From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
To: netdev@vger.kernel.org
Subject: Re: IGMP joins come from the wrong SA/interface
Date: Tue, 4 Feb 2014 23:08:09 +0100 [thread overview]
Message-ID: <20140204220809.GB7526@sesse.net> (raw)
In-Reply-To: <20140130224411.GG25336@order.stressinduktion.org>
On Thu, Jan 30, 2014 at 11:44:11PM +0100, Hannes Frederic Sowa wrote:
> The routing lookup is done at IP_ADD_MEMBERSHIP time. I really wonder why you
> have routed the 239.0.0.0/8 range to eth0.11. It seems to me that the kernel
> does what you told it to do. ;)
>
> multicast flag on ip route is just used for multicast forwarding and does not
> matter for local multicast. Also if we find unicast route first (more
> specific) kernel does not do backtracking if destination is in multicast
> scope.
Hah, you're right. The issue was a combination of:
1. mediatomb's initscript on Debian at some point started to add a bogus
239.0.0.0/8 route (and I didn't notice this because I earlier tested with
addresses outside this range).
2. I didn't properly understand that the multicast flag on the route did not
matter (although it really should!).
3. rp_filter ate the data packets when they actually arrived. (I don't know
why I never had this problem before, but I certainly didn't.)
So in various debugging rounds, I managed to fix #1 and #2 to various
degrees, but then #3 would come and make it appear like nothing actually
happened. I didn't see this before tracking it all the way up to the upstream
routers and observing that they actually _did_ send out packets...
/* Steinar */
--
Homepage: http://www.sesse.net/
next prev parent reply other threads:[~2014-02-04 22:08 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-18 19:11 IGMP joins come from the wrong SA/interface Steinar H. Gunderson
2014-01-18 19:17 ` Steinar H. Gunderson
2014-01-19 18:18 ` Hannes Frederic Sowa
2014-01-20 18:40 ` Steinar H. Gunderson
2014-01-30 10:47 ` Steinar H. Gunderson
2014-01-30 14:17 ` Hannes Frederic Sowa
2014-01-30 20:31 ` Steinar H. Gunderson
2014-01-30 18:08 ` Flavio Leitner
2014-01-30 18:12 ` Steinar H. Gunderson
2014-01-30 22:44 ` Hannes Frederic Sowa
2014-01-31 8:51 ` Julian Anastasov
2014-01-31 11:32 ` Hannes Frederic Sowa
2014-02-04 22:08 ` Steinar H. Gunderson [this message]
2014-02-04 23:32 ` Hannes Frederic Sowa
2014-02-04 23:34 ` Steinar H. Gunderson
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