From: Cong Wang <amw...@redhat.com>
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 <da...@davemloft.net>
Cc: Jesse Gross <je...@nicira.com>
Signed-off-by: Cong Wang <amw...@redhat.com>
Signed-off-by: Jesse Gross <je...@nicira.com>
---
net/openvswitch/actions.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
index ac2defe..d4d5363 100644
--- a/net/openvswitch/actions.c
+++ b/net/openvswitch/actions.c
@@ -58,7 +58,7 @@ static int __pop_vlan_tci(struct sk_buff *skb, __be16
*current_tci)
if (skb->ip_summed == CHECKSUM_COMPLETE)
skb->csum = csum_sub(skb->csum, csum_partial(skb->data
- + ETH_HLEN, VLAN_HLEN, 0));
+ + (2 * ETH_ALEN), VLAN_HLEN, 0));
vhdr = (struct vlan_hdr *)(skb->data + ETH_HLEN);
*current_tci = vhdr->h_vlan_TCI;
@@ -115,7 +115,7 @@ static int push_vlan(struct sk_buff *skb, const struct
ovs_action_push_vlan *vla
if (skb->ip_summed == CHECKSUM_COMPLETE)
skb->csum = csum_add(skb->csum, csum_partial(skb->data
- + ETH_HLEN, VLAN_HLEN, 0));
+ + (2 * ETH_ALEN), VLAN_HLEN, 0));
}
__vlan_hwaccel_put_tag(skb, ntohs(vlan->vlan_tci) & ~VLAN_TAG_PRESENT);
--
1.7.10.4
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