From: Vlad Yasevich <vyasevic@xxxxxxxxxx>
This patch has been added to the 3.12 stable tree. If you have any
objections, please let us know.
===============
[ Upstream commit cbdb04279ccaefcc702c8757757eea8ed76e50cf ]
The following is a problematic configuration:
VM1: virtio-net device connected to macvtap0@eth0
VM2: e1000 device connect to macvtap1@eth0
The problem is is that virtio-net supports checksum offloading
and thus sends the packets to the host with CHECKSUM_PARTIAL set.
On the other hand, e1000 does not support any acceleration.
For small TCP packets (and this includes the 3-way handshake),
e1000 ends up receiving packets that only have a partial checksum
set. This causes TCP to fail checksum validation and to drop
packets. As a result tcp connections can not be established.
Commit 3e4f8b787370978733ca6cae452720a4f0c296b8
macvtap: Perform GSO on forwarding path.
fixes this issue for large packets wthat will end up undergoing GSO.
This commit adds a check for the non-GSO case and attempts to
compute the checksum for partially checksummed packets in the
non-GSO case.
CC: Daniel Lezcano <daniel.lezcano@xxxxxxx>
CC: Patrick McHardy <kaber@xxxxxxxxx>
CC: Andrian Nord <nightnord@xxxxxxxxx>
CC: Eric Dumazet <eric.dumazet@xxxxxxxxx>
CC: Michael S. Tsirkin <mst@xxxxxxxxxx>
CC: Jason Wang <jasowang@xxxxxxxxxx>
Signed-off-by: Vlad Yasevich <vyasevic@xxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
drivers/net/macvtap.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 5895e4dbbf2a..d0f165f2877b 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -315,6 +315,15 @@ static int macvtap_forward(struct net_device *dev, struct sk_buff *skb)
segs = nskb;
}
} else {
+ /* If we receive a partial checksum and the tap side
+ * doesn't support checksum offload, compute the checksum.
+ * Note: it doesn't matter which checksum feature to
+ * check, we either support them all or none.
+ */
+ if (skb->ip_summed == CHECKSUM_PARTIAL &&
+ !(features & NETIF_F_ALL_CSUM) &&
+ skb_checksum_help(skb))
+ goto drop;
skb_queue_tail(&q->sk.sk_receive_queue, skb);
}
--
1.9.3
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