Date: Tue, 15 Jan 2008 09:59:22 +0000 From: Tom Judge <tom@tomjudge.com> To: "Bruce M. Simpson" <bms@FreeBSD.org> Cc: freebsd-net@freebsd.org Subject: Re: Programming interface MAC filter without enabling PROMISC on an interface from user space. Message-ID: <478C83FA.7070907@tomjudge.com> In-Reply-To: <478BAE70.9050702@FreeBSD.org> References: <478B7AB7.5010208@tomjudge.com> <478B88EE.7090307@FreeBSD.org> <478B9020.3000402@tomjudge.com> <478B982B.304@FreeBSD.org> <478BAC60.9030506@tomjudge.com> <478BAE70.9050702@FreeBSD.org>
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Bruce M. Simpson wrote: > Tom Judge wrote: <SNIP> >> Personally I can't see why this approach would be a problem, but I am >> not a expert. The address is defined in IEEE Std 802.1D-2004 as to >> not be forwarded by bridges (which I interpret as it being link local >> in a sense as switches/bridges are not allowed to forward the frame), >> so I can't see it being a problem registered on multiple interfaces. > > SIOCADDMULTI memberships are specific to the interface you request them > on. I can't speak for the bridging code -- I don't think it does any > special handling of multicast frames, however I'm not sure if it's smart > enough not to forward this group. Like IN_LOCALGROUP() it might need its > own 'don't forward this' clause. > Just for the record it seems that if_bridge replaces the destination MAC of a Ethernet multicast packet with its own MAC therefore making sure that the packets are not forwarded. Andrew can you confirm this assumption? (Based on sys/net/if_bridge.c lines 2011-2018 on RELENG_6_2) Tom
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