From: Stefano Brivio <sbri...@redhat.com> Date: Tue, 4 Aug 2020 07:53:41 +0200
> Currently, PMTU discovery for UDP tunnels only works if packets are > routed to the encapsulating interfaces, not bridged. > > This results from the fact that we generally don't have valid routes > to the senders we can use to relay ICMP and ICMPv6 errors, and makes > PMTU discovery completely non-functional for VXLAN and GENEVE ports of > both regular bridges and Open vSwitch instances. > > If the sender is local, and packets are forwarded to the port by a > regular bridge, all it takes is to generate a corresponding route > exception on the encapsulating device. The bridge then finds the route > exception carrying the PMTU value estimate as it forwards frames, and > relays ICMP messages back to the socket of the local sender. Patch 1/6 > fixes this case. > > If the sender resides on another node, we actually need to reply to > IP and IPv6 packets ourselves and send these ICMP or ICMPv6 errors > back, using the same encapsulating device. Patch 2/6, based on an > original idea by Florian Westphal, adds the needed functionality, > while patches 3/6 and 4/6 add matching support for VXLAN and GENEVE. > > Finally, 5/6 and 6/6 introduce selftests for all combinations of > inner and outer IP versions, covering both VXLAN and GENEVE, with > both regular bridges and Open vSwitch instances. > > v2: Add helper to check for any bridge port, skip oif check for PMTU > routes for bridge ports only, split IPv4 and IPv6 helpers and > functions (all suggested by David Ahern) Series applied with the extraneous newline in the selftest changes of patch #5 removed. Thank you.
