WSL2-Linux-Kernel/Documentation/networking
David Howells 372ee16386 rxrpc: Fix races between skb free, ACK generation and replying
Inside the kafs filesystem it is possible to occasionally have a call
processed and terminated before we've had a chance to check whether we need
to clean up the rx queue for that call because afs_send_simple_reply() ends
the call when it is done, but this is done in a workqueue item that might
happen to run to completion before afs_deliver_to_call() completes.

Further, it is possible for rxrpc_kernel_send_data() to be called to send a
reply before the last request-phase data skb is released.  The rxrpc skb
destructor is where the ACK processing is done and the call state is
advanced upon release of the last skb.  ACK generation is also deferred to
a work item because it's possible that the skb destructor is not called in
a context where kernel_sendmsg() can be invoked.

To this end, the following changes are made:

 (1) kernel_rxrpc_data_consumed() is added.  This should be called whenever
     an skb is emptied so as to crank the ACK and call states.  This does
     not release the skb, however.  kernel_rxrpc_free_skb() must now be
     called to achieve that.  These together replace
     rxrpc_kernel_data_delivered().

 (2) kernel_rxrpc_data_consumed() is wrapped by afs_data_consumed().

     This makes afs_deliver_to_call() easier to work as the skb can simply
     be discarded unconditionally here without trying to work out what the
     return value of the ->deliver() function means.

     The ->deliver() functions can, via afs_data_complete(),
     afs_transfer_reply() and afs_extract_data() mark that an skb has been
     consumed (thereby cranking the state) without the need to
     conditionally free the skb to make sure the state is correct on an
     incoming call for when the call processor tries to send the reply.

 (3) rxrpc_recvmsg() now has to call kernel_rxrpc_data_consumed() when it
     has finished with a packet and MSG_PEEK isn't set.

 (4) rxrpc_packet_destructor() no longer calls rxrpc_hard_ACK_data().

     Because of this, we no longer need to clear the destructor and put the
     call before we free the skb in cases where we don't want the ACK/call
     state to be cranked.

 (5) The ->deliver() call-type callbacks are made to return -EAGAIN rather
     than 0 if they expect more data (afs_extract_data() returns -EAGAIN to
     the delivery function already), and the caller is now responsible for
     producing an abort if that was the last packet.

 (6) There are many bits of unmarshalling code where:

 		ret = afs_extract_data(call, skb, last, ...);
		switch (ret) {
		case 0:		break;
		case -EAGAIN:	return 0;
		default:	return ret;
		}

     is to be found.  As -EAGAIN can now be passed back to the caller, we
     now just return if ret < 0:

 		ret = afs_extract_data(call, skb, last, ...);
		if (ret < 0)
			return ret;

 (7) Checks for trailing data and empty final data packets has been
     consolidated as afs_data_complete().  So:

		if (skb->len > 0)
			return -EBADMSG;
		if (!last)
			return 0;

     becomes:

		ret = afs_data_complete(call, skb, last);
		if (ret < 0)
			return ret;

 (8) afs_transfer_reply() now checks the amount of data it has against the
     amount of data desired and the amount of data in the skb and returns
     an error to induce an abort if we don't get exactly what we want.

Without these changes, the following oops can occasionally be observed,
particularly if some printks are inserted into the delivery path:

general protection fault: 0000 [#1] SMP
Modules linked in: kafs(E) af_rxrpc(E) [last unloaded: af_rxrpc]
CPU: 0 PID: 1305 Comm: kworker/u8:3 Tainted: G            E   4.7.0-fsdevel+ #1303
Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014
Workqueue: kafsd afs_async_workfn [kafs]
task: ffff88040be041c0 ti: ffff88040c070000 task.ti: ffff88040c070000
RIP: 0010:[<ffffffff8108fd3c>]  [<ffffffff8108fd3c>] __lock_acquire+0xcf/0x15a1
RSP: 0018:ffff88040c073bc0  EFLAGS: 00010002
RAX: 6b6b6b6b6b6b6b6b RBX: 0000000000000000 RCX: ffff88040d29a710
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88040d29a710
RBP: ffff88040c073c70 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: ffff88040be041c0 R15: ffffffff814c928f
FS:  0000000000000000(0000) GS:ffff88041fa00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa4595f4750 CR3: 0000000001c14000 CR4: 00000000001406f0
Stack:
 0000000000000006 000000000be04930 0000000000000000 ffff880400000000
 ffff880400000000 ffffffff8108f847 ffff88040be041c0 ffffffff81050446
 ffff8803fc08a920 ffff8803fc08a958 ffff88040be041c0 ffff88040c073c38
Call Trace:
 [<ffffffff8108f847>] ? mark_held_locks+0x5e/0x74
 [<ffffffff81050446>] ? __local_bh_enable_ip+0x9b/0xa1
 [<ffffffff8108f9ca>] ? trace_hardirqs_on_caller+0x16d/0x189
 [<ffffffff810915f4>] lock_acquire+0x122/0x1b6
 [<ffffffff810915f4>] ? lock_acquire+0x122/0x1b6
 [<ffffffff814c928f>] ? skb_dequeue+0x18/0x61
 [<ffffffff81609dbf>] _raw_spin_lock_irqsave+0x35/0x49
 [<ffffffff814c928f>] ? skb_dequeue+0x18/0x61
 [<ffffffff814c928f>] skb_dequeue+0x18/0x61
 [<ffffffffa009aa92>] afs_deliver_to_call+0x344/0x39d [kafs]
 [<ffffffffa009ab37>] afs_process_async_call+0x4c/0xd5 [kafs]
 [<ffffffffa0099e9c>] afs_async_workfn+0xe/0x10 [kafs]
 [<ffffffff81063a3a>] process_one_work+0x29d/0x57c
 [<ffffffff81064ac2>] worker_thread+0x24a/0x385
 [<ffffffff81064878>] ? rescuer_thread+0x2d0/0x2d0
 [<ffffffff810696f5>] kthread+0xf3/0xfb
 [<ffffffff8160a6ff>] ret_from_fork+0x1f/0x40
 [<ffffffff81069602>] ? kthread_create_on_node+0x1cf/0x1cf

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-08-06 00:08:40 -04:00
..
caif Documentation/networking/caif: Update documentation 2012-06-25 16:44:12 -07:00
dsa Documentation: networking: dsa: Describe port_vlan_filtering 2016-05-25 12:45:40 -07:00
mac80211_hwsim
timestamping Doc: networking: txtimestamp: fix printf format warning 2015-06-05 07:59:10 +09:00
00-INDEX Documentation/networking: add checksum-offloads.txt to explain LCO 2016-02-12 05:52:16 -05:00
3c509.txt drivers/net: delete all code/drivers depending on CONFIG_MCA 2012-05-17 16:37:41 -04:00
6lowpan.txt documentation: networking: add 6lowpan documentation 2015-08-11 22:05:36 +02:00
6pack.txt
LICENSE.qla3xxx
LICENSE.qlcnic qlcnic: Updating copyright information. 2013-02-04 21:08:48 -05:00
LICENSE.qlge qlge: Updating Schultz LICENSE.qlge file. 2012-02-04 15:59:30 -05:00
Makefile Documentation: use subdir-y to avoid unnecessary built-in.o files 2014-09-26 11:02:55 +02:00
PLIP.txt
README.ipw2100
README.ipw2200 Fix common misspellings 2011-03-31 11:26:23 -03:00
README.sb1000
alias.txt
altera_tse.txt Documentation: networking: fix spelling mistakes 2016-04-28 14:21:13 -04:00
arcnet-hardware.txt
arcnet.txt Documentation: Fix references to defunct linux-net@vger.kernel.org 2013-07-09 12:42:19 -07:00
atm.txt
ax25.txt
batman-adv.txt batman-adv: Switch to HTTPS version of links 2016-02-03 09:54:39 +08:00
baycom.txt Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
bonding.txt bonding: update documentation section after dev->trans_start removal 2016-05-04 17:07:13 -04:00
bridge.txt bridge: update documentation references 2012-07-19 10:48:07 -07:00
can.txt can: bcm: add documentation for CAN FD support 2016-06-17 15:39:47 +02:00
cdc_mbim.txt net: cdc_mbim: add driver documentation 2014-05-13 17:46:09 -04:00
checksum-offloads.txt Documentation/networking: more accurate LCO explanation 2016-05-08 23:50:31 -04:00
cops.txt
cs89x0.txt networking/cs89x0.txt: delete stale information about hand patching 2013-01-11 16:52:26 -08:00
cxacru-cf.py
cxacru.txt
cxgb.txt
dccp.txt doc: spelling error changes 2014-05-05 15:32:05 +02:00
dctcp.txt tcp: add rfc3168, section 6.1.1.1. fallback 2015-05-19 16:53:37 -04:00
de4x5.txt
decnet.txt
dl2k.txt Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
dm9000.txt
dmfe.txt Documentation: networking: dmfe.txt: Remove the maintainer of orphan networking driver 2011-09-15 14:49:43 -04:00
dns_resolver.txt KEYS: Allow special keyrings to be cleared 2012-01-19 14:38:51 +11:00
driver.txt doc, net: Update ndo_start_xmit return type and values 2012-04-06 02:43:13 -04:00
e100.txt e100.txt: Cleanup license info in kernel doc 2015-12-03 12:58:10 -08:00
e1000.txt Documentation/networking/: Update Intel wired LAN driver documentation 2013-08-27 16:05:26 -04:00
e1000e.txt Documentation/networking/: Update Intel wired LAN driver documentation 2013-08-27 16:05:26 -04:00
eql.txt
fib_trie.txt fib_trie.txt: fix typo 2014-12-15 11:45:15 -05:00
filter.txt The most interesting thing (IMO) this time around is some beginning 2016-05-19 18:07:25 -07:00
fore200e.txt Doc: Change wikipedia's URL from http to https 2015-06-22 10:14:05 -06:00
framerelay.txt
gen_stats.txt net: sched: do not acquire qdisc spinlock in qdisc/class stats dump 2016-06-07 16:37:14 -07:00
generic-hdlc.txt
generic_netlink.txt Docs/Kconfig: Update: osdl.org -> linuxfoundation.org 2010-11-15 23:50:13 +01:00
gianfar.txt gianfar: Remove sysfs stubs for FIFOCFG and stashing 2014-02-18 15:03:02 -05:00
i40e.txt i40e: adds FCoE to build and updates its documentation 2014-08-02 19:41:13 -07:00
i40evf.txt i40evf: add driver to kernel build system 2013-12-31 16:27:49 -08:00
ieee802154.txt ieee802154: docs: fix project name to linux-wpan as well as some typos 2015-09-17 13:20:05 +02:00
igb.txt igb: doc don't refer to ifconfig 2015-04-09 22:03:20 -07:00
igbvf.txt Documentation/networking/: Update Intel wired LAN driver documentation 2013-08-27 16:05:26 -04:00
ip-sysctl.txt Documentation: ip-sysctl.txt: clarify secure_redirects 2016-05-29 22:40:53 -07:00
ip_dynaddr.txt
ipddp.txt
iphase.txt
ipsec.txt xfrm: Add file to document IPsec corner case 2013-12-16 12:54:05 +01:00
ipv6.txt Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
ipvlan.txt Documentation: networking: fix spelling mistakes 2016-04-28 14:21:13 -04:00
ipvs-sysctl.txt ipvs: add sysctl to ignore tunneled packets 2015-09-17 11:50:02 +09:00
irda.txt
ixgb.txt ixgb: remove references to ifconfig 2015-04-09 22:04:04 -07:00
ixgbe.txt ixgbe: fix documentation 2015-04-09 22:03:54 -07:00
ixgbevf.txt Documentation/networking/: Update Intel wired LAN driver documentation 2013-08-27 16:05:26 -04:00
kcm.txt kcm: Add description in Documentation 2016-03-09 16:36:16 -05:00
l2tp.txt l2tp: remove references to modprobe in documentation 2015-09-25 12:27:23 -07:00
lapb-module.txt
ltpc.txt Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
mac80211-auth-assoc-deauth.txt mac80211: set HT channel before association 2012-04-10 14:54:07 -04:00
mac80211-injection.txt mac80211: document only injected *_RADIOTAP_* flags 2016-04-05 10:48:57 +02:00
mpls-sysctl.txt mpls: Per-device enabling of packet input 2015-04-22 14:24:54 -04:00
multiqueue.txt
netconsole.txt netconsole: implement extended console support 2015-06-25 17:00:39 -07:00
netdev-FAQ.txt doc:net: Fix typo in Documentation/networking 2013-10-30 17:10:20 -04:00
netdev-features.txt net: remove NETDEV_TX_LOCKED support 2016-04-26 15:53:05 -04:00
netdevices.txt net: remove NETDEV_TX_LOCKED support 2016-04-26 15:53:05 -04:00
netif-msg.txt
nf_conntrack-sysctl.txt netfilter: conntrack: allow increasing bucket size via sysctl too 2016-06-24 11:03:28 +02:00
nfc.txt NFC: add Documentation/networking/nfc.txt 2011-07-05 15:26:58 -04:00
openvswitch.txt openvswitch: Add support for unique flow IDs. 2015-01-26 15:45:50 -08:00
operstates.txt doc:net: Fix typo in Documentation/networking 2013-10-30 17:10:20 -04:00
packet_mmap.txt af_packet: pass checksum validation status to the user 2015-03-23 22:01:28 -04:00
phonet.txt Phonet: kill the ST-Ericsson pipe controller Kconfig 2011-03-09 11:59:33 -08:00
phy.txt Documentation: networking: phy.txt: Add missing functions 2016-03-14 15:00:04 -04:00
pktgen.txt Documentation: networking: fix spelling mistakes 2016-04-28 14:21:13 -04:00
policy-routing.txt
ppp_generic.txt ppp: Move ioctl definitions from if_ppp.h to new ppp-ioctl.h 2012-03-04 20:41:38 -05:00
proc_net_tcp.txt
radiotap-headers.txt
ray_cs.txt
rds.txt Documentation: RDS: Document Multipath RDS (mprds) 2016-07-15 11:36:58 -07:00
regulatory.txt cfg80211: consolidate passive-scan and no-ibss flags 2013-11-25 20:49:35 +01:00
rxrpc.txt rxrpc: Fix races between skb free, ACK generation and replying 2016-08-06 00:08:40 -04:00
s2io.txt neterion: remove reference to ifconfig 2015-03-08 19:11:44 -04:00
scaling.txt net: rfs: fix crash in get_rps_cpus() 2015-04-26 16:07:57 -04:00
sctp.txt net: sctp: trivial: update mailing list address 2013-07-24 17:53:38 -07:00
secid.txt
segmentation-offloads.txt Documentation: Add documentation for TSO and GSO features 2016-04-14 16:23:41 -04:00
skfp.txt
smc9.txt
spider_net.txt doc: fix double words 2014-03-21 13:16:58 +01:00
stmmac.txt drivers: net: stmmac: reworking the PCS code. 2016-06-28 08:54:23 -04:00
switchdev.txt switchdev: Use switch ID in suggested udev rule 2016-04-05 15:07:54 -04:00
tc-actions-env-rules.txt net: sched: use counter to break reclassify loops 2015-05-13 15:08:14 -04:00
tcp-thin.txt
tcp.txt tcp: remove unused min_cwnd member of tcp_congestion_ops 2014-02-13 18:22:34 -05:00
team.txt net: introduce ethernet teaming device 2011-11-13 16:10:10 -05:00
timestamping.txt sock: document timestamping via cmsg in Documentation 2016-04-04 15:50:30 -04:00
tlan.txt
tproxy.txt netfilter: tproxy: remove nf_tproxy_core, keep tw sk assigned to skb 2013-07-31 16:39:40 +02:00
tuntap.txt net: docs: document multiqueue tuntap API 2013-03-06 14:56:10 -05:00
udplite.txt Doc: networking: Fix URL for wiki.wireshark.org in udplite.txt 2015-06-12 14:21:29 -07:00
vortex.txt doc:net: Fix typo in Documentation/networking 2013-10-30 17:10:20 -04:00
vrf.txt net: vrf: Address comments from last documentation update 2016-07-13 18:04:17 -07:00
vxge.txt neterion: remove reference to ifconfig 2015-03-08 19:11:44 -04:00
vxlan.txt documentation: bring vxlan documentation more up-to-date 2015-08-12 16:46:30 -07:00
x25-iface.txt doc:net: Fix typo in Documentation/networking 2013-10-30 17:10:20 -04:00
x25.txt
xfrm_proc.txt
xfrm_sync.txt Documentation: networking: fix spelling mistakes 2016-04-28 14:21:13 -04:00
xfrm_sysctl.txt
z8530drv.txt

README.sb1000

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 <fventuri@mediaone.net>.  He deserves
a great deal of thanks for this wonderful piece of code!

-----------------------------------------------------------------------------

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://web.archive.org/web/*/http://home.adelphia.net/~siglercm/sb1000.html
      http://web.archive.org/web/*/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

-----------------------------------------------------------------------------

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.

-----------------------------------------------------------------------------

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!

-----------------------------------------------------------------------------

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