linux_kernel/Documentation/networking

sb1000 is a module network device driver for the General Instrument (also known
as NextLevel) SURFboard1000 internal cable modem board. This is an ISA card
which is used by a number of cable TV companies to provide cable modem access.
It's a one-way downstream-only cable modem, meaning that your upstream net link
is provided by your regular phone modem.

This driver was written by Franco Venturi . He deserves
a great deal of thanks for this wonderful piece of code!

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Support for this device is now a part of the standard Linux kernel. The
driver source code file is drivers/net/sb1000.c. In addition to this
you will need:

1.) The "cmconfig" program. This is a utility which supplements "ifconfig"
to configure the cable modem and network interface (usually called "cm0");
and

2.) Several PPP scripts which live in /etc/ppp to make connecting via your
cable modem easy.

These utilities can be obtained from:

http://www.jacksonville.net/~fventuri/

in Franco's original source code distribution .tar.gz file. Support for
the sb1000 driver can be found at:

http://home.adelphia.net/~siglercm/sb1000.html
http://linuxpower.cx/~cable/

along with these utilities.

3.) The standard isapnp tools. These are necessary to configure your SB1000
card at boot time (or afterwards by hand) since it's a PnP card.

If you don't have these installed as a standard part of your Linux
distribution, you can find them at:

http://www.roestock.demon.co.uk/isapnptools/

or check your Linux distribution binary CD or their web site. For help with
isapnp, pnpdump, or /etc/isapnp.conf, go to:

http://www.roestock.demon.co.uk/isapnptools/isapnpfaq.html

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To make the SB1000 card work, follow these steps:

1.) Run `make config', or `make menuconfig', or `make xconfig', whichever
you prefer, in the top kernel tree directory to set up your kernel
configuration. Make sure to say "Y" to "Prompt for development drivers"
and to say "M" to the sb1000 driver. Also say "Y" or "M" to all the standard
networking questions to get TCP/IP and PPP networking support.

2.) *BEFORE* you build the kernel, edit drivers/net/sb1000.c. Make sure
to redefine the value of READ_DATA_PORT to match the I/O address used
by isapnp to access your PnP cards. This is the value of READPORT in
/etc/isapnp.conf or given by the output of pnpdump.

3.) Build and install the kernel and modules as usual.

4.) Boot your new kernel following the usual procedures.

5.) Set up to configure the new SB1000 PnP card by capturing the output
of "pnpdump" to a file and editing this file to set the correct I/O ports,
IRQ, and DMA settings for all your PnP cards. Make sure none of the settings
conflict with one another. Then test this configuration by running the
"isapnp" command with your new config file as the input. Check for
errors and fix as necessary. (As an aside, I use I/O ports 0x110 and
0x310 and IRQ 11 for my SB1000 card and these work well for me. YMMV.)
Then save the finished config file as /etc/isapnp.conf for proper configuration
on subsequent reboots.

6.) Download the original file sb1000-1.1.2.tar.gz from Franco's site or one of
the others referenced above. As root, unpack it into a temporary directory and
do a `make cmconfig' and then `install -c cmconfig /usr/local/sbin'. Don't do
`make install' because it expects to find all the utilities built and ready for
installation, not just cmconfig.

7.) As root, copy all the files under the ppp/ subdirectory in Franco's
tar file into /etc/ppp, being careful not to overwrite any files that are
already in there. Then modify ppp@gi-on to set the correct login name,
phone number, and frequency for the cable modem. Also edit pap-secrets
to specify your login name and password and any site-specific information
you need.

8.) Be sure to modify /etc/ppp/firewall to use ipchains instead of
the older ipfwadm commands from the 2.0.x kernels. There's a neat utility to
convert ipfwadm commands to ipchains commands:

http://users.dhp.com/~whisper/ipfwadm2ipchains/

You may also wish to modify the firewall script to implement a different
firewalling scheme.

9.) Start the PPP connection via the script /etc/ppp/ppp@gi-on. You must be
root to do this. It's better to use a utility like sudo to execute
frequently used commands like this with root permissions if possible. If you
connect successfully the cable modem interface will come up and you'll see a
driver message like this at the console:

cm0: sb1000 at (0x110,0x310), csn 1, S/N 0x2a0d16d8, IRQ 11.
sb1000.c:v1.1.2 6/01/98 (fventuri@mediaone.net)

The "ifconfig" command should show two new interfaces, ppp0 and cm0.
The command "cmconfig cm0" will give you information about the cable modem
interface.

10.) Try pinging a site via `ping -c 5 www.yahoo.com', for example. You should
see packets received.

11.) If you can't get site names (like www.yahoo.com) to resolve into
IP addresses (like 204.71.200.67), be sure your /etc/resolv.conf file
has no syntax errors and has the right nameserver IP addresses in it.
If this doesn't help, try something like `ping -c 5 204.71.200.67' to
see if the networking is running but the DNS resolution is where the
problem lies.

12.) If you still have problems, go to the support web sites mentioned above
and read the information and documentation there.

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Common problems:

1.) Packets go out on the ppp0 interface but don't come back on the cm0
interface. It looks like I'm connected but I can't even ping any
numerical IP addresses. (This happens predominantly on Debian systems due
to a default boot-time configuration script.)

Solution -- As root `echo 0 > /proc/sys/net/ipv4/conf/cm0/rp_filter' so it
can share the same IP address as the ppp0 interface. Note that this
command should probably be added to the /etc/ppp/cablemodem script
*right*between* the "/sbin/ifconfig" and "/sbin/cmconfig" commands.
You may need to do this to /proc/sys/net/ipv4/conf/ppp0/rp_filter as well.
If you do this to /proc/sys/net/ipv4/conf/default/rp_filter on each reboot
(in rc.local or some such) then any interfaces can share the same IP
addresses.

2.) I get "unresolved symbol" error messages on executing `insmod sb1000.o'.

Solution -- You probably have a non-matching kernel source tree and
/usr/include/linux and /usr/include/asm header files. Make sure you
install the correct versions of the header files in these two directories.
Then rebuild and reinstall the kernel.

3.) When isapnp runs it reports an error, and my SB1000 card isn't working.

Solution -- There's a problem with later versions of isapnp using the "(CHECK)"
option in the lines that allocate the two I/O addresses for the SB1000 card.
This first popped up on RH 6.0. Delete "(CHECK)" for the SB1000 I/O addresses.
Make sure they don't conflict with any other pieces of hardware first! Then
rerun isapnp and go from there.

4.) I can't execute the /etc/ppp/ppp@gi-on file.

Solution -- As root do `chmod ug+x /etc/ppp/ppp@gi-on'.

5.) The firewall script isn't working (with 2.2.x and higher kernels).

Solution -- Use the ipfwadm2ipchains script referenced above to convert the
/etc/ppp/firewall script from the deprecated ipfwadm commands to ipchains.

6.) I'm getting *tons* of firewall deny messages in the /var/kern.log,
/var/messages, and/or /var/syslog files, and they're filling up my /var
partition!!!

Solution -- First, tell your ISP that you're receiving DoS (Denial of Service)
and/or portscanning (UDP connection attempts) attacks! Look over the deny
messages to figure out what the attack is and where it's coming from. Next,
edit /etc/ppp/cablemodem and make sure the ",nobroadcast" option is turned on
to the "cmconfig" command (uncomment that line). If you're not receiving these
denied packets on your broadcast interface (IP address xxx.yyy.zzz.255
typically), then someone is attacking your machine in particular. Be careful
out there....

7.) Everything seems to work fine but my computer locks up after a while
(and typically during a lengthy download through the cable modem)!

Solution -- You may need to add a short delay in the driver to 'slow down' the
SURFboard because your PC might not be able to keep up with the transfer rate
of the SB1000. To do this, it's probably best to download Franco's
sb1000-1.1.2.tar.gz archive and build and install sb1000.o manually. You'll
want to edit the 'Makefile' and look for the 'SB1000_DELAY'
define. Uncomment those 'CFLAGS' lines (and comment out the default ones)
and try setting the delay to something like 60 microseconds with:
'-DSB1000_DELAY=60'. Then do `make' and as root `make install' and try
it out. If it still doesn't work or you like playing with the driver, you may
try other numbers. Remember though that the higher the delay, the slower the
driver (which slows down the rest of the PC too when it is actively
used). Thanks to Ed Daiga for this tip!

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Credits: This README came from Franco Venturi's original README file which is
still supplied with his driver .tar.gz archive. I and all other sb1000 users
owe Franco a tremendous "Thank you!" Additional thanks goes to Carl Patten
and Ralph Bonnell who are now managing the Linux SB1000 web site, and to
the SB1000 users who reported and helped debug the common problems listed
above.


Clemmitt Sigler
csigler@vt.edu