From 8a35747a5d13b99e076b0222729e0caa48cb69b6 Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Wed, 21 Jul 2010 21:44:31 +0000 Subject: macvtap: Limit packet queue length Mark Wagner reported OOM symptoms when sending UDP traffic over a macvtap link to a kvm receiver. This appears to be caused by the fact that macvtap packet queues are unlimited in length. This means that if the receiver can't keep up with the rate of flow, then we will hit OOM. Of course it gets worse if the OOM killer then decides to kill the receiver. This patch imposes a cap on the packet queue length, in the same way as the tuntap driver, using the device TX queue length. Please note that macvtap currently has no way of giving congestion notification, that means the software device TX queue cannot be used and packets will always be dropped once the macvtap driver queue fills up. This shouldn't be a great problem for the scenario where macvtap is used to feed a kvm receiver, as the traffic is most likely external in origin so congestion notification can't be applied anyway. Of course, if anybody decides to complain about guest-to-guest UDP packet loss down the track, then we may have to revisit this. Incidentally, this patch also fixes a real memory leak when macvtap_get_queue fails. Chris Wright noticed that for this patch to work, we need a non-zero TX queue length. This patch includes his work to change the default macvtap TX queue length to 500. Reported-by: Mark Wagner Signed-off-by: Herbert Xu Acked-by: Chris Wright Acked-by: Arnd Bergmann Signed-off-by: David S. Miller --- drivers/net/macvtap.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) (limited to 'drivers/net/macvtap.c') diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index a8a94e2f6ddc..ff02b836c3c4 100644 --- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -180,11 +180,18 @@ static int macvtap_forward(struct net_device *dev, struct sk_buff *skb) { struct macvtap_queue *q = macvtap_get_queue(dev, skb); if (!q) - return -ENOLINK; + goto drop; + + if (skb_queue_len(&q->sk.sk_receive_queue) >= dev->tx_queue_len) + goto drop; skb_queue_tail(&q->sk.sk_receive_queue, skb); wake_up_interruptible_poll(sk_sleep(&q->sk), POLLIN | POLLRDNORM | POLLRDBAND); - return 0; + return NET_RX_SUCCESS; + +drop: + kfree_skb(skb); + return NET_RX_DROP; } /* @@ -235,8 +242,15 @@ static void macvtap_dellink(struct net_device *dev, macvlan_dellink(dev, head); } +static void macvtap_setup(struct net_device *dev) +{ + macvlan_common_setup(dev); + dev->tx_queue_len = TUN_READQ_SIZE; +} + static struct rtnl_link_ops macvtap_link_ops __read_mostly = { .kind = "macvtap", + .setup = macvtap_setup, .newlink = macvtap_newlink, .dellink = macvtap_dellink, }; -- cgit v1.2.1