From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cong Wang Subject: [PATCH 1/2] openvswitch: fix the calculation of checksum for vlan header Date: Fri, 22 Feb 2013 17:32:26 +0800 Message-ID: <1361525547-21808-1-git-send-email-amwang@redhat.com> Cc: "David S. Miller" , Jesse Gross , Cong Wang To: netdev@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:50834 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756324Ab3BVJcv (ORCPT ); Fri, 22 Feb 2013 04:32:51 -0500 Sender: netdev-owner@vger.kernel.org List-ID: From: Cong Wang 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 --- net/openvswitch/actions.c | 4 ++-- 1 files 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); -- 1.7.7.6