[PATCH] net/veth: Fix packet checksumming

[PATCH] net/veth: Fix packet checksumming

[Michał Mirosław]

We can't change ip_summed from CHECKSUM_PARTIAL to CHECKSUM_NONE
or CHECKSUM_UNNECESSARY because checksum in packet's headers is
not valid and will cause invalid checksum when frame is forwarded.

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
---
 drivers/net/veth.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 0bbc0c3..cca6a71 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -166,7 +166,9 @@ static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (!(rcv->flags & IFF_UP))
 		goto tx_drop;
 
-	if (dev->features & NETIF_F_NO_CSUM)
+	/* don't change ip_summed == CHECKSUM_PARTIAL, as that
+	   will cause bad checksum on forwarded packets */
+	if (skb->ip_summed == CHECKSUM_NONE)
 		skb->ip_summed = rcv_priv->ip_summed;
 
 	length = skb->len + ETH_HLEN;
-- 
1.7.2.3

Re: [PATCH] net/veth: Fix packet checksumming

[David Miller]

From: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Date: Tue, 14 Dec 2010 23:35:13 +0100 (CET)

> We can't change ip_summed from CHECKSUM_PARTIAL to CHECKSUM_NONE
> or CHECKSUM_UNNECESSARY because checksum in packet's headers is
> not valid and will cause invalid checksum when frame is forwarded.
> 
> Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>

Applied to net-2.6, thanks.