v0.2.0

internal/keymgr/portalloc.go

@@ -0,0 +1,47 @@
+package keymgr
+
+import "ssh-access-tui/internal/model"
+
+// AllocatedForward is a model.Forward together with the local port it will
+// be bound to on the user's machine.
+type AllocatedForward struct {
+	model.Forward
+	LocalPort int
+}
+
+// localPortBase is where fallback local ports are handed out from once a
+// forward's natural remote port is already taken locally by another
+// forward. Chosen high enough to avoid colliding with well-known ports the
+// user's own machine might already be using.
+const localPortBase = 20000
+
+// AllocateLocalPorts assigns every forward a local port, all of which the
+// user opens at once over a single ssh connection (one LocalForward line
+// per forward — see RenderClientConfig). This is the actual answer to
+// "avoid collisions when forwarding everything simultaneously": many hosts
+// commonly expose the same remote port (e.g. 22, or an app port like 7888
+// repeated across ten hosts), but only one of them can bind to that same
+// port number locally. Each forward keeps its remote port as the local
+// port when that's still free (so the common case reads naturally, e.g.
+// remote 7888 -> local 7888), and falls back to the next free port from
+// localPortBase upward on collision. Assignment is a pure function of the
+// input order and set, so re-exporting an unchanged host list reproduces
+// the same local ports.
+func AllocateLocalPorts(forwards []model.Forward) []AllocatedForward {
+	used := make(map[int]bool, len(forwards))
+	next := localPortBase
+	out := make([]AllocatedForward, 0, len(forwards))
+	for _, f := range forwards {
+		lp := f.Port
+		if lp <= 0 || lp > 65535 || used[lp] {
+			for used[next] {
+				next++
+			}
+			lp = next
+			next++
+		}
+		used[lp] = true
+		out = append(out, AllocatedForward{Forward: f, LocalPort: lp})
+	}
+	return out
+}