)

It unfortunately doesn't seem possible, even with a custom ruleguard rule, to mark a function as requiring it's return value be used, it looks like you have to go all in on a linter that rejects *any* unused return values.

Fixes #15523

Uses latest https://github.com/coder/tailscale which includes coder/tailscale#85 to stop selecting paths with small MTU for direct connections.

Also updates the tailnet integration test to reproduce the issue. The previous version had the 2 peers connected by a single veth, but this allows the OS to fragment the packet. In the new version, the 2 peers (and server) are all connected by a central router. The link between peer 1 and the router has an adjustable MTU. IPv6 does not allow packets to be fragmented by intermediate routers, so sending a too-large packet in this scenario forces the router to drop packets and reproduce the issue (without the tailscale changes).