RELENG_6_3 ping and DUP packets

[Damian Weber]

On Thu, 10 Apr 2008, Jeremy Chadwick wrote:

> Date: Thu, 10 Apr 2008 23:52:56 -0700
> From: Jeremy Chadwick <koitsu at freebsd.org>
> To: Damian Weber <dweber at htw-saarland.de>
> Cc: freebsd-stable at freebsd.org
> Subject: Re: RELENG_6_3 ping and DUP packets
> 
> 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.

Bingo!

No duplicates anymore.

Is this considered as a permanent solution or just a "hack"?
In any case, I've summarized it on 
http://www-crypto.htw-saarland.de/weber/misc/unix/freebsd-dup-packets/

including the output of the mptable command (MSI disabled/enabled).

Thanks a lot,

  Damian