socket option IP_MSFILTER questions and observations

3 messages, 3 authors, 2012-03-26 · open the first message on its own page

socket option IP_MSFILTER questions and observations

From: Cedric Jehasse <hidden>
Date: 2012-03-26 15:48:51

Hi,

I'm trying to use source specific multicast by setting the IP_MSFILTER 
socket option. I noticed i need to join the group with IP_ADD_MEMBERSHIP 
before setting the source filter. This is not the behavior i expected 
after reading RFC3678.
A potential issue i'm thinking of with this approach: an IGMP report 
could be sent after joining a group but before the filter is set.
Is there a way to prevent this?

Thanks,
Cedric

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Re: socket option IP_MSFILTER questions and observations

From: David Stevens <hidden>
Date: 2012-03-26 16:36:08

I'm trying to use source specific multicast by setting the IP_MSFILTER 
socket option. I noticed i need to join the group with IP_ADD_MEMBERSHIP 
before setting the source filter. This is not the behavior i expected 
after reading RFC3678.
        RFC3678 doesn't say that an IP_MSFILTER will join a group
automatically. The model is that you join a group once and then
dynamically set the source filters as they change over time.
A potential issue i'm thinking of with this approach: an IGMP report 
could be sent after joining a group but before the filter is set.
Is there a way to prevent this?
        Adding or changing the source filters triggers a new report
but you can use IP_ADD_SOURCE_MEMBERSHIP which does explicitly join
a group with a source filter. In the kernel, this is done with an
"any" join followed by setting a source filter which actually will result
in 2 reports too, if there are no other processes using that group.

                                                        +-DLS

Re: socket option IP_MSFILTER questions and observations

From: David Miller <davem@davemloft.net>
Date: 2012-03-26 20:15:02

From: Cedric Jehasse <redacted>
Date: Mon, 26 Mar 2012 17:40:56 +0200
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