Fix hang in SNMP device_tracker implementation (#112815)

Co-authored-by: J. Nick Koston <nick@koston.org>

CODEOWNERS

@@ -1249,6 +1249,8 @@ build.json @home-assistant/supervisor
 /homeassistant/components/sms/ @ocalvo
 /homeassistant/components/snapcast/ @luar123
 /tests/components/snapcast/ @luar123
+/homeassistant/components/snmp/ @nmaggioni
+/tests/components/snmp/ @nmaggioni
 /homeassistant/components/snooz/ @AustinBrunkhorst
 /tests/components/snooz/ @AustinBrunkhorst
 /homeassistant/components/solaredge/ @frenck

homeassistant/components/snmp/device_tracker.py

@@ -5,8 +5,19 @@ from __future__ import annotations
 import binascii
 import logging
 
-from pysnmp.entity import config as cfg
+from pysnmp.error import PySnmpError
-from pysnmp.entity.rfc3413.oneliner import cmdgen
+from pysnmp.hlapi.asyncio import (
+    CommunityData,
+    ContextData,
+    ObjectIdentity,
+    ObjectType,
+    SnmpEngine,
+    Udp6TransportTarget,
+    UdpTransportTarget,
+    UsmUserData,
+    bulkWalkCmd,
+    isEndOfMib,
+)
 import voluptuous as vol
 
 from homeassistant.components.device_tracker import (
@@ -24,7 +35,13 @@ from .const import (
     CONF_BASEOID,
     CONF_COMMUNITY,
     CONF_PRIV_KEY,
+    DEFAULT_AUTH_PROTOCOL,
     DEFAULT_COMMUNITY,
+    DEFAULT_PORT,
+    DEFAULT_PRIV_PROTOCOL,
+    DEFAULT_TIMEOUT,
+    DEFAULT_VERSION,
+    SNMP_VERSIONS,
 )
 
 _LOGGER = logging.getLogger(__name__)
@@ -40,9 +57,12 @@ PLATFORM_SCHEMA = PARENT_PLATFORM_SCHEMA.extend(
 )
 
 
-def get_scanner(hass: HomeAssistant, config: ConfigType) -> SnmpScanner | None:
+async def async_get_scanner(
+    hass: HomeAssistant, config: ConfigType
+) -> SnmpScanner | None:
     """Validate the configuration and return an SNMP scanner."""
     scanner = SnmpScanner(config[DOMAIN])
+    await scanner.async_init()
 
     return scanner if scanner.success_init else None
 
@@ -51,39 +71,75 @@ class SnmpScanner(DeviceScanner):
     """Queries any SNMP capable Access Point for connected devices."""
 
     def __init__(self, config):
-        """Initialize the scanner."""
+        """Initialize the scanner and test the target device."""
+        host = config[CONF_HOST]
+        community = config[CONF_COMMUNITY]
+        baseoid = config[CONF_BASEOID]
+        authkey = config.get(CONF_AUTH_KEY)
+        authproto = DEFAULT_AUTH_PROTOCOL
+        privkey = config.get(CONF_PRIV_KEY)
+        privproto = DEFAULT_PRIV_PROTOCOL
 
-        self.snmp = cmdgen.CommandGenerator()
+        try:
-
+            # Try IPv4 first.
-        self.host = cmdgen.UdpTransportTarget((config[CONF_HOST], 161))
+            target = UdpTransportTarget((host, DEFAULT_PORT), timeout=DEFAULT_TIMEOUT)
-        if CONF_AUTH_KEY not in config or CONF_PRIV_KEY not in config:
+        except PySnmpError:
-            self.auth = cmdgen.CommunityData(config[CONF_COMMUNITY])
+            # Then try IPv6.
-        else:
+            try:
-            self.auth = cmdgen.UsmUserData(
+                target = Udp6TransportTarget(
-                config[CONF_COMMUNITY],
+                    (host, DEFAULT_PORT), timeout=DEFAULT_TIMEOUT
-                config[CONF_AUTH_KEY],
-                config[CONF_PRIV_KEY],
-                authProtocol=cfg.usmHMACSHAAuthProtocol,
-                privProtocol=cfg.usmAesCfb128Protocol,
                 )
-        self.baseoid = cmdgen.MibVariable(config[CONF_BASEOID])
+            except PySnmpError as err:
-        self.last_results = []
+                _LOGGER.error("Invalid SNMP host: %s", err)
+                return
 
-        # Test the router is accessible
+        if authkey is not None or privkey is not None:
-        data = self.get_snmp_data()
+            if not authkey:
+                authproto = "none"
+            if not privkey:
+                privproto = "none"
+
+            request_args = [
+                SnmpEngine(),
+                UsmUserData(
+                    community,
+                    authKey=authkey or None,
+                    privKey=privkey or None,
+                    authProtocol=authproto,
+                    privProtocol=privproto,
+                ),
+                target,
+                ContextData(),
+            ]
+        else:
+            request_args = [
+                SnmpEngine(),
+                CommunityData(community, mpModel=SNMP_VERSIONS[DEFAULT_VERSION]),
+                target,
+                ContextData(),
+            ]
+
+        self.request_args = request_args
+        self.baseoid = baseoid
+        self.last_results = []
+        self.success_init = False
+
+    async def async_init(self):
+        """Make a one-off read to check if the target device is reachable and readable."""
+        data = await self.async_get_snmp_data()
         self.success_init = data is not None
 
-    def scan_devices(self):
+    async def async_scan_devices(self):
         """Scan for new devices and return a list with found device IDs."""
-        self._update_info()
+        await self._async_update_info()
         return [client["mac"] for client in self.last_results if client.get("mac")]
 
-    def get_device_name(self, device):
+    async def async_get_device_name(self, device):
         """Return the name of the given device or None if we don't know."""
         # We have no names
         return None
 
-    def _update_info(self):
+    async def _async_update_info(self):
         """Ensure the information from the device is up to date.
 
         Return boolean if scanning successful.
@@ -91,20 +147,24 @@ class SnmpScanner(DeviceScanner):
         if not self.success_init:
             return False
 
-        if not (data := self.get_snmp_data()):
+        if not (data := await self.async_get_snmp_data()):
             return False
 
         self.last_results = data
         return True
 
-    def get_snmp_data(self):
+    async def async_get_snmp_data(self):
         """Fetch MAC addresses from access point via SNMP."""
         devices = []
 
-        errindication, errstatus, errindex, restable = self.snmp.nextCmd(
+        walker = bulkWalkCmd(
-            self.auth, self.host, self.baseoid
+            *self.request_args,
+            0,
+            50,
+            ObjectType(ObjectIdentity(self.baseoid)),
+            lexicographicMode=False,
         )
-
+        async for errindication, errstatus, errindex, res in walker:
             if errindication:
                 _LOGGER.error("SNMPLIB error: %s", errindication)
                 return
@@ -112,14 +172,14 @@ class SnmpScanner(DeviceScanner):
                 _LOGGER.error(
                     "SNMP error: %s at %s",
                     errstatus.prettyPrint(),
-                errindex and restable[int(errindex) - 1][0] or "?",
+                    errindex and res[int(errindex) - 1][0] or "?",
                 )
                 return
 
-        for resrow in restable:
+            for _oid, value in res:
-            for _, val in resrow:
+                if not isEndOfMib(res):
                     try:
-                    mac = binascii.hexlify(val.asOctets()).decode("utf-8")
+                        mac = binascii.hexlify(value.asOctets()).decode("utf-8")
                     except AttributeError:
                         continue
                     _LOGGER.debug("Found MAC address: %s", mac)

homeassistant/components/snmp/manifest.json

@@ -1,7 +1,7 @@
 {
   "domain": "snmp",
   "name": "SNMP",
-  "codeowners": [],
+  "codeowners": ["@nmaggioni"],
   "documentation": "https://www.home-assistant.io/integrations/snmp",
   "iot_class": "local_polling",
   "loggers": ["pyasn1", "pysmi", "pysnmp"],