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Date:      Mon, 20 Nov 2000 09:06:42 -0800
From:      Nick Sayer <nsayer@quack.kfu.com>
To:        jgarman@wedgie.org
Cc:        Jordan Hubbard <jkh@winston.osd.bsdi.com>, Marko Cuk <cuk@nu.cuk.nu>, stable@FreeBSD.ORG
Subject:   Re: FreeBSD 4.2-RELEASE delayed until November 20th.
Message-ID:  <3A195A22.C835C3DD@quack.kfu.com>
References:  <cuk@nu.cuk.nu> <49687.974363227@winston.osd.bsdi.com> <20001119212157.A93256@got.wedgie.org>

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Jason Garman wrote:
> 
> [...]
> Could someone elaborate on the details here? 

Check the cvs logs for /src/sys/net/bridge.c:

I noticed for a while that broadcast UDP packets were corrupted going
through the bridge. Archie helped me figure out what was going wrong.
Somewhere in the UDP code, the mbuf rules are not being respected (a
packet being futzed with without calling m_pullup() first or some such).
The workaround was to modify both the Luigi bridge and the ng_bridge
node to use m_dup() instead of m_copypacket() for copying broadcasted
packets. This is a performance hit, but it can't be helped until the
root cause of the problem is found.

I believe the fix went into -stable somewhere between 4.1.1-RELEASE and
4.2. The symptom is that TCP works just fine, but any service relying on
broadcast UDP (such as netbios queries) fails. tcpdump on broadcast
packets shows that UDP broadcasts are corrupted, but ARP broadcasts (for
example) are fine.


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