netdev - Re: [PATCH] IPv4: skip loopback checksums in ip

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Message-Id: <200910192256.52780.schmto@hrz.tu-chemnitz.de>
Date:	Mon, 19 Oct 2009 22:56:52 +0200
From:	Torsten Schmidt <torsten.schmidt@...06.tu-chemnitz.de>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH] IPv4: skip loopback checksums in ip_rcv()

Eric Dumazet wrotes:
> This is bogus IMHO.
> 
> One bit could be corrupted in iph, and ntohl(iph->daddr) becomes 0x7fxxyyzz,
> we then accept a bogus frame. This is a RFC violation.
> 
> This also slows down non loopback devices, adding an extra test.
> 
> ip_fast_csum() is really fast (about 16 instructions).

Yes, you are right. So it would be better to only skip csum if *dev is 
our loopback interface ? Right ?
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