netdev - Re: IGMP Join dropping multicast packets

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Message-ID: <91bdcedb0903151904x1066ac24h63557b588e7c4967@mail.gmail.com>
Date:	Sun, 15 Mar 2009 21:04:21 -0500
From:	Dave Boutcher <daveboutcher@...il.com>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	netdev@...r.kernel.org
Subject: Re: IGMP Join dropping multicast packets

On Sat, Mar 14, 2009 at 9:37 PM, Eric Dumazet <dada1@...mosbay.com> wrote:
> Dave Boutcher a écrit :
>> I'm running into an interesting problem with joining multiple
>> multicast feeds.  If you join multiple multicast feeds using
>> setsockopt(...,IP_ADD_MEMBERSHIP...) it causes packets on UNRELATED
>> multicast feeds to get dropped.  We have a multicast feed on a rock
>> solid network, and we were very surprised to see dropped packets.  The
>> cause was a different process/program being run by a different user
>> joining a bunch of mulitcast feeds.
>
> I could not reproduce the problem on my machines (bnx2 adapter), even if changing
> NUMSOCK from 55 to 200 in joiner.c

Thanks for trying Eric.  Based on your email I did some more testing
and thus far I've
only recreated this on x86_64 arches, not on i386.  Which arch did you
try it on?

> Is your network a 100Mb one or Gigabit ?
> Try to slow down your joiner ?
> (Could be a flood of IGMP messages your router/switch cannot cope with)
>
> Please describe your "rock solid" network setup (kind of network adapters you have, kind of router...)

The problem originally manifest itself at work on a 24-core Dell
server with 6 NICs.   The network
is gigabit with a Cisco 4900 switch.  I recreated it in my basement on
my little white-box
system and a cheap netgear switch.  The NIC at work is Intel e1000e
driver, the one
at home is also e1000.

> If using tcpdump to force promiscuous mode on the device also triggers packet losses ?
>
> (see also ifconfig ethX promisc|allmulti)

I haven't had a chance to play with promiscuous yet...

-- 
Dave B
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