Find Dante PoE devices by MAC automatically instead of hard-coding ports.

Every 10 minutes the watchdog maps each Dante device: name and IP from
Companion, MAC from NA Ingest's ARP table, switch port and PoE state from
the Netgear switches in dante_switches, saved to dante-map.json. A DANTE hold
on a missing PoE-powered device power-cycles the port it is on now (found
live by MAC, or its last known port if it has aged out and nothing else is
there); never a port with more than 2 devices. Re-patching, adding or
renaming devices needs no config change. First live map: 19 devices, the 4
Studio B boxes on PoE.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

netgear.py

@@ -108,6 +108,7 @@ MAC_RE = re.compile(r"(?:[0-9A-Fa-f]{2}:){5}[0-9A-Fa-f]{2}")
 
 
 def poe_cycle(host, port, expect_mac=None):
+    # Used directly only for a known port; poe_cycle_device finds the port by MAC.
     """Power-cycle PoE on ONE port ("poe reset" in Interface Config mode). Nothing is saved
     to the switch's startup config: the port's settings are unchanged afterwards.
 
@@ -136,6 +137,79 @@ def poe_cycle(host, port, expect_mac=None):
     print("POE RESET %s %s ok%s" % (host, port, (": " + answer.strip()) if answer.strip() else ""))
 
 
+# --- Find devices by MAC, wherever they are plugged in ---------------------
+
+TABLE_RE = re.compile(r"((?:[0-9A-Fa-f]{2}:){5}[0-9A-Fa-f]{2})\s+(\d+/\d+)")
+MAX_SHARED = 2   # more devices than this on one port means an uplink: never power-cycle it
+
+
+def parse_mac_table(text):
+    """'show mac-addr-table' -> ({mac: port}, {port: number of MACs learned on it})."""
+    where, counts = {}, {}
+    for mac, port in TABLE_RE.findall(text or ""):
+        where[mac.lower()] = port
+        counts[port] = counts.get(port, 0) + 1
+    return where, counts
+
+
+def best_ports(tables, macs):
+    """tables: {switch: table text}. -> {mac: (switch, port, devices on that port)}.
+    A MAC is seen on every switch it crosses; its own port is where it has the fewest
+    neighbours (on the far switch it shows up on the uplink with everything else)."""
+    best = {}
+    for host, text in tables.items():
+        where, counts = parse_mac_table(text)
+        for mac in macs:
+            if mac in where:
+                cand = (host, where[mac], counts[where[mac]])
+                if mac not in best or cand[2] < best[mac][2]:
+                    best[mac] = cand
+    return best
+
+
+def poe_delivering(text):
+    return bool(re.search(r"(?i)delivering power", text or ""))
+
+
+def survey(switches, macs):
+    """Read-only: {mac: {"switch", "port", "shared", "poe"}} for every MAC found."""
+    macs = [m.lower() for m in macs]
+    user, password = credentials()
+    sessions, tables = {}, {}
+    try:
+        for host in switches:
+            sessions[host] = Switch(host, user, password)
+            tables[host] = sessions[host].run("show mac-addr-table")
+        found = {}
+        for mac, (host, port, shared) in best_ports(tables, macs).items():
+            poe = shared <= MAX_SHARED and poe_delivering(sessions[host].run("show poe port info %s" % port))
+            found[mac] = {"switch": host, "port": port, "shared": shared, "poe": poe}
+        return found
+    finally:
+        for sw in sessions.values():
+            sw.close()
+
+
+def poe_cycle_device(switches, mac, last_known=None):
+    """Power-cycle the PoE port a device is on NOW, found by its MAC. If it has aged out of
+    the switch tables (dead long enough), use its last known port - poe_cycle then refuses
+    unless that port is empty of other devices. Never touches a port shared by more than
+    MAX_SHARED devices. Returns (switch, port, how it was found)."""
+    mac = mac.lower()
+    live = survey(switches, [mac]).get(mac)
+    if live:
+        if live["shared"] > MAX_SHARED:
+            raise RuntimeError("%s is behind %s port %s with %d devices (an uplink) - not power-cycling"
+                               % (mac, live["switch"], live["port"], live["shared"]))
+        host, port, how = live["switch"], live["port"], "found now"
+    elif last_known and last_known.get("switch") and last_known.get("port"):
+        host, port, how = last_known["switch"], last_known["port"], "last known port"
+    else:
+        raise RuntimeError("%s is not on any Dante switch and has no last known port" % mac)
+    poe_cycle(host, port, expect_mac=mac)
+    return host, port, how
+
+
 if __name__ == "__main__":
     if len(sys.argv) >= 3 and sys.argv[1] == "lookup":
         lookup(sys.argv[2:])