Fix state based relaying for acknowledgements (cosmos#488)

* fix flipped acknowledgement query for state based relaying

* fix bug

* revert comment

* update changelog

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Relayer
 
+* [\#488](https://github.com/cosmos/relayer/pull/488) Fix state based relaying for acknowledgements.
 * [\#474](https://github.com/cosmos/relayer/pull/474) Fix validator set mismatch when updating IBC client.
 * [\#456](https://github.com/cosmos/relayer/pull/456) Fix bug which incorrectly set the timeout on a transfer.
 * [\#455](https://github.com/cosmos/relayer/pull/455) Set default client parameter to allow governance to update the client if expiry or misbehaviour freezing occurs. 

relayer/naive-strategy.go

@@ -423,26 +423,30 @@ func (nrs *NaiveStrategy) RelayAcknowledgements(src, dst *Chain, sp *RelaySequen
 		return err
 	}
 
-	// add messages for sequences on src
-	for _, seq := range sp.Src {
-		// SRC wrote ack, so we query packet and send to DST
+	// add messages for received packets on dst
+	for _, seq := range sp.Dst {
+		// dst wrote the ack. acknowledgementFromSequence will query the acknowledgement
+		// from the counterparty chain (second chain provided in the arguments). The message
+		// should be sent to src.
 		relayAckMsgs, err := acknowledgementFromSequence(src, dst, seq)
 		if err != nil {
 			return err
 		}
 
-		msgs.Dst = append(msgs.Dst, relayAckMsgs...)
+		msgs.Src = append(msgs.Src, relayAckMsgs...)
 	}
 
-	// add messages for sequences on dst
-	for _, seq := range sp.Dst {
-		// DST wrote ack, so we query packet and send to SRC
+	// add messages for received packets on src
+	for _, seq := range sp.Src {
+		// src wrote the ack. acknowledgementFromSequence will query the acknowledgement
+		// from the counterparty chain (second chain provided in the arguments). The message
+		// should be sent to dst.
 		relayAckMsgs, err := acknowledgementFromSequence(dst, src, seq)
 		if err != nil {
 			return err
 		}
 
-		msgs.Src = append(msgs.Src, relayAckMsgs...)
+		msgs.Dst = append(msgs.Dst, relayAckMsgs...)
 	}
 
 	if !msgs.Ready() {
@@ -617,7 +621,7 @@ func relayPacketFromSequence(src, dst *Chain, seq uint64) ([]sdk.Msg, []sdk.Msg,
 
 // source is the sending chain, destination is the receiving chain
 func acknowledgementFromSequence(src, dst *Chain, seq uint64) ([]sdk.Msg, error) {
-	txs, err := src.QueryTxs(src.MustGetLatestLightHeight(), 1, 1000, ackPacketQuery(src.PathEnd.ChannelID, int(seq)))
+	txs, err := dst.QueryTxs(dst.MustGetLatestLightHeight(), 1, 1000, ackPacketQuery(dst.PathEnd.ChannelID, int(seq)))
 	switch {
 	case err != nil:
 		return nil, err
@@ -627,7 +631,7 @@ func acknowledgementFromSequence(src, dst *Chain, seq uint64) ([]sdk.Msg, error)
 		return nil, fmt.Errorf("more than one transaction returned with query")
 	}
 
-	acks, err := acknowledgementsFromResultTx(dst.PathEnd, src.PathEnd, txs[0])
+	acks, err := acknowledgementsFromResultTx(src.PathEnd, dst.PathEnd, txs[0])
 	switch {
 	case err != nil:
 		return nil, err
@@ -739,7 +743,7 @@ func relayPacketsFromResultTx(src, dst *Chain, res *ctypes.ResultTx) ([]relayPac
 }
 
 // acknowledgementsFromResultTx looks through the events in a *ctypes.ResultTx and returns
-//relayPackets with the appropriate data
+// relayPackets with the appropriate data
 func acknowledgementsFromResultTx(src, dst *PathEnd,
 	res *ctypes.ResultTx) ([]*relayMsgPacketAck, error) {
 	var ackPackets []*relayMsgPacketAck