Subject: Re: bpf performance suckage
To: Darren Reed <>
From: None <>
List: tech-net
Date: 06/20/2000 14:12:22
>> 	new code will behave just like traditional 4.4BSDdoes, so packets will
>> 	be packed like this:
>> 	- single header mbuf (MHLEN) if len <= MHLEN
>> 	- header mbuf + normal mbuf (MHLEN + MLEN) if len <= MHLEN + MLEN
>> 	- single cluster mbuf (MCLBYTES), or multiple cluster mbufs otherwise
>> 	with the new code, upper-layer headers on a IPv6 packet would exceed
>> 	the first mbuf easily.  if bpf code looks at first mbuf only, we will
>> 	fail to catch IPv6 packet by bpf.
>Hmmm.  I've changed my local bpf_filter() to be like this:
>        if (buflen == 0) {
>                m = (struct mbuf *)p;
>                p = mtod(m, char *);
>                buflen = m->m_len;		<---
>        } else
>                m = NULL;

>I believe that will work for you ?  Do you want me to send you the
>bpf_filter.c I'm testing so you can test it with your changes ?

	this does not work for me, and other case where bpf insns are
	interested in non-first mbuf.  the line marked with arrow is the
	prime suspect.  (from code inspection)