Hello:

This patch was applied to netdev/net.git (main)
by Florian Westphal [off-list ref]:

On Thu,  2 Jul 2026 15:34:28 +0800 you wrote:

When an ICMP Fragmentation Needed error is received for a tunneled IPVS
connection, ip_vs_in_icmp() recomputes the MTU that the original packet
can use by subtracting the tunnel overhead from the reported next-hop
MTU.

The current code always subtracts sizeof(struct iphdr), which is only
the IPIP overhead. For GUE and GRE tunnels, ipvs_udp_decap() and
ipvs_gre_decap() already compute the additional tunnel header length,
but that value is scoped to the decapsulation block and is lost before
the ICMP_FRAG_NEEDED handling. As a result, the ICMP error sent back to
the client advertises an MTU that is too large, so PMTUD can fail to
converge for GUE/GRE-tunneled real servers.

[...]

Here is the summary with links:
  - [net,v2] ipvs: fix PMTU for GUE/GRE tunnel ICMP errors
    https://git.kernel.org/netdev/net/c/6b335af0d0d1

You are awesome, thank you!
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