bpo-44077: Expose IP_RECVTOS in the socket module (GH-25992)

Co-authored-by: Pablo Galindo <pablogsal@gmail.com>

Doc/library/socket.rst

@@ -379,6 +379,9 @@ Constants
       On Windows, ``TCP_KEEPIDLE``, ``TCP_KEEPINTVL`` appear if run-time Windows
       supports.
 
+   .. versionchanged:: 3.10
+      ``IP_RECVTOS`` was added.
+
 .. data:: AF_CAN
           PF_CAN
           SOL_CAN_*

Doc/whatsnew/3.10.rst

@@ -1219,6 +1219,9 @@ The exception :exc:`socket.timeout` is now an alias of :exc:`TimeoutError`.
 Add option to create MPTCP sockets with ``IPPROTO_MPTCP``
 (Contributed by Rui Cunha in :issue:`43571`.)
 
+Add ``IP_RECVTOS`` option to receive the type of service (ToS) or DSCP/ECN fields
+(Contributed by Georg Sauthoff in :issue:`44077`.)
+
 ssl
 ---
 

Misc/NEWS.d/next/Library/2021-05-13-19-44-38.bpo-44077.04b2a4.rst

@@ -0,0 +1,3 @@
+It's now possible to receive the type of service (ToS), a.k.a. differentiated
+services (DS), a.k.a. differenciated services code point (DSCP) and excplicit
+congestion notification (ECN) IP header fields with ``socket.IP_RECVTOS``.

Modules/socketmodule.c

@@ -8024,6 +8024,9 @@ PyInit__socket(void)
 #ifdef  IP_RECVRETOPTS
     PyModule_AddIntMacro(m, IP_RECVRETOPTS);
 #endif
+#ifdef  IP_RECVTOS
+    PyModule_AddIntMacro(m, IP_RECVTOS);
+#endif
 #ifdef  IP_RECVDSTADDR
     PyModule_AddIntMacro(m, IP_RECVDSTADDR);
 #endif