[ovs-discuss] trace route for vxlan overlay network

Jesse Gross jesse at kernel.org
Wed Dec 23 00:45:57 UTC 2015


On Tue, Dec 22, 2015 at 7:53 AM, Avi Cohen <avi.cohen at huawei.com> wrote:
> Hello all
>
> I saw in https://www.mail-archive.com/discuss@openvswitch.org/msg15373.html
> ,
>
> that trace-route is not implemented yet in OVS.

Well, that discussion is not really related to this since its about
traceroute where OVS is a transit switch.

> I need to implement a more enhanced trace-route for vxlan overlay.
>
> As we use the OVS as a vTEP device I need to trace-route the actual
> data-path for a given vxlan-segment (since there are multi ecmp paths – this
> should traverse a specific path based on the source UDP port)
>
> This is  done by transmitting a series an vxlan encapsulated packets with an
> incremental TTL , IP-destined to the remote vTEP.   an intermediate device
> (which are generally traditional routers in the underlay)  replies with ICMP
> ttl expired.
>
> 2 questions:
>
> -          How to initiate  these packets transmission in the originating
> vTEP ? can I do it from the vTEP/ a local application ?

Packets can be injected from OVS userspace, similar to STP/BFD. When
setting up the encapsulation parameters, you can set the TTL.

> -          How the ICMP  replies  can be delivered/ if any  to a local
> application that is connected to the vTEP via a TAP device ?

I think you could probably capture ICMP errors using a raw socket.



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