does without this option).
.TP
.B -p
Same as the
.B passive
option.
.TP
.B +pap
Require the peer to authenticate itself using PAP.
.TP
.B -pap
Don't agree to authenticate using PAP.
.TP
.B papcrypt
Indicates that all secrets in the /etc/ppp/pap-secrets file which
are used for checking the identity of the peer are encrypted, and thus
.I ipppd 
should not accept a password which (before encryption) is
identical to the secret from the /etc/ppp/pap-secrets file.
.TP
.B pap-max-authreq \fI<n>
Set the maximum number of PAP authenticate-request transmissions 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-timeout \fI<n>
Set the maximum time that
.I ipppd
will wait for the peer to authenticate itself with PAP to
<n> seconds (0 means no limit).
.TP
.B pass-filter \fIfilter-expression
Specifies a packet filter to applied to data packets being sent or
received to determine which packets should be allowed to pass.
Packets which are rejected by the filter are silently discarded. This
option can be used to prevent specific network daemons (such as
routed) using up link bandwidth, or to provide a basic firewall
capability.
The \fIfilter-expression\fR syntax is as described for tcpdump(1),
except that qualifiers which are inappropriate for a PPP link, such as
\fBether\fR and \fBarp\fR, are not permitted. Generally the filter
expression should be enclosed in single-quotes to prevent whitespace
in the expression from being interpreted by the shell. Note that it
is possible to apply different constraints to incoming and outgoing
packets using the \fBinbound\fR and \fBoutbound\fR qualifiers. This
option is currently only available if both the kernel and ipppd were
compiled with IPPP_FILTER defined.
.TP
.B -pc
Disable protocol field compression negotiation (use default, i.e.
protocol field compression disabled).
.TP
.B pidfile <filename>
Use <filename> instead of 
.I /var/run/ipppd.pid
.TP
.B pred1comp
Attempt to request that the peer send the local system frames which
have been compressed by the Predictor-1 compression. The compression
protocols must be loaded or this option will be ignored.
.TP
.B -pred1comp
Do not accept Predictor-1 comprssion, even if the peer wants to send
this type of compression and support has been defined in the kernel.
.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 \-proxyarp
Disable the \fBproxyarp\fR option.  The system administrator who
wishes to prevent users from creating proxy ARP entries with
\fIipppd\fR can do so by placing this option in the /etc/ppp/ioptions
file.
.TP
.B remotename \fI<n>
Set the assumed name of the remote system for authentication purposes
to <n>.
.TP
.B set_userip
You may define valid IPs in 
.I /etc/ppp/useriptab
.TP
.B silent
With this option,
.I ipppd
will not transmit LCP packets to initiate a connection until a valid
LCP packet is received from the peer (as for the `passive' option with
ancient versions of \fIipppd\fR).
.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 usefirstip
Gets the remote address from the first entry in
the auth file (if there is an IP address entry). This address 
should be a full IP address not an address from a masked area.
Ipppd calls 'gethostbyname()' and negotiates the result.
IP from auth file will overwrite the remote address gotten
from the interface.  'usefirstip' is UNTESTED!
.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 usepeerdns
Same as 
.B ms-get-dns
for compatibility with async pppd.
.TP
.B user \fI<u>
Set the user name to use for authenticating this machine with the peer
using PAP to <u>.
.TP
.B useifip
will get (if not set to 0.0.0.0) the IP address
for the negotiation from the attached network-interface.
(also: \fIipppd\fR will try to negotiate 'pointopoint' IP as remote IP)
interface address -> local IP
pointopoint address -> remote IP
.TP
.B -vj
Disable negotiation of Van Jacobson style TCP/IP header compression (use
default, i.e. no compression).
.TP
.B -vjccomp
Disable the connection-ID compression option in Van Jacobson style
TCP/IP header compression.  With this option, \fIipppd\fR will not omit
the connection-ID byte from Van Jacobson compressed TCP/IP headers,
nor ask the peer to do so.
.TP
.B vj-max-slots \fIn
Sets the number of connection slots to be used by the Van Jacobson
TCP/IP header compression and decompression code to \fIn\fR, which
must be between 2 and 16 (inclusive).
.SH OPTIONS FILES
Options can be taken from files as well as the command line.  
.I ipppd
reads options from the file /etc/ppp/ioptions 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 ipppd
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/ioptions file, where the
administrator can place options to require authentication whenever
.I ipppd
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 ipppd
is to agree to authenticate if requested, and to not
require authentication from the peer.  However, 
.I ipppd
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 ipppd
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 name, server name, 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, \fIipppd\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 \fBpapcrypt\fR option is given, the
first (unencrypted) comparison is omitted, for better security.
.LP
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.  Typically, when using the
\fBlogin\fR option, the secret in /etc/ppp/pap-secrets would be "", to
avoid the need to have the same secret in two places.
.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, \fIipppd\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.
.LP
In some cases it is desirable to allow some hosts which can't
authenticate themselves to connect and use one of a restricted set of
IP addresses, even when the local host generally requires
authentication.  If the peer refuses to authenticate itself when
requested, \fIipppd\fR takes that as equivalent to authenticating with
PAP using the empty string for the username and password.  Thus, by
adding a line to the pap-secrets file which specifies the empty string
for the client and password, it is possible to allow restricted access
to hosts which refuse to authenticate themselves.
.SH ROUTING
.LP
When IPCP negotiation is completed successfully,
.I ipppd
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 \fIipppd\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 \fIipppd\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, \fIipppd\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 DIAGNOSTICS
.LP
Messages are sent to the syslog daemon using facility LOG_DAEMON.
(This can be overridden by recompiling \fIipppd\fR with the macro
LOG_PPP defined as the desired facility.)  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
The \fBdebug\fR option causes the contents of all control packets sent
or received to be logged, that is, all LCP, PAP, CHAP or IPCP packets.
This can be useful if the PPP negotiation does not succeed.
If debugging is enabled at compile time, the \fBdebug\fR option also
causes other debugging messages to be logged.
.LP
Debugging can also be enabled or disabled by sending a
SIGUSR1 to the
.I ipppd
process.  This signal acts as a toggle.
.SH FILES
.TP
.B /var/run/ipppd.pid \fR
Process-ID for \fIipppd\fR process on ppp interface unit \fIn\fR.
.TP
.B /etc/ppp/ip-up
A program or script which is executed when the link is available for
sending and receiving IP packets (that is, IPCP has come up).  It is
executed with the parameters
.IP
\fIinterface-name tty-device speed local-IP-address
remote-IP-address\fR
.IP
and with its standard input,
output and error streams redirected to \fB/dev/null\fR.
.IP
This program or script is executed with the same real and effective
user-ID as \fIipppd\fR, that is, at least the effective user-ID and
possibly the real user-ID will be \fBroot\fR.  This is so that it can
be used to manipulate routes, run privileged daemons (e.g.
\fBsendmail\fR), etc.  Be careful that the contents of the
/etc/ppp/ip-up and /etc/ppp/ip-down scripts do not compromise your
system's security.
.TP
.B /etc/ppp/ip-down
A program or script which is executed when the link is no longer
available for sending and receiving IP packets.  This script can be
used for undoing the effects of the /etc/ppp/ip-up script.  It is
invoked with the same parameters as the ip-up script, and the same
security considerations apply, since it is executed with the same
effective and real user-IDs as \fIipppd\fR.
.TP
.B /etc/ppp/ipx-up
A program or script which is executed when the link is available for
sending and receiving IPX packets (that is, IPXCP has come up).  It is
executed with the parameters
.IP
\fIinterface-name tty-device speed network-number local-IPX-node-address
remote-IPX-node-address local-IPX-routing-protocol remote-IPX-routing-protocol
local-IPX-router-name remote-IPX-router-name ipparam ipppd-pid\fR 
.IP
and with its standard input,
output and error streams redirected to \fB/dev/null\fR.
.br
.IP
The local-IPX-routing-protocol and remote-IPX-routing-protocol field
may be one of the following:
.IP
NONE      to indicate that there is no routing protocol
.br
RIP       to indicate that RIP/SAP should be used
.br
NLSP      to indicate that Novell NLSP should be used
.br
RIP NLSP  to indicate that both RIP/SAP and NLSP should be used
.br
.IP
This program or script is executed with the same real and effective
user-ID as \fIipppd\fR, that is, at least the effective user-ID and
possibly the real user-ID will be \fBroot\fR.  This is so that it can
be used to manipulate routes, run privileged daemons (e.g.
\fBripd\fR), etc.  Be careful that the contents of the
/etc/ppp/ipx-up and /etc/ppp/ipx-down scripts do not compromise your
system's security.
.TP
.B /etc/ppp/ipx-down
A program or script which is executed when the link is no longer
available for sending and receiving IPX packets.  This script can be
used for undoing the effects of the /etc/ppp/ipx-up script.  It is
invoked with the same parameters as the ipx-up script, and the same
security considerations apply, since it is executed with the same
effective and real user-IDs as \fIipppd\fR.
.TP
.B /etc/ppp/auth-up
This program or script is executed after successful authentication with
the following parameters:
.I interface name,
.I authentication user name,
.I username of ipppd,
.I devicename,
.I speed,
.I remote number
.TP
.B /etc/ppp/auth-down
This program or script is executed after a disconnection with
the following parameters:
.I interface name,
.I authentication user name,
.I username of ipppd,
.I devicename,
.I speed,
.I remote number
.TP
.B /etc/ppp/auth-fail
This program or script is executed after a authentication failure with
the following parameters:
.I interface name,
.I authentication user name,
.I username of ipppd,
.I devicename,
.I speed,
.I remote number,
.I failure reason
 Valid reasons are: 
  1 = Timeout during pap auth
  2 = pap protocol rejected
  3 = pap secrets invalid
  9 = Timeout during chap auth
 10 = chap protocol rejected
 11 = chap secrets invalid
.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/ioptions
System default options for
.I ipppd,
read before user default options or command-line options.
.SH SEE ALSO
.TP
.BR ttyI "(4), " isdnctrl "(8), " ipppstats "(8), "
.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 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.
.TP
.B RFC1548
Simpson, W.A.
.I The Point\-to\-Point Protocol (PPP).
1993 December.
.TP
.B RFC1549
Simpson, W.A.
.I PPP in HDLC Framing.
1993 December
.SH NOTES
The following signals have the specified effect when sent to the
.I ipppd
process.
.TP
.B SIGINT, SIGTERM
These signals cause \fBipppd\fR to terminate the link (by closing LCP),
restore the serial device settings, and exit.
.TP
.B SIGHUP
This signal causes \fBipppd\fR to terminate the link, restore the
serial device settings, and close the serial device.  If the
\fBpersist\fR option has been specified, \fBipppd\fR will try to reopen
the serial device and start another connection.  Otherwise \fBipppd\fR
will exit.
.TP
.B SIGUSR2
This signal causes
.B ipppd
to renegotiate compression.  This can be useful to re-enable
compression after it has been disabled as a result of a fatal
decompression error.  With the BSD Compress scheme, fatal
decompression errors generally indicate a bug in one or other
implementation.
.SH AUTHORS
Originally written by
Drew Perkins,
Brad Clements,
Karl Fox,
Greg Christy,
Brad Parker,
Paul Mackerras <paulus@cs.anu.edu.au> 
for (original) pppd.
.PP
Changes for ipppd by Klaus Franken <kfr@suse.de> and
Michael Hipp <Michael.Hipp@student.uni-tuebingen.de>.
.PP
Removal of pppd specific options and polish                  
by Frank Elsner <Elsner@zrz.TU-Berlin.DE>.