Date: Tue, 8 Jun 1999 13:43:59 +0200 (MET DST) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: alden@math.ohio-state.edu (Dave Alden) Cc: freebsd-net@FreeBSD.ORG Subject: Re: bridging and multicast (in FreeBSD 3.2-RELEASE) Message-ID: <199906081143.NAA00580@labinfo.iet.unipi.it> In-Reply-To: <19990608100251.B28732@zaphod.mps.ohio-state.edu> from "Dave Alden" at Jun 8, 99 10:02:32 am
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> Hi, > Has anyone had any trouble (or success for that matter :-) using the > builtin bridge(4) with multicast packets? I'm running 3.2-RELEASE. > When I run tcpdump on a Sun that is behind the bridge, I get the > following (note that both machinea and machineb are on the 'outside' > of my bridge): hi, this is a known (to me and one other FreeBSD'er in the UK at least :) problem -- the protocol stack does some NTOH*() on the packets passed to the local stack. Because mbufs are shared, if there is a local receiver for multicast traffic this might cause the bridged packets to be scrambled before they go out. A solution (which i think is implemented on my local version but i haven't committed yet 'cause of lack of time) is to do an m_pullup() of enough stuff so that the headers are kept in a separate place. There is a performance penalty of course in doing that, but correctness is more important in these cases... cheers luigi -----------------------------------+------------------------------------- Luigi RIZZO, luigi@iet.unipi.it . Dip. di Ing. dell'Informazione http://www.iet.unipi.it/~luigi/ . Universita` di Pisa TEL/FAX: +39-050-568.533/522 . via Diotisalvi 2, 56126 PISA (Italy) http://www.iet.unipi.it/~luigi/ngc99/ ==== First International Workshop on Networked Group Communication ==== -----------------------------------+------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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