Re: [Qemu-devel] [RFC Patch v2 06/10] virtio-net rsc: IPv4 checksum

[Jason Wang <jasowang@redhat.com>]

On 02/01/2016 02:13 AM, wexu@redhat.com wrote:
> From: Wei Xu <wei@wei-thinkpad.nay.redhat.com>
>
> If a field in the IPv4 header is modified, then the checksum
> have to be recalculated before sending it out.

This in fact breaks bisection. I think you need either squash this into
previous patch or introduce virtio_net_rsc_ipv4_checksum() as a helper
before the patch of ipv4 coalescing.

>
> Signed-off-by: Wei Xu <wexu@redhat.com>
> ---
>  hw/net/virtio-net.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
>
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 93df0d5..88fc4f8 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -1630,6 +1630,18 @@ static int virtio_net_load_device(VirtIODevice *vdev, QEMUFile *f,
>      return 0;
>  }
>  
> +static void virtio_net_rsc_ipv4_checksum(NetRscSeg *seg)
> +{
> +    uint32_t sum;
> +    struct ip_header *ip;
> +
> +    ip = (struct ip_header *)(seg->buf + IP_OFFSET);
> +
> +    ip->ip_sum = 0;
> +    sum = net_checksum_add_cont(sizeof(struct ip_header), (uint8_t *)ip, 0);
> +    ip->ip_sum = cpu_to_be16(net_checksum_finish(sum));
> +}
> +
>  static void virtio_net_rsc_purge(void *opq)
>  {
>      int ret = 0;
> @@ -1643,6 +1655,10 @@ static void virtio_net_rsc_purge(void *opq)
>              continue;
>          }
>  
> +        if ((chain->proto == ETH_P_IP) && seg->is_coalesced) {
> +            virtio_net_rsc_ipv4_checksum(seg);
> +        }
> +
>          ret = virtio_net_do_receive(seg->nc, seg->buf, seg->size);
>          QTAILQ_REMOVE(&chain->buffers, seg, next);
>          g_free(seg->buf);
> @@ -1853,6 +1869,9 @@ static size_t virtio_net_rsc_callback(NetRscChain *chain, NetClientState *nc,
>      QTAILQ_FOREACH_SAFE(seg, &chain->buffers, next, nseg) {
>          ret = coalesce(chain, seg, buf, size);
>          if (RSC_FINAL == ret) {
> +            if ((chain->proto == ETH_P_IP) && seg->is_coalesced) {
> +                virtio_net_rsc_ipv4_checksum(seg);
> +            }
>              ret = virtio_net_do_receive(seg->nc, seg->buf, seg->size);
>              QTAILQ_REMOVE(&chain->buffers, seg, next);
>              g_free(seg->buf);