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
diff --git a/openbsc/src/gprs/gtphub.c b/openbsc/src/gprs/gtphub.c
index e96088c..6762825 100644
--- a/openbsc/src/gprs/gtphub.c
+++ b/openbsc/src/gprs/gtphub.c
@@ -1502,9 +1502,27 @@
tei_from_ie = ntoh32(p->ie[ie_idx]->tv4.v);
/* Make sure an entry for this peer address with default port
- * exists. */
+ * exists.
+ *
+ * Exception: if sgsn_use_sender is set, instead use the
+ * sender's address and port for Ctrl -- the User port is not
+ * known until the first User packet arrives.
+ *
+ * Note: doing this here is just an optimization, because
+ * gtphub_handle_buf() has code to replace the tunnel
+ * endpoints' addresses with the sender (needed for User
+ * plane). We could just ignore sgsn_use_sender here. But if we
+ * set up a default port here and replace it in
+ * gtphub_handle_buf(), we'd be creating a peer port just to
+ * expire it right away. */
+ if (hub->sgsn_use_sender && (side_idx == GTPH_SIDE_SGSN)) {
+ gsn_addr_from_sockaddr(&use_addr, &use_port, &from_ctrl->sa);
+ } else {
+ use_port = gtphub_plane_idx_default_port[plane_idx];
+
+ }
+
struct gtphub_peer_port *peer_from_ie;
- use_port = gtphub_plane_idx_default_port[plane_idx];
peer_from_ie = gtphub_port_have(hub,
&hub->to_gsns[side_idx][plane_idx],
&use_addr, use_port);
@@ -2417,6 +2435,7 @@
gtphub_init(hub);
hub->restart_counter = restart_counter;
+ hub->sgsn_use_sender = cfg->sgsn_use_sender? 1 : 0;
/* If a Ctrl plane proxy is configured, ares will never be used. */
if (!cfg->proxy[GTPH_SIDE_GGSN][GTPH_PLANE_CTRL].addr_str) {