K 10
svn:author
V 5
andre
K 8
svn:date
V 27
2012-11-19T18:09:00.332863Z
K 7
svn:log
V 1057
Convert the NIC drivers to the new checksum offloading semantics on
the inbound path in a first step.

This is a mostly mechanical conversion and the new semantics are
not introduced.

In short for inbound there are two levels the offloading NIC can
set:

 CSUM_L3_CALC	for an IP layer 3 checksum calculated by the NIC;
 CSUM_L3_VALID	set when the calculated checksum matches the one
		in the packet;
 CSUM_L4_CALC	for an UDP/TCP/SCTP layer 4 checksum calculated by
		the NIC;
 CSUM_L4_VALID	set when the calculated checksum matche the one
		in the packet.

From this follows that a packet failed checksum verification when
only *_CALC is set but not *_VALID.  The NIC is expected to deliver
a failed packet up the stack anyways for capture by BPF and to
record protocol specific checksum mismatch statistics.

Please note that many NIC's do not or only partially follow these
semantics.  Some drop all packets with a failed checksum and most
do not report a L4 failure but pass it on without any checksum flags
set.  They will have to be cleaned up later.

END