Subject: Re: bpf breakage
To: David Young <>
From: None <>
List: tech-net
Date: 07/03/2004 12:43:49
>On Sat, Jul 03, 2004 at 10:40:54AM +0900, wrote:
>> 	due to this change in sys/net/bpf.c (bpf_measure -> m_length),
>> 	bpf on many interfaces (which prepends address family by integer)
>> 	is broken.  the length will become off by 4, and you'll see
>> 	"truncated-ip" message from tcpdump.  please back it out.
>> 	my guess is the culprit is "optimize m_length" (2nd paragraph from the
>> 	bottom).
>On which interfaces is it broken, Itojun?  Why do those interfaces
>assemble packets with incorrect m_pkthdr.len?

	i got a breakage report on ppp interface (but the originator mentioned
	that he would like to remain anonymous, so i don't cc: him).
#	i've forwarded those to you privately.
	some of the interfaces (like loopback) prepends 4byte mbuf (address
	family is set inside) on bpf_mtap.  in such case, m_pkthdr.len
	will not be useful.