Rechannel: don't ack old chunk_ids in the block channel

Discard the ack packet if the chunk_id of the packet does not match the current chunk_id of the message being sent.

rechannel/src/channel/block.rs

@@ -25,6 +25,7 @@ pub(crate) struct SliceMessage {
 #[derive(Debug, Clone)]
 struct PacketSent {
     acked: bool,
+    chunk_id: u16,
     slice_ids: Vec<u32>,
 }
 
@@ -100,8 +101,12 @@ impl Default for BlockChannelConfig {
 }
 
 impl PacketSent {
-    fn new(slice_ids: Vec<u32>) -> Self {
-        Self { acked: false, slice_ids }
+    fn new(chunk_id: u16, slice_ids: Vec<u32>) -> Self {
+        Self {
+            chunk_id,
+            slice_ids,
+            acked: false,
+        }
     }
 }
 
@@ -193,7 +198,7 @@ impl ChunkSender {
 
     fn process_ack(&mut self, ack: u16) {
         if let Some(sent_packet) = self.packets_sent.get_mut(ack) {
-            if sent_packet.acked {
+            if sent_packet.acked || sent_packet.chunk_id != self.chunk_id {
                 return;
             }
             sent_packet.acked = true;
@@ -379,7 +384,7 @@ impl Channel for BlockChannel {
             }
         }
 
-        let packet_sent = PacketSent::new(slice_ids);
+        let packet_sent = PacketSent::new(self.sender.chunk_id, slice_ids);
         self.sender.packets_sent.insert(sequence, packet_sent);
 
         Some(ChannelPacketData {
@@ -511,12 +516,11 @@ mod tests {
     fn block_channel_queue() {
         let mut channel = BlockChannel::new(BlockChannelConfig {
             resend_time: Duration::ZERO,
-            ..Default::default()   
+            ..Default::default()
         });
         let first_message = Bytes::from(vec![3; 2000]);
         let second_message = Bytes::from(vec![5; 2000]);
         channel.send_message(first_message.clone());
-        // Add second message to queue
         channel.send_message(second_message.clone());
 
         // First message
@@ -540,4 +544,28 @@ mod tests {
         let block_channel_data = channel.get_messages_to_send(u64::MAX, 2);
         assert!(block_channel_data.is_none());
     }
+
+    #[test]
+    fn acking_packet_with_old_chunk_id() {
+        let mut channel = BlockChannel::new(BlockChannelConfig {
+            resend_time: Duration::ZERO,
+            ..Default::default()
+        });
+        let first_message = Bytes::from(vec![5; 400 * 3]);
+        let second_message = Bytes::from(vec![3; 400]);
+        channel.send_message(first_message);
+        channel.send_message(second_message);
+
+        let _ = channel.get_messages_to_send(u64::MAX, 0).unwrap();
+        let _ = channel.get_messages_to_send(u64::MAX, 1).unwrap();
+
+        channel.process_ack(0);
+        let _ = channel.get_messages_to_send(u64::MAX, 2).unwrap();
+
+        channel.process_ack(1);
+        assert!(channel.sender.sending);
+
+        channel.process_ack(2);
+        assert!(!channel.sender.sending);
+    }
 }