gtphub: implement sgsn_use_sender for NAT.

If an SGSN is behind NAT, we cannot rely on the default ports. Specifically,
if a GGSN sends a message, the forwarding to the SGSN should go to whichever
port the SGSN last sent from (whether sequence nr is known or not).

Add sgsn_use_sender config and VTY command, and store the sender instead
of the GSN Address IE and default port if set.

Sponsored-by: On-Waves ehi

1 files changed, 28 insertions, 0 deletions

diff --git a/openbsc/src/gprs/gtphub_vty.c b/openbsc/src/gprs/gtphub_vty.c
index 204d1deeb..324d155b9 100644
--- a/openbsc/src/gprs/gtphub_vty.c
+++ b/openbsc/src/gprs/gtphub_vty.c
@@ -87,6 +87,10 @@ static int config_write_gtphub(struct vty *vty)
 		    &g_cfg->to_gsns[GTPH_SIDE_GGSN][GTPH_PLANE_CTRL].bind,
 		    &g_cfg->to_gsns[GTPH_SIDE_GGSN][GTPH_PLANE_USER].bind);
 
+	if (g_cfg->sgsn_use_sender) {
+		vty_out(vty, "sgsn-use-sender%s", VTY_NEWLINE);
+	}
+
 	if (g_cfg->proxy[GTPH_SIDE_SGSN][GTPH_PLANE_CTRL].addr_str) {
 		write_addrs(vty, "sgsn-proxy",
 			    &g_cfg->proxy[GTPH_SIDE_SGSN][GTPH_PLANE_CTRL],
@@ -237,6 +241,28 @@ DEFUN(cfg_gtphub_sgsn_proxy, cfg_gtphub_sgsn_proxy_cmd,
 }
 
 
+#define SGSN_USE_SENDER_STR \
+	"Ignore SGSN's Address IEs, use sender address and port (useful over NAT)\n"
+
+DEFUN(cfg_gtphub_sgsn_use_sender,
+      cfg_gtphub_sgsn_use_sender_cmd,
+      "sgsn-use-sender",
+      SGSN_USE_SENDER_STR)
+{
+	g_cfg->sgsn_use_sender = 1;
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_gtphub_no_sgsn_use_sender,
+      cfg_gtphub_no_sgsn_use_sender_cmd,
+      "no sgsn-use-sender",
+      NO_STR SGSN_USE_SENDER_STR)
+{
+	g_cfg->sgsn_use_sender = 0;
+	return CMD_SUCCESS;
+}
+
+
 /* Copied from sgsn_vty.h */
 DEFUN(cfg_grx_ggsn, cfg_grx_ggsn_cmd,
 	"grx-dns-add A.B.C.D",
@@ -425,6 +451,8 @@ int gtphub_vty_init(struct gtphub *global_hub, struct gtphub_cfg *global_cfg)
 	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);
+	install_element(GTPHUB_NODE, &cfg_gtphub_sgsn_use_sender_cmd);
+	install_element(GTPHUB_NODE, &cfg_gtphub_no_sgsn_use_sender_cmd);
 	install_element(GTPHUB_NODE, &cfg_grx_ggsn_cmd);
 
 	return 0;