NAME
sliplogin —
attach a serial line network
interface
SYNOPSIS
sliplogin |
[loginname] |
DESCRIPTION
sliplogin is used to turn the terminal
line on standard input 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. 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 particular 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 superuser 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 executed 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 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 whitespace 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 appropriate IP netmask. These arguments are passed directly to ifconfig(8). Opt-args are optional arguments used to configure the line.
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 is only executable by users in group network. To
permit use, place a user into that group. Users in that group are of course
also able to use sliplogin to place terminal lines
in an unusable state and/or deny access to legitimate users of a remote slip
line.
DIAGNOSTICS
sliplogin 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.
- ioctl (TCGETS): reason
- A
TCGETSioctl() to get the line parameters failed. - ioctl (TCSETS): reason
- A
TCSETSioctl() 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.
- attaching slip unit unit for loginname
- SLIP unit unit was successfully attached.