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Date:      Wed, 24 Jun 2015 17:13:13 +0200 (CEST)
From:      Emeric POUPON <emeric.poupon@stormshield.eu>
To:        freebsd-net@freebsd.org
Subject:   Re: Multicast routing questions
Message-ID:  <886014477.4193151.1435158793240.JavaMail.zimbra@stormshield.eu>
In-Reply-To: <1192147789.4088965.1435134165130.JavaMail.zimbra@stormshield.eu>
References:  <1192147789.4088965.1435134165130.JavaMail.zimbra@stormshield.eu>

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Hi,

Actually, I don't really understand why imo.imo_multicast_loop is set to 1 =
in send_packet, ip_mroute.c

It seems we don't need to loop the packet once it is mrouted?
If the packet is emitted locally, the imo_multicast_loop set by the socket =
option makes the packet loop back if necessary.

Emeric


----- Mail original -----
De: "Emeric POUPON" <emeric.poupon@stormshield.eu>
=C3=80: freebsd-net@freebsd.org
Envoy=C3=A9: Mercredi 24 Juin 2015 10:22:45
Objet: Multicast routing questions

Hello,

I'm testing multicast routing on FreeBSD 9.3 and I have a question:

In packet reception, it seems the packet is received locally as many times =
the packet is rerouted + 1:
ip_input -> ip_mforward -> ip_output (as many times there are dst interface=
s in the route cache entry) -> ip_mloopback -> if_simloop (rcvif becomes th=
e ifp of the output interface) -> ip_input -> ip_mforward -> ...
In ip_input, after each ip_mforward call, the packet is processed locally (=
using the goto "ours:")
Futhermore it seems this infinite loop is actually broken thanks to a test =
in ip_mforward that checks the ifp is the same as the registered one in the=
 cache entry.

Maybe I missed something, but it does not seem to be working as expected.
What do you think?

Emeric


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