From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH v2 net 1/2] mactap: Fix checksum errors for non-gso packets in bridge mode Date: Tue, 29 Apr 2014 16:21:16 +0300 Message-ID: <20140429132115.GA18119@redhat.com> References: <1398780591-10644-1-git-send-email-vyasevic@redhat.com> <1398780591-10644-2-git-send-email-vyasevic@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, daniel.lezcano@free.fr, nightnord@gmail.com, kaber@trash.net, eric.dumazet@gmail.com, jasowang@redhat.com To: Vlad Yasevich Return-path: Received: from mx1.redhat.com ([209.132.183.28]:49249 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750952AbaD2OUk (ORCPT ); Tue, 29 Apr 2014 10:20:40 -0400 Content-Disposition: inline In-Reply-To: <1398780591-10644-2-git-send-email-vyasevic@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Apr 29, 2014 at 10:09:50AM -0400, Vlad Yasevich wrote: > 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 Acked-by: Michael S. Tsirkin > --- > 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