Unambiguous packet query (informalsystems#613)

Before, a `query_txs` for a packet on a given chain would filter only
by the packet source port, source channel and sequence.
With 2 chains, there can be at most a single packet matching such
filter, and this fact was assumed in the code.

However, this assumption does not hold with more than 2 chains. To
understand why, consider the following example with chains `ibc-0`,
`ibc-1` and `ibc-2`:
- a channel handshake occurs between `ibc-0` and `ibc-1`; the channel
identifiers are `channel-0` on both ends
- a channel handshake occurs between `ibc-1` and `ibc-2`; the channel
identifier on `ibc-1` is `channel-1` and on `ibc-2` is `channel-0`

If now both `ibc-0` and `ibc-2` send packets to `ibc-1` and we do a
packet query filtering only by the source, such query will return
packets from both `ibc-0` and `ibc-1` (as both have `channel-0` as
the source channel in their packets).

In this commit, we start filtering also by the destination port and
destination channel. This makes the packet query unambiguous.

relayer/src/chain/cosmos.rs

@@ -825,6 +825,14 @@ fn packet_query(request: &QueryPacketEventDataRequest, seq: &Sequence) -> Result
         format!("{}.packet_src_port", request.event_id.as_str()),
         request.source_port_id.to_string(),
     )
+    .and_eq(
+        format!("{}.packet_dst_channel", request.event_id.as_str()),
+        request.destination_channel_id.to_string(),
+    )
+    .and_eq(
+        format!("{}.packet_dst_port", request.event_id.as_str()),
+        request.destination_port_id.to_string(),
+    )
     .and_eq(
         format!("{}.packet_sequence", request.event_id.as_str()),
         seq.to_string(),
@@ -840,6 +848,7 @@ fn packet_from_tx_search_response(
     seq: Sequence,
     response: &tendermint_rpc::endpoint::tx_search::Response,
 ) -> Result<Option<IBCEvent>, Error> {
+    // TODO: remove loop as `response.txs.len() <= 1`
     for r in response.txs.iter() {
         let height = r.height;
         if height.value() > request.height.revision_height {
@@ -869,6 +878,8 @@ fn packet_from_tx_search_response(
             let packet = packet.unwrap();
             if packet.source_port != request.source_port_id
                 || packet.source_channel != request.source_channel_id
+                || packet.destination_port != request.destination_port_id
+                || packet.destination_channel != request.destination_channel_id
                 || packet.sequence != seq
             {
                 continue;

relayer/src/link.rs

@@ -372,6 +372,8 @@ impl RelayPath {
             event_id: IBCEventType::SendPacket,
             source_port_id: self.src_port_id().clone(),
             source_channel_id: self.src_channel_id().clone(),
+            destination_port_id: self.dst_port_id().clone(),
+            destination_channel_id: self.dst_channel_id().clone(),
             sequences,
             height: self.src_height,
         })?;
@@ -442,6 +444,8 @@ impl RelayPath {
                 event_id: IBCEventType::WriteAck,
                 source_port_id: self.dst_port_id().clone(),
                 source_channel_id: self.dst_channel_id().clone(),
+                destination_port_id: self.src_port_id().clone(),
+                destination_channel_id: self.src_channel_id().clone(),
                 sequences,
                 height: query_height,
             })