nat: Remember where the BTS is listening for things.

Extract the port from the BSS's MGCP Gateway so we know
where to forward the data to.

3 files changed, 31 insertions, 1 deletions

diff --git a/openbsc/include/openbsc/bsc_nat.h b/openbsc/include/openbsc/bsc_nat.h
index 6ec666a17..e27234911 100644
--- a/openbsc/include/openbsc/bsc_nat.h
+++ b/openbsc/include/openbsc/bsc_nat.h
@@ -205,5 +205,6 @@ void bsc_mgcp_forward(struct bsc_connection *bsc, struct msgb *msg);
 
 int bsc_mgcp_parse_response(const char *str, int *code, char transaction[60]);
 int bsc_mgcp_extract_ci(const char *resp);
+int bsc_mgcp_extract_port(const char *resp);
 
 #endif
diff --git a/openbsc/src/nat/bsc_mgcp_utils.c b/openbsc/src/nat/bsc_mgcp_utils.c
index 74ef67bb5..82eeefc6b 100644
--- a/openbsc/src/nat/bsc_mgcp_utils.c
+++ b/openbsc/src/nat/bsc_mgcp_utils.c
@@ -185,7 +185,7 @@ void bsc_mgcp_forward(struct bsc_connection *bsc, struct msgb *msg)
 	struct msgb *output;
 	struct bsc_endpoint *bsc_endp = NULL;
 	struct mgcp_endpoint *endp = NULL;
-	int i, code;
+	int i, code, port;
 	char transaction_id[60];
 
 	/* Some assumption that our buffer is big enough.. and null terminate */
@@ -223,6 +223,9 @@ void bsc_mgcp_forward(struct bsc_connection *bsc, struct msgb *msg)
 
 	/* make it point to our endpoint */
 	endp->ci = bsc_mgcp_extract_ci((const char *) msg->l2h);
+	port = bsc_mgcp_extract_port((const char *) msg->l2h);
+	endp->bts_rtp = htons(port);
+	endp->bts_rtcp = htons(port + 1);
 	output = bsc_mgcp_rewrite((char * ) msg->l2h, msgb_l2len(msg),
 				  bsc->nat->mgcp_cfg->source_addr, endp->rtp_port);
 	if (!output) {
@@ -254,6 +257,18 @@ int bsc_mgcp_extract_ci(const char *str)
 	return ci;
 }
 
+int bsc_mgcp_extract_port(const char *str)
+{
+	int port;
+	char *res = strstr(str, "m=audio ");
+	if (!res)
+		return 0;
+
+	if (sscanf(res, "m=audio %d RTP/AVP %*d", &port) != 1)
+		return 0;
+	return port;
+}
+
 /* we need to replace some strings... */
 struct msgb *bsc_mgcp_rewrite(char *input, int length, const char *ip, int port)
 {
diff --git a/openbsc/tests/bsc-nat/bsc_nat_test.c b/openbsc/tests/bsc-nat/bsc_nat_test.c
index def6bfec8..705372c8d 100644
--- a/openbsc/tests/bsc-nat/bsc_nat_test.c
+++ b/openbsc/tests/bsc-nat/bsc_nat_test.c
@@ -482,6 +482,19 @@ static void test_mgcp_parse(void)
 	}
 }
 
+static void test_mgcp_parse_port(void)
+{
+	int port;
+
+	fprintf(stderr, "Test MGCP port parsing.\n");
+
+	port = bsc_mgcp_extract_port(mdcx_resp);
+	if (port != 4002) {
+		fprintf(stderr, "Could not parse port. Got: %d\n", port);
+		abort();
+	}
+}
+
 int main(int argc, char **argv)
 {
 	struct debug_target *stderr_target;
@@ -497,6 +510,7 @@ int main(int argc, char **argv)
 	test_mgcp_find();
 	test_mgcp_rewrite();
 	test_mgcp_parse();
+	test_mgcp_parse_port();
 	return 0;
 }