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[2a01:cb05:8032:4c00:ef50:764:1596:9b7f]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49ce58da3acsm234561285e9.0.2026.09.03.02.28.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Sep 2026 02:28:08 -0700 (PDT) Date: Thu, 3 Sep 2026 11:28:05 +0200 From: Guillaume Nault To: Ido Schimmel Cc: netdev@vger.kernel.org, davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, edumazet@google.com, dsahern@kernel.org, horms@kernel.org, aconole@redhat.com, sbrivio@redhat.com, laikabcprice@gmail.com, aroslavdudkov622@gmail.com, rough.rock3059@datachamp.fr, stable@vger.kernel.org Subject: Re: [PATCH net] tunnels: Drop stale dst when building an ICMP error for PMTUD Message-ID: References: <20260902190112.4126199-1-idosch@nvidia.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260902190112.4126199-1-idosch@nvidia.com> On Wed, Sep 02, 2026 at 10:01:12PM +0300, Ido Schimmel wrote: > Bridged UDP tunnels such as VXLAN and GENEVE build an ICMP error packet > around an overlay packet if the packet is going to exceed the underlay > path MTU. The ICMP error packet is then injected back into the Rx path > with the source and destination addresses swapped, so that it will be > delivered to the overlay source. > > If the overlay packet was routed to the UDP tunnel or locally generated, > then it is already carrying a valid dst entry and this entry is not > dropped when transforming the packet to an ICMP error packet. This > causes the IP layer to reuse the dst entry, leading to the ICMP error > packet being dropped or routed out of the UDP tunnel interface in case > of forwarding. Good catch, thanks! Reviewed-by: Guillaume Nault