tailcat: replace AllowedClients with an AllowClient hook, add KeySet and DisconnectClient - #134
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…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>
This was referenced Sep 26, 2026
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it solves my problem, so I'm completely fine with it, I appreciate the mention to my work aswell 😄 First open source contribution ever 🎉 |
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@ybaelli, congrats! :) Sorry I couldn't take your change more directly, but we had ~3 things coming in all in conflict with each other, so I had to kinda merge them together in some coherent form. |
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No problem at all, I had a quick look, it's solving the problem I had, all good ! |
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@jormenjanssen also approves in #119 (comment) |
This was referenced Sep 26, 2026
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Bump github.com/tailscale/tailcat to 7d80847ede15, which replaces Server.AllowedClients with a Server.AllowClient hook and adds the KeySet type: tailscale/tailcat@7d80847ede15 mote now builds a KeySet from allowed.txt and installs its Contains method as the hook when the file has any keys. With no keys the hook stays nil, so the server still answers everyone, as before. The "answering N allowed client keys" log line moves into startTailcat, where the count is known, since the server no longer exposes the list. Updates tailscale/tailcat#119 Updates tailscale/tailcat#134
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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 (@jormenjanssen)
Co-authored-by: Yann (@ybaelli)