Devices: each headset its own SSH connection, and each server keeps its own headset (review round 27)

ssh's %C hashes only address, user and port, so two headsets reached at one
address shared a ControlMaster and one's commands could run on the other: the
ControlPath now names the headset. Another Frame Control server choosing a
different headset no longer moves this one's commands mid-install.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

tests/test_devices.py

@@ -184,6 +184,17 @@ class SharedFile(Base):
         self.assertIn("100.101.1.2", hosts)
         self.assertIn("100.101.1.2", [a["host"] for a in other.get(d["id"])["addresses"]])  # and it sees it
 
+    def test_another_servers_choice_of_headset_doesnt_move_this_one(self):
+        self.reg.sync_from_config(seed=False)
+        other = fd.Registry(self.dir / "devices.json")
+        mine, theirs = self.reg.by_alias("frame")["id"], self.reg.by_alias("frame-2")["id"]
+        self.reg.set_active(mine)
+        other.set_active(theirs)
+        self.assertEqual(self.reg.active(), mine)  # after a refresh
+        self.reg.add_address(mine, "192.0.2.9")  # and after a change reloads the file
+        self.assertEqual(self.reg.active(), mine)
+        self.assertEqual(fd.Registry(self.dir / "devices.json").active(), mine)  # last to save: next start
+
 class ConfigRewrite(Base):
     def test_hostname_user_and_port_change_only_inside_the_block(self):
         cfg = self.ssh / "config"

tests/test_link.py

@@ -348,8 +348,21 @@ class Connecting(unittest.TestCase):
         self.assertEqual(s["phase"], "connected", s["error"])
         self.assertTrue(s["device"]["transient"])
         # Where ~/.ssh/config sends it, pinned down for the connection (ssh's own known_hosts).
-        self.assertEqual(self.routes[-1], ("frame-bare", ["-o", "HostName=localhost", "-o", f"Port={self.port}",
-                                                          "-o", "User=tester"]))
+        alias, opts = self.routes[-1]
+        self.assertEqual((alias, opts[2:]), ("frame-bare", ["-o", "HostName=localhost", "-o", f"Port={self.port}",
+                                                            "-o", "User=tester"]))
+        self.assertEqual(opts[:2], ["-o", "ControlPath=" + fl.frame_host.control_path(fl.Link.control_tag(s["device"]))])
+
+    def test_each_headset_has_its_own_shared_connection(self):
+        """ssh's %C hashes only address, user and port: two headsets at one address
+        (one moved) must still never share a ControlMaster."""
+        a, b = (dict(fl.Link.bare("x"), id=i, transient=False, user="steamos", port=22) for i in ("aaaa1111", "bbbb2222"))
+        pa, pb = (next(o for o in self.link.host_opts(d, "192.0.2.5") if o.startswith("ControlPath=")) for d in (a, b))
+        self.assertNotEqual(pa, pb)
+        self.assertIn("aaaa1111", pa)
+        long_alias = fl.Link.bare("x" * 64)
+        path = next(o for o in self.link.host_opts(long_alias, None) if o.startswith("ControlPath="))
+        self.assertLess(len(path) - len("ControlPath=") - len("%C") + 40 + 17, 104)  # fits a macOS socket path
 
     def test_a_bare_alias_keeps_its_pinned_route_for_reconnects_and_terminals(self):
         self.link.override = "frame-bare"