fix: bind to a specific local IPv6 address during pair verify

aiohomekit/controller/coap/connection.py

@@ -19,6 +19,7 @@
 import asyncio
 import logging
 import random
+import socket
 import struct
 from typing import Any
 import uuid
@@ -170,7 +171,13 @@ async def post_bytes(self, payload: bytes, timeout: int = 16.0):
             except (NetworkError, asyncio.TimeoutError):
                 raise AccessoryDisconnectedError("Request timeout")
 
-            if response.code != Code.CHANGED:
+            if response.code == Code.NOT_FOUND:
+                # maybe the accessory lost power or was otherwise rebooted
+                logger.error("CoAP POST returned 404, our session is gone.")
+                await self.coap_ctx.shutdown()
+                self.coap_ctx = None
+                raise AccessoryDisconnectedError("Accessory lost our session")
+            elif response.code != Code.CHANGED:
                 logger.warning(f"CoAP POST returned unexpected code {response}")
 
             return await self._decrypt_response(response)
@@ -244,8 +251,10 @@ def __init__(self, owner, host, port):
         self.address = f"[{host}]:{port}"
         self.connection_lock = asyncio.Lock()
         self.enc_ctx = None
+        self.host = host
         self.owner = owner
         self.pair_setup_client = None
+        self.port = port
 
     async def reconnect_soon(self):
         if not self.enc_ctx:
@@ -322,14 +331,29 @@ async def do_pair_setup_finish(self, pin, salt, srpB):
 
         return pairing
 
+    def _get_local_ipv6_addr(self, remote):
+        s = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
+        s.connect(remote)
+        addr = s.getsockname()[0]
+        s.close()
+        return addr
+
     async def do_pair_verify(self, pairing_data):
         if self.is_connected:
             logger.warning("Connecting to connected device?")
             await self.enc_ctx.coap_ctx.shutdown()
             self.enc_ctx = None
 
+        try:
+            local_address = self._get_local_ipv6_addr((self.host, self.port))
+        except Exception as e:
+            logger.warning(
+                f"Unable to get local IPv6 address to connect to {self.address}: {e}"
+            )
+            raise AccessoryDisconnectedError("Unable to get local IPv6 address") from e
+
         root = resource.Site()
-        coap_client = await Context.create_server_context(root, bind=("::", 0))
+        coap_client = await Context.create_server_context(root, bind=(local_address, 0))
         uri = "coap://%s/2" % (self.address)
         logger.debug(f"Pair verify uri={uri}")
 

aiohomekit/controller/coap/pairing.py

@@ -53,6 +53,8 @@ def _async_endpoint_changed(self) -> None:
         self.connection.address = (
             f"[{self.description.address}]:{self.description.port}"
         )
+        self.connection.host = self.description.address
+        self.connection.port = self.description.port
         async_create_task(self.connection.reconnect_soon())
 
     @property