Bypass proxy lookups in requests backend for Unix domain hostname paths

Addresses issue found by CI for hostname labels >63 characters. Also the tests have
been adapted to always use a Unix domain socket path of 96 bytes length, which is
the maximum portably supported length.

Author: ntninja

ipfshttpclient/http_requests.py

@@ -71,9 +71,10 @@ def map_args_to_requests(
 
 
 class ClientSync(ClientSyncBase[requests.Session]):  # type: ignore[name-defined]
-	__slots__ = ("_base_url", "_default_timeout", "_session_props")
+	__slots__ = ("_base_url", "_default_timeout", "_request_proxies", "_session_props")
 	#_base_url: str
 	#_default_timeout: timeout_t
+	#_request_proxies: ty.Optional[ty.Dict[str, str]]
 	#_session_props: ty.Dict[str, ty.Any]
 
 	def _init(self, addr: addr_t, base: str, *,  # type: ignore[no-any-unimported]
@@ -82,7 +83,7 @@ def _init(self, addr: addr_t, base: str, *,  # type: ignore[no-any-unimported]
 	          headers: headers_t,
 	          params: params_t,
 	          timeout: timeout_t) -> None:
-		self._base_url, _, family, host_numeric = multiaddr_to_url_data(addr, base)
+		self._base_url, uds_path, family, host_numeric = multiaddr_to_url_data(addr, base)
 
 		self._session_props = map_args_to_requests(
 			auth=auth,
@@ -93,6 +94,17 @@ def _init(self, addr: addr_t, base: str, *,  # type: ignore[no-any-unimported]
 		self._default_timeout = timeout
 		if PATCH_REQUESTS:  # pragma: no branch (always enabled in production)
 			self._session_props["family"] = family
+		
+		# Ensure that no proxy lookups are done for the UDS pseudo-hostname
+		#
+		# I'm well aware of the `.proxies` attribute of the session object: As it turns out,
+		# setting *that* attribute will *not* bypass system proxy resolution – only the
+		# per-request keyword-argument can do *that*…!
+		self._request_proxies = None  # type: ty.Optional[ty.Dict[str, str]]
+		if uds_path:
+			self._request_proxies = {
+				"no_proxy": urllib.parse.quote(uds_path, safe=""),
+			}
 
 	def _make_session(self) -> requests.Session:  # type: ignore[name-defined]
 		session = requests.Session()  # type: ignore[attr-defined]
@@ -159,6 +171,7 @@ def _request(
 						headers=headers,
 						timeout=(timeout if timeout is not None else self._default_timeout),
 					),
+					proxies=self._request_proxies,
 					data=data,
 					stream=True,
 				)

test/unit/test_http.py

@@ -7,7 +7,10 @@
 TestHttp -- A TCP client for interacting with an IPFS daemon
 """
 
+import codecs
+import errno
 import json
+import locale
 import os
 import socket
 import tempfile
@@ -35,6 +38,34 @@ def http_server(request):
 	return server
 
 
+def make_temp_maxlen_socket_path():
+	"""Generate a socket filepath of exactly 96 bytes length
+	
+	When using this as part of the hostname value, the first label will definitely be longer then
+	the maximum permitted label length of 63 characters (issue found by CI). At the same time
+	the total binary path length will exceed the portably usable maximum of 96 bytes for the
+	path length in the `sockaddr_un.sun_path` C socket datastructure (as documented in the
+	``unix(7)`` Linux man-page).
+	"""
+	# The following was inspired by the `tempfile.mktemp` standard library function
+	temp_dir_bin = tempfile.gettempdir().encode(locale.getpreferredencoding())
+	with socket.socket(socket.AF_UNIX, socket.SOCK_STREAM, 0) as sock:
+		for _ in range(tempfile.TMP_MAX):
+			uds_name_len = (96 - len(temp_dir_bin) - len(os.sep) - len(b".sock"))
+			uds_name_bin = codecs.encode(os.urandom((uds_name_len + 2) // 2), "hex")[:uds_name_len]
+			uds_path_bin = os.path.join(temp_dir_bin, uds_name_bin + b".sock")
+			uds_path_str = uds_path_bin.decode(locale.getpreferredencoding())
+			if not os.path.exists(uds_path_bin):
+				try:
+					sock.bind(uds_path_bin)
+				except IOError:
+					continue
+				else:
+					return uds_path_str
+		
+		raise FileExistsError(errno.EEXIST, "No usable temporary filepath found")
+
+
 @pytest.fixture(scope="module")
 def http_server_uds(request):
 	"""Like :func:`http_server` but will listen on a Unix domain socket instead
@@ -45,7 +76,7 @@ def http_server_uds(request):
 	if not hasattr(socket, "AF_UNIX"):
 		pytest.skip("Platform does not support Unix domain sockets")
 
-	uds_path = tempfile.mktemp(".sock")
+	uds_path = make_temp_maxlen_socket_path()
 	def remove_uds_path():
 		try:
 			os.remove(uds_path)
@@ -122,7 +153,6 @@ def test_successful_request_uds(http_client_uds, http_server_uds):
 
 	res = http_client_uds.request("/okay")
 	assert res == b"okay"
-	print(http_server_uds.requests[0].headers)
 
 def test_generic_failure(http_client, http_server):
 	"""Tests that a failed http request raises an HTTPError."""