fix(fixtures): skip getfqdn (fixes macOS CI hang)

host_guard::run_allows_loopback_when_escape_hatch_set timed out
~30s on macOS CI only. Root cause: Python stdlib
http.server.HTTPServer.server_bind() calls socket.getfqdn(host), a
reverse-DNS lookup that blocks on macOS GitHub runners. It is the
sole fresh consumer of mock-http-server.py (http_transport uses
httpmock; this fixture isn't otherwise spawned), so only this test
hit it; bumping the test timeout could not help (hang >= the DNS
timeout).

Fix at the root in both HTTP/SSE fixtures: a _Server subclass binds
via socketserver.TCPServer.server_bind (no getfqdn) and sets
server_name/port directly, so LISTENING is emitted immediately on
every platform. mock-sse-server.py shares the identical latent bug
(not yet triggered) — fixed preventively for consistency.

Local: ci-checks.sh green; 16/16 host_guard/http/sse tests pass;
LISTENING smoke immediate. macOS reverse-DNS path is removed
entirely, not merely given more time.

Author: Teerapat-Vatpitak

crates/mcp-loadtest/tests/fixtures/mock-http-server.py

@@ -12,6 +12,7 @@
 import argparse
 import json
 import signal
+import socketserver
 import sys
 import threading
 from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
@@ -93,13 +94,28 @@ def log_message(self, fmt, *args):  # silence per-request stderr logging
         pass
 
 
+class _Server(ThreadingHTTPServer):
+    """`http.server.HTTPServer.server_bind()` calls `socket.getfqdn(host)`, a
+    reverse-DNS lookup that can block ~30s on macOS CI runners (and is not
+    needed for a loopback test mock). Bind via the plain TCPServer path and
+    set `server_name`/`server_port` directly so `LISTENING:` is emitted
+    immediately on every platform.
+    """
+
+    def server_bind(self):
+        socketserver.TCPServer.server_bind(self)
+        host, port = self.server_address[:2]
+        self.server_name = host
+        self.server_port = port
+
+
 def main():
     parser = argparse.ArgumentParser()
     parser.add_argument("--port", type=int, default=0)
     parser.add_argument("--host", default="127.0.0.1")
     args = parser.parse_args()
 
-    server = ThreadingHTTPServer((args.host, args.port), Handler)
+    server = _Server((args.host, args.port), Handler)
     host, port = server.server_address[0], server.server_address[1]
     sys.stdout.write(f"LISTENING: {host}:{port}\n")
     sys.stdout.flush()

crates/mcp-loadtest/tests/fixtures/mock-sse-server.py

@@ -20,6 +20,7 @@
 import json
 import queue
 import signal
+import socketserver
 import sys
 import threading
 from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
@@ -102,7 +103,10 @@ def do_GET(self):  # noqa: N802
 
         my_queue = _swap_outbound()
 
-        host = self.headers.get("Host") or f"{self.server.server_address[0]}:{self.server.server_address[1]}"  # type: ignore[attr-defined]
+        host = (
+            self.headers.get("Host")
+            or f"{self.server.server_address[0]}:{self.server.server_address[1]}"
+        )  # type: ignore[attr-defined]
         endpoint_url = f"http://{host}/post"
 
         self.send_response(200)
@@ -128,9 +132,7 @@ def do_GET(self):  # noqa: N802
                 if item is _STOP:
                     return
                 data = json.dumps(item)
-                self.wfile.write(
-                    f"event: message\ndata: {data}\n\n".encode("utf-8")
-                )
+                self.wfile.write(f"event: message\ndata: {data}\n\n".encode("utf-8"))
                 self.wfile.flush()
         except (BrokenPipeError, ConnectionResetError, OSError):
             # Client disconnected — that's fine, just exit the handler.
@@ -165,13 +167,28 @@ def log_message(self, fmt, *args):
         pass
 
 
+class _Server(ThreadingHTTPServer):
+    """`http.server.HTTPServer.server_bind()` calls `socket.getfqdn(host)`, a
+    reverse-DNS lookup that can block ~30s on macOS CI runners (and is not
+    needed for a loopback test mock). Bind via the plain TCPServer path and
+    set `server_name`/`server_port` directly so `LISTENING:` is emitted
+    immediately on every platform.
+    """
+
+    def server_bind(self):
+        socketserver.TCPServer.server_bind(self)
+        host, port = self.server_address[:2]
+        self.server_name = host
+        self.server_port = port
+
+
 def main():
     parser = argparse.ArgumentParser()
     parser.add_argument("--port", type=int, default=0)
     parser.add_argument("--host", default="127.0.0.1")
     args = parser.parse_args()
 
-    server = ThreadingHTTPServer((args.host, args.port), Handler)
+    server = _Server((args.host, args.port), Handler)
     host, port = server.server_address[0], server.server_address[1]
     sys.stdout.write(f"LISTENING: {host}:{port}\n")
     sys.stdout.flush()