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Date: Tue, 02 Dec 2008 15:18:48 +0000 From: Ben Hutchings <bhutchings@...arflare.com> To: Andrew Gallatin <gallatin@...i.com> Cc: David Miller <davem@...emloft.net>, ossthema@...ibm.com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, tklein@...ibm.com, raisch@...ibm.com, jb.billaud@...il.com, hering2@...ibm.com Subject: Re: [PATCH] lro: IP fragment checking On Tue, 2008-12-02 at 09:42 -0500, Andrew Gallatin wrote: > Ben Hutchings wrote: > > On Mon, 2008-12-01 at 19:02 -0500, Andrew Gallatin wrote: > >> Ben Hutchings wrote: [...] > >>> If your hardware/firmware wrongly claims to be able to verify the > >>> TCP/UDP checksum for an IP fragment, it seems to me you should deal with > >>> that in your driver or fix the firmware. > >> We do partial checksums. > > > > So you should check for IP fragmentation in your get_frag_header() along > > with all the other checks you've got to do. > > Indeed, and that is the patch I intend to submit if the fragment > check in inet_lro is rejected. I still think the check belongs > in the inet lro code though, and I'm worried it is being rejected > for the wrong reasons.. There's a wide variety of capabilities of different hardware: 1. No checksum offload. Probably not worth using LRO. 2. Full-checksum generation. Driver passes packets to inet_lro; get_frag_header() or get_skb_header() parses packets to check that they are TCP/IPv4 and to validate the checksum. inet_lro does further checks. 3. L4 packet parsing and checksum validation. Driver passes TCP/IPv4 packets to inet_lro. inet_lro does further checks. 4. Hardware/firmware LRO. inet_lro not needed. You seem to be proposing that a check that is only needed in case (2) should also be applied in case (3). Maybe it would make more sense to define a generic implementation of get_frag_header() for full-checksum devices, if that's possible? Ben. -- Ben Hutchings, Senior Software Engineer, Solarflare Communications Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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