Commits on Feb 16, 2024

1. Use 65000 MTU upper bound for interfaces in encap mode …

   OVS configures the MTU for tunnel ports to 65000.
   In some cases (e.g., Kind clusters), the MTU of the transport interface
   can be larger than that, and so can be the calculated MTU of antrea-gw0
   and of Pod interfaces. When this happens, packets can be dropped.
   To handle this edge case (real clusters are unlikely to use that kind of
   MTU), we set an upper bound of 65000 for the calculated MTU.
   
   Note that setting the tunnel port's MTU to 65535, or even to the
   calculated MTU, is not an option, as it may not work on all systems.
   
   An alternative would be to find the MTU for the tunnel interface
   dynamically and use that as an upper bound, rather than rely on this
   hardcoded constant (65000). However, that constant has remained
   unchanged for 7 years, and finding the MTU dynamically would require
   re-organizing the Agent initialization code, as we currently caclulate
   the MTU before creating the OVS tunnel port. So the current solution
   seems lower risk. Even if the constant is changed in OVS, it should not
   have any real impact on Antrea.
   
   Fixes antrea-io#5940
   
   Signed-off-by: Antonin Bas <antonin.bas@broadcom.com>

   

   antoninbas committed Feb 16, 2024
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