[ovs-discuss] GRE packets show up on host, but not on GRE port

Srini Seetharaman srini.seetharaman at gmail.com
Tue Oct 21 17:14:17 UTC 2014


Hi
I'm running into a problem with using GRE tunnels between two hosts (VMs
running Ubuntu 14.04 kernel version 3.13.0-36-generic) running mininet
where the GRE traffic flows fine for a while and then after 5 idle mins it
does not work, i.e., The GRE packet arrives on the host, but it is not
received by the port 'gre1' and instead being dropped. Has anyone seen this
issue?

More on my setup:
- The mininet host on each side is connected to s1-eth1.
- The mininet host IP address on one side is 10.0.0.1 and other side is
10.0.0.2.
- On the bridge s1, I have just the 'normal' action rule, and in bridge
br-tun I have explicit rules to map the tun_id to the vlan_vid and forward
out of port 1 (patch-int).
- On both ends, this is how the setup looks like.

    Bridge s1
        Port "s1-eth1"
            tag: 1
            Interface "s1-eth1"
        Port br-int
            Interface br-int
                type: internal
        Port patch-tun
            Interface patch-tun
                type: patch
                options: {peer=patch-int}
    Bridge br-tun
        Port patch-int
            Interface patch-int
                type: patch
                options: {peer=patch-tun}
        Port "gre1"
            Interface "gre1"
                type: gre
                options: {in_key=flow, out_key=flow,
remote_ip="192.168.50.16"}
        Port br-tun
            Interface br-tun
                type: internal
    ovs_version: "2.3.0"

Troubleshooting performed:
- The dump-ports shows that the packet counters are not incrementing.
- I checked the ovs-vswitchd.log (as well as /var/log/messages and syslog
and dmesg), and there is nothing reported there.
- The GRE packets look right to me when inspected in wireshark.

Workarounds:
- The strange thing is that once I start a reverse direction ping from
10.0.0.2 to 10.0.0.1, everything magically starts working. After that, if I
stop the ping and retry after 300 secs, the problem again comes up where
the GRE packets are not received by the gre1 port.
- If I change the tunnel type to "vxlan", everything works ok.

Could there a problem with GRE on this kernel?  Please let me know if you
need more information. I will simplify my setup and keep trying.

Thanks
Srini.
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