Added optional packet metadata to the packet and message types

docs/apps/transfer/events.md

@@ -23,6 +23,7 @@ order: 5
 | fungible_token_packet | denom         | {denom}         |
 | fungible_token_packet | amount        | {amount}        |
 | fungible_token_packet | success       | {ackSuccess}    |
+| fungible_token_packet | metadata      | {metadata}      |
 | denomination_trace    | trace_hash    | {hex_hash}      |
 
 ## `OnAcknowledgePacket` callback
@@ -34,6 +35,7 @@ order: 5
 | fungible_token_packet | receiver        | {receiver}        |
 | fungible_token_packet | denom           | {denom}           |
 | fungible_token_packet | amount          | {amount}          |
+| fungible_token_packet | metadata        | {metadata}        |
 | fungible_token_packet | acknowledgement | {ack.String()}    |
 | fungible_token_packet | success | error | {ack.Response}    |
 
@@ -45,3 +47,4 @@ order: 5
 | fungible_token_packet | refund_receiver | {receiver}      |
 | fungible_token_packet | denom           | {denom}         |
 | fungible_token_packet | amount          | {amount}        |
+| fungible_token_packet | metadata        | {metadata}      |

docs/apps/transfer/messages.md

@@ -17,6 +17,7 @@ type MsgTransfer struct {
   Receiver          string
   TimeoutHeight     ibcexported.Height
   TimeoutTimestamp  uint64
+  Metadata          []byte
 }
 ```
 

docs/ibc/proto-docs.md

@@ -2255,6 +2255,7 @@ https://github.com/cosmos/ibc/tree/master/spec/app/ics-020-fungible-token-transf
 | `receiver` | [string](#string) |  | the recipient address on the destination chain |
 | `timeout_height` | [ibc.core.client.v1.Height](#ibc.core.client.v1.Height) |  | Timeout height relative to the current block height. The timeout is disabled when set to 0. |
 | `timeout_timestamp` | [uint64](#uint64) |  | Timeout timestamp in absolute nanoseconds since unix epoch. The timeout is disabled when set to 0. |
+| `metadata` | [bytes](#bytes) |  | optional metadata |
 
 
 
@@ -2269,7 +2270,7 @@ MsgTransferResponse defines the Msg/Transfer response type.
 
 | Field | Type | Label | Description |
 | ----- | ---- | ----- | ----------- |
-| `sequence` | [uint64](#uint64) |  | sequence number of the packet on the channel. |
+| `sequence` | [uint64](#uint64) |  | sequence number of the transfer packet sent |
 
 
 
@@ -2316,6 +2317,7 @@ https://github.com/cosmos/ibc/tree/master/spec/app/ics-020-fungible-token-transf
 | `amount` | [string](#string) |  | the token amount to be transferred |
 | `sender` | [string](#string) |  | the sender address |
 | `receiver` | [string](#string) |  | the recipient address on the destination chain |
+| `metadata` | [bytes](#bytes) |  | optional metadata |
 
 
 

go.mod

@@ -43,7 +43,7 @@ require (
 	github.com/bgentry/go-netrc v0.0.0-20140422174119-9fd32a8b3d3d // indirect
 	github.com/bgentry/speakeasy v0.1.0 // indirect
 	github.com/btcsuite/btcd v0.22.1 // indirect
-	github.com/cenkalti/backoff/v4 v4.1.3 // indirect
+	github.com/cenkalti/backoff/v4 v4.1.1 // indirect
 	github.com/cespare/xxhash v1.1.0 // indirect
 	github.com/cespare/xxhash/v2 v2.1.2 // indirect
 	github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e // indirect

go.sum

@@ -180,9 +180,8 @@ github.com/c-bata/go-prompt v0.2.2/go.mod h1:VzqtzE2ksDBcdln8G7mk2RX9QyGjH+OVqOC
 github.com/casbin/casbin/v2 v2.1.2/go.mod h1:YcPU1XXisHhLzuxH9coDNf2FbKpjGlbCg3n9yuLkIJQ=
 github.com/cenkalti/backoff v2.2.1+incompatible h1:tNowT99t7UNflLxfYYSlKYsBpXdEet03Pg2g16Swow4=
 github.com/cenkalti/backoff v2.2.1+incompatible/go.mod h1:90ReRw6GdpyfrHakVjL/QHaoyV4aDUVVkXQJJJ3NXXM=
+github.com/cenkalti/backoff/v4 v4.1.1 h1:G2HAfAmvm/GcKan2oOQpBXOd2tT2G57ZnZGWa1PxPBQ=
 github.com/cenkalti/backoff/v4 v4.1.1/go.mod h1:scbssz8iZGpm3xbr14ovlUdkxfGXNInqkPWOWmG2CLw=
-github.com/cenkalti/backoff/v4 v4.1.3 h1:cFAlzYUlVYDysBEH2T5hyJZMh3+5+WCBvSnK6Q8UtC4=
-github.com/cenkalti/backoff/v4 v4.1.3/go.mod h1:scbssz8iZGpm3xbr14ovlUdkxfGXNInqkPWOWmG2CLw=
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/cespare/cp v0.1.0/go.mod h1:SOGHArjBr4JWaSDEVpWpo/hNg6RoKrls6Oh40hiwW+s=
 github.com/cespare/xxhash v1.1.0 h1:a6HrQnmkObjyL+Gs60czilIUGqrzKutQD6XZog3p+ko=

modules/apps/transfer/client/cli/tx.go

@@ -22,6 +22,7 @@ const (
 	flagPacketTimeoutHeight    = "packet-timeout-height"
 	flagPacketTimeoutTimestamp = "packet-timeout-timestamp"
 	flagAbsoluteTimeouts       = "absolute-timeouts"
+	flagMetadata               = "metadata"
 )
 
 // NewTransferTxCmd returns the command to create a NewMsgTransfer transaction
@@ -76,6 +77,11 @@ corresponding to the counterparty channel. Any timeout set to 0 is disabled.`),
 				return err
 			}
 
+			metadataStr, err := cmd.Flags().GetString(flagMetadata)
+			if err != nil {
+				return err
+			}
+
 			// if the timeouts are not absolute, retrieve latest block height and block timestamp
 			// for the consensus state connected to the destination port/channel
 			if !absoluteTimeouts {
@@ -111,7 +117,7 @@ corresponding to the counterparty channel. Any timeout set to 0 is disabled.`),
 			}
 
 			msg := types.NewMsgTransfer(
-				srcPort, srcChannel, coin, sender, receiver, timeoutHeight, timeoutTimestamp,
+				srcPort, srcChannel, coin, sender, receiver, timeoutHeight, timeoutTimestamp, []byte(metadataStr),
 			)
 			return tx.GenerateOrBroadcastTxCLI(clientCtx, cmd.Flags(), msg)
 		},

modules/apps/transfer/ibc_module.go

@@ -1,6 +1,7 @@
 package transfer
 
 import (
+	"encoding/hex"
 	"fmt"
 	"math"
 	"strings"
@@ -194,6 +195,7 @@ func (im IBCModule) OnRecvPacket(
 		sdk.NewAttribute(types.AttributeKeyReceiver, data.Receiver),
 		sdk.NewAttribute(types.AttributeKeyDenom, data.Denom),
 		sdk.NewAttribute(types.AttributeKeyAmount, data.Amount),
+		sdk.NewAttribute(types.AttributeKeyMetadata, hex.EncodeToString(data.Metadata)),
 		sdk.NewAttribute(types.AttributeKeyAckSuccess, fmt.Sprintf("%t", ack.Success())),
 	}
 
@@ -240,6 +242,7 @@ func (im IBCModule) OnAcknowledgementPacket(
 			sdk.NewAttribute(types.AttributeKeyReceiver, data.Receiver),
 			sdk.NewAttribute(types.AttributeKeyDenom, data.Denom),
 			sdk.NewAttribute(types.AttributeKeyAmount, data.Amount),
+			sdk.NewAttribute(types.AttributeKeyMetadata, hex.EncodeToString(data.Metadata)),
 			sdk.NewAttribute(types.AttributeKeyAck, ack.String()),
 		),
 	)
@@ -286,6 +289,7 @@ func (im IBCModule) OnTimeoutPacket(
 			sdk.NewAttribute(types.AttributeKeyRefundReceiver, data.Sender),
 			sdk.NewAttribute(types.AttributeKeyRefundDenom, data.Denom),
 			sdk.NewAttribute(types.AttributeKeyRefundAmount, data.Amount),
+			sdk.NewAttribute(types.AttributeKeyMetadata, hex.EncodeToString(data.Metadata)),
 		),
 	)
 

modules/apps/transfer/keeper/mbt_relay_test.go

@@ -146,7 +146,8 @@ func FungibleTokenPacketFromTla(packet TlaFungibleTokenPacket) FungibleTokenPack
 			DenomFromTla(packet.Data.Denom),
 			packet.Data.Amount,
 			AddressFromString(packet.Data.Sender),
-			AddressFromString(packet.Data.Receiver)),
+			AddressFromString(packet.Data.Receiver),
+			nil),
 	}
 }
 
@@ -346,7 +347,8 @@ func (suite *KeeperTestSuite) TestModelBasedRelay() {
 							sender,
 							tc.packet.Data.Receiver,
 							clienttypes.NewHeight(1, 110),
-							0)
+							0,
+							nil)
 					}
 				case "OnRecvPacket":
 					err = suite.chainB.GetSimApp().TransferKeeper.OnRecvPacket(suite.chainB.GetContext(), packet, tc.packet.Data)

modules/apps/transfer/keeper/msg_server.go

@@ -2,7 +2,6 @@ package keeper
 
 import (
 	"context"
-
 	sdk "github.com/cosmos/cosmos-sdk/types"
 
 	"github.com/cosmos/ibc-go/v6/modules/apps/transfer/types"
@@ -21,7 +20,7 @@ func (k Keeper) Transfer(goCtx context.Context, msg *types.MsgTransfer) (*types.
 
 	sequence, err := k.sendTransfer(
 		ctx, msg.SourcePort, msg.SourceChannel, msg.Token, sender, msg.Receiver, msg.TimeoutHeight, msg.TimeoutTimestamp,
-	)
+		msg.Metadata)
 	if err != nil {
 		return nil, err
 	}

modules/apps/transfer/keeper/msg_server_test.go

@@ -54,6 +54,7 @@ func (suite *KeeperTestSuite) TestMsgTransfer() {
 			path.EndpointA.ChannelID,
 			coin, suite.chainA.SenderAccount.GetAddress().String(), suite.chainB.SenderAccount.GetAddress().String(),
 			suite.chainB.GetTimeoutHeight(), 0, // only use timeout height
+			[]byte("custom metadata"),
 		)
 
 		tc.malleate()

modules/apps/transfer/keeper/relay.go

@@ -59,6 +59,7 @@ func (k Keeper) SendTransfer(
 	receiver string,
 	timeoutHeight clienttypes.Height,
 	timeoutTimestamp uint64,
+	metadata []byte,
 ) error {
 	_, err := k.sendTransfer(
 		ctx,
@@ -69,6 +70,7 @@ func (k Keeper) SendTransfer(
 		receiver,
 		timeoutHeight,
 		timeoutTimestamp,
+		metadata,
 	)
 	return err
 }
@@ -83,6 +85,7 @@ func (k Keeper) sendTransfer(
 	receiver string,
 	timeoutHeight clienttypes.Height,
 	timeoutTimestamp uint64,
+	metadata []byte,
 ) (uint64, error) {
 	if !k.GetSendEnabled(ctx) {
 		return 0, types.ErrSendDisabled
@@ -173,7 +176,7 @@ func (k Keeper) sendTransfer(
 	}
 
 	packetData := types.NewFungibleTokenPacketData(
-		fullDenomPath, token.Amount.String(), sender.String(), receiver,
+		fullDenomPath, token.Amount.String(), sender.String(), receiver, metadata,
 	)
 
 	packet := channeltypes.NewPacket(

modules/apps/transfer/keeper/relay_test.go

@@ -18,10 +18,11 @@ import (
 // chainA and coin that orignate on chainB
 func (suite *KeeperTestSuite) TestSendTransfer() {
 	var (
-		amount sdk.Coin
-		path   *ibctesting.Path
-		sender sdk.AccAddress
-		err    error
+		amount   sdk.Coin
+		path     *ibctesting.Path
+		sender   sdk.AccAddress
+		err      error
+		metadata []byte
 	)
 
 	testCases := []struct {
@@ -37,6 +38,14 @@ func (suite *KeeperTestSuite) TestSendTransfer() {
 				amount = sdk.NewCoin(sdk.DefaultBondDenom, sdk.NewInt(100))
 			}, true, true,
 		},
+		{
+			"successful transfer from source chain with metadata",
+			func() {
+				suite.coordinator.CreateTransferChannels(path)
+				amount = sdk.NewCoin(sdk.DefaultBondDenom, sdk.NewInt(100))
+				metadata = []byte("metadata")
+			}, true, true,
+		},
 		{
 			"successful transfer with coin from counterparty chain",
 			func() {
@@ -45,6 +54,15 @@ func (suite *KeeperTestSuite) TestSendTransfer() {
 				amount = types.GetTransferCoin(path.EndpointA.ChannelConfig.PortID, path.EndpointA.ChannelID, sdk.DefaultBondDenom, sdk.NewInt(100))
 			}, false, true,
 		},
+		{
+			"successful transfer with coin from counterparty chain with metadata",
+			func() {
+				// send coin from chainA back to chainB
+				suite.coordinator.CreateTransferChannels(path)
+				amount = types.GetTransferCoin(path.EndpointA.ChannelConfig.PortID, path.EndpointA.ChannelID, sdk.DefaultBondDenom, sdk.NewInt(100))
+				metadata = []byte("metadata")
+			}, false, true,
+		},
 		{
 			"source channel not found",
 			func() {
@@ -121,12 +139,12 @@ func (suite *KeeperTestSuite) TestSendTransfer() {
 			if !tc.sendFromSource {
 				// send coin from chainB to chainA
 				coinFromBToA := sdk.NewCoin(sdk.DefaultBondDenom, sdk.NewInt(100))
-				transferMsg := types.NewMsgTransfer(path.EndpointB.ChannelConfig.PortID, path.EndpointB.ChannelID, coinFromBToA, suite.chainB.SenderAccount.GetAddress().String(), suite.chainA.SenderAccount.GetAddress().String(), clienttypes.NewHeight(1, 110), 0)
+				transferMsg := types.NewMsgTransfer(path.EndpointB.ChannelConfig.PortID, path.EndpointB.ChannelID, coinFromBToA, suite.chainB.SenderAccount.GetAddress().String(), suite.chainA.SenderAccount.GetAddress().String(), clienttypes.NewHeight(1, 110), 0, nil)
 				_, err = suite.chainB.SendMsgs(transferMsg)
 				suite.Require().NoError(err) // message committed
 
 				// receive coin on chainA from chainB
-				fungibleTokenPacket := types.NewFungibleTokenPacketData(coinFromBToA.Denom, coinFromBToA.Amount.String(), suite.chainB.SenderAccount.GetAddress().String(), suite.chainA.SenderAccount.GetAddress().String())
+				fungibleTokenPacket := types.NewFungibleTokenPacketData(coinFromBToA.Denom, coinFromBToA.Amount.String(), suite.chainB.SenderAccount.GetAddress().String(), suite.chainA.SenderAccount.GetAddress().String(), nil)
 				packet := channeltypes.NewPacket(fungibleTokenPacket.GetBytes(), 1, path.EndpointB.ChannelConfig.PortID, path.EndpointB.ChannelID, path.EndpointA.ChannelConfig.PortID, path.EndpointA.ChannelID, clienttypes.NewHeight(1, 110), 0)
 
 				// get proof of packet commitment from chainB
@@ -143,6 +161,7 @@ func (suite *KeeperTestSuite) TestSendTransfer() {
 			err = suite.chainA.GetSimApp().TransferKeeper.SendTransfer(
 				suite.chainA.GetContext(), path.EndpointA.ChannelConfig.PortID, path.EndpointA.ChannelID, amount,
 				sender, suite.chainB.SenderAccount.GetAddress().String(), suite.chainB.GetTimeoutHeight(), 0,
+				metadata,
 			)
 
 			if tc.expPass {
@@ -163,6 +182,7 @@ func (suite *KeeperTestSuite) TestOnRecvPacket() {
 		trace    types.DenomTrace
 		amount   math.Int
 		receiver string
+		metadata []byte
 	)
 
 	testCases := []struct {
@@ -172,7 +192,13 @@ func (suite *KeeperTestSuite) TestOnRecvPacket() {
 		expPass      bool
 	}{
 		{"success receive on source chain", func() {}, true, true},
+		{"success receive on source chain with metadata", func() {
+			metadata = []byte("metadata")
+		}, true, true},
 		{"success receive with coin from another chain as source", func() {}, false, true},
+		{"success receive with coin from another chain as source with metadata", func() {
+			metadata = []byte("metadata")
+		}, false, true},
 		{"empty coin", func() {
 			trace = types.DenomTrace{}
 			amount = sdk.ZeroInt()
@@ -219,7 +245,7 @@ func (suite *KeeperTestSuite) TestOnRecvPacket() {
 			if tc.recvIsSource {
 				// send coin from chainB to chainA, receive them, acknowledge them, and send back to chainB
 				coinFromBToA := sdk.NewCoin(sdk.DefaultBondDenom, sdk.NewInt(100))
-				transferMsg := types.NewMsgTransfer(path.EndpointB.ChannelConfig.PortID, path.EndpointB.ChannelID, coinFromBToA, suite.chainB.SenderAccount.GetAddress().String(), suite.chainA.SenderAccount.GetAddress().String(), clienttypes.NewHeight(1, 110), 0)
+				transferMsg := types.NewMsgTransfer(path.EndpointB.ChannelConfig.PortID, path.EndpointB.ChannelID, coinFromBToA, suite.chainB.SenderAccount.GetAddress().String(), suite.chainA.SenderAccount.GetAddress().String(), clienttypes.NewHeight(1, 110), 0, metadata)
 				res, err := suite.chainB.SendMsgs(transferMsg)
 				suite.Require().NoError(err) // message committed
 
@@ -238,13 +264,13 @@ func (suite *KeeperTestSuite) TestOnRecvPacket() {
 			}
 
 			// send coin from chainA to chainB
-			transferMsg := types.NewMsgTransfer(path.EndpointA.ChannelConfig.PortID, path.EndpointA.ChannelID, sdk.NewCoin(trace.IBCDenom(), amount), suite.chainA.SenderAccount.GetAddress().String(), receiver, clienttypes.NewHeight(1, 110), 0)
+			transferMsg := types.NewMsgTransfer(path.EndpointA.ChannelConfig.PortID, path.EndpointA.ChannelID, sdk.NewCoin(trace.IBCDenom(), amount), suite.chainA.SenderAccount.GetAddress().String(), receiver, clienttypes.NewHeight(1, 110), 0, metadata)
 			_, err := suite.chainA.SendMsgs(transferMsg)
 			suite.Require().NoError(err) // message committed
 
 			tc.malleate()
 
-			data := types.NewFungibleTokenPacketData(trace.GetFullDenomPath(), amount.String(), suite.chainA.SenderAccount.GetAddress().String(), receiver)
+			data := types.NewFungibleTokenPacketData(trace.GetFullDenomPath(), amount.String(), suite.chainA.SenderAccount.GetAddress().String(), receiver, metadata)
 			packet := channeltypes.NewPacket(data.GetBytes(), seq, path.EndpointA.ChannelConfig.PortID, path.EndpointA.ChannelID, path.EndpointB.ChannelConfig.PortID, path.EndpointB.ChannelID, clienttypes.NewHeight(1, 100), 0)
 
 			err = suite.chainB.GetSimApp().TransferKeeper.OnRecvPacket(suite.chainB.GetContext(), packet, data)
@@ -317,7 +343,7 @@ func (suite *KeeperTestSuite) TestOnAcknowledgementPacket() {
 
 			tc.malleate()
 
-			data := types.NewFungibleTokenPacketData(trace.GetFullDenomPath(), amount.String(), suite.chainA.SenderAccount.GetAddress().String(), suite.chainB.SenderAccount.GetAddress().String())
+			data := types.NewFungibleTokenPacketData(trace.GetFullDenomPath(), amount.String(), suite.chainA.SenderAccount.GetAddress().String(), suite.chainB.SenderAccount.GetAddress().String(), nil)
 			packet := channeltypes.NewPacket(data.GetBytes(), 1, path.EndpointA.ChannelConfig.PortID, path.EndpointA.ChannelID, path.EndpointB.ChannelConfig.PortID, path.EndpointB.ChannelID, clienttypes.NewHeight(1, 100), 0)
 
 			preCoin := suite.chainA.GetSimApp().BankKeeper.GetBalance(suite.chainA.GetContext(), suite.chainA.SenderAccount.GetAddress(), trace.IBCDenom())
@@ -413,7 +439,7 @@ func (suite *KeeperTestSuite) TestOnTimeoutPacket() {
 
 			tc.malleate()
 
-			data := types.NewFungibleTokenPacketData(trace.GetFullDenomPath(), amount.String(), sender, suite.chainB.SenderAccount.GetAddress().String())
+			data := types.NewFungibleTokenPacketData(trace.GetFullDenomPath(), amount.String(), sender, suite.chainB.SenderAccount.GetAddress().String(), nil)
 			packet := channeltypes.NewPacket(data.GetBytes(), 1, path.EndpointA.ChannelConfig.PortID, path.EndpointA.ChannelID, path.EndpointB.ChannelConfig.PortID, path.EndpointB.ChannelID, clienttypes.NewHeight(1, 100), 0)
 
 			preCoin := suite.chainA.GetSimApp().BankKeeper.GetBalance(suite.chainA.GetContext(), suite.chainA.SenderAccount.GetAddress(), trace.IBCDenom())

modules/apps/transfer/transfer_test.go

@@ -54,7 +54,7 @@ func (suite *TransferTestSuite) TestHandleMsgTransfer() {
 	coinToSendToB := sdk.NewCoin(sdk.DefaultBondDenom, amount)
 
 	// send from chainA to chainB
-	msg := types.NewMsgTransfer(path.EndpointA.ChannelConfig.PortID, path.EndpointA.ChannelID, coinToSendToB, suite.chainA.SenderAccount.GetAddress().String(), suite.chainB.SenderAccount.GetAddress().String(), timeoutHeight, 0)
+	msg := types.NewMsgTransfer(path.EndpointA.ChannelConfig.PortID, path.EndpointA.ChannelID, coinToSendToB, suite.chainA.SenderAccount.GetAddress().String(), suite.chainB.SenderAccount.GetAddress().String(), timeoutHeight, 0, nil)
 	res, err := suite.chainA.SendMsgs(msg)
 	suite.Require().NoError(err) // message committed
 
@@ -80,7 +80,7 @@ func (suite *TransferTestSuite) TestHandleMsgTransfer() {
 	suite.coordinator.Setup(pathBtoC)
 
 	// send from chainB to chainC
-	msg = types.NewMsgTransfer(pathBtoC.EndpointA.ChannelConfig.PortID, pathBtoC.EndpointA.ChannelID, coinSentFromAToB, suite.chainB.SenderAccount.GetAddress().String(), suite.chainC.SenderAccount.GetAddress().String(), timeoutHeight, 0)
+	msg = types.NewMsgTransfer(pathBtoC.EndpointA.ChannelConfig.PortID, pathBtoC.EndpointA.ChannelID, coinSentFromAToB, suite.chainB.SenderAccount.GetAddress().String(), suite.chainC.SenderAccount.GetAddress().String(), timeoutHeight, 0, nil)
 	res, err = suite.chainB.SendMsgs(msg)
 	suite.Require().NoError(err) // message committed
 
@@ -104,7 +104,7 @@ func (suite *TransferTestSuite) TestHandleMsgTransfer() {
 	suite.Require().Zero(balance.Amount.Int64())
 
 	// send from chainC back to chainB
-	msg = types.NewMsgTransfer(pathBtoC.EndpointB.ChannelConfig.PortID, pathBtoC.EndpointB.ChannelID, coinSentFromBToC, suite.chainC.SenderAccount.GetAddress().String(), suite.chainB.SenderAccount.GetAddress().String(), timeoutHeight, 0)
+	msg = types.NewMsgTransfer(pathBtoC.EndpointB.ChannelConfig.PortID, pathBtoC.EndpointB.ChannelID, coinSentFromBToC, suite.chainC.SenderAccount.GetAddress().String(), suite.chainB.SenderAccount.GetAddress().String(), timeoutHeight, 0, nil)
 	res, err = suite.chainC.SendMsgs(msg)
 	suite.Require().NoError(err) // message committed
 

modules/apps/transfer/types/events.go

@@ -18,4 +18,5 @@ const (
 	AttributeKeyAck            = "acknowledgement"
 	AttributeKeyAckError       = "error"
 	AttributeKeyTraceHash      = "trace_hash"
+	AttributeKeyMetadata       = "metadata"
 )

modules/apps/transfer/types/msgs.go

@@ -22,6 +22,7 @@ func NewMsgTransfer(
 	sourcePort, sourceChannel string,
 	token sdk.Coin, sender, receiver string,
 	timeoutHeight clienttypes.Height, timeoutTimestamp uint64,
+	metadata []byte,
 ) *MsgTransfer {
 	return &MsgTransfer{
 		SourcePort:       sourcePort,
@@ -31,6 +32,7 @@ func NewMsgTransfer(
 		Receiver:         receiver,
 		TimeoutHeight:    timeoutHeight,
 		TimeoutTimestamp: timeoutTimestamp,
+		Metadata:         metadata,
 	}
 }