fix(server): restore keeps connectivity alert for connections dropped to unknown

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Uc9V1v7iXruubpoLiSE24M

hbd/server/udp.py

@@ -351,6 +351,7 @@ def restore_connection_timers(hbdclass, ctx):
                 restored += 1
 
             elif state == hbdclass.Connection.OVERDUE:
+                host_overdue = host.status() == "overdue"
                 elapsed_overdue = now - conn.statetime
                 remaining = DROPOVERDUE - elapsed_overdue
                 if remaining <= 1:
@@ -360,6 +361,9 @@ def restore_connection_timers(hbdclass, ctx):
                         "Marking %s/%s UNKNOWN (overdue %.1f days)",
                         uname, afam, elapsed_overdue / 86400,
                     )
+                    # A connection dropped to UNKNOWN keeps its alert, like the
+                    # UNKNOWN branch above and on_unknown do.
+                    host_overdue = True
                 else:
                     conn.reset_overdue_timer(remaining, on_unknown)
                     logger.debug(
@@ -369,7 +373,7 @@ def restore_connection_timers(hbdclass, ctx):
                 # Ensure the connectivity alert is set — it may be missing if
                 # hbd was shut down before the on_overdue callback had a chance
                 # to record it.
-                if host.status() == "overdue":
+                if host_overdue:
                     _set_connectivity_alert(host, afam, "CRITICAL")
                 restored += 1
 

tests/test_udp_presence.py

@@ -171,3 +171,49 @@ def test_restore_skips_absent_and_sets_no_alert_for_simplex():
             c.cancel_overdue_timer()
 
     asyncio.run(scenario())
+
+
+def _past_drop(conn):
+    conn.state, conn.statetime = C.OVERDUE, time.time() - (udp.DROPOVERDUE + 10)
+
+
+def test_restore_past_drop_window_keeps_alert_single_family():
+    ctx = _ctx()
+
+    async def scenario():
+        _fresh("pres-drop-single")
+        _send("pres-drop-single", "127.0.0.1", ctx)
+        h = hbdclass.Host.hosts["pres-drop-single"]
+        _past_drop(h.connections["IPv4"])
+        udp.restore_connection_timers(hbdclass, ctx)
+        assert h.connections["IPv4"].state == C.UNKNOWN
+        assert "connectivity.IPv4" in h.alert_states
+
+    asyncio.run(scenario())
+
+
+def test_restore_past_drop_window_keeps_alerts_dual_family():
+    ctx = _ctx()
+
+    async def scenario():
+        h = _dual_stack("pres-drop-dual", ctx)
+        for c in h.connections.values():
+            _past_drop(c)
+        udp.restore_connection_timers(hbdclass, ctx)
+        assert {"connectivity.IPv4", "connectivity.IPv6"} <= set(h.alert_states)
+
+    asyncio.run(scenario())
+
+
+def test_v4_only_host_overdue_is_single_critical(monkeypatch):
+    events = _events(monkeypatch)
+    ctx = _ctx()
+    _fresh("pres-v4only")
+    _send("pres-v4only", "127.0.0.1", ctx)
+    h = hbdclass.Host.hosts["pres-v4only"]
+    on_overdue, _ = udp._make_timer_callbacks("pres-v4only", h, ctx)
+    asyncio.run(on_overdue(h.connections["IPv4"]))
+    assert [e for e in events if e[0] == "CRITICAL"] == [("CRITICAL", "IPv4 overdue")]
+    assert "connectivity.IPv4" in h.alert_states
+    asyncio.run(on_overdue(h.connections["IPv4"]))
+    assert len([e for e in events if e[0] == "CRITICAL"]) == 1