Re: [Qemu-devel] [PATCH v2] rocker: don't queue receive pkts when port is disabled

[Fam Zheng <famz@redhat.com>]

On Tue, 06/30 19:25, sfeldma@gmail.com wrote:
> From: Scott Feldman <sfeldma@gmail.com>
> 
> Commit 6e99c63 ("net/socket: Drop net_socket_can_send") changed the
> semantics around .can_receive for sockets to now require the device to
> flush queued pkts when transitioning to a .can_receive=true state.  Rocker
> device was not flushing the queue on .can_receive=true transition, so the
> receiver was stuck.
> 
> But, turns out we really don't want any queuing at all on the port when the
> port is disabled, otherwise when the port transitions to enabled, we'd
> receive and forward stale pkts that really should have been dropped.  So,
> let's remove .can_receive so avoid queuing and drop the pkt in .receive if
> the port is disabled.
> 
> Signed-off-by: Scott Feldman <sfeldma@gmail.com>
> ---
> v2: return -1 to drop pkt, review comment from famz@redhat.com
> 
>  hw/net/rocker/rocker_fp.c |   18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/hw/net/rocker/rocker_fp.c b/hw/net/rocker/rocker_fp.c
> index d8d934c..c693ae5 100644
> --- a/hw/net/rocker/rocker_fp.c
> +++ b/hw/net/rocker/rocker_fp.c
> @@ -125,18 +125,21 @@ int fp_port_eg(FpPort *port, const struct iovec *iov, int iovcnt)
>      return ROCKER_OK;
>  }
>  
> -static int fp_port_can_receive(NetClientState *nc)
> -{
> -    FpPort *port = qemu_get_nic_opaque(nc);
> -
> -    return port->enabled;
> -}
> -
>  static ssize_t fp_port_receive_iov(NetClientState *nc, const struct iovec *iov,
>                                     int iovcnt)
>  {
>      FpPort *port = qemu_get_nic_opaque(nc);
>  
> +    /* If the port is disabled, we want to drop this pkt
> +     * now rather than queing it for later.  We don't want
> +     * any stale pkts getting into the device when the port
> +     * transitions to enabled.
> +     */
> +
> +    if (!port->enabled) {
> +        return -1;
> +    }
> +
>      return world_ingress(port->world, port->pport, iov, iovcnt);
>  }
>  
> @@ -165,7 +168,6 @@ static void fp_port_set_link_status(NetClientState *nc)
>  static NetClientInfo fp_port_info = {
>      .type = NET_CLIENT_OPTIONS_KIND_NIC,
>      .size = sizeof(NICState),
> -    .can_receive = fp_port_can_receive,
>      .receive = fp_port_receive,
>      .receive_iov = fp_port_receive_iov,
>      .cleanup = fp_port_cleanup,
> -- 
> 1.7.10.4
> 
> 

Reviewed-by: Fam Zheng <famz@redhat.com>