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, 3 insertions, 0 deletions

diff --git a/openbsc/include/openbsc/gtphub.h b/openbsc/include/openbsc/gtphub.h
index c98603b4e..1bff68127 100644
--- a/openbsc/include/openbsc/gtphub.h
+++ b/openbsc/include/openbsc/gtphub.h
@@ -361,6 +361,7 @@ struct gtphub_cfg_bind {
 struct gtphub_cfg {
 	struct gtphub_cfg_bind to_gsns[GTPH_SIDE_N][GTPH_PLANE_N];
 	struct gtphub_cfg_addr proxy[GTPH_SIDE_N][GTPH_PLANE_N];
+	int sgsn_use_sender; /* Use sender, not GSN addr IE with std ports */
 };
 
 
@@ -454,6 +455,8 @@ struct gtphub {
 	struct expiry expire_slowly;
 
 	uint8_t restart_counter;
+
+	int sgsn_use_sender;
 };
 
 struct gtp_packet_desc;