From owner-freebsd-net  Tue Feb 27  5:10:42 2001
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Message-ID: <3A9BA720.3AFB0A9@elischer.org>
Date: Tue, 27 Feb 2001 05:09:52 -0800
From: Julian Elischer <julian@elischer.org>
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To: Satyajeet Seth <sseth@sasken.com>
Cc: net@freebsd.org
Subject: Re: Problem in configuring netgraph
References: <Pine.GSO.4.30.0102270141460.28244-100000@suns3.sasi.com>
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Satyajeet Seth wrote:
> 
> Hi
> 
> I tried to use ng_ether and ng_bpf as follows:
> 
> fxp0(lower) --- (bhook)[bpf](nomatch)(hook1)----(upper)fxp0
>                        [   ]( match )(hook2)----not connected
> 
> $ ngctl mkpeer fxp0: bpf divert bhook
> 
> $ ngctl name fxp0:divert bpf0
> 
> $ ngctl
> +  msg bpf0: setprogram { thisHook="bhook" ifMatch="hook2"
>    ifNotMatch="hook1" bpf_prog_len=1 bpf_prog=[ { code=6 } ] }
> 
> Now 'nghook -a bpf0: hook1' shows output while 'nghook -a bpf0: hook2'
> doesn't.
> 
> $ ngctl connect fxp0: bpf0: upper hook1
> 
> 1. After this I am unable to ping any of the lan machines.
>  Could you suggest what I could be doing wrong?
> 
> 2. I am writing a BPF program(for filtering packets destined to particular
> MAC addresses) by converting instructions like:
>  BPF_STMT(BPF_LD+BPF_H+BPF_ABS,12), BPF_STMT(BPF_RET+BPF_K,0)
> into:
> [ {code=28 jt=0 jf=0 k=0x0c} {code=6 jt=0 jf=0 k=0}]
> After seeing the definitions of BPF_STMT,BPF_LD etc. in /sys/net/bpf.h. Is
> this the correct way?
> 
> 3. I noticed a problem that the filter could not be set as :
> ngctl msg bpf0: setprogram {...}
> It gave the message:
> ngctl: send msg: Invalid argument

that's becaue you must escape the arguments so that the shell does not try
to interpret things.

> 
> I am using FreeBSD 4.1.
> 
> Thanks
> Satya
> 
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the man page for -current ng_bpf (you can get it from 
http://www.freebsd.org/cgi/cvsweb.cgi/src/share/man/man4/ng_bpf.4

shows how to program a bpf node with a good example
(it was not in the 4.x man page)


-- 
      __--_|\  Julian Elischer
     /       \ julian@elischer.org
    (   OZ    ) World tour 2000-2001
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