From: "Michael S. Tsirkin" <mst@redhat•com>
To: Vlad Yasevich <vyasevic@redhat•com>
Cc: netdev@vger•kernel.org, daniel.lezcano@free•fr,
nightnord@gmail•com, kaber@trash•net, eric.dumazet@gmail•com,
jasowang@redhat•com
Subject: Re: [PATCH 1/2] mactap: Fix checksum errors for non-gso packets in bridge mode
Date: Wed, 23 Apr 2014 22:20:22 +0300 [thread overview]
Message-ID: <20140423192022.GA28446@redhat.com> (raw)
In-Reply-To: <1398271901-32534-2-git-send-email-vyasevic@redhat.com>
On Wed, Apr 23, 2014 at 12:51:40PM -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 <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>
> ---
> drivers/net/macvtap.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
> index ff111a8..ba91084 100644
> --- a/drivers/net/macvtap.c
> +++ b/drivers/net/macvtap.c
> @@ -322,6 +322,13 @@ 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.
> + */
> + if (skb->ip_summed == CHECKSUM_PARTIAL &&
> + !(features & NETIF_F_ALL_CSUM) &&
> + skb_checksum_help(skb))
> + goto drop;
Hmm confused by NETIF_F_ALL_CSUM here.
features come from here:
feature_mask = NETIF_F_HW_CSUM;
if (arg & (TUN_F_TSO4 | TUN_F_TSO6)) {
if (arg & TUN_F_TSO_ECN)
feature_mask |= NETIF_F_TSO_ECN;
if (arg & TUN_F_TSO4)
feature_mask |= NETIF_F_TSO;
if (arg & TUN_F_TSO6)
feature_mask |= NETIF_F_TSO6;
}
if (arg & TUN_F_UFO)
feature_mask |= NETIF_F_UFO;
okay so why not just check that NETIF_F_HW_CSUM is set?
Also does it matter whether specific offloads are enabled?
> skb_queue_tail(&q->sk.sk_receive_queue, skb);
> }
>
> --
> 1.9.0
next prev parent reply other threads:[~2014-04-23 19:19 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-23 16:51 [PATCH 0/2] Fix macvtap checksum errors in bridge mode Vlad Yasevich
2014-04-23 16:51 ` [PATCH 1/2] mactap: Fix checksum errors for non-gso packets " Vlad Yasevich
2014-04-23 19:20 ` Michael S. Tsirkin [this message]
2014-04-23 19:39 ` Vlad Yasevich
2014-04-23 20:10 ` Michael S. Tsirkin
2014-04-23 20:30 ` Vlad Yasevich
2014-04-24 7:26 ` Michael S. Tsirkin
2014-04-24 14:05 ` Vlad Yasevich
2014-04-23 16:51 ` [PATCH 2/2] Revert "macvlan : fix checksums error when we are in bridge mode" Vlad Yasevich
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