[Network] TCP MSS clamping in Gateway #3176
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Hi @cheina97. Thanks for your PR! I am @adamjensenbot.
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Description
This PR implements the TCP MSS Clamping action inside the FirewallConfiguration controller and apply it inside the gateways. It is enabled by default and does not require manual configuration.
VPN tunnels introduce extra overhead that reduces the effective Maximum Transmission Unit (MTU), causing standard-sized internet packets to exceed the tunnel's capacity and be dropped. TCP MSS Clamping resolves this by intercepting the initial connection handshake and dynamically rewriting the Maximum Segment Size (MSS) value to match the smaller available space of the tunnel interface. This crucial adjustment forces the remote server to generate smaller data packets that fit perfectly inside the VPN tunnel, effectively preventing fragmentation issues and the common "black hole" phenomenon where connections establish but data transfer hangs indefinitely.
This concept, applied inside the gateway, allows us to: