netdev - Re: [PATCH net-next v2 0/6] Support PMTU discovery with bridged UDP tunnels

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Message-Id: <20200804.130219.1503615086211769091.davem@davemloft.net>
Date:   Tue, 04 Aug 2020 13:02:19 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     sbrivio@...hat.com
Cc:     fw@...len.de, dsahern@...il.com, aconole@...hat.com,
        nusiddiq@...hat.com, kuba@...nel.org, pshelar@....org,
        roopa@...ulusnetworks.com, nikolay@...ulusnetworks.com,
        lu@...o.net, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 0/6] Support PMTU discovery with bridged
 UDP tunnels

From: Stefano Brivio <sbrivio@...hat.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.