diff options
authorNeels Hofmeyr <>2017-03-16 16:14:34 +0100
committerNeels Hofmeyr <>2017-06-18 17:49:00 +0200
commitee19c9ab609e04726d26166426beb6d58aec7456 (patch)
parent61692adb2b0cd090c8fb8c81376a28bca099d079 (diff)
mgcp: hack RAB success from nano3G: patch first RTP payload
The ip.access nano3G needs the first RTP payload's first two bytes to read hex 'e400', or it will reject the RAB assignment. Add flag patched_first_rtp_payload to mgcp_rtp_state to detect the first RTP payload on a stream, and overwrite its first bytes with e400. This should probably be configurable, but seems to not harm other femto cells (as long as we patch only the first RTP payload in each stream). Only do this when sending to the BTS side. Change-Id: I31a4475f42d59fd5704d52ee6e473e270db6d779
2 files changed, 8 insertions, 0 deletions
diff --git a/openbsc/include/openbsc/mgcp_internal.h b/openbsc/include/openbsc/mgcp_internal.h
index b58eb9b..4e215b8 100644
--- a/openbsc/include/openbsc/mgcp_internal.h
+++ b/openbsc/include/openbsc/mgcp_internal.h
@@ -64,6 +64,7 @@ struct mgcp_rtp_state {
uint32_t stats_jitter;
int32_t stats_transit;
int stats_cycles;
+ bool patched_first_rtp_payload;
struct mgcp_rtp_codec {
diff --git a/openbsc/src/libmgcp/mgcp_network.c b/openbsc/src/libmgcp/mgcp_network.c
index c9fe179..a1c7e85 100644
--- a/openbsc/src/libmgcp/mgcp_network.c
+++ b/openbsc/src/libmgcp/mgcp_network.c
@@ -667,6 +667,13 @@ int mgcp_send(struct mgcp_endpoint *endp, int dest, int is_rtp,
forward_data(rtp_end->rtp.fd, &endp->taps[tap_idx],
buf, len);
+ if (tap_idx == MGCP_TAP_BTS_OUT
+ && !rtp_state->patched_first_rtp_payload) {
+ uint8_t *data = (uint8_t*)&buf[12];
+ osmo_hexparse("e400", data, 2);
+ rtp_state->patched_first_rtp_payload = true;
+ }
rc = mgcp_udp_send(rtp_end->rtp.fd,
rtp_end->rtp_port, buf, len);