From: Cong Wang Date: Fri, 22 Feb 2013 09:32:26 +0000 (+0800) Subject: openvswitch: fix the calculation of checksum for vlan header X-Git-Tag: v3.9-rc4~27^2~18^2~1 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7b024082b2b279af58e24ebd46e81777723d58da;p=pandora-kernel.git openvswitch: 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 Cc: Jesse Gross Signed-off-by: Cong Wang Signed-off-by: Jesse Gross --- Reading git-diff-tree failed