Add GTP hub initial code base.

First steps towards a new GTP hub. The aim is to mux GTP connections, so that
multiple SGSN <--> GGSN links can pass through a single point. Background:
allow having more than one SGSN, possibly in various remote locations.

The recent addition of OAP to GSUP is related to the same background idea.

(This is a collapsed patch of various changes that do not make sense to review
in chronological order anymore, since a lot of it has thorougly transmorphed
after it was first committed.)

Sponsored-by: On-Waves ehf
diff --git a/openbsc/src/gprs/gtphub_vty.c b/openbsc/src/gprs/gtphub_vty.c
new file mode 100644
index 0000000..aead178
--- /dev/null
+++ b/openbsc/src/gprs/gtphub_vty.c
@@ -0,0 +1,258 @@
+/* (C) 2015 by sysmocom s.f.m.c. GmbH
+ * All Rights Reserved
+ *
+ * Author: Neels Hofmeyr
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <string.h>
+
+#include <osmocom/core/talloc.h>
+#include <osmocom/vty/command.h>
+
+#include <openbsc/vty.h>
+#include <openbsc/gtphub.h>
+
+static struct gtphub_cfg *g_cfg = 0;
+
+static struct cmd_node gtphub_node = {
+	GTPHUB_NODE,
+	"%s(config-gtphub)# ",
+	1,
+};
+
+#define GTPH_DEFAULT_CONTROL_PORT 2123
+#define GTPH_DEFAULT_USER_PORT 2152
+
+static void write_addrs(struct vty *vty, const char *name,
+			struct gtphub_cfg_addr *c, struct gtphub_cfg_addr *u)
+{
+	if ((c->port == GTPH_DEFAULT_CONTROL_PORT)
+	    && (u->port == GTPH_DEFAULT_USER_PORT)
+	    && (strcmp(c->addr_str, u->addr_str) == 0)) {
+		/* Default port numbers and same IP address: write "short"
+		 * variant. */
+		vty_out(vty, " %s %s%s",
+			name,
+			c->addr_str,
+			VTY_NEWLINE);
+		return;
+	}
+
+	vty_out(vty, " %s ctrl %s %d user %s %d%s",
+		name,
+		c->addr_str, (int)c->port,
+		u->addr_str, (int)u->port,
+		VTY_NEWLINE);
+}
+
+static int config_write_gtphub(struct vty *vty)
+{
+	vty_out(vty, "gtphub%s", VTY_NEWLINE);
+
+	write_addrs(vty, "bind-to-sgsns",
+		    &g_cfg->to_sgsns[GTPH_PLANE_CTRL].bind,
+		    &g_cfg->to_sgsns[GTPH_PLANE_USER].bind);
+
+	write_addrs(vty, "bind-to-ggsns",
+		    &g_cfg->to_ggsns[GTPH_PLANE_CTRL].bind,
+		    &g_cfg->to_ggsns[GTPH_PLANE_USER].bind);
+
+	if (g_cfg->ggsn_proxy[GTPH_PLANE_CTRL].addr_str) {
+		write_addrs(vty, "ggsn-proxy",
+			    &g_cfg->ggsn_proxy[GTPH_PLANE_CTRL],
+			    &g_cfg->ggsn_proxy[GTPH_PLANE_USER]);
+	}
+
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_gtphub, cfg_gtphub_cmd,
+      "gtphub",
+      "Configure the GTP hub")
+{
+	vty->node = GTPHUB_NODE;
+	return CMD_SUCCESS;
+}
+
+#define BIND_ARGS  "ctrl ADDR <0-65535> user ADDR <0-65535>"
+#define BIND_DOCS  \
+	"Set GTP-C bind\n" \
+	"GTP-C local IP address (v4 or v6)\n" \
+	"GTP-C local port\n" \
+	"Set GTP-U bind\n" \
+	"GTP-U local IP address (v4 or v6)\n" \
+	"GTP-U local port\n"
+
+
+DEFUN(cfg_gtphub_bind_to_sgsns_short, cfg_gtphub_bind_to_sgsns_short_cmd,
+	"bind-to-sgsns ADDR",
+	"GTP Hub Parameters\n"
+	"Set the local bind address to listen for SGSNs, for both GTP-C and GTP-U\n"
+	"Local IP address (v4 or v6)\n"
+	)
+{
+	int i;
+	for (i = 0; i < GTPH_PLANE_N; i++)
+		g_cfg->to_sgsns[i].bind.addr_str = talloc_strdup(tall_vty_ctx, argv[0]);
+	g_cfg->to_sgsns[GTPH_PLANE_CTRL].bind.port = GTPH_DEFAULT_CONTROL_PORT;
+	g_cfg->to_sgsns[GTPH_PLANE_USER].bind.port = GTPH_DEFAULT_USER_PORT;
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_gtphub_bind_to_ggsns_short, cfg_gtphub_bind_to_ggsns_short_cmd,
+	"bind-to-ggsns ADDR",
+	"GTP Hub Parameters\n"
+	"Set the local bind address to listen for GGSNs, for both GTP-C and GTP-U\n"
+	"Local IP address (v4 or v6)\n"
+	)
+{
+	int i;
+	for (i = 0; i < GTPH_PLANE_N; i++)
+		g_cfg->to_ggsns[i].bind.addr_str = talloc_strdup(tall_vty_ctx, argv[0]);
+	g_cfg->to_ggsns[GTPH_PLANE_CTRL].bind.port = GTPH_DEFAULT_CONTROL_PORT;
+	g_cfg->to_ggsns[GTPH_PLANE_USER].bind.port = GTPH_DEFAULT_USER_PORT;
+	return CMD_SUCCESS;
+}
+
+
+static int handle_binds(struct gtphub_cfg_bind *b, const char **argv)
+{
+	b[GTPH_PLANE_CTRL].bind.addr_str = talloc_strdup(tall_vty_ctx, argv[0]);
+	b[GTPH_PLANE_CTRL].bind.port = atoi(argv[1]);
+	b[GTPH_PLANE_USER].bind.addr_str = talloc_strdup(tall_vty_ctx, argv[2]);
+	b[GTPH_PLANE_USER].bind.port = atoi(argv[3]);
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_gtphub_bind_to_sgsns, cfg_gtphub_bind_to_sgsns_cmd,
+	"bind-to-sgsns " BIND_ARGS,
+	"GTP Hub Parameters\n"
+	"Set the local bind addresses and ports to listen for SGSNs\n"
+	BIND_DOCS
+	)
+{
+	return handle_binds(g_cfg->to_sgsns, argv);
+}
+
+DEFUN(cfg_gtphub_bind_to_ggsns, cfg_gtphub_bind_to_ggsns_cmd,
+	"bind-to-ggsns " BIND_ARGS,
+	"GTP Hub Parameters\n"
+	"Set the local bind addresses and ports to listen for GGSNs\n"
+	BIND_DOCS
+	)
+{
+	return handle_binds(g_cfg->to_ggsns, argv);
+}
+
+DEFUN(cfg_gtphub_ggsn_proxy_short, cfg_gtphub_ggsn_proxy_short_cmd,
+	"ggsn-proxy ADDR",
+	"GTP Hub Parameters\n"
+	"Redirect all GGSN bound traffic to default ports on this address (another gtphub)\n"
+	"Remote IP address (v4 or v6)\n"
+	)
+{
+	g_cfg->ggsn_proxy[GTPH_PLANE_CTRL].addr_str = talloc_strdup(tall_vty_ctx, argv[0]);
+	g_cfg->ggsn_proxy[GTPH_PLANE_CTRL].port = GTPH_DEFAULT_CONTROL_PORT;
+	g_cfg->ggsn_proxy[GTPH_PLANE_USER].addr_str = talloc_strdup(tall_vty_ctx, argv[0]);
+	g_cfg->ggsn_proxy[GTPH_PLANE_USER].port = GTPH_DEFAULT_USER_PORT;
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_gtphub_ggsn_proxy, cfg_gtphub_ggsn_proxy_cmd,
+	"ggsn-proxy " BIND_ARGS,
+	"GTP Hub Parameters\n"
+	"Redirect all GGSN bound traffic to these addresses and ports (another gtphub)\n"
+	BIND_DOCS
+	)
+{
+	g_cfg->ggsn_proxy[GTPH_PLANE_CTRL].addr_str = talloc_strdup(tall_vty_ctx, argv[0]);
+	g_cfg->ggsn_proxy[GTPH_PLANE_CTRL].port = atoi(argv[1]);
+	g_cfg->ggsn_proxy[GTPH_PLANE_USER].addr_str = talloc_strdup(tall_vty_ctx, argv[2]);
+	g_cfg->ggsn_proxy[GTPH_PLANE_USER].port = atoi(argv[3]);
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_gtphub_sgsn_proxy_short, cfg_gtphub_sgsn_proxy_short_cmd,
+	"sgsn-proxy ADDR",
+	"GTP Hub Parameters\n"
+	"Redirect all SGSN bound traffic to default ports on this address (another gtphub)\n"
+	"Remote IP address (v4 or v6)\n"
+	)
+{
+	g_cfg->sgsn_proxy[GTPH_PLANE_CTRL].addr_str = talloc_strdup(tall_vty_ctx, argv[0]);
+	g_cfg->sgsn_proxy[GTPH_PLANE_CTRL].port = GTPH_DEFAULT_CONTROL_PORT;
+	g_cfg->sgsn_proxy[GTPH_PLANE_USER].addr_str = talloc_strdup(tall_vty_ctx, argv[0]);
+	g_cfg->sgsn_proxy[GTPH_PLANE_USER].port = GTPH_DEFAULT_USER_PORT;
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_gtphub_sgsn_proxy, cfg_gtphub_sgsn_proxy_cmd,
+	"sgsn-proxy " BIND_ARGS,
+	"GTP Hub Parameters\n"
+	"Redirect all SGSN bound traffic to these addresses and ports (another gtphub)\n"
+	BIND_DOCS
+	)
+{
+	g_cfg->sgsn_proxy[GTPH_PLANE_CTRL].addr_str = talloc_strdup(tall_vty_ctx, argv[0]);
+	g_cfg->sgsn_proxy[GTPH_PLANE_CTRL].port = atoi(argv[1]);
+	g_cfg->sgsn_proxy[GTPH_PLANE_USER].addr_str = talloc_strdup(tall_vty_ctx, argv[2]);
+	g_cfg->sgsn_proxy[GTPH_PLANE_USER].port = atoi(argv[3]);
+	return CMD_SUCCESS;
+}
+
+DEFUN(show_gtphub, show_gtphub_cmd, "show gtphub",
+      SHOW_STR "Display information about the GTP hub")
+{
+	vty_out(vty, "gtphub has nothing to say yet%s", VTY_NEWLINE);
+	return CMD_SUCCESS;
+}
+
+
+int gtphub_vty_init(void)
+{
+	install_element_ve(&show_gtphub_cmd);
+
+	install_element(CONFIG_NODE, &cfg_gtphub_cmd);
+	install_node(&gtphub_node, config_write_gtphub);
+	vty_install_default(GTPHUB_NODE);
+
+	install_element(GTPHUB_NODE, &cfg_gtphub_bind_to_sgsns_short_cmd);
+	install_element(GTPHUB_NODE, &cfg_gtphub_bind_to_sgsns_cmd);
+	install_element(GTPHUB_NODE, &cfg_gtphub_bind_to_ggsns_short_cmd);
+	install_element(GTPHUB_NODE, &cfg_gtphub_bind_to_ggsns_cmd);
+	install_element(GTPHUB_NODE, &cfg_gtphub_ggsn_proxy_short_cmd);
+	install_element(GTPHUB_NODE, &cfg_gtphub_ggsn_proxy_cmd);
+	install_element(GTPHUB_NODE, &cfg_gtphub_sgsn_proxy_short_cmd);
+	install_element(GTPHUB_NODE, &cfg_gtphub_sgsn_proxy_cmd);
+
+	return 0;
+}
+
+int gtphub_cfg_read(struct gtphub_cfg *cfg, const char *config_file)
+{
+	int rc;
+
+	g_cfg = cfg;
+
+	rc = vty_read_config_file(config_file, NULL);
+	if (rc < 0) {
+		fprintf(stderr, "Failed to parse the config file: '%s'\n", config_file);
+		return rc;
+	}
+
+	return 0;
+}