rtp/rtcp: add RTCP Generic NACK packet send (RFC 4585 6.2.1)

include/re_rtp.h

@@ -268,6 +268,8 @@ int   rtcp_send_app(struct rtp_sock *rs, const char name[4],
 		    const uint8_t *data, size_t len);
 int   rtcp_send_fir(struct rtp_sock *rs, uint32_t ssrc);
 int   rtcp_send_nack(struct rtp_sock *rs, uint16_t fsn, uint16_t blp);
+int   rtcp_send_gnack(struct rtp_sock *rs, uint32_t ssrc, uint16_t fsn,
+		    uint16_t blp);
 int   rtcp_send_pli(struct rtp_sock *rs, uint32_t fb_ssrc);
 int   rtcp_send_fir_rfc5104(struct rtp_sock *rs, uint32_t ssrc,
 			    uint8_t fir_seqn);

src/rtp/rtcp.c

@@ -89,6 +89,36 @@ int rtcp_send_nack(struct rtp_sock *rs, uint16_t fsn, uint16_t blp)
 }
 
 
+static int encode_gnack(struct mbuf *mb, void *arg)
+{
+	struct gnack *fci = arg;
+
+	int err = mbuf_write_u16(mb, htons(fci->pid));
+	err |= mbuf_write_u16(mb, htons(fci->blp));
+	return err;
+}
+
+
+/**
+ * Send an RTCP Generic NACK packet (RFC 4585 6.2.1)
+ *
+ * @param rs   RTP Socket
+ * @param ssrc SSRC of the target encoder
+ * @param fsn  First Sequence Number lost
+ * @param blp  Bitmask of lost packets
+ *
+ * @return 0 for success, otherwise errorcode
+ */
+int rtcp_send_gnack(struct rtp_sock *rs, uint32_t ssrc, uint16_t fsn,
+		    uint16_t blp)
+{
+	struct gnack fci = {fsn, blp};
+	return rtcp_quick_send(rs, RTCP_RTPFB, RTCP_RTPFB_GNACK,
+			       rtp_sess_ssrc(rs), ssrc, &encode_gnack,
+			       &fci);
+}
+
+
 /**
  * Send an RTCP Picture Loss Indication (PLI) packet
  *

test/rtcp.c

@@ -198,6 +198,8 @@ struct agent {
 	struct sa laddr_rtcp;
 	unsigned rtp_count;
 	unsigned psfb_count;
+	unsigned rtpfb_count;
+	unsigned gnack_count;
 };
 
 
@@ -222,6 +224,12 @@ static void rtcp_recv_handler(const struct sa *src, struct rtcp_msg *msg,
 
 	switch (msg->hdr.pt) {
 
+	case RTCP_RTPFB:
+		if (msg->r.fb.fci.gnackv->pid == 42)
+			++ag->gnack_count;
+		++ag->rtpfb_count;
+		break;
+
 	case RTCP_PSFB:
 		++ag->psfb_count;
 		re_cancel();
@@ -266,6 +274,9 @@ static int test_rtcp_loop_base(bool mux)
 	rtcp_start(a.rtp_sock, "cname", &b.laddr_rtcp);
 	rtcp_start(b.rtp_sock, "cname", &a.laddr_rtcp);
 
+	err = rtcp_send_gnack(a.rtp_sock, rtp_sess_ssrc(b.rtp_sock), 42, 0);
+	TEST_ERR(err);
+
 	err = rtcp_send_pli(a.rtp_sock, rtp_sess_ssrc(b.rtp_sock));
 	TEST_ERR(err);
 
@@ -276,6 +287,8 @@ static int test_rtcp_loop_base(bool mux)
 	ASSERT_EQ(0, a.psfb_count);
 	ASSERT_EQ(0, b.rtp_count);
 	ASSERT_EQ(1, b.psfb_count);
+	ASSERT_EQ(1, b.rtpfb_count);
+	ASSERT_EQ(1, b.gnack_count);
 
  out:
 	mem_deref(b.rtp_sock);