On Fri, Nov 16, 2018 at 12:00:15AM -0700, Matthew Cover wrote:
> When writing packets to a descriptor associated with a combined queue, the
> packets should end up on that queue.
>
> Before this change all packets written to any descriptor associated with a
> tap interface end up on rx-0, even when the descriptor is associated with a
> different queue.
>
> The rx traffic can be generated by either of the following.
> 1. a simple tap program which spins up multiple queues and writes packets
> to each of the file descriptors
> 2. tx from a qemu vm with a tap multiqueue netdev
>
> The queue for rx traffic can be observed by either of the following (done
> on the hypervisor in the qemu case).
> 1. a simple netmap program which opens and reads from per-queue
> descriptors
> 2. configuring RPS and doing per-cpu captures with rxtxcpu
>
> Alternatively, if you printk() the return value of skb_get_rx_queue() just
> before each instance of netif_receive_skb() in tun.c, you will get 65535
> for every skb.
>
> Calling skb_record_rx_queue() to set the rx queue to the queue_index fixes
> the association between descriptor and rx queue.
>
> Signed-off-by: Matthew Cover <matthew.co...@stackpath.com>
Acked-by: Michael S. Tsirkin <m...@redhat.com>
stable material?
> ---
> drivers/net/tun.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index a65779c6d72f..ce8620f3ea5e 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1536,6 +1536,7 @@ static void tun_rx_batched(struct tun_struct *tun,
> struct tun_file *tfile,
>
> if (!rx_batched || (!more && skb_queue_empty(queue))) {
> local_bh_disable();
> + skb_record_rx_queue(skb, tfile->queue_index);
> netif_receive_skb(skb);
> local_bh_enable();
> return;
> @@ -1555,8 +1556,11 @@ static void tun_rx_batched(struct tun_struct *tun,
> struct tun_file *tfile,
> struct sk_buff *nskb;
>
> local_bh_disable();
> - while ((nskb = __skb_dequeue(&process_queue)))
> + while ((nskb = __skb_dequeue(&process_queue))) {
> + skb_record_rx_queue(nskb, tfile->queue_index);
> netif_receive_skb(nskb);
> + }
> + skb_record_rx_queue(skb, tfile->queue_index);
> netif_receive_skb(skb);
> local_bh_enable();
> }
> @@ -2452,6 +2456,7 @@ static int tun_xdp_one(struct tun_struct *tun,
> !tfile->detached)
> rxhash = __skb_get_hash_symmetric(skb);
>
> + skb_record_rx_queue(skb, tfile->queue_index);
> netif_receive_skb(skb);
>
> stats = get_cpu_ptr(tun->pcpu_stats);
> --
> 2.15.2 (Apple Git-101.1)
