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b99d02b7a9
On a continuous reconcile felhom-sshd itself listens on the claimed port, so re-probing isFree(persisted) found it 'busy' by our own daemon and thrashed to another candidate every tick. A persisted port is ours — keep it. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01PSK5g6qYLknKj8u3QAFEr6
43 lines
1.9 KiB
Go
43 lines
1.9 KiB
Go
package felhomsshd
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import "fmt"
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// Candidates is the ordered OOB-port candidate list (spike §2). First free wins; NEVER :22 or a
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// random port. Package-var (not const) so tests can shrink it.
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var Candidates = []int{8822, 2222, 8022, 62222}
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// ErrPortsExhausted is returned when every candidate is busy — a LOUD failure [SF-4/trap 6], never a
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// silent fallback to :22 or a random high port.
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var ErrPortsExhausted = fmt.Errorf("felhomsshd: all candidate OOB ports are busy — refusing to fall back to :22 or a random port")
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// portProbe reports whether a TCP port is free (nothing listening AND a real bind succeeds). Injected
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// for tests; production impl = probeFree (ss + net.Listen).
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type portProbe func(port int) bool
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// claimPort returns the OOB port:
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// - if a port is already PERSISTED (and != 22) → keep it unconditionally. It is OUR port; on a
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// continuous reconcile felhom-sshd is itself LISTENING on it, so re-probing with isFree would
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// (wrongly) find it "busy" by our own daemon and thrash to another candidate every tick. Once
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// claimed, the port is stable (the belt @ssh_port and the operator's known port depend on it).
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// - else the FIRST free candidate → persist + return (isFree = ss-empty AND a real bind succeeds).
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// - else ErrPortsExhausted (LOUD — never :22 or a random port).
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//
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// persist writes the port file; readPersisted reads it. isFree is the probe. All injected for tests.
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func claimPort(candidates []int, isFree portProbe, readPersisted func() (int, bool), persist func(int) error) (int, error) {
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if cur, ok := readPersisted(); ok && cur != 22 {
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return cur, nil // persisted = ours; keep it (no thrash — felhom-sshd holds it)
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}
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for _, p := range candidates {
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if p == 22 {
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continue // defensive: never :22
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}
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if isFree(p) {
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if err := persist(p); err != nil {
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return 0, fmt.Errorf("felhomsshd: persist claimed port %d: %w", p, err)
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}
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return p, nil
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}
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}
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return 0, ErrPortsExhausted
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}
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