gh-124761: add socket.SO_REUSEPORT_LB (#124961)

Author: graingert

Doc/library/socket.rst

@@ -674,6 +674,14 @@ Constants
 
   .. availability:: Linux >= 3.9
 
+.. data:: SO_REUSEPORT_LB
+
+   Constant to enable duplicate address and port bindings with load balancing.
+
+  .. versionadded:: next
+
+  .. availability:: FreeBSD >= 12.0
+
 .. data:: AF_HYPERV
           HV_PROTOCOL_RAW
           HVSOCKET_CONNECT_TIMEOUT

Misc/NEWS.d/next/Library/2024-10-04-09-56-45.gh-issue-124761.N4pSD6.rst

@@ -0,0 +1 @@
+Add :data:`~socket.SO_REUSEPORT_LB` constant to :mod:`socket` for FreeBSD.

Modules/socketmodule.c

@@ -7916,6 +7916,9 @@ socket_exec(PyObject *m)
     ADD_INT_MACRO(m, SO_REUSEPORT);
 #endif
 #endif
+#ifdef  SO_REUSEPORT_LB
+    ADD_INT_MACRO(m, SO_REUSEPORT_LB);
+#endif
 #ifdef  SO_SNDBUF
     ADD_INT_MACRO(m, SO_SNDBUF);
 #endif