SLIPLOGIN(8) BSD System Manager's Manual SLIPLOGIN(8)NAMEsliplogin — attach a serial line network interface
SYNOPSISsliplogin [loginname [device]]
DESCRIPTION
The sliplogin utility is used to turn the terminal line on standard input
(or device) into a Serial Line IP (SLIP) link to a remote host. To do
this, the program searches the file /etc/sliphome/slip.hosts for an entry
matching loginname (which defaults to the current login name if omitted).
If a matching entry is found, the line is configured appropriately for
slip (8-bit transparent i/o) and converted to SLIP line discipline using
the optional line discipline parameters.
The optional line discipline parameters consist of one or more of the
following; ‘normal’, ‘compress’, ‘noicmp’, or ‘autocomp’ which correspond
respectively to ‘use normal line discipline’ (no header compression),
‘enable VJ header compression’, ‘throw away ICMP packets’, and ‘auto
enable VJ header compression’ (only if the remote end of the link also
supports it).
Then a shell script is invoked to initialize the slip interface with the
appropriate local and remote IP address, netmask, etc.
The usual initialization script is /etc/sliphome/slip.login but, if par‐
ticular hosts need special initialization, the file
/etc/sliphome/slip.login.loginname will be executed instead if it exists.
The script is invoked with the parameters
slipunit The unit number of the slip interface assigned to this line.
E.g., 0 for sl0.
speed The speed of the line.
args The arguments from the /etc/sliphome/slip.hosts entry, in order
starting with loginname.
Only the super-user may attach a network interface. The interface is
automatically detached when the other end hangs up or the sliplogin
process dies. If the kernel slip module has been configured for it, all
routes through that interface will also disappear at the same time. If
there is other processing a site would like done on hangup, the file
/etc/sliphome/slip.logout or /etc/sliphome/slip.logout.loginname is exe‐
cuted if it exists. It is given the same arguments as the login script.
Format of /etc/sliphome/slip.hosts
Comments (lines starting with a `#') and blank lines (or started with
space) are ignored. Other lines must start with a loginname but the
remaining arguments can be whatever is appropriate for the slip.login
file that will be executed for that name. Arguments are separated by
white space and follow normal sh(1) quoting conventions (however,
loginname cannot be quoted). Usually, lines have the form
loginname local-address remote-address netmask opt-args
where local-address and remote-address are the IP host names or addresses
of the local and remote ends of the slip line and netmask is the appro‐
priate IP netmask. These arguments are passed directly to ifconfig(8).
Opt-args are optional arguments used to configure the line.
FreeBSD Additions
An additional SLIP configuration file (if present) is
/etc/sliphome/slip.slparms. If particular hosts need different configu‐
rations, the file /etc/sliphome/slip.slparms.loginname will be parsed
instead if it exists.
Format of /etc/sliphome/slip.slparms*
Comments (lines starting with a `#') and blank lines (or started with
space) are ignored. This file contains from one to three numeric parame‐
ters separated with spaces, in order: keepalive, outfill and slunit.
keepalive Set SLIP "keep alive" timeout in seconds. If FRAME_END is not
received in this amount of time, sliplogin closes the line and
exits. The default value is no timeout (zero).
outfill Set SLIP "out fill" timeout in seconds. It forces at least
one FRAME_END to be sent during this time period, which is
necessary for the "keep alive" timeout on the remote side.
The default value is no timeout (zero).
slunit Set the SLIP unit number directly. Use with caution, because
no check is made for two interfaces with same number. By
default sliplogin dynamically assigns the unit number.
If latter two parameters are omitted, they will not affect the corre‐
sponding SLIP configuration. If any of first two parameters is equal to
zero, it will not affect the corresponding SLIP configuration.
FILES
/etc/sliphome/slip.hosts
list of host login names and parameters.
/etc/sliphome/slip.login
script executed when a connection is made.
/etc/sliphome/slip.login.loginname
script executed when a connection is made by loginname.
/etc/sliphome/slip.logout
script executed when a connection is lost.
/etc/sliphome/slip.logout.loginname
script executed when a connection is lost by loginname.
/etc/sliphome/slip.slparms
extra parameters file.
/etc/sliphome/slip.slparms.loginname
extra parameters file for loginname.
/var/run/ttyXn.if
contains the name of the network interface used by the sliplogin
process on ttyXn.
/var/run/slX.pid
contains the PID of the sliplogin process which is using inter‐
face slX.
EXAMPLES
The normal use of sliplogin is to create a /etc/passwd entry for each
legal, remote slip site with sliplogin as the shell for that entry.
E.g.,
Sfoo:ikhuy6:2010:1:slip line to foo:/tmp:/usr/sbin/sliplogin
(Our convention is to name the account used by remote host hostname as
Shostname.) Then an entry is added to slip.hosts that looks like:
Sfoo `hostname` foo netmask
where `hostname` will be evaluated by sh(1) to the local host name and
netmask is the local host IP netmask.
Note that sliplogin must be setuid to root and, while not a security
hole, moral defectives can use it to place terminal lines in an unusable
state and/or deny access to legitimate users of a remote slip line. To
prevent this, sliplogin is installed as user root, group network and mode
4550 so that only members of group network may run sliplogin. The system
administrator should make sure that all legitimate users are a member of
the correct group.
DIAGNOSTICS
The sliplogin utility logs various information to the system log daemon,
syslogd(8), with a facility code of daemon. The messages are listed
here, grouped by severity level.
Error Severity
ioctl (TCGETS): reason
A TCGETS ioctl() to get the line parameters failed.
ioctl (TCSETS): reason
A TCSETS ioctl() to set the line parameters failed.
/etc/sliphome/slip.hosts: reason
The /etc/sliphome/slip.hosts file could not be opened.
access denied for user
No entry for user was found in /etc/sliphome/slip.hosts.
Notice Severity
attaching slip unit unit for loginname
SLIP unit unit was successfully attached.
SEE ALSOslattach(8), syslogd(8)
/usr/share/examples/sliplogin
HISTORY
The sliplogin utility appeared in 4.3BSD-Reno.
BSD January 5, 1994 BSD
