A nil tags slice marshals to JSON `null`; the clear-tagged migration
read that as tagged and cleared user_id. Exclude it, and recover
already-detached nodes from their pre-auth key.
Fixes#3323
The First()-by-machine-key getter returned an undefined node when a machine
key mapped to several nodes. It was used only by RegisterNodeForTest; match on
(machine_key, user_id) there instead and remove the getter.
Updates #3312
Collapse the single-pick machine-key lookups onto GetNodesByMachineKeyAllUsers
so callers see every node sharing a machine key and reject the ambiguous or
impossible cases (tagged and user-owned coexistence; a tagged key with several
user-owned candidates) instead of mutating an arbitrarily-picked node.
Updates #3312
Tagged nodes disable key expiry by default but can still have one set
explicitly, and changing tags leaves expiry unchanged, matching Tailscale.
Updates #3312
Concurrent registrations of one machine key each saw no existing node and
created their own, duplicating nodes and IPs. Hold a per-machine lock across
the find-then-create section.
Updates #3312
Re-registration mutated the node store before the database write and did not
revert on failure, so a restart could drop the client's current node key.
Snapshot the node and restore it if the write fails.
Updates #3312
An unknown or deleted key returned a bare error matching neither the
not-found nor pre-auth-key checks, so registration returned a server error
instead of 401. Wrap gorm.ErrRecordNotFound.
Updates #3312
A reusable key on a converted node, or a tagged key on a user-owned node,
fell through to new-node creation, leaving two nodes per machine. Match by
machine key and update or convert in place.
Updates #3312
The lookup returned the first map match, so re-auth branch choice varied
with map order once a machine key had more than one node. Prefer the tagged
node, else the lowest node ID.
Updates #3312
The pre-auth-key path wrote the client node key without the collision check
the auth path applies, so a re-registration could claim another node's key
and poison the node-key index. Reject keys bound to a different machine.
Updates #3312
The re-registration fast-path skipped validation for a matching node key
without checking expiry, so an expired node could re-auth with a spent key.
Gate it on the node not being expired.
Updates #3312
A node converted to tagged is re-indexed under no user, so re-registration
keyed on the key's owner missed it and rejected the spent one-shot key.
Match the existing tagged node by machine key.
Fixes#3312
Kristoffer Dalby
Kristoffer Dalby