linux-kernel - a problem with NETPOLL/KGDBoE

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Date:	Thu, 6 Dec 2007 20:22:15 +0200
From:	"Ramagudi Naziir" <naziirr@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	mpm@...enic.com, kgdb-bugreport@...ts.sourceforge.net,
	jason.wessel@...driver.com
Subject: a problem with NETPOLL/KGDBoE

Hi all,

It's probably only me, but I can't connect to a kgdb host because
of bouncing ICMP unreachables. I'll be glad if you could take a look
to see if it's a bug or not.

Details:
- running a cloned  version of kgdb_2.6.23 branch of Jason's
git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/linux-2.6-kgdb.git

- "modprobe kgdboe kgdboe='@...0.0.28/,@10.0.0.11/'" works fine,
and var/log/messages get filled with six kgdboe network configuration
messages (local port 6443, local ip 10.0.0.28, interface eth0,
remote port 6442, remote ip 10.0.0.11, remote mac ff:ff:ff:ff:ff:ff).

- "netstat -aun" does not show an open 6643 UDP port (should it ?)

- When trying to connect via remote gdb, I get a connection refused:

(gdb) target remote udp:10.0.0.28:6433
warning: The remote protocol may be unreliable over UDP.
Some events may be lost, rendering further debugging impossible.
Remote debugging using udp:10.0.0.28:6433
Remote communication error: Connection refused.

- tcpdump ouput shows two UDP messages traveling to the kgdb host
only to immediately invoke ICMP unreachables:

19:30:53.424248 IP 10.0.0.11.32785 > 10.0.0.28.6433: UDP, length 5
19:30:53.424323 IP 10.0.0.11.32785 > 10.0.0.28.6433: UDP, length 14
19:30:53.426292 IP 10.0.0.28 > 10.0.0.11: ICMP 10.0.0.28 udp port 6433
unreachable, length 41
19:30:53.427542 IP 10.0.0.28 > 10.0.0.11: ICMP 10.0.0.28 udp port 6433
unreachable, length 50

- Network between 10.0.0.28 and 10.0.0.11 is just fine; I successfully work
on NFS mounts (with 10.0.0.28 as a client)

- the kgdb host has selinux=0 and  iptables with accept-all policies

- i386 (running inside a bridged qemu/vmplayer host)

- config attached

If you have any idea how to further debug this problem,
or maybe if you know if I did something wrong,
please share !

Thanks,
naziir.

Download attachment ".config.gz" of type "application/x-gzip" (21063 bytes)