[3.16.y-ckt stable] Patch "macvtap: Fix csum_start when VLAN tags are present" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    macvtap: Fix csum_start when VLAN tags are present

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt2.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 21ddb3372123662092a92300ac452ed8d0e40d2d Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert at gondor.apana.org.au>
Date: Mon, 3 Nov 2014 14:01:25 +0800
Subject: macvtap: Fix csum_start when VLAN tags are present

commit 3ce9b20f1971690b8b3b620e735ec99431573b39 upstream.

When VLAN is in use in macvtap_put_user, we end up setting
csum_start to the wrong place.  The result is that the whoever
ends up doing the checksum setting will corrupt the packet instead
of writing the checksum to the expected location, usually this
means writing the checksum with an offset of -4.

This patch fixes this by adjusting csum_start when VLAN tags are
detected.

Fixes: f09e2249c4f5 ("macvtap: restore vlan header on user read")
Signed-off-by: Herbert Xu <herbert at gondor.apana.org.au>

Cheers,
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/net/macvtap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 0c6adaaf898c..ff1acf99c10b 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -626,6 +626,8 @@ static void macvtap_skb_to_vnet_hdr(const struct sk_buff *skb,
 	if (skb->ip_summed == CHECKSUM_PARTIAL) {
 		vnet_hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
 		vnet_hdr->csum_start = skb_checksum_start_offset(skb);
+		if (vlan_tx_tag_present(skb))
+			vnet_hdr->csum_start += VLAN_HLEN;
 		vnet_hdr->csum_offset = skb->csum_offset;
 	} else if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
 		vnet_hdr->flags = VIRTIO_NET_HDR_F_DATA_VALID;
--
2.1.0