Subject: Re: tcp/udp vector h/w checksum
To: Jonathan Stone <>
From: john heasley <>
List: tech-net
Date: 02/07/2005 09:39:05
Sun, Feb 06, 2005 at 12:58:57PM -0800, Jonathan Stone:
> I can (I once suggested it!) very easily see hardware designers doing
> a full, 1s-complemented UDP sum for non-fragmented, single-frame UDP
> received packets; but doing the non-1s-complement, non-pseudo header
> sum for fragmented packets.
> OK, so that example doesn't work so for TX, but you can see how keying
> upper-level behaviour off per-interface quirk flags may be problematic:
> the quirkiness may depend on size or oather attributes of the packet!
> So I want to think a little more carefully about the semantics of
> mbuf-header quirk csum flags, versus per-interface Rx/Tx csum flags,
> before we start resuing mbuf csum-quirk flags to if_csum_flags_{tx,rx}.
> (That's why I suggested an XXX comment.)
> (Does that make more sense now?)

Could I ask you to lead that discussion/change?  I'm reluctant to mess with
the mbuf code myself.