vty: Make TCP port configurable and introduce telnet_init_default

Extend the vty_bind_cmd VTY command to allow to optionally specify
a port in addition to the IPv4 address.

Introduce telnet_init_default to relieve client code from having
to query the bind IPv4 address (and now the TCP port). Instead a
client only needs to pass the default TCP port to use.

Client code should use it like:

	int rc = telnet_init_default(ctx, priv, OSMO_VTY_PORT_SGSN);

Change-Id: Id5fb2faaf4311bd7284ee870526a6f87b7e260f3

include/osmocom/vty/telnet_interface.h

@@ -47,6 +47,7 @@ struct telnet_connection {
 
 int telnet_init(void *tall_ctx, void *priv, int port);
 int telnet_init_dynif(void *tall_ctx, void *priv, const char *ip, int port);
+int telnet_init_default(void *tall_ctx, void *priv, int default_port);
 
 void telnet_exit(void);
 

include/osmocom/vty/vty.h

@@ -210,6 +210,8 @@ int vty_go_parent(struct vty *vty);
 
 /* Return IP address passed to the 'line vty'/'bind' command, or "127.0.0.1" */
 const char *vty_get_bind_addr(void);
+/** Returns configured port passed to the 'line vty'/'bind' command or default_port. */
+int vty_get_bind_port(int default_port);
 
 extern void *tall_vty_ctx;
 

src/vty/telnet_interface.c

@@ -105,6 +105,18 @@ int telnet_init_dynif(void *tall_ctx, void *priv, const char *ip, int port)
 	return 0;
 }
 
+/*! Initializes telnet based VTY interface using the configured bind addr/port.
+ *  \param[in] tall_ctx \ref talloc context
+ *  \param[in] priv private data to be passed to callback
+ *  \param[in] default_port TCP port number to bind to if not explicitely configured
+ */
+int telnet_init_default(void *tall_ctx, void *priv, int default_port)
+{
+	return telnet_init_dynif(tall_ctx, priv, vty_get_bind_addr(),
+				 vty_get_bind_port(default_port));
+}
+
+
 extern struct host host;
 
 /*! close a telnet connection */

src/vty/vty.c

@@ -90,6 +90,8 @@ char *vty_cwd = NULL;
  * use NULL and VTY_BIND_ADDR_DEFAULT instead. */
 static const char *vty_bind_addr = NULL;
 #define VTY_BIND_ADDR_DEFAULT "127.0.0.1"
+/* Port the VTY should bind to. -1 means not configured */
+static int vty_bind_port = -1;
 
 /* Configure lock. */
 static int vty_config;
@@ -1612,12 +1614,13 @@ DEFUN(no_vty_login,
 }
 
 /* vty bind */
-DEFUN(vty_bind, vty_bind_cmd, "bind A.B.C.D",
+DEFUN(vty_bind, vty_bind_cmd, "bind A.B.C.D [<0-65535>]",
       "Accept VTY telnet connections on local interface\n"
       "Local interface IP address (default: " VTY_BIND_ADDR_DEFAULT ")\n")
 {
 	talloc_free((void*)vty_bind_addr);
 	vty_bind_addr = talloc_strdup(tall_vty_ctx, argv[0]);
+	vty_bind_port = argc > 1 ? atoi(argv[1]) : -1;
 	return CMD_SUCCESS;
 }
 
@@ -1628,6 +1631,13 @@ const char *vty_get_bind_addr(void)
 	return vty_bind_addr;
 }
 
+int vty_get_bind_port(int default_port)
+{
+	if (vty_bind_port >= 0)
+		return vty_bind_port;
+	return default_port;
+}
+
 DEFUN(service_advanced_vty,
       service_advanced_vty_cmd,
       "service advanced-vty",
@@ -1700,8 +1710,14 @@ static int vty_config_write(struct vty *vty)
 		vty_out(vty, " login%s", VTY_NEWLINE);
 
 	/* bind */
-	if (vty_bind_addr && (strcmp(vty_bind_addr, VTY_BIND_ADDR_DEFAULT) != 0))
-		vty_out(vty, " bind %s%s", vty_bind_addr, VTY_NEWLINE);
+	if (vty_bind_addr && (strcmp(vty_bind_addr, VTY_BIND_ADDR_DEFAULT) != 0 || vty_bind_port >= 0)) {
+		if (vty_bind_port >= 0) {
+			vty_out(vty, " bind %s %d%s", vty_bind_addr,
+				vty_bind_port, VTY_NEWLINE);
+		} else {
+			vty_out(vty, " bind %s%s", vty_bind_addr, VTY_NEWLINE);
+		}
+	}
 
 	vty_out(vty, "!%s", VTY_NEWLINE);