From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vlad Yasevich Subject: [PATCH v2 net 1/2] mactap: Fix checksum errors for non-gso packets in bridge mode Date: Tue, 29 Apr 2014 10:09:50 -0400 Message-ID: <1398780591-10644-2-git-send-email-vyasevic@redhat.com> References: <1398780591-10644-1-git-send-email-vyasevic@redhat.com> Cc: daniel.lezcano@free.fr, nightnord@gmail.com, kaber@trash.net, eric.dumazet@gmail.com, mst@redhat.com, jasowang@redhat.com, Vlad Yasevich To: netdev@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:14999 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751447AbaD2O2Y (ORCPT ); Tue, 29 Apr 2014 10:28:24 -0400 In-Reply-To: <1398780591-10644-1-git-send-email-vyasevic@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: 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 CC: Patrick McHardy CC: Andrian Nord CC: Eric Dumazet CC: Michael S. Tsirkin CC: Jason Wang Signed-off-by: Vlad Yasevich --- drivers/net/macvtap.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index ff111a8..3381c4f 100644 --- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -322,6 +322,15 @@ static rx_handler_result_t macvtap_handle_frame(struct sk_buff **pskb) 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); } -- 1.9.0