commit 33cb4a62bf6848093b7a05c9794582d204798b1b
author Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> Mon Jan 06 05:28:27 2020 -0800
committer Jason R. Coombs <jaraco@jaraco.com> Mon Jan 06 08:28:27 2020 -0500
tree 9bd11f10cb682506e552813bd8b7e47bbb480136
parent 5ed9d60bc53e2eb0a88f07d5afe5299acdc0b216

bpo-38907: Suppress any exception when attempting to set V6ONLY. (GH-17864) (GH-17865)

Fixes error attempting to bind to IPv4 address.
(cherry picked from commit 7cdc31a14c824000cbe8b487900c9826a33f6940)

Co-authored-by: Jason R. Coombs <jaraco@jaraco.com>

Co-authored-by: Jason R. Coombs <jaraco@jaraco.com>

Lib/http/server.py

diff --git a/Lib/http/server.py b/Lib/http/server.py
index 0fe44bd..38f7acc 100644
--- a/Lib/http/server.py
+++ b/Lib/http/server.py
@@ -103,6 +103,7 @@
 import sys
 import time
 import urllib.parse
+import contextlib
 from functools import partial
 
 from http import HTTPStatus
@@ -1284,7 +1285,10 @@
     # ensure dual-stack is not disabled; ref #38907
     class DualStackServer(ThreadingHTTPServer):
         def server_bind(self):
-            self.socket.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 0)
+            # suppress exception when protocol is IPv4
+            with contextlib.suppress(Exception):
+                self.socket.setsockopt(
+                    socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 0)
             return super().server_bind()
 
     test(