vty: add ctrl section for Control interface bind address

This may seem like overkill for a mere const char * config item, but it makes
the Control interface VTY commands reusable in any main() scope (inspired by
libosmo-abis' VTY config).

Add API functions ctrl_vty_init() and ctrl_vty_get_bind_addr(), in new files
src/ctrl/control_vty.c and include/osmocom/ctrl/control_vty.h, compiled and/or
installed dependent on ENABLE_VTY.

Using these functions allows configuring a static const char* with the VTY
commands

    ctrl
     bind A.B.C.D

which callers shall subsequently use to bind the Control interface to a
specific local interface address, by passing the return value of
ctrl_vty_get_bind_addr() to control_interface_setup().

Add CTRL_NODE to enum node_type, "eating" RESERVED4_NODE to heed that comment
on avoiding ABI changes.

include/Makefile.am

@@ -117,7 +117,8 @@ nobase_include_HEADERS += \
                           osmocom/vty/telnet_interface.h \
                           osmocom/vty/vector.h \
                           osmocom/vty/vty.h \
-                          osmocom/vty/ports.h
+                          osmocom/vty/ports.h \
+                          osmocom/ctrl/control_vty.h
 endif
 
 noinst_HEADERS = \

include/osmocom/ctrl/control_vty.h

@@ -0,0 +1,9 @@
+#pragma once
+
+/* Add the 'ctrl' section to VTY, containing the 'bind' command. */
+int ctrl_vty_init(void *ctx);
+
+/* Obtain the IP address configured by the 'ctrl'/'bind A.B.C.D' VTY command.
+ * This should be fed to ctrl_interface_setup() once the configuration has been
+ * read. */
+const char *ctrl_vty_get_bind_addr(void);

include/osmocom/vty/command.h

@@ -83,6 +83,7 @@ enum node_type {
 	L_IPA_NODE,		/*!< \brief IPA proxying commands in libosmo-abis. */
 	L_NS_NODE,		/*!< \brief NS node in libosmo-gb. */
 	L_BSSGP_NODE,		/*!< \brief BSSGP node in libosmo-gb. */
+	L_CTRL_NODE,		/*!< \brief Control interface node. */
 
 	/*
 	 * When adding new nodes to the libosmocore project, these nodes can be
@@ -91,7 +92,6 @@ enum node_type {
 	RESERVED1_NODE,		/*!< \brief Reserved for later extensions */
 	RESERVED2_NODE,		/*!< \brief Reserved for later extensions */
 	RESERVED3_NODE,		/*!< \brief Reserved for later extensions */
-	RESERVED4_NODE,		/*!< \brief Reserved for later extensions */
 
 	_LAST_OSMOVTY_NODE
 };

src/ctrl/Makefile.am

@@ -13,3 +13,7 @@ libosmoctrl_la_LIBADD = \
 	$(top_builddir)/src/libosmocore.la \
 	$(top_builddir)/src/gsm/libosmogsm.la \
 	$(top_builddir)/src/vty/libosmovty.la
+
+if ENABLE_VTY
+libosmoctrl_la_SOURCES += control_vty.c
+endif

src/ctrl/control_vty.c

@@ -0,0 +1,88 @@
+/* VTY configuration for Control interface
+ *
+ * (C) 2016 by sysmocom s.m.f.c. GmbH <info@sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <stdlib.h>
+#include <talloc.h>
+#include <osmocom/ctrl/control_vty.h>
+#include <osmocom/vty/command.h>
+
+static void *ctrl_vty_ctx = NULL;
+static const char *ctrl_vty_bind_addr = NULL;
+
+DEFUN(cfg_ctrl_bind_addr,
+      cfg_ctrl_bind_addr_cmd,
+      "bind A.B.C.D",
+      "Set bind address to listen for Control connections\n"
+      "Local IP address (default 127.0.0.1)\n")
+{
+	talloc_free((char*)ctrl_vty_bind_addr);
+	ctrl_vty_bind_addr = NULL;
+	ctrl_vty_bind_addr = talloc_strdup(ctrl_vty_ctx, argv[0]);
+	return CMD_SUCCESS;
+}
+
+const char *ctrl_vty_get_bind_addr(void)
+{
+	if (!ctrl_vty_bind_addr)
+		return "127.0.0.1";
+	return ctrl_vty_bind_addr;
+}
+
+static struct cmd_node ctrl_node = {
+	L_CTRL_NODE,
+	"%s(config-ctrl)# ",
+	1,
+};
+
+DEFUN(cfg_ctrl,
+      cfg_ctrl_cmd,
+      "ctrl", "Configure the Control Interface")
+{
+	vty->index = NULL;
+	vty->node = L_CTRL_NODE;
+
+	return CMD_SUCCESS;
+}
+
+static int config_write_ctrl(struct vty *vty)
+{
+	/* So far there's only one element. Omit the entire section if the bind
+	 * element is omitted. */
+	if (!ctrl_vty_bind_addr)
+		return CMD_SUCCESS;
+
+	vty_out(vty, "ctrl%s", VTY_NEWLINE);
+	vty_out(vty, " bind %s%s", ctrl_vty_bind_addr, VTY_NEWLINE);
+
+	return CMD_SUCCESS;
+}
+
+int ctrl_vty_init(void *ctx)
+{
+	ctrl_vty_ctx = ctx;
+	install_element(CONFIG_NODE, &cfg_ctrl_cmd);
+	install_node(&ctrl_node, config_write_ctrl);
+
+	install_element(L_CTRL_NODE, &cfg_ctrl_bind_addr_cmd);
+	return 0;
+}
+