Added gethostbyname_ex(), which returns the same kind of data as

gethostbyaddr().  (Plain gethostbyname() returns only the IP address.)
This moves the code shared by gethostbyaddr() and gethostbyname_ex()
to a subroutine.

Original patch by Dan Stromberg; some tweaks by GvR.

Modules/socketmodule.c

@@ -1314,49 +1314,18 @@ static char gethostbyname_doc[] =
 Return the IP address (a string of the form '255.255.255.255') for a host.";
 
 
-/* Python interface to gethostbyaddr(IP). */
+/* Convenience function common to gethostbyname_ex and gethostbyaddr */
 
-/*ARGSUSED*/
 static PyObject *
-BUILD_FUNC_DEF_2(PySocket_gethostbyaddr,PyObject *,self, PyObject *, args)
-{
-        struct sockaddr_in addr;
-	char *ip_num;
+gethost_common(h, addr)
 	struct hostent *h;
+	struct sockaddr_in *addr;
+{
 	char **pch;
 	PyObject *rtn_tuple = (PyObject *)NULL;
 	PyObject *name_list = (PyObject *)NULL;
 	PyObject *addr_list = (PyObject *)NULL;
 	PyObject *tmp;
-#ifdef HAVE_GETHOSTBYNAME_R
-	struct hostent hp_allocated;
-	char buf[16384];
-	int buf_len = (sizeof buf) - 1;
-	int errnop;
-#endif /* HAVE_GETHOSTBYNAME_R */
-
-	if (!PyArg_Parse(args, "s", &ip_num))
-		return NULL;
-	if (setipaddr(ip_num, &addr) < 0)
-		return NULL;
-	Py_BEGIN_ALLOW_THREADS
-#ifdef HAVE_GETHOSTBYNAME_R
-	h = gethostbyaddr_r((char *)&addr.sin_addr,
-			    sizeof(addr.sin_addr),
-			    AF_INET, 
-			    &hp_allocated, buf, buf_len, &errnop);
-#else /* not HAVE_GETHOSTBYNAME_R */
-#if defined(WITH_THREAD) && !defined(MS_WINDOWS)
-	acquire_lock(gethostbyname_lock,1);
-#endif
-	h = gethostbyaddr((char *)&addr.sin_addr,
-			  sizeof(addr.sin_addr),
-			  AF_INET);
-#if defined(WITH_THREAD) && !defined(MS_WINDOWS)
-	release_lock(gethostbyname_lock);
-#endif
-#endif /* HAVE_GETHOSTBYNAME_R */
-	Py_END_ALLOW_THREADS
 	if (h == NULL) {
 #ifdef HAVE_HSTRERROR
 	        /* Let's get real error message to return */
@@ -1383,8 +1352,8 @@ BUILD_FUNC_DEF_2(PySocket_gethostbyaddr,PyObject *,self, PyObject *, args)
 	}
 	for (pch = h->h_addr_list; *pch != NULL; pch++) {
 		int status;
-		memcpy((char *) &addr.sin_addr, *pch, h->h_length);
-		tmp = makeipaddr(&addr);
+		memcpy((char *) &addr->sin_addr, *pch, h->h_length);
+		tmp = makeipaddr(addr);
 		if (tmp == NULL)
 			goto err;
 		status = PyList_Append(addr_list, tmp);
@@ -1399,6 +1368,98 @@ BUILD_FUNC_DEF_2(PySocket_gethostbyaddr,PyObject *,self, PyObject *, args)
 	return rtn_tuple;
 }
 
+
+/* Python interface to gethostbyname_ex(name). */
+
+/*ARGSUSED*/
+static PyObject *
+BUILD_FUNC_DEF_2(PySocket_gethostbyname_ex,PyObject *,self, PyObject *,args)
+{
+	char *name;
+	struct hostent *h;
+	struct sockaddr_in addr;
+	PyObject *addr_list = (PyObject *)NULL;
+	char **pch;
+	PyObject *tmp;
+#ifdef HAVE_GETHOSTBYNAME_R
+	struct hostent hp_allocated;
+	char buf[16384];
+	int buf_len = (sizeof buf) - 1;
+	int errnop;
+#endif /* HAVE_GETHOSTBYNAME_R */
+	if (!PyArg_Parse(args, "s", &name))
+		return NULL;
+	if (setipaddr(name, &addr) < 0)
+		return NULL;
+	Py_BEGIN_ALLOW_THREADS
+#ifdef HAVE_GETHOSTBYNAME_R
+	h = gethostbyname_r(name, &hp_allocated, buf, buf_len, &errnop);
+#else /* not HAVE_GETHOSTBYNAME_R */
+#if defined(WITH_THREAD) && !defined(MS_WINDOWS)
+	acquire_lock(gethostbyname_lock,1);
+#endif
+	h = gethostbyname(name);
+#if defined(WITH_THREAD) && !defined(MS_WINDOWS)
+	release_lock(gethostbyname_lock);
+#endif
+#endif /* HAVE_GETHOSTBYNAME_R */
+	Py_END_ALLOW_THREADS
+	return gethost_common(h,&addr);
+}
+
+static char ghbn_ex_doc[] =
+"gethostbyname_ex(host) -> (name, aliaslist, addresslist)\n\
+\n\
+Return the true host name, a list of aliases, and a list of IP addresses,\n\
+for a host.  The host argument is a string giving a host name or IP number.";
+
+
+/* Python interface to gethostbyaddr(IP). */
+
+/*ARGSUSED*/
+static PyObject *
+BUILD_FUNC_DEF_2(PySocket_gethostbyaddr,PyObject *,self, PyObject *, args)
+{
+        struct sockaddr_in addr;
+	char *ip_num;
+	struct hostent *h;
+	char **pch;
+	PyObject *rtn_tuple = (PyObject *)NULL;
+	PyObject *name_list = (PyObject *)NULL;
+	PyObject *addr_list = (PyObject *)NULL;
+	PyObject *tmp;
+#ifdef HAVE_GETHOSTBYNAME_R
+	struct hostent hp_allocated;
+	char buf[16384];
+	int buf_len = (sizeof buf) - 1;
+	int errnop;
+#endif /* HAVE_GETHOSTBYNAME_R */
+
+	if (!PyArg_Parse(args, "s", &ip_num))
+		return NULL;
+	if (setipaddr(ip_num, &addr) < 0)
+		return NULL;
+	Py_BEGIN_ALLOW_THREADS
+#ifdef HAVE_GETHOSTBYNAME_R
+	h = gethostbyaddr_r((char *)&addr.sin_addr,
+			    sizeof(addr.sin_addr),
+			    AF_INET, 
+			    &hp_allocated, buf, buf_len, &errnop);
+#else /* not HAVE_GETHOSTBYNAME_R */
+#if defined(WITH_THREAD) && !defined(MS_WINDOWS)
+	acquire_lock(gethostbyname_lock,1);
+#endif
+	h = gethostbyaddr((char *)&addr.sin_addr,
+			  sizeof(addr.sin_addr),
+			  AF_INET);
+#if defined(WITH_THREAD) && !defined(MS_WINDOWS)
+	release_lock(gethostbyname_lock);
+#endif
+#endif /* HAVE_GETHOSTBYNAME_R */
+	Py_END_ALLOW_THREADS
+	return gethost_common(h,&addr);
+}
+
 static char gethostbyaddr_doc[] =
 "gethostbyaddr(host) -> (name, aliaslist, addresslist)\n\
 \n\
@@ -1623,6 +1684,7 @@ Convert a 32-bit integer from host to network byte order.";
 
 static PyMethodDef PySocket_methods[] = {
 	{"gethostbyname",	PySocket_gethostbyname, 0, gethostbyname_doc},
+	{"gethostbyname_ex",	PySocket_gethostbyname_ex, 0, ghbn_ex_doc},
 	{"gethostbyaddr",	PySocket_gethostbyaddr, 0, gethostbyaddr_doc},
 	{"gethostname",		PySocket_gethostname, 0, gethostname_doc},
 	{"getservbyname",	PySocket_getservbyname, 0, getservbyname_doc},