NETFILTER: NAT: fix NOTRACK checksum handling
The whole idea with the NOTRACK netfilter target is that you can force the netfilter code to avoid connection tracking, and all costs assosciated with it, by making traffic match a NOTRACK rule. But this is totally broken by the fact that we do a checksum calculation over the packet before we do the NOTRACK bypass check, which is very expensive. People setup NOTRACK rules explicitly to avoid all of these kinds of costs. This patch from Patrick, already in Linus's tree, fixes the bug. Move the check for ip_conntrack_untracked before the call to skb_checksum_help to fix NOTRACK excemptions from NAT. Pre-2.6.19 NAT code breaks TSO by invalidating hardware checksums for every packet, even if explicitly excluded from NAT through NOTRACK. 2.6.19 includes a fix that makes NAT and TSO live in harmony, but the performance degradation caused by this deserves making at least the workaround work properly in -stable. Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Adrian Bunk <bunk@stusta.de>
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