ggsn: Add ability to specify local IP addresses for GTP-C and GTP-U

In case the GGSN is behind some kind of DNAT, the public GTP-C and
GTP-U IP addresses as exposed inside the GTP payload information
elements are different from the (internal, behind-nat) IP address
to which it listens/binds.

Change-Id: I548c9011c9abd66d46f963b1def61575f3dabb89

ggsn/ggsn.c

@@ -693,6 +693,14 @@ int ggsn_start(struct ggsn_ctx *ggsn)
 	}
 	ggsn->gsn->priv = ggsn;
 
+	/* patch in different addresses to use (in case we're behind NAT, the listen
+	 * address is different from what we advertise externally) */
+	if (ggsn->cfg.gtpc_addr.v4.s_addr)
+		ggsn->gsn->gsnc = ggsn->cfg.gtpc_addr.v4;
+
+	if (ggsn->cfg.gtpu_addr.v4.s_addr)
+		ggsn->gsn->gsnu = ggsn->cfg.gtpu_addr.v4;
+
 	/* Register File Descriptors */
 	osmo_fd_setup(&ggsn->gtp_fd0, ggsn->gsn->fd0, BSC_FD_READ, ggsn_gtp_fd_cb, ggsn, 0);
 	rc = osmo_fd_register(&ggsn->gtp_fd0);

ggsn/ggsn.h

@@ -99,6 +99,10 @@ struct ggsn_ctx {
 		struct apn_ctx *default_apn;
 		/* ADdress to which we listen for GTP */
 		struct in46_addr listen_addr;
+		/* Local GTP-C address advertised in GTP */
+		struct in46_addr gtpc_addr;
+		/* Local GTP-U address advertised in GTP */
+		struct in46_addr gtpu_addr;
 		/* directory for state file */
 		char *state_dir;
 		/* administratively shut-down (true) or not (false) */

ggsn/ggsn_vty.c

@@ -165,8 +165,8 @@ DEFUN(cfg_no_ggsn, cfg_no_ggsn_cmd,
 	return CMD_SUCCESS;
 }
 
-DEFUN(cfg_ggsn_local_ip, cfg_ggsn_local_ip_cmd,
-	"gtp local-ip A.B.C.D",
+DEFUN(cfg_ggsn_bind_ip, cfg_ggsn_bind_ip_cmd,
+	"gtp bind-ip A.B.C.D",
 	"GTP Parameters\n"
 	"Set the IP address for the local GTP bind\n"
 	"IPv4 Address\n")
@@ -179,6 +179,34 @@ DEFUN(cfg_ggsn_local_ip, cfg_ggsn_local_ip_cmd,
 	return CMD_SUCCESS;
 }
 
+DEFUN(cfg_ggsn_gtpc_ip, cfg_ggsn_gtpc_ip_cmd,
+	"gtp control-ip A.B.C.D",
+	"GTP Parameters\n"
+	"Set the IP address states as local IP in GTP-C messages\n"
+	"IPv4 Address\n")
+{
+	struct ggsn_ctx *ggsn = (struct ggsn_ctx *) vty->index;
+	size_t t;
+
+	ippool_aton(&ggsn->cfg.gtpc_addr, &t, argv[0], 0);
+
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_ggsn_gtpu_ip, cfg_ggsn_gtpu_ip_cmd,
+	"gtp user-ip A.B.C.D",
+	"GTP Parameters\n"
+	"Set the IP address states as local IP in GTP-U messages\n"
+	"IPv4 Address\n")
+{
+	struct ggsn_ctx *ggsn = (struct ggsn_ctx *) vty->index;
+	size_t t;
+
+	ippool_aton(&ggsn->cfg.gtpu_addr, &t, argv[0], 0);
+
+	return CMD_SUCCESS;
+}
+
 DEFUN(cfg_ggsn_state_dir, cfg_ggsn_state_dir_cmd,
 	"gtp state-dir PATH",
 	"GTP Parameters\n"
@@ -633,7 +661,11 @@ static int config_write_ggsn(struct vty *vty)
 		if (ggsn->cfg.description)
 			vty_out(vty, " description %s%s", ggsn->cfg.description, VTY_NEWLINE);
 		vty_out(vty, " gtp state-dir %s%s", ggsn->cfg.state_dir, VTY_NEWLINE);
-		vty_out(vty, " gtp local-ip %s%s", in46a_ntoa(&ggsn->cfg.listen_addr), VTY_NEWLINE);
+		vty_out(vty, " gtp bind-ip %s%s", in46a_ntoa(&ggsn->cfg.listen_addr), VTY_NEWLINE);
+		if (ggsn->cfg.gtpc_addr.v4.s_addr)
+			vty_out(vty, " gtp control-ip %s%s", in46a_ntoa(&ggsn->cfg.gtpc_addr), VTY_NEWLINE);
+		if (ggsn->cfg.gtpu_addr.v4.s_addr)
+			vty_out(vty, " gtp user-ip %s%s", in46a_ntoa(&ggsn->cfg.gtpu_addr), VTY_NEWLINE);
 		llist_for_each_entry(apn, &ggsn->apn_list, list)
 			config_write_apn(vty, apn);
 		if (ggsn->cfg.default_apn)
@@ -806,7 +838,9 @@ int ggsn_vty_init(void)
 	install_element(GGSN_NODE, &cfg_no_description_cmd);
 	install_element(GGSN_NODE, &cfg_ggsn_shutdown_cmd);
 	install_element(GGSN_NODE, &cfg_ggsn_no_shutdown_cmd);
-	install_element(GGSN_NODE, &cfg_ggsn_local_ip_cmd);
+	install_element(GGSN_NODE, &cfg_ggsn_bind_ip_cmd);
+	install_element(GGSN_NODE, &cfg_ggsn_gtpc_ip_cmd);
+	install_element(GGSN_NODE, &cfg_ggsn_gtpu_ip_cmd);
 	install_element(GGSN_NODE, &cfg_ggsn_state_dir_cmd);
 	install_element(GGSN_NODE, &cfg_ggsn_apn_cmd);
 	install_element(GGSN_NODE, &cfg_ggsn_no_apn_cmd);