Date: Thu, 06 Jun 2002 14:43:23 -0700 From: Vadim Egorov <egorovv@attbi.com> To: freebsd-net@FreeBSD.org Subject: Re: IP_MULTICAST_LOOP Message-ID: <86r8jkrslg.fsf@my.egorovv.net> In-Reply-To: <20020606113237.N40292-100000@gateway.posi.net> (Kelly Yancey's message of "Thu, 6 Jun 2002 11:36:10 -0700 (PDT)") References: <86vg8wu5cw.fsf@my.egorovv.net> <20020606113237.N40292-100000@gateway.posi.net>
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Sorry guys for beeng so stupid :(
But the problem still in place - it actually boils down to the multicast
example from Stivens 'Unix Network Programming' - it casts and lstens to the
same group. I tried it on Linux - turning IP_MULTICAST_LOOP off does blocks
traffic looping, but on FreeBSD it doesn't seem to have any effect.
I think I can live with this, I just feel that somthing is wrong here.
> On Thu, 6 Jun 2002, Vadim Egorov wrote:
>> I'm playing with multicasting (-stable), and I want to disable looping back
>> my outgoing packets setting IP_MULTICAST_LOOP option to 0 but it doen't
>> have any effect. My app is listening to the same group it is casting.
>>
>> > After some grepping I came across some code in netinet/ip_output.c:
>> > (imo == NULL || imo->imo_multicast_loop)) {
>> > /*
>> > * If we belong to the destination multicast group
>> > * on the outgoing interface, and the caller did not
>> > * forbid loopback, loop back a copy.
>> > */
>> >
>> > The comment says 'and' but the code says '||' -- looks like an error to me.
>> > Except this I've got no idea what it means - does it make amy sence?
Kelly Yancey <kbyanc@posi.net> writes:
> You definately wouldn't want this to be && because if imo is NULL you
> certainly wouldn't want to dereference it. :) The comment's logic matches the
> code, it is just that the phrasing is inverted.
>
> Kelly
"Wilbert de Graaf" <wilbertdg@hetnet.nl> writes:
> Hi Vadim
>
> I wondered if in general your application does the right thing. You can either:
> 1) let the sender listen to another group: logically split your protocol
> 2) use IGMPv3 and simply block yourself from listening
> I have a patch + examples how to do this at:
> http://home.hetnet.nl/~wilbertdg/igmpv3.html
>
> Thanks, Wilbert
--
Thanks,
Vadim
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