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AddAllowedClient could add a key while running but nothing could take one back: revoking a client meant restarting serve with a shorter --allow, which also drops every other client until they re-meow. RemoveAllowedClient deletes the key from the allowlist and, if the client is connected, drops it from the network map so its tunnel is torn down. Client IDs now come from a counter instead of len(clients)+2, which would collide with a live peer after a removal. Fixes tailscale#124
bradfitz
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Sep 26, 2026
…and DisconnectClient Server.AllowedClients and Server.AddAllowedClient are replaced by a single Server.AllowClient func(key.NodePublic) bool, asked about each client as it connects. A nil hook allows all clients, which is the one fail-open rule. The old slice's "empty means open" semantics forced the CLI's --allow=none to insert a zero key as a sentinel; an empty KeySet now simply allows nobody. The hook runs with the backend mutex released, so unlike the hook proposed in #120 it may block on an external lookup and may call other Server methods. onMeow already runs in its own goroutine per meow ping, so a slow answer delays only that client. A pendingAllow map keeps a client's once-a-second meow retries from starting a second call for the same key while one is in flight. The new KeySet type is a mutex-guarded set of node keys whose Contains method is the ready-made hook for a fixed or hand-maintained list, so the runtime add that AddAllowedClient offered is still available, and removal comes with it. The new Server.DisconnectClient drops a connected client from the network map so its traffic is blackholed in both directions; it does not reset its connections. Revoking a client is then two orthogonal steps the caller composes: make the hook reject the key, then disconnect it. Client IDs now come from a counter that is never reused, since after a removal len(clients)+2 could collide with a live peer. Supersedes #120 and #125, which each added a second admission form alongside the slice. Fixes #119 Fixes #124 Co-authored-by: Jormen Janssen <j.janssen@riwo.eu> Co-authored-by: Yann <y.baelli05@gmail.com>
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Merged, but folded into #134 |
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Counterpart of AddAllowedClient: revoke a key while the server runs, and drop the client if it is connected, instead of restarting serve and disconnecting everyone. Verified in the new test that a revoked client's dial fails within seconds, so no engine-level peer eviction was needed.
Fixes #124