socket: add source_address argument to create_connection

gevent/socket.py

@@ -553,7 +553,7 @@ try:
 except AttributeError:
     _GLOBAL_DEFAULT_TIMEOUT = object()
 
-def create_connection(address, timeout=_GLOBAL_DEFAULT_TIMEOUT):
+def create_connection(address, timeout=_GLOBAL_DEFAULT_TIMEOUT, source_address=None):
     """Connect to *address* and return the socket object.
 
     Convenience function.  Connect to *address* (a 2-tuple ``(host,
@@ -561,7 +561,9 @@ def create_connection(address, timeout=_GLOBAL_DEFAULT_TIMEOUT):
     *timeout* parameter will set the timeout on the socket instance
     before attempting to connect.  If no *timeout* is supplied, the
     global default timeout setting returned by :func:`getdefaulttimeout`
-    is used.
+    is used. If *source_address* is set it must be a tuple of (host, port)
+    for the socket to bind as a source address before making the connection.
+    An host of '' or port 0 tells the OS to use the default.
     """
 
     msg = "getaddrinfo returns an empty list"
@@ -573,6 +575,8 @@ def create_connection(address, timeout=_GLOBAL_DEFAULT_TIMEOUT):
             sock = socket(af, socktype, proto)
             if timeout is not _GLOBAL_DEFAULT_TIMEOUT:
                 sock.settimeout(timeout)
+            if source_address:
+                sock.bind(source_address)
             sock.connect(sa)
             return sock
         except error, msg: