Fix SystemMonitor IP address sensor (#16394)

homeassistant/components/sensor/systemmonitor.py

@@ -6,6 +6,7 @@ https://home-assistant.io/components/sensor.systemmonitor/
 """
 import logging
 import os
+import socket
 
 import voluptuous as vol
 
@@ -61,9 +62,9 @@ IO_COUNTER = {
     'packets_in': 3,
 }
 
-IF_ADDRS = {
-    'ipv4_address': 0,
-    'ipv6_address': 1,
+IF_ADDRS_FAMILY = {
+    'ipv4_address': socket.AF_INET,
+    'ipv6_address': socket.AF_INET6,
 }
 
 
@@ -165,7 +166,9 @@ class SystemMonitorSensor(Entity):
         elif self.type == 'ipv4_address' or self.type == 'ipv6_address':
             addresses = psutil.net_if_addrs()
             if self.argument in addresses:
-                self._state = addresses[self.argument][IF_ADDRS[self.type]][1]
+                for addr in addresses[self.argument]:
+                    if addr.family == IF_ADDRS_FAMILY[self.type]:
+                        self._state = addr.address
             else:
                 self._state = None
         elif self.type == 'last_boot':