Re: [PATCH RFC 5/6] net: orphan frags on receive

On Wed, May 09, 2012 at 02:54:52PM +0100, Ian Campbell wrote:

On Mon, 2012-05-07 at 14:54 +0100, Michael S. Tsirkin wrote:

quoted

zero copy packets are normally sent to the outside
network, but bridging, tun etc might loop them
back to host networking stack. If this happens
destructors will never be called, so orphan
the frags immediately on receive.

I think this deceptively simply patch is actually the meat of the
series.
It's been a long time since I dug into the bridging code. Am I right
that this function is only reached when an SKB is going to be delivered
locally and not when forwarding to another port on the bridge?

Ian.

I think so - bridge uses netdev_rx_handler_unregister
so it does not go through packet handlers.

quoted

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 net/core/dev.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index a2be59f..c0cdc00 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c

@@ -1630,6 +1630,8 @@ static inline int deliver_skb(struct sk_buff *skb,
 			      struct packet_type *pt_prev,
 			      struct net_device *orig_dev)
 {
+	if (unlikely(skb_orphan_frags(skb, GFP_ATOMIC)))
+		return -ENOMEM;
 	atomic_inc(&skb->users);
 	return pt_prev->func(skb, skb->dev, pt_prev, orig_dev);
 }