Re: [Qemu-devel] [PATCH v4 05/11] netfilter: hook packets before net queue send

[Jason Wang]

On 08/04/2015 04:30 PM, Yang Hongyang wrote:
> Capture packets that will be sent.
>
> Signed-off-by: Yang Hongyang <address@hidden>
> ---
>  net/net.c | 66 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 65 insertions(+), 1 deletion(-)
>
> diff --git a/net/net.c b/net/net.c
> index 03b2296..efccd56 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -569,6 +569,42 @@ int qemu_can_send_packet(NetClientState *sender)
>      return 1;
>  }
>  
> +static ssize_t filter_receive_iov(NetClientState *nc, int chain,
> +                                  NetClientState *sender,
> +                                  unsigned flags,
> +                                  const struct iovec *iov,
> +                                  int iovcnt)
> +{
> +    ssize_t ret = 0;
> +    NetFilterState *nf = NULL;
> +    ssize_t size = iov_size(iov, iovcnt);
> +
> +    QTAILQ_FOREACH(nf, &nc->filters, next) {
> +        if (nf->chain == chain || nf->chain == NET_FILTER_ALL) {
> +            ret = nf->info->receive_iov(nf, sender, flags, iov, iovcnt);
> +            if (ret == size) {
> +                return ret;
> +            }
> +        }
> +    }
> +
> +    return ret;
> +}
> +
> +static ssize_t filter_receive(NetClientState *nc, int chain,
> +                              NetClientState *sender,
> +                              unsigned flags,
> +                              const uint8_t *data,
> +                              size_t size)
> +{
> +    struct iovec iov = {
> +        .iov_base = (void *)data,
> +        .iov_len = size
> +    };
> +
> +    return filter_receive_iov(nc, chain, sender, flags, &iov, 1);
> +}
> +
>  ssize_t qemu_deliver_packet(NetClientState *sender,
>                              unsigned flags,
>                              const uint8_t *data,
> @@ -640,6 +676,7 @@ static ssize_t 
> qemu_send_packet_async_with_flags(NetClientState *sender,
>                                                   NetPacketSent *sent_cb)
>  {
>      NetQueue *queue;
> +    int ret;
>  
>  #ifdef DEBUG_NET
>      printf("qemu_send_packet_async:\n");
> @@ -650,6 +687,18 @@ static ssize_t 
> qemu_send_packet_async_with_flags(NetClientState *sender,
>          return size;
>      }
>  
> +    /* Let filters handle the packet first */
> +    ret = filter_receive(sender, NET_FILTER_OUT, sender, flags, buf, size);
> +    if (ret == size) {
> +        return size;
> +    }
> +
> +    ret = filter_receive(sender->peer, NET_FILTER_IN,
> +                         sender, flags, buf, size);
> +    if (ret == size) {
> +        return size;
> +    }

I think we can just trust the return value of filter_receive(), no need
to check it against iov_size.

Also sent_cb was lost track if the packet was held by filter which seems
wrong.

[...]