| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.14 102/140] mactap: Fix checksum errors for non-gso packets in bridge mode | Date | Wed, 28 May 2014 21:34:01 -0700 |
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3.14-stable review patch. If anyone has any objections, please let me know.
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From: Vlad Yasevich <vyasevic@redhat.com>
[ 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@free.fr> CC: Patrick McHardy <kaber@trash.net> CC: Andrian Nord <nightnord@gmail.com> CC: Eric Dumazet <eric.dumazet@gmail.com> CC: Michael S. Tsirkin <mst@redhat.com> CC: Jason Wang <jasowang@redhat.com> Signed-off-by: Vlad Yasevich <vyasevic@redhat.com> Acked-by: Jason Wang <jasowang@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- drivers/net/macvtap.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -322,6 +322,15 @@ static rx_handler_result_t macvtap_handl 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); }
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