From 9a45bfe6f4aedd2a9d94cb12aa276057b15d8b63 Mon Sep 17 00:00:00 2001
From: Erlend Egeberg Aasland <erlend.aasland@innova.no>
Date: Sun, 17 May 2020 08:32:46 +0200
Subject: bpo-35569: Expose RFC 3542 IPv6 socket options on macOS (GH-19526)

---
 Lib/test/test_socket.py                            | 31 ++++++++++++++++++++++
 .../macOS/2020-04-15-00-02-47.bpo-35569.02_1MV.rst |  1 +
 setup.py                                           |  8 ++++--
 3 files changed, 38 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/macOS/2020-04-15-00-02-47.bpo-35569.02_1MV.rst

diff --git a/Lib/test/test_socket.py b/Lib/test/test_socket.py
index 4a436cf..aefba4f 100755
--- a/Lib/test/test_socket.py
+++ b/Lib/test/test_socket.py
@@ -959,6 +959,37 @@ class GeneralModuleTests(unittest.TestCase):
         socket.IPPROTO_L2TP
         socket.IPPROTO_SCTP
 
+    @unittest.skipUnless(sys.platform == 'darwin', 'macOS specific test')
+    @unittest.skipUnless(socket_helper.IPV6_ENABLED, 'IPv6 required for this test')
+    def test3542SocketOptions(self):
+        # Ref. issue #35569 and https://tools.ietf.org/html/rfc3542
+        opts = {
+            'IPV6_CHECKSUM',
+            'IPV6_DONTFRAG',
+            'IPV6_DSTOPTS',
+            'IPV6_HOPLIMIT',
+            'IPV6_HOPOPTS',
+            'IPV6_NEXTHOP',
+            'IPV6_PATHMTU',
+            'IPV6_PKTINFO',
+            'IPV6_RECVDSTOPTS',
+            'IPV6_RECVHOPLIMIT',
+            'IPV6_RECVHOPOPTS',
+            'IPV6_RECVPATHMTU',
+            'IPV6_RECVPKTINFO',
+            'IPV6_RECVRTHDR',
+            'IPV6_RECVTCLASS',
+            'IPV6_RTHDR',
+            'IPV6_RTHDRDSTOPTS',
+            'IPV6_RTHDR_TYPE_0',
+            'IPV6_TCLASS',
+            'IPV6_USE_MIN_MTU',
+        }
+        for opt in opts:
+            self.assertTrue(
+                hasattr(socket, opt), f"Missing RFC3542 socket option '{opt}'"
+            )
+
     def testHostnameRes(self):
         # Testing hostname resolution mechanisms
         hostname = socket.gethostname()
diff --git a/Misc/NEWS.d/next/macOS/2020-04-15-00-02-47.bpo-35569.02_1MV.rst b/Misc/NEWS.d/next/macOS/2020-04-15-00-02-47.bpo-35569.02_1MV.rst
new file mode 100644
index 0000000..ed48efd
--- /dev/null
+++ b/Misc/NEWS.d/next/macOS/2020-04-15-00-02-47.bpo-35569.02_1MV.rst
@@ -0,0 +1 @@
+Expose RFC 3542 IPv6 socket options.
diff --git a/setup.py b/setup.py
index 68fc312..0f92a9c 100644
--- a/setup.py
+++ b/setup.py
@@ -1116,8 +1116,12 @@ class PyBuildExt(build_ext):
     def detect_socket(self):
         # socket(2)
         if not VXWORKS:
-            self.add(Extension('_socket', ['socketmodule.c'],
-                               depends=['socketmodule.h']))
+            kwargs = {'depends': ['socketmodule.h']}
+            if MACOS:
+                # Issue #35569: Expose RFC 3542 socket options.
+                kwargs['extra_compile_args'] = ['-D__APPLE_USE_RFC_3542']
+
+            self.add(Extension('_socket', ['socketmodule.c'], **kwargs))
         elif self.compiler.find_library_file(self.lib_dirs, 'net'):
             libs = ['net']
             self.add(Extension('_socket', ['socketmodule.c'],
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