netdev - Re: [Patch net-next] vxlan: revert "vxlan: Bypass encapsulation if the destination is local"

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Date:	Thu, 11 Apr 2013 16:59:59 -0700
From:	Sridhar Samudrala <sri@...ibm.com>
To:	Cong Wang <amwang@...hat.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: [Patch net-next] vxlan: revert "vxlan: Bypass encapsulation if
 the destination is local"

On Thu, 2013-04-11 at 01:55 -0400, Cong Wang wrote:
> 
> ----- Original Message -----
> > On 4/10/2013 7:10 PM, Cong Wang wrote:
> > >> - when source and destination endpoints belonging to different vni's
> > >>    are on 2 different bridges on the same host. encap bypass is done
> > >>    in this scenario by checking if rt_flags has RTCF_LOCAL set. I think
> > >>    you must be hitting this path and the following patch should fix
> > >>    it by only doing bypass if the source and dest devices belong to
> > >>    the same net. Can you try it and see if it fixes your tests?
> > > I just tested it, unfortunately it doesn't work, the bug still exists.
> > >
> > > If you need any other info, please let me know.
> > So does it mean that you are hitting the if condition that does encap
> > bypass
> > even afterthe net_eq() check? Do the tests pass If you comment out the
> > 'if' block?
> 
> Yes, after adding a printk inside the 'if' block, I got:
> 
> [   71.456329] vxlan: dev: vxlan0, dst: 224.8.8.8, dst dev: veth0
> [   71.596551] vxlan: dev: vxlan0, dst: 224.8.8.8, dst dev: veth1
> [   72.028574] vxlan: dev: vxlan0, dst: 224.8.8.8, dst dev: veth0
> [   72.436384] vxlan: dev: vxlan0, dst: 224.8.8.8, dst dev: veth1
> [   73.028576] vxlan: dev: vxlan0, dst: 224.8.8.8, dst dev: veth0
> [   73.185134] vxlan: dev: vxlan0, dst: 224.8.8.8, dst dev: veth0
> [   73.436582] vxlan: dev: vxlan0, dst: 224.8.8.8, dst dev: veth1
> [   74.184251] vxlan: dev: vxlan0, dst: 224.8.8.8, dst dev: veth0
> 
> It seems the dst dev is the dev which vxlan0 setup on, so
> there is no way to know if the packet is targeted for a different netns
> on the same host, at least I don't find such RTCF_* flag.

OK. i was able to setup vxlan between 2 net namespaces and reproduce
the issue.

The following patch fixes the issue for me. can you try it out?

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 9a64715..d6509de 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -1013,7 +1013,7 @@ static netdev_tx_t vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
 	}
 
 	/* Bypass encapsulation if the destination is local */
-	if (rt->rt_flags & RTCF_LOCAL) {
+	if (rt->dst.dev->flags & IFF_LOOPBACK) {
 		struct vxlan_dev *dst_vxlan;
 
 		ip_rt_put(rt);


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