Add helper to filter duplicate acks

pkg/ccfb/duplicate_ack_filter.go

@@ -0,0 +1,25 @@
+package ccfb
+
+type DuplicateAckFilter struct {
+	highestAckedBySSRC map[uint32]int64
+}
+
+func NewDuplicateAckFilter() *DuplicateAckFilter {
+	return &DuplicateAckFilter{
+		highestAckedBySSRC: make(map[uint32]int64),
+	}
+}
+
+func (f *DuplicateAckFilter) Filter(reports Report) {
+	for ssrc, prs := range reports.SSRCToPacketReports {
+		n := 0
+		for _, report := range prs {
+			if highest, ok := f.highestAckedBySSRC[ssrc]; !ok || report.SeqNr > highest {
+				f.highestAckedBySSRC[ssrc] = report.SeqNr
+				prs[n] = report
+				n++
+			}
+		}
+		reports.SSRCToPacketReports[ssrc] = prs[:n]
+	}
+}

pkg/ccfb/duplicate_ack_filter_test.go

@@ -0,0 +1,106 @@
+package ccfb
+
+import (
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDuplicateAckFilter(t *testing.T) {
+	cases := []struct {
+		in     []Report
+		expect []Report
+	}{
+		{
+			in:     []Report{},
+			expect: []Report{},
+		},
+		{
+			in: []Report{
+				{
+					SSRCToPacketReports: map[uint32][]PacketReport{
+						0: {},
+					},
+				},
+			},
+			expect: []Report{
+				{
+					Arrival:   time.Time{},
+					Departure: time.Time{},
+					SSRCToPacketReports: map[uint32][]PacketReport{
+						0: {},
+					},
+				},
+			},
+		},
+		{
+			in: []Report{
+				{
+					SSRCToPacketReports: map[uint32][]PacketReport{
+						0: {
+							{
+								SeqNr: 1,
+							},
+							{
+								SeqNr: 2,
+							},
+						},
+					},
+				},
+				{
+					SSRCToPacketReports: map[uint32][]PacketReport{
+						0: {
+							{
+								SeqNr: 1,
+							},
+							{
+								SeqNr: 2,
+							},
+							{
+								SeqNr: 3,
+							},
+						},
+					},
+				},
+			},
+			expect: []Report{
+				{
+					Arrival:   time.Time{},
+					Departure: time.Time{},
+					SSRCToPacketReports: map[uint32][]PacketReport{
+						0: {
+							{
+								SeqNr: 1,
+							},
+							{
+								SeqNr: 2,
+							},
+						},
+					},
+				},
+				{
+					Arrival:   time.Time{},
+					Departure: time.Time{},
+					SSRCToPacketReports: map[uint32][]PacketReport{
+						0: {
+							{
+								SeqNr: 3,
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+	for i, tc := range cases {
+		t.Run(fmt.Sprintf("%v", i), func(t *testing.T) {
+			daf := NewDuplicateAckFilter()
+			for i, m := range tc.in {
+				daf.Filter(m)
+				assert.Equal(t, tc.expect[i], m)
+			}
+		})
+	}
+}