From owner-freebsd-current  Tue May 19 15:03:10 1998
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To: Luigi Rizzo <luigi@labinfo.iet.unipi.it>
cc: current@FreeBSD.ORG
Subject: Re: and again on forwarding... 
In-reply-to: Your message of "Tue, 19 May 1998 18:24:50 +0200."
             <199805191624.SAA09951@labinfo.iet.unipi.it> 
From: David Greenman <dg@root.com>
Reply-To: dg@root.com
Date: Tue, 19 May 1998 15:02:39 -0700
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>forgot to mention: on each forwarded packet, our code does the
>following (in ip_input.c, function ip_forward() ):
>
>        /*
>         * Save at most 64 bytes of the packet in case
>         * we need to generate an ICMP message to the src.
>         */
>        mcopy = m_copy(m, 0, imin((int)ip->ip_len, 64));
>
>is this necessary or the work can be avoided ?

   ICMP messages get generated when the host is unreachable or when the TTL
decrements to 0. Both or these cases are handled in the ip_flow code and
the slow path (of which the above is part of) will be taken.

-DG

David Greenman
Co-founder/Principal Architect, The FreeBSD Project

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