net: local checksum offload for encapsulation

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The arithmetic properties of the ones-complement checksum mean that a
 correctly checksummed inner packet, including its checksum, has a ones
 complement sum depending only on whatever value was used to initialise
 the checksum field before checksumming (in the case of TCP and UDP,
 this is the ones complement sum of the pseudo header, complemented).
Consequently, if we are going to offload the inner checksum with
 CHECKSUM_PARTIAL, we can compute the outer checksum based only on the
 packed data not covered by the inner checksum, and the initial value of
 the inner checksum field.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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Edward Cree 2016-02-11 20:48:04 +00:00 • committed by David S. Miller

parent e51271d4ce

commit 179bc67f69

4 changed files with 46 additions and 22 deletions

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24

include/linux/skbuff.h

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10

net/ipv4/ip_tunnel_core.c

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20

net/ipv4/udp.c

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14

net/ipv6/ip6_checksum.c

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