Slip.xif - freemint/freemint GitHub Wiki

Here are some notes on the new SLIP driver, slip.xif.

Slip.xif is a new, hardware independent SLIP driver for MintNet. It uses Mint devices to write/read data to/from serial ports. Note that you can use only devices that support Fselect()! Modm0dev by T. Bousch does this, Mint pty's work too. All the Mint builtin serial devices support this in Mint versions >= 1.11. If you are going to use the Mint builtin devices, ie /dev/modem[12] or /dev/serial[12], note the following: The Mint builtin serial devices use the BIOS Bcon* functions. They are rather slow and buggy. So if you want to do SLIP at 19200 baud or higher you WILL NEED to get a replacement for them. I use hsmodem4 by Harun Scheutzow, a set of programs that replace the TOS serial routines with bugfree and faster ones on ST, STe, TT, Falcon. You can get hsmodem from most ftp sites and mailboxes that archive Atari software. Harun writes in one of the README's in that the drivers have to be run AFTER mint.prg. This is wrong -- you MUST MUST MUST first run the serial drivers and then Mint! Without such a replacement you will get endless receiver overruns at speeds > 9600 baud on 8MHz ST(e)s!

Establishing a SLIP connection (dialout)

You must have the loopback interface -- lo0 -- set up and running first. Do this with the command

/etc/ifconfig lo0 addr 127.0.0.1 up

Then connect (dial in) to the remote machine using for example /dev/modem1 -- much like with the old SLIP driver. Then suspend your comms program without hanging up the line. MintNet provides a utility called slattach to setup a SLIP connection. This command does all the dirty work for you, eg set the tty into raw mode, choose a free SLIP interface, attach the tty device to the SLIP interface, setup the SLIP interface, make routing table entries. After having done this slattach usually waits until it receives one of the following signals: SIGINT, SIGQUIT, SIGTERM, SIGHUP. Then it shuts down the SLIP interface, resets the tty modes, deletes routing table entries and hangs up the line (dropping DTR works ONLY with /dem/modem1 and modm0dev, so be careful!) and exits.

So usually you issue the following command to attach eg /dev/modem1 to a SLIP interface when the remote host's IP address is 149.10.1.1 and the local IP address is 149.10.1.2:

/etc/slattach -t /dev/modem1 -r 149.10.1.1 -l 149.10.1.2 &

If the -t option is missing, slattach tries to use stdin as the device, so

/dev/slattach -r 149.10.1.1 -l 149.10.1.2 < /dev/modem1 &

does the same job. Note that slattach calls /etc/route and /etc/ifconfig, so you must copy or link them there (note that ifconfig and route need to be run as root). If you are done with the connection, send slattach one of the above signals or simply bring it to the foreground and press Control-C. Slattach uses about 40 kB of memory when waiting in the background. If you need this memory for other things, you can give slattach the option -e telling it to exit after having set up the connection. Note that you have then to shut down the interface, reset tty modes and hangup the line yourself when finished with the connection! The -t option instructs slattach to NOT hang up the line when exiting. The -p {slip,ppp,cslip} option specifies the protocol type that should be used. Default is slip. Give slattach the -d option to tell it NOT to install a default routing entry. The -s $speed sets the line speed to $speed. You may also use the program "dip" to establish slip connections, which is not contained in this archive. Dip uses a simple script language to automate the login process. Look for the file dip-337u-01.tgz.

Dialin SLIP

You can use slattach for dialin purposes, too. I have a line

slip:abcdefg:1010:100:SLIP account:/tmp:/etc/slip

in my /etc/passwd. /etc/slip is a shell script which asks the user for its hosts name and then runs slattach on the login tty:

#!/bin/sh /etc/slip
export SHELL=/bin/sh
echo "Your hostname: "
read RHOST
exec /etc/slattach -p cslip -r $RHOST -l 149.10.1.2

This may look a bit wired to experienced shell programmers :), but that's because of some oddities with the MintLib and the login program.

/usr/bin/login doesn't allow to give parameters to the login program in /etc/passwd, so something like
```
slip:abc:1010:1000:SLIP account:/tmp/:/bin/sh /etc/slip
```
does not work. -> Must use shell bang (ie shell script starting with #!).
Earlier versions of the MintLibs shell bang emulation code call the interpreter (/bin/sh) with argv[0] as the file to emulate -- which is "-slip" because of /usr/bin/login. (Cured in PL 44). -> Must use #!/bin/sh /etc/slip instead of #!/bin/sh
/usr/bin/login sets SHELL to the login program, ie /etc/slip. popen uses $SHELL as the interpreter, ie /etc/slip. Thus we need to set SHELL to /bin/sh and export it to make popen() (used in slattach) use /bin/sh.

For this script to work you must set UNIXMODE in /etc/rc* or mint.cnf to something containing 's'. This tells the MintLibs to elmulate shell scripts. Second, /etc/slattach must be setuid root (chmod u+s /etc/slattach). So I can log in as 'slip' over modem. Then I will be asked for the hostname and slattach will be run putting the tty line into SLIP mode. When I hang up my modem, slattach will receive a HUP signal (only if you use modm0dev) and exit.