netdev - Re: IP_ADD_MEMBERSHIP with imr_ifindex!=0 for multiple processes with different interfaces

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Message-ID: <361cdca0-679a-cc16-6de1-b35479fbbb83@gmail.com>
Date:   Mon, 23 Apr 2018 06:29:52 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "Klebsch, Mario" <Mario.Klebsch@...-actia.de>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: IP_ADD_MEMBERSHIP with imr_ifindex!=0 for multiple processes with
 different interfaces



On 04/23/2018 06:22 AM, Klebsch, Mario wrote:
> Hi, 
> 
> I have a problem with multicast reception in the linux kernel and I hope, this is the right place to ask for help or to report a bug.
> 
> I need to receive multicasts on a single interface. I have written a small program, which executes IP_ADD_MEMBERSHIP with imr.imr_ifindex set to the interface index. The program works well, as long as only a single instance of this program is running. If I start a second instance on a different network interface, both programs receive multicast frames from both interfaces. 
> 
> When called without argument, the test program list the network interfaces. When called with an interface name as argument, if starts receiving multicasts on that interface.
> 
> I am running vanilla Linux kernel 4.12.0.
> 
> # uname -a
> Linux c627 4.12.0 #1 SMP Mon Apr 23 14:08:24 CEST 2018 i686 Intel(R) Core(TM) i5-7400 CPU @ 3.00GHz GenuineIntel GNU/Linux
> # 
> 
> P.S. The program runs fine on MacOSX.
>

It looks like your program needs to use SO_BINDTODEVICE if it really wants this device filtering ?