Messages in this thread | | | From | "Brandeburg, Jesse" <> | Date | Mon, 24 Nov 2008 13:04:33 -0800 | Subject | RE: [RFC PATCH] lro: ip fragment checking |
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Ben Hutchings wrote: > On Mon, 2008-11-24 at 16:56 +0100, Jan-Bernd Themann wrote: >> Currently there is no checking in the LRO receive path whether >> TCP packets are ip fragmented. We should not consider >> those packets for aggregation. >> I'm not sure if this checking is actually required. Does anyone >> know if it is possible to get fragmented TCP packets without >> the tcp stack changing the MSS size? >> This patch introduces explicit checking. Any objections? > > LRO depends on the hardware performing TCP checksum offload, and the > TCP checksum cannot be verified for IP fragments in isolation. So I > think drivers should not be passing fragments into inet_lro or should > reject them in its get_frag_header() or get_skb_header() method. > Certainly sfc doesn't pass fragments into inet_lro because they have > not been checksummed.
The fragments, definitely will not have checksums offloaded, but what about the first packet in the chain? I haven't verified in ixgbe or igb whether or not it could try and aggregate a packet with MF set if it was the first fragment in a series of IP fragments.
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