refactor module

use appropriate naming for function, make _getsockname more generic and
doc more useful

NOTICE

@@ -122,3 +122,11 @@ util/unlink.py
 --------------
 
 backport frop python3 Lib/test/support.py
+
+
+gunicorn.socketfromfd
+---------------------
+
+Under Apache License 2
+
+Copyright (C) 2016  Christian Heimes

gunicorn/socketfromfd.py

@@ -1,9 +1,20 @@
-# Copyright (C) 2016  Christian Heimes
-"""socketfromfd -- socket.fromd() with auto-discovery
+# -*- coding: utf-8 -
+#
+# This file is part of gunicorn
+# See the NOTICE for more information.
 
-ATTENTION: Do not remove this backport till the minimum required version is
-           Python 3.7. See https://bugs.python.org/issue28134 for details.
+# Copyright (C) 2016  Christian Heimes under Apache License 2
+
+# source code based on https://github.com/tiran/socketfromfd/blob/master/socketfromfd.py
+# and https://github.com/python/cpython/blob/master/Modules/socketmodule.c
+
+"""socketfromfd -- create a socket from its file descriptor
+This module detect the socket properties.
+
+note: Before python 3.7 auto detecting the socket was not working.
+See  https://bugs.python.org/issue28134 for details.
 """
+
 from __future__ import print_function
 
 import ctypes
@@ -43,7 +54,7 @@ def _errcheck_errno(result, func, arguments):
 
 if platform.system() == 'SunOS':
     _libc_getsockopt = libc._so_getsockopt
-    _libc_getsockname = libc._so_getsockname
+    _lib_getsockname = libc._so_getsockname
 else:
     _libc_getsockopt = libc.getsockopt
     _libc_getsockname = libc.getsockname
@@ -65,13 +76,17 @@ class SockAddr(ctypes.Structure):
         ('sa_family', ctypes.c_uint8),
         ('sa_data', ctypes.c_char * 14)
     ]
+
+
 _libc_getsockname.argtypes = [
     ctypes.c_int,
     ctypes.POINTER(SockAddr),
     ctypes.POINTER(ctypes.c_int)
 ]
+_libc_getsockname.restype = ctypes.c_int  # 0: ok, -1: err
+_libc_getsockname.errcheck = _errcheck_errno
 
-def _raw_getsockopt(fd, level, optname):
+def _getsockopt(fd, level, optname):
     """Make raw getsockopt() call for int32 optval
 
     :param fd: socket fd
@@ -85,11 +100,11 @@ def _raw_getsockopt(fd, level, optname):
                      ctypes.byref(optval), ctypes.byref(optlen))
     return optval.value
 
-def _raw_getsockname(fd):
+def _getsockname(fd):
     sockaddr = SockAddr()
     sockaddrlen = ctypes.c_int(ctypes.sizeof(sockaddr))
     _libc_getsockname(fd, sockaddr, sockaddrlen)
-    return sockaddr.sa_family
+    return sockaddr
 
 def fromfd(fd, keep_fd=True):
     """Create a socket from a file descriptor
@@ -108,13 +123,15 @@ def fromfd(fd, keep_fd=True):
     :return: socket.socket instance
     :raises OSError: for invalid socket fd
     """
-    family = _raw_getsockname(fd)
+    sockaddr = _getsockname(fd)
+    family = sockaddr.sa_family
     if hasattr(socket, 'SO_TYPE'):
-        typ = _raw_getsockopt(fd, socket.SOL_SOCKET, getattr(socket, 'SO_TYPE'))
+        typ = _getsockopt(fd, socket.SOL_SOCKET, getattr(socket, 'SO_TYPE'))
     else:
         typ = socket.SOCK_STREAM
+
     if hasattr(socket, 'SO_PROTOCOL'):
-        proto = _raw_getsockopt(fd, socket.SOL_SOCKET, getattr(socket, 'SO_PROTOCOL'))
+        proto = _getsockopt(fd, socket.SOL_SOCKET, getattr(socket, 'SO_PROTOCOL'))
     else:
         proto = 0
     if keep_fd: