bpo-32394: Remove some TCP options on old version Windows. (GH-5523)

(cherry picked from commit 19e7d48c)
Co-authored-by: animalize <animalize@users.noreply.github.com>

Doc/library/socket.rst

@@ -320,9 +320,16 @@ Constants
       ``SO_DOMAIN``, ``SO_PROTOCOL``, ``SO_PEERSEC``, ``SO_PASSSEC``,
       ``TCP_USER_TIMEOUT``, ``TCP_CONGESTION`` were added.
 
+   .. versionchanged:: 3.6.5
+      On Windows, ``TCP_FASTOPEN``, ``TCP_KEEPCNT`` appear if run-time Windows
+      supports.
+
    .. versionchanged:: 3.7
       ``TCP_NOTSENT_LOWAT`` was added.
 
+      On Windows, ``TCP_KEEPIDLE``, ``TCP_KEEPINTVL`` appear if run-time Windows
+      supports.
+
 .. data:: AF_CAN
           PF_CAN
           SOL_CAN_*

Lib/test/test_socket.py

@@ -5945,6 +5945,27 @@ class LinuxKernelCryptoAPI(unittest.TestCase):
             with self.assertRaises(TypeError):
                 sock.sendmsg_afalg(op=socket.ALG_OP_ENCRYPT, assoclen=-1)
 
+@unittest.skipUnless(sys.platform.startswith("win"), "requires Windows")
+class TestMSWindowsTCPFlags(unittest.TestCase):
+    knownTCPFlags = {
+                       # avaliable since long time ago
+                       'TCP_MAXSEG',
+                       'TCP_NODELAY',
+                       # available starting with Windows 10 1607
+                       'TCP_FASTOPEN',
+                       # available starting with Windows 10 1703
+                       'TCP_KEEPCNT',
+                       # available starting with Windows 10 1709
+                       'TCP_KEEPIDLE',
+                       'TCP_KEEPINTVL'
+                       }
+
+    def test_new_tcp_flags(self):
+        provided = [s for s in dir(socket) if s.startswith('TCP')]
+        unknown = [s for s in provided if s not in self.knownTCPFlags]
+
+        self.assertEqual([], unknown,
+            "New TCP flags were discovered. See bpo-32394 for more information")
 
 def test_main():
     tests = [GeneralModuleTests, BasicTCPTest, TCPCloserTest, TCPTimeoutTest,
@@ -6005,6 +6026,7 @@ def test_main():
         SendfileUsingSendTest,
         SendfileUsingSendfileTest,
     ])
+    tests.append(TestMSWindowsTCPFlags)
 
     thread_info = support.threading_setup()
     support.run_unittest(*tests)

Misc/NEWS.d/next/Library/2018-02-10-13-51-56.bpo-32394.dFM9SI.rst

+socket: Remove TCP_FASTOPEN,TCP_KEEPCNT,TCP_KEEPIDLE,TCP_KEEPINTVL flags on
+older version Windows during run-time.

Modules/socketmodule.c

@@ -305,6 +305,70 @@ http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/net/getaddrinfo.c.diff?r1=1.82&
 /* Provides the IsWindows7SP1OrGreater() function */
 #include <VersionHelpers.h>
 
+/* remove some flags on older version Windows during run-time.
+   https://msdn.microsoft.com/en-us/library/windows/desktop/ms738596.aspx */
+typedef struct {
+    DWORD build_number;  /* available starting with this Win10 BuildNumber */
+    const char flag_name[20];
+} FlagRuntimeInfo;
+
+/* IMPORTANT: make sure the list ordered by descending build_number */
+static FlagRuntimeInfo win_runtime_flags[] = {
+    /* available starting with Windows 10 1709 */
+    {16299, "TCP_KEEPIDLE"},
+    {16299, "TCP_KEEPINTVL"},
+    /* available starting with Windows 10 1703 */
+    {15063, "TCP_KEEPCNT"},
+    /* available starting with Windows 10 1607 */
+    {14393, "TCP_FASTOPEN"}
+};
+
+static void
+remove_unusable_flags(PyObject *m)
+{
+    PyObject *dict;
+    OSVERSIONINFOEX info;
+    DWORDLONG dwlConditionMask;
+
+    dict = PyModule_GetDict(m);
+    if (dict == NULL) {
+        return;
+    }
+
+    /* set to Windows 10, except BuildNumber. */
+    memset(&info, 0, sizeof(info));
+    info.dwOSVersionInfoSize = sizeof(info);
+    info.dwMajorVersion = 10;
+    info.dwMinorVersion = 0;
+
+    /* set Condition Mask */
+    dwlConditionMask = 0;
+    VER_SET_CONDITION(dwlConditionMask, VER_MAJORVERSION, VER_GREATER_EQUAL);
+    VER_SET_CONDITION(dwlConditionMask, VER_MINORVERSION, VER_GREATER_EQUAL);
+    VER_SET_CONDITION(dwlConditionMask, VER_BUILDNUMBER, VER_GREATER_EQUAL);
+
+    for (int i=0; i<sizeof(win_runtime_flags)/sizeof(FlagRuntimeInfo); i++) {
+        info.dwBuildNumber = win_runtime_flags[i].build_number;
+        /* greater than or equal to the specified version? 
+           Compatibility Mode will not cheat VerifyVersionInfo(...) */
+        if (VerifyVersionInfo(
+                &info,
+                VER_MAJORVERSION|VER_MINORVERSION|VER_BUILDNUMBER,
+                dwlConditionMask)) {
+            break;
+        }
+        else {
+            if (PyDict_GetItemString(
+                    dict,
+                    win_runtime_flags[i].flag_name) != NULL) {
+                PyDict_DelItemString(
+                    dict,
+                    win_runtime_flags[i].flag_name);
+            }
+        }
+    }
+}
+
 #endif
 
 #include <stddef.h>
@@ -7890,5 +7954,11 @@ PyInit__socket(void)
 #if defined(USE_GETHOSTBYNAME_LOCK) || defined(USE_GETADDRINFO_LOCK)
     netdb_lock = PyThread_allocate_lock();
 #endif
+
+#ifdef MS_WINDOWS
+    /* remove some flags on older version Windows during run-time */
+    remove_unusable_flags(m);
+#endif
+
     return m;
 }