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by zamadatix 1015 days ago
For TCP sockets I'd rather just MSS clamp on the internet gateway. On top of too many things just dropping PMTUD, enabling it results in a slower process while MSS clamping hijacks the initial TCP open messages directly.
1 comments

There's PMTUD that doesn't depend on ICMP.
For TCP in Linux the only thing I know of is net.ipv4.tcp_mtu_probing=2 which is still slower than clamping at the edge. You can also run into weird slowdowns in cases with packet loss even after the initial discovery. If you don't have a way to clamp but absolutely need the interface to have jumbo enabled for local traffic performance it's probably the best fallback but even then I'm not sure it's worth the extra headache it causes.