[ovs-discuss] UDP Packets not forwarded by OVS

Justin Pettit jpettit at ovn.org
Fri May 26 20:27:06 UTC 2017


> On May 17, 2017, at 7:02 AM, Advith Nagappa <advith.nagappa at gmail.com> wrote:
> 
> I have created two namespaces ns1 and ns2 and attached them to the ovs-tap ports (using veth pairs).
> 
> I am able to send TCP and ICMP packets between the two namespaces. 
> eg: ip netns exec ns1 traceroute -I 10.1.1.1  && ip netns exec ns1 traceroute -T 10.1.1.1.1
> 
> but doing the same with UDP fails (doesn't find hops)
> ip netns exec ns1 traceroute 10.1.1.1
> 
> 
> I have disabled iptables and ufw (firewall). 
> 
> Also, if i add a rule for UDP specifically:
> ovs-ofctl add-flow br0  priority=1111,dl_type=0x0800,nw_proto=17,nw_dst=10.1.1.1,tp_dst=9877,actions=NORMAL,
> 
> i see that this rule is hit.(packet count increases in dump-flows), but forwarding is not done.
> 
> Has anyone gone through a similar issue and come out with new wisdom to share? Would be be very helpful..

That sounds very strange, and I don't see how OVS could be at fault.  You could dump the datapath flows to make sure that they're in fact forwarding the packets.  If they are, then it's almost certainly outside of OVS.  Have you checked to make sure that there are no firewall rules or other issues in the namespaces?  You may want to run tcpdump in various spots to see where the packets are getting dropped.

--Justin




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