Automated cherry pick of #5997: Use 65000 MTU upper bound for interfaces in encap mode #6006
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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 <[email protected]>
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Cherry pick of #5997 on release-1.14.
#5997: Use 65000 MTU upper bound for interfaces in encap mode
For details on the cherry pick process, see the cherry pick requests page.