fix: use tailscale that avoids small MTU paths #18323
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deansheather
approved these changes
Jun 11, 2025
| // . │ │fdac:38fa:ffff:2::1 | ||
| // . └──────────────┘ | ||
| // The veth link between Client 1 and the router has a configurable MTU via Client1MTU. | ||
| func (n TriangleNetwork) SetupNetworking(t *testing.T, l slog.Logger) TestNetworking { |
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It's not really a triangle anymore unfortunately, more of a pitchfork 🤣
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You should redo the diagram to be triforce 🤣
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Not sure unicode has the correct (60°) diagonals
ethanndickson
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Jun 11, 2025
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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).