--- name: "sliplogin" section: "8" platform: "linux" package: "sliplogin" version: "2.0.2-3" release: "Debian 2.2 (Potato)" platforms: ["linux"] url: "https://new.carta.tech/sliplogin" --- # sliplogin(8) attach a serial line network interface ## 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). The loginname '\*' in slip.hosts matches every user so everyone who can execute sliplogin and is not listed in slip.hosts will use this default entry. If you really need a default user, please put this entry at the last line in slip.hosts, so it will be used if the sliplogin user is not listed in slip.hosts. If you put the default user as first entry in slip.hosts all other entries will be ignored. Another symbolic loginname is '+'. If a loginname starts with '+' sliplogin will try to read the NIS map slip.hosts instead of slip.hosts. You can override the local IP found in the NIS map by entering it after the '+' sign. 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 (slip.login) is invoked to initialize the slip interface with the appropriate local and remote IP address, netmask, etc. A line in slip.hosts usually consists of the fields loginname, local address, remote address, netmask, slipmode, timeout and perhaps up to 3 more options which will be passed to slip.login. 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. If you use the default user '\*' sliplogin looks for slip.login.\*, but '\*' is not used as a wildcard. If no slip.login.\* exists, the usual slip.login will be used. The script is invoked with the parameters - *slipunit* The unit identifier of the slip interface assigned to this line. E.g., **sl0**. - *speed* The speed of the line. - *pid* The process id of sliplogin. - *args* The arguments from the */etc/slip.hosts* entry: *loginname,* *local* *address,* *remote* *address,* *netmask* *and* *the* *options.* Only the super-user may attach a network interface. The interface is automatically detached when the other end hangs up, the **sliplogin** process dies or the client didn't send a packet while the specified timeout in /etc/slip.hosts. 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. For default user '\*' sliplogin looks for slip.logout.\* and if it doesn't exist, it uses slip.logout. ### Format of /etc/slip.hosts Comments (lines starting with a \`#') and blank lines are ignored. Other lines must start with a *loginname* Arguments are separated by white space and follow normal [sh(1)](/sh/1.md) quoting conventions (however, *loginname* cannot be quoted). Usually, lines have the form ``` loginname local-address remote-address netmask slipmode timeout opt-args ``` where *local-address* is the IP host name or address of the local end of the slip line. *remote-address* is the IP host name or address of the remote end of the slip line or the DYNAMIC keyword which will be translated into an address from the slip.tty file. *netmask* is the appropriate IP netmask. These arguments are passed directly to [ifconfig(8)](/ifconfig/8.md). *slipmode* is either normal, compressed, ax25, 6bit or auto where auto uses the kernel auto detection to find out if the client uses normal or compressed (Van Jacobson) slip. *timeout* is ignored if negative or else used as value in seconds to wait for packets to be sent from the client before **sliplogin** sliplogin terminates. *Opt-args* are optional arguments used to configure the line. ### The Format of /etc/slip.tty is simple. A line that starts with '#' is treated as a comment otherwise **sliplogin** expects in column 1 the name of the slipdevice and in column 2 the IP host name or adress that you wish to assign to this device. ## 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:ikhuy6:2010:1:slip line to foo:/tmp:/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 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 */sbin/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)](/syslogd/8.md), 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/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. ## BUGS No bugs found yet. ## SEE ALSO [slattach(8)](/slattach/8.md), [syslogd(8)](/syslogd/8.md), [dip(8)](/dip/8.md) ## HISTORY The **sliplogin** command