[ovs-git] Open vSwitch: datapath: fix the calculation of checksum for vlan header (branch-1.9)

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- Log -----------------------------------------------------------------
commit cec7c9e681200336c5b35dcf851ec90e66206481
Diffs: http://openvswitch.org/cgi-bin/gitweb.cgi?p=openvswitch;a=commitdiff;h=cec7c9e681200336c5b35dcf851ec90e66206481
Author: Cong Wang <amwang at redhat.com>
		
datapath: fix the calculation of checksum for vlan header
		
In vlan_insert_tag(), we insert a 4-byte VLAN header _after_
mac header:

        memmove(skb->data, skb->data + VLAN_HLEN, 2 * ETH_ALEN);
        ...
        veth->h_vlan_proto = htons(ETH_P_8021Q);
        ...
        veth->h_vlan_TCI = htons(vlan_tci);

so after it, we should recompute the checksum to include these 4 bytes.
skb->data still points to the mac header, therefore VLAN header is at
(2 * ETH_ALEN = 12) bytes after it, not (ETH_HLEN = 14) bytes.

This can also be observed via tcpdump:

         0x0000:  ffff ffff ffff 5254 005d 6f6e 8100 000a
         0x0010:  0806 0001 0800 0604 0001 5254 005d 6f6e
         0x0020:  c0a8 026e 0000 0000 0000 c0a8 0282

Similar for __pop_vlan_tci(), the vlan header we remove is the one
overwritten in:

	memmove(skb->data + VLAN_HLEN, skb->data, 2 * ETH_ALEN);

Therefore the VLAN_HLEN = 4 bytes after 2 * ETH_ALEN is the part
we want to sub from checksum.

Cc: David S. Miller <davem at davemloft.net>
Cc: Jesse Gross <jesse at nicira.com>
Signed-off-by: Cong Wang <amwang at redhat.com>
Signed-off-by: Jesse Gross <jesse at nicira.com>


-----------------------------------------------------------------------

Summary of changes:
 datapath/actions.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)


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