Date: Wed, 16 Jan 2008 08:48:04 +1300 From: Andrew Thompson <thompsa@FreeBSD.org> To: Tom Judge <tom@tomjudge.com> Cc: freebsd-net@freebsd.org, "Bruce M. Simpson" <bms@FreeBSD.org> Subject: Re: Programming interface MAC filter without enabling PROMISC on an interface from user space. Message-ID: <20080115194804.GA10076@heff.fud.org.nz> In-Reply-To: <478C83FA.7070907@tomjudge.com> 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> <478C83FA.7070907@tomjudge.com>
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On Tue, Jan 15, 2008 at 09:59:22AM +0000, Tom Judge wrote: > 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) No, the only multicast address that the bridge does not forward is the STP one (01:80:c2:00:00:00). It will pass LLDP frames. Andrew
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