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/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/slip.login but, if
particular hosts need special initialization, the file
/etc/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.

args The arguments from the /etc/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/slip.logout or
/etc/slip.logout.loginname is executed if it exists. It is given
the same arguments as the login script.

Format of /etc/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 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 speed 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). speed is the baud rate of the slip line. MachTen
currently supports the following baud rates: 300, 600, 1200, 1800,
2400, 4800, 9600 and 19200. Specifing a speed of 0 will use the
baud rate previously assigned to the line. Opt-args are optional
arguments used to configure the line. The options supported are:
normal, compress, noicmp and autocomp. TCP header compressions is
enabled by the compress option. The autocomp options will enable
TCP header compression if the other end of the slip line is
compressing TCP headers. The option noicmp prevents icmp messages
from traversing the line.

EXAMPLE
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:ikhuy6:250:1:slip line to foo:/tmp:/etc/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 speed

where ‘hostname‘ will be evaluated by sh 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, a site can create a group, say
slip, that only the slip login accounts are put in then make sure
that /etc/sliplogin is in group slip and mode 4550 (setuid root,
only group slip can execute binary).

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.

Err Severity

ioctl (TCGETS): reason
A ioctl to get the line parameters failed.

ioctl (TCSETS): reason
A ioctl to set the line parameters failed.

/etc/slip.hosts: reason
The /etc/slip.hosts file could not be opened.

access denied for user
No entry for user was found in /etc/slip.hosts.

Notice Severity

attaching slip unit unit for loginname
SLIP unit unit was successfully attached.