[ovs-dev] Path MTU discovery on GRE interfaces

Matthias May matthias.may at westermo.com
Wed Jun 23 14:48:29 UTC 2021

Hi Jesse, Hi List

I'm currently fighting with issues where TCP/UDP frames that are larger than the MTU of a GRE tunnel are dropped.
I'm aware of the whys and how to work around the issue, but while looking for solutions i stumbled over the fact that:
* [1] added PMTUD support to OVS
* [2] disabled/removed with v1.9.0 respectively v1.10.0 the feature

Even after some significant time looking through the history i haven't found a reason why this was removed, just that it
was removed.

I started some preliminary work to add PMTUD support to OVS (again), but the fact that it was removed 8 years ago seems
to me like a red flag to not do it (again).

Could someone fluent with the OVS history from 8 years ago shed some light on why PMTUD support was dropped?
Any pointers to a thread on this topic?


[1] https://mail.openvswitch.org/pipermail/ovs-git/2010-March/009936.html
[2] https://www.openvswitch.org/releases/NEWS-2.15.0.txt

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