Allow non-TCP sockets to be passed in via the 'sock' option

This commit guards against a setsockopt() failure when passing a
non-TCP socket (such as a socketpair) to AsyncSSH via the 'sock'
option. Thanks go to Christian Wendt for reporting this problem
and proposing a fix.

asyncssh/connection.py

@@ -1269,7 +1269,9 @@ def connection_made(self, transport: asyncio.BaseTransport) -> None:
         if sock:
             sock.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE,
                             self._tcp_keepalive)
-            sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
+
+            if sock.family in (socket.AF_INET, socket.AF_INET6):
+                sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
 
         sockname = cast(SockAddr, transport.get_extra_info('sockname'))
 

tests/test_connection.py

@@ -418,6 +418,24 @@ async def test_connect_sock(self):
         async with asyncssh.connect(sock=sock):
             pass
 
+    @unittest.skipUnless(nc_available, 'Netcat not available')
+    @asynctest
+    async def test_connect_non_tcp_sock(self):
+        """Test connecting using an non-TCP socket"""
+
+        sock1, sock2 = socket.socketpair()
+
+        proc = await asyncio.create_subprocess_exec(
+            'nc', str(self._server_addr), str(self._server_port),
+            stdin=sock1, stdout=sock1, stderr=sock1)
+
+        async with asyncssh.connect(
+                self._server_addr, self._server_port, sock=sock2):
+            pass
+
+        await proc.wait()
+        sock1.close()
+
     @asynctest
     async def test_run_client(self):
         """Test running an SSH client on an already-connected socket"""