Prevent crash in RTCP nack writing.

Author: pthatcher

src/transport_feedbacks/transport_layer_nack/mod.rs

@@ -226,10 +226,13 @@ pub fn nack_pairs_from_sequence_numbers(seq_nos: &[u16]) -> Vec<NackPair> {
 
     let mut pairs = vec![];
 
-    for seq in seq_nos.iter().skip(1) {
-        if seq - nack_pair.packet_id > 16 {
+    for &seq in seq_nos.iter().skip(1) {
+        if seq == nack_pair.packet_id {
+            continue;
+        }
+        if seq <= nack_pair.packet_id || seq - nack_pair.packet_id > 16 {
             pairs.push(nack_pair.clone());
-            nack_pair.packet_id = *seq;
+            nack_pair.packet_id = seq;
             continue;
         }
 

src/transport_feedbacks/transport_layer_nack/transport_layer_nack_test.rs

@@ -250,6 +250,15 @@ fn test_transport_layer_nack_pair_generation() {
                 lost_packets: 0x0,
             }],
         ),
+        // Make sure it doesn't crash.
+        (
+            "Single Sequence Number (duplicates)",
+            vec![100u16, 100],
+            vec![NackPair {
+                packet_id: 100,
+                lost_packets: 0x0,
+            }],
+        ),
         (
             "Multiple in range, Single NACKPair",
             vec![100, 101, 105, 115],
@@ -276,6 +285,50 @@ fn test_transport_layer_nack_pair_generation() {
                 },
             ],
         ),
+        (
+            "Multiple Ranges, Multiple NACKPair",
+            vec![100, 117, 500, 501, 502],
+            vec![
+                NackPair {
+                    packet_id: 100,
+                    lost_packets: 0,
+                },
+                NackPair {
+                    packet_id: 117,
+                    lost_packets: 0,
+                },
+                NackPair {
+                    packet_id: 500,
+                    lost_packets: 0x3,
+                },
+            ],
+        ),
+        (
+            "Multiple Ranges, Multiple NACKPair (with rollover)",
+            vec![100, 117, 65535, 0, 1, 99],
+            vec![
+                NackPair {
+                    packet_id: 100,
+                    lost_packets: 0,
+                },
+                NackPair {
+                    packet_id: 117,
+                    lost_packets: 0,
+                },
+                NackPair {
+                    packet_id: 65535,
+                    lost_packets: 0,
+                },
+                NackPair {
+                    packet_id: 0,
+                    lost_packets: 1,
+                },
+                NackPair {
+                    packet_id: 99,
+                    lost_packets: 1,
+                },
+            ],
+        ),
     ];
 
     for (name, seq_numbers, expected) in test {