From 88fbce262f269093b361a4fe39b0b6870f809537 Mon Sep 17 00:00:00 2001
From: Juliusz Chroboczek <jch@irif.fr>
Date: Thu, 21 May 2020 00:24:10 +0200
Subject: [PATCH] Implement sendFIR.

---
 client.go | 35 +++++++++++++++++++++++++++++++++++
 conn.go   |  2 ++
 group.go  |  1 +
 3 files changed, 38 insertions(+)

diff --git a/client.go b/client.go
index 0551ddb..ff9a0cf 100644
--- a/client.go
+++ b/client.go
@@ -908,6 +908,41 @@ func sendPLI(pc *webrtc.PeerConnection, ssrc uint32) error {
 	})
 }
 
+func (up *upConnection) sendFIR(track *upTrack, increment bool) error {
+	// we need to reliably increment the seqno, even if we are going
+	// to drop the packet due to rate limiting.
+	var seqno uint8
+	if increment {
+		seqno = uint8(atomic.AddUint32(&track.firSeqno, 1) & 0xFF)
+	} else {
+		seqno = uint8(atomic.LoadUint32(&track.firSeqno) & 0xFF)
+	}
+
+	if !track.hasRtcpFb("ccm", "fir") {
+		return ErrUnsupportedFeedback
+	}
+	last := atomic.LoadUint64(&track.lastFIR)
+	now := mono.Microseconds()
+	if now >= last && now-last < 200000 {
+		return ErrRateLimited
+	}
+	atomic.StoreUint64(&track.lastFIR, now)
+	return sendFIR(up.pc, track.track.SSRC(), seqno)
+}
+
+func sendFIR(pc *webrtc.PeerConnection, ssrc uint32, seqno uint8) error {
+	return pc.WriteRTCP([]rtcp.Packet{
+		&rtcp.FullIntraRequest{
+			FIR: []rtcp.FIREntry{
+				rtcp.FIREntry{
+					SSRC:           ssrc,
+					SequenceNumber: seqno,
+				},
+			},
+		},
+	})
+}
+
 func sendREMB(pc *webrtc.PeerConnection, ssrc uint32, bitrate uint64) error {
 	return pc.WriteRTCP([]rtcp.Packet{
 		&rtcp.ReceiverEstimatedMaximumBitrate{
diff --git a/conn.go b/conn.go
index 5edb185..01803f0 100644
--- a/conn.go
+++ b/conn.go
@@ -31,6 +31,8 @@ type upTrack struct {
 	jitter               *jitter.Estimator
 	maxBitrate           uint64
 	lastPLI              uint64
+	lastFIR              uint64
+	firSeqno             uint32
 	lastSenderReport     uint32
 	lastSenderReportTime uint32
 
diff --git a/group.go b/group.go
index 6e150e6..b769a6b 100644
--- a/group.go
+++ b/group.go
@@ -112,6 +112,7 @@ func addGroup(name string, desc *groupDescription) (*group, error) {
 				{"goog-remb", ""},
 				{"nack", ""},
 				{"nack", "pli"},
+				{"ccm", "fir"},
 			},
 			"",
 		))