RELENG_6_3 ping and DUP packets

[Jeremy Chadwick]

On Fri, Apr 11, 2008 at 08:48:10AM +0200, Damian Weber wrote:
> > From: Chuck Swiger <cswiger at mac.com>
> > To: Damian Weber <dweber at htw-saarland.de>
> > Cc: freebsd-stable at freebsd.org
> > Subject: Re: RELENG_6_3 ping and DUP packets
> > 
> > On Apr 10, 2008, at 1:58 PM, Damian Weber wrote:
> > > But here is the problem, pinging the machine from remote gives
> > > 
> > > A.B.C.X$ ping A.B.C.D
> > > PING A.B.C.D (A.B.C.D): 56 data bytes
> > > 64 bytes from A.B.C.D: icmp_seq=0 ttl=64 time=0.272 ms
> > > 64 bytes from A.B.C.D: icmp_seq=0 ttl=255 time=0.391 ms (DUP!)
> > 
> > Please run "tcpdump -e icmp" on this box and repeat your testing.  It
> > will be most interesting to know whether you're seeing the same MAC
> > address....
> 
> good point, but it's the same
> 
> A.B.C.X# tcpdump -e icmp
> tcpdump: listening on rl0, link-type EN10MB
> 08:41:51.136023 0:20:ed:5f:3:3b 0:19:99:33:7c:9 ip 98: A.B.C.X > A.B.C.D: icmp: echo request
> 08:41:51.136171 0:19:99:33:7c:9 0:20:ed:5f:3:3b ip 98: A.B.C.D: icmp: echo reply
> 08:41:51.136343 0:19:99:33:7c:9 0:20:ed:5f:3:3b ip 98: A.B.C.D: icmp: echo reply
> 08:41:52.138366 0:20:ed:5f:3:3b 0:19:99:33:7c:9 ip 98: A.B.C.X > A.B.C.D: icmp: echo request
> 08:41:52.138447 0:19:99:33:7c:9 0:20:ed:5f:3:3b ip 98: A.B.C.D: icmp: echo reply
> 08:41:52.138692 0:19:99:33:7c:9 0:20:ed:5f:3:3b ip 98: A.B.C.D: icmp: echo reply
> ^C
> 169 packets received by filter
> 0 packets dropped by kernel

Possibly an interrupt is being called twice on the same packet?

Shot in the dark, but try disabling MSI/MSI-X and see if the problem
recurs.  Put this in /boot/loader.conf:

hw.pci.enable_msi="0"
hw.pci.enable_msix="0"

Reboot, and see if the problem continues.

-- 
| Jeremy Chadwick                                    jdc at parodius.com |
| Parodius Networking                           http://www.parodius.com/ |
| UNIX Systems Administrator                      Mountain View, CA, USA |
| Making life hard for others since 1977.                  PGP: 4BD6C0CB |