net: local checksum offload for encapsulation
authorEdward Cree <ecree@solarflare.com>
Thu, 11 Feb 2016 20:48:04 +0000 (20:48 +0000)
committerDavid S. Miller <davem@davemloft.net>
Fri, 12 Feb 2016 10:52:15 +0000 (05:52 -0500)
commit179bc67f69b6cb53ad68cfdec5a917c2a2248355
tree9c3251d5226c75826a19f10d33e3b7279d6f0969
parente51271d4ce7b229f5c02903e3c44bf92c0dbef6b
net: local checksum offload for encapsulation

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>
include/linux/skbuff.h
net/ipv4/ip_tunnel_core.c
net/ipv4/udp.c
net/ipv6/ip6_checksum.c