rtp: split osmo_rtp_parse in two functions

This patch splits osmo_rtp_parse in two functions:

osmo_rtp_get_hdr
osmo_rtp_get_payload

So we can validate corrent RTP header to access its fields. Then,
obtain the payload.

4 files changed, 35 insertions, 30 deletions

diff --git a/examples/rtp-udp-test-client.c b/examples/rtp-udp-test-client.c
index 4163703..97ec6ff 100644
--- a/examples/rtp-udp-test-client.c
+++ b/examples/rtp-udp-test-client.c
@@ -39,7 +39,7 @@ static struct osmo_rtp_handle *rtp;
 static int read_cb(struct osmo_dgram_conn *conn)
 {
 	struct msgb *msg;
-	int payload_type;
+	struct rtp_hdr *rtph;
 
 	LOGP(DLINP, LOGL_DEBUG, "received message\n");
 
@@ -53,15 +53,16 @@ static int read_cb(struct osmo_dgram_conn *conn)
 		LOGP(DRTP_TEST, LOGL_ERROR, "cannot receive message\n");
 		return -1;
 	}
-	payload_type = osmo_rtp_parse(msg);
-	if (payload_type < 0) {
+
+	rtph = osmo_rtp_get_hdr(msg);
+	if (rtph == NULL) {
 		msgb_free(msg);
 		LOGP(DRTP_TEST, LOGL_ERROR, "cannot parse RTP message\n");
 		return -1;
 	}
 
-	LOGP(DLINP, LOGL_DEBUG, "received message with payload type: %d "
-		"and size: %d (%s)\n", payload_type, msg->len, msg->data);
+	LOGP(DLINP, LOGL_DEBUG, "received message with payload type: %d\n",
+		rtph->payload_type);
 
 	msgb_free(msg);
 	return 0;
diff --git a/examples/rtp-udp-test-server.c b/examples/rtp-udp-test-server.c
index 5efd920..2f7f291 100644
--- a/examples/rtp-udp-test-server.c
+++ b/examples/rtp-udp-test-server.c
@@ -38,7 +38,7 @@ int read_cb(struct osmo_dgram_conn *conn)
 {
 	struct msgb *msg;
 	char dummy_data[RTP_PT_GSM_FULL_PAYLOAD_LEN] = "payload test";
-	int payload_type;
+	struct rtp_hdr *rtph;
 
 	LOGP(DRTP_TEST, LOGL_DEBUG, "received message from datagram\n");
 
@@ -51,14 +51,14 @@ int read_cb(struct osmo_dgram_conn *conn)
 		LOGP(DRTP_TEST, LOGL_ERROR, "cannot receive message\n");
 		return -1;
 	}
-	payload_type = osmo_rtp_parse(msg);
-	if (payload_type < 0) {
+	rtph = osmo_rtp_get_hdr(msg);
+	if (rtph == NULL) {
 		msgb_free(msg);
 		LOGP(DRTP_TEST, LOGL_ERROR, "cannot parse RTP message\n");
 		return -1;
 	}
-	LOGP(DLINP, LOGL_DEBUG, "received message with RTP payload type: %d "
-		"and size: %d (%s)\n", payload_type, msg->len, msg->data);
+	LOGP(DLINP, LOGL_DEBUG, "received message with RTP payload type: %d\n",
+		rtph->payload_type);
 
 	/*
 	 * ... now build gsm_data_frame, set callref and msg_type based
diff --git a/include/osmocom/netif/rtp.h b/include/osmocom/netif/rtp.h
index e65bd15..6888cc3 100644
--- a/include/osmocom/netif/rtp.h
+++ b/include/osmocom/netif/rtp.h
@@ -57,7 +57,9 @@ int osmo_rtp_handle_tx_set_sequence(struct osmo_rtp_handle *h, uint16_t seq);
 int osmo_rtp_handle_tx_set_ssrc(struct osmo_rtp_handle *h, uint32_t ssrc);
 int osmo_rtp_handle_tx_set_timestamp(struct osmo_rtp_handle *h, uint32_t timestamp);
 
-int osmo_rtp_parse(struct msgb *msg);
+struct rtp_hdr *osmo_rtp_get_hdr(struct msgb *msg);
+void *osmo_rtp_get_payload(struct rtp_hdr *rtph, struct msgb *msg);
+
 struct msgb *osmo_rtp_build(struct osmo_rtp_handle *h, uint8_t payload_type, uint32_t payload_len, const void *data, uint32_t duration);
 
 /* supported RTP payload types. */
diff --git a/src/rtp.c b/src/rtp.c
index 0e66502..77f3d5f 100644
--- a/src/rtp.c
+++ b/src/rtp.c
@@ -68,41 +68,45 @@ int osmo_rtp_handle_tx_set_timestamp(struct osmo_rtp_handle *h, uint32_t timesta
 	return 0;
 }
 
-/* decode and pull RTP header out and return payload_type. The msg->data
-   points to data payload after this is called. This function returns the
-   RTP payload type on success. */
-int osmo_rtp_parse(struct msgb *msg)
+struct rtp_hdr *osmo_rtp_get_hdr(struct msgb *msg)
 {
 	struct rtp_hdr *rtph = (struct rtp_hdr *)msg->data;
-	struct rtp_x_hdr *rtpxh;
-	uint8_t *payload;
-	int payload_len;
-	int x_len;
-	int csrc_len;
 
 	if (msg->len < sizeof(struct rtp_hdr)) {
 		DEBUGPC(DLMUX, "received RTP frame too short (len = %d)\n",
 			msg->len);
-		return -EINVAL;
+		return NULL;
 	}
 	if (rtph->version != RTP_VERSION) {
 		DEBUGPC(DLMUX, "received RTP version %d not supported.\n",
 			rtph->version);
-		return -EINVAL;
+		return NULL;
 	}
+
+	return rtph;
+}
+
+void *osmo_rtp_get_payload(struct rtp_hdr *rtph, struct msgb *msg)
+{
+	struct rtp_x_hdr *rtpxh;
+	uint8_t *payload;
+	int payload_len;
+	int x_len;
+	int csrc_len;
+
 	csrc_len = rtph->csrc_count << 2;
 	payload = msg->data + sizeof(struct rtp_hdr) + csrc_len;
 	payload_len = msg->len - sizeof(struct rtp_hdr) - csrc_len;
 	if (payload_len < 0) {
 		DEBUGPC(DLMUX, "received RTP frame too short (len = %d, "
 			"csrc count = %d)\n", msg->len, rtph->csrc_count);
-		return -EINVAL;
+		return NULL;
 	}
 	if (rtph->extension) {
 		if (payload_len < sizeof(struct rtp_x_hdr)) {
 			DEBUGPC(DLMUX, "received RTP frame too short for "
 				"extension header\n");
-			return -EINVAL;
+			return NULL;
 		}
 		rtpxh = (struct rtp_x_hdr *)payload;
 		x_len = ntohs(rtpxh->length) * 4 + sizeof(struct rtp_x_hdr);
@@ -111,26 +115,24 @@ int osmo_rtp_parse(struct msgb *msg)
 		if (payload_len < 0) {
 			DEBUGPC(DLMUX, "received RTP frame too short, "
 				"extension header exceeds frame length\n");
-			return -EINVAL;
+			return NULL;
 		}
 	}
 	if (rtph->padding) {
 		if (payload_len < 0) {
 			DEBUGPC(DLMUX, "received RTP frame too short for "
 				"padding length\n");
-			return -EINVAL;
+			return NULL;
 		}
 		payload_len -= payload[payload_len - 1];
 		if (payload_len < 0) {
 			DEBUGPC(DLMUX, "received RTP frame with padding "
 				"greater than payload\n");
-			return -EINVAL;
+			return NULL;
 		}
 	}
 
-	msgb_pull(msg, msg->len - payload_len);
-
-	return rtph->payload_type;
+	return (uint8_t *)msg->data + msg->len - payload_len;
 }
 
 struct msgb *