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tuntap: fix multiqueue rx

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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.cover@stackpath.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Matthew Cover 2018-11-18 00:46:00 -07:00 committed by David S. Miller
parent 7ddacfa564
commit 8ebebcba55
1 changed files with 6 additions and 1 deletions
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7
drivers/net/tun.c
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@ -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();
}
@ -2451,6 +2455,7 @@ static int tun_xdp_one(struct tun_struct *tun,
if (!rcu_dereference(tun->steering_prog))
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);