gh-118986: expose socket.IPV6_RECVERR (#118987)

Author: chrysn

Doc/library/socket.rst

@@ -451,8 +451,8 @@ Constants
       network interface instead of its name.
 
    .. versionchanged:: 3.14
-      Added missing ``IP_RECVERR``, ``IP_RECVTTL``, and ``IP_RECVORIGDSTADDR``
-      on Linux.
+      Added missing ``IP_RECVERR``, ``IPV6_RECVERR``, ``IP_RECVTTL``, and
+      ``IP_RECVORIGDSTADDR`` on Linux.
 
    .. versionchanged:: 3.14
       Added support for ``TCP_QUICKACK`` on Windows platforms when available.

Misc/NEWS.d/next/Library/2024-05-13-10-09-41.gh-issue-118986.-r4W9h.rst

@@ -0,0 +1 @@
+Add :data:`!socket.IPV6_RECVERR` constant (available since Linux 2.2).

Modules/socketmodule.c

@@ -8578,6 +8578,9 @@ socket_exec(PyObject *m)
 #ifdef IPV6_RECVDSTOPTS
     ADD_INT_MACRO(m, IPV6_RECVDSTOPTS);
 #endif
+#ifdef IPV6_RECVERR
+    ADD_INT_MACRO(m, IPV6_RECVERR);
+#endif
 #ifdef IPV6_RECVHOPLIMIT
     ADD_INT_MACRO(m, IPV6_RECVHOPLIMIT);
 #endif