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xen-netback: Timeout packets in RX path

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A malicious or buggy guest can leave its queue filled indefinitely, in which
case qdisc start to queue packets for that VIF. If those packets came from an
another guest, it can block its slots and prevent shutdown. To avoid that, we
make sure the queue is drained in every 10 seconds.
The QDisc queue in worst case takes 3 round to flush usually.

Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Zoltan Kiss 2014-03-06 21:48:30 +00:00 • committed by David S. Miller
parent e3377f36ca
commit 093507885a
3 changed files with 61 additions and 5 deletions
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23
drivers/net/xen-netback/netback.c
View file

@ -55,6 +55,13 @@
bool separate_tx_rx_irq = 1;
module_param(separate_tx_rx_irq, bool, 0644);
/* When guest ring is filled up, qdisc queues the packets for us, but we have
* to timeout them, otherwise other guests' packets can get stucked there
*/
unsigned int rx_drain_timeout_msecs = 10000;
module_param(rx_drain_timeout_msecs, uint, 0444);
unsigned int rx_drain_timeout_jiffies;
/*
* This is the maximum slots a skb can have. If a guest sends a skb
* which exceeds this limit it is considered malicious.
@ -1694,8 +1701,9 @@ void xenvif_idx_unmap(struct xenvif *vif, u16 pending_idx)
static inline int rx_work_todo(struct xenvif *vif)
{
return !skb_queue_empty(&vif->rx_queue) &&
xenvif_rx_ring_slots_available(vif, vif->rx_last_skb_slots);
return (!skb_queue_empty(&vif->rx_queue) &&
xenvif_rx_ring_slots_available(vif, vif->rx_last_skb_slots)) ||
vif->rx_queue_purge;
}
static inline int tx_work_todo(struct xenvif *vif)
@ -1782,12 +1790,19 @@ int xenvif_kthread_guest_rx(void *data)
if (kthread_should_stop())
break;
if (vif->rx_queue_purge) {
skb_queue_purge(&vif->rx_queue);
vif->rx_queue_purge = false;
}
if (!skb_queue_empty(&vif->rx_queue))
xenvif_rx_action(vif);
if (skb_queue_empty(&vif->rx_queue) &&
netif_queue_stopped(vif->dev))
netif_queue_stopped(vif->dev)) {
del_timer_sync(&vif->wake_queue);
xenvif_start_queue(vif);
}
cond_resched();
}
@ -1838,6 +1853,8 @@ static int __init netback_init(void)
if (rc)
goto failed_init;
rx_drain_timeout_jiffies = msecs_to_jiffies(rx_drain_timeout_msecs);
return 0;
failed_init: