gh-156439: Gate socket.if_{nametoindex, indextoname} on respective OS capability (#156708)

Co-authored-by: Stan Ulbrych <stan@python.org>
Co-authored-by: Malcolm Smith <smith@chaquo.com>

Author: 3 people

Misc/NEWS.d/next/Library/2026-08-31-09-01-22.gh-issue-156439.j9WHCc.rst

@@ -0,0 +1,3 @@
+:func:`socket.if_nametoindex` and :func:`socket.if_indextoname` are now
+available on platforms that provide them but not
+``if_nameindex``, such as Android before API level 24.

Modules/clinic/socketmodule.c.h

@@ -631,14 +631,14 @@ _PyLong_##NAME##_Converter(PyObject *obj, void *ptr)                \
     return 1;                                                       \
 }
 
-#if defined(HAVE_IF_NAMEINDEX) || defined(MS_WINDOWS)
+#if defined(HAVE_IF_INDEXTONAME) || defined(MS_WINDOWS)
 # ifdef MS_WINDOWS
     UNSIGNED_INT_CONVERTER(NetIfindex, NET_IFINDEX)
 # else
 #   define _PyLong_NetIfindex_Converter _PyLong_UnsignedInt_Converter
 #   define NET_IFINDEX unsigned int
 # endif
-#endif // defined(HAVE_IF_NAMEINDEX) || defined(MS_WINDOWS)
+#endif // defined(HAVE_IF_INDEXTONAME) || defined(MS_WINDOWS)
 
 /*[python input]
 class NET_IFINDEX_converter(CConverter):
@@ -7403,6 +7403,9 @@ _socket_if_nameindex_impl(PyObject *module)
 #endif
 }
 
+#endif // defined(HAVE_IF_NAMEINDEX) || defined(MS_WINDOWS)
+
+#if defined(HAVE_IF_NAMETOINDEX) || defined(MS_WINDOWS)
 
 /*[clinic input]
 _socket.if_nametoindex
@@ -7432,6 +7435,9 @@ _socket_if_nametoindex_impl(PyObject *module, PyObject *oname)
     return PyLong_FromUnsignedLong(index);
 }
 
+#endif // defined(HAVE_IF_NAMETOINDEX) || defined(MS_WINDOWS)
+
+#if defined(HAVE_IF_INDEXTONAME) || defined(MS_WINDOWS)
 
 /*[clinic input]
 @permit_long_summary
@@ -7456,7 +7462,7 @@ _socket_if_indextoname_impl(PyObject *module, NET_IFINDEX index)
     return PyUnicode_DecodeFSDefault(name);
 }
 
-#endif // defined(HAVE_IF_NAMEINDEX) || defined(MS_WINDOWS)
+#endif // defined(HAVE_IF_INDEXTONAME) || defined(MS_WINDOWS)
 
 
 #ifdef CMSG_LEN

Modules/socketmodule.c

@@ -5528,7 +5528,8 @@ AC_CHECK_FUNCS([ \
   getgrnam_r getgrouplist gethostname getitimer getloadavg getlogin getlogin_r \
   getpeername getpgid getpid getppid getpriority _getpty \
   getpwent getpwnam_r getpwuid getpwuid_r getresgid getresuid getrusage getsid getspent \
-  getspnam gettid getuid getwd grantpt if_nameindex initgroups kill killpg lchown linkat \
+  getspnam gettid getuid getwd grantpt if_indextoname if_nameindex \
+  if_nametoindex initgroups kill killpg lchown linkat \
   lockf lstat lutimes madvise mbrtowc memrchr mkdirat mkfifo mkfifoat \
   mknod mknodat mktime mmap mremap nice openat opendir pathconf pause \
   pidfd_open pidfd_getfd pidfd_send_signal pipe \

configure

@@ -751,9 +751,15 @@
 /* Define to 1 if you have the <iconv.h> header file. */
 #undef HAVE_ICONV_H
 
+/* Define to 1 if you have the 'if_indextoname' function. */
+#undef HAVE_IF_INDEXTONAME
+
 /* Define to 1 if you have the 'if_nameindex' function. */
 #undef HAVE_IF_NAMEINDEX
 
+/* Define to 1 if you have the 'if_nametoindex' function. */
+#undef HAVE_IF_NAMETOINDEX
+
 /* Define if you have the 'inet_aton' function. */
 #undef HAVE_INET_ATON