If we fail to transmit a packet, we assume the queue is full and put
the skb into last_xmit_skb. However, if more space frees up before we
xmit it, we loop, and the result can be transmitting the same skb twice.
Fix is simple: set skb to NULL if we've used it in some way, and check
before sending.
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
---
drivers/net/virtio_net.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff -r 564237b31993 drivers/net/virtio_net.c
--- a/drivers/net/virtio_net.c Mon May 19 12:22:00 2008 +1000
+++ b/drivers/net/virtio_net.c Mon May 19 12:24:58 2008 +1000
@@ -287,21 +287,25 @@ again:
free_old_xmit_skbs(vi);
/* If we has a buffer left over from last time, send it now. */
- if (vi->last_xmit_skb) {
+ if (unlikely(vi->last_xmit_skb)) {
if (xmit_skb(vi, vi->last_xmit_skb) != 0) {
/* Drop this skb: we only queue one. */
vi->dev->stats.tx_dropped++;
kfree_skb(skb);
+ skb = NULL;
goto stop_queue;
}
vi->last_xmit_skb = NULL;
}
/* Put new one in send queue and do transmit */
- __skb_queue_head(&vi->send, skb);
- if (xmit_skb(vi, skb) != 0) {
- vi->last_xmit_skb = skb;
- goto stop_queue;
+ if (likely(skb)) {
+ __skb_queue_head(&vi->send, skb);
+ if (xmit_skb(vi, skb) != 0) {
+ vi->last_xmit_skb = skb;
+ skb = NULL;
+ goto stop_queue;
+ }
}
done:
vi->svq->vq_ops->kick(vi->svq);
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