Add SendPacket rpc and OnSendPacket callback

[colin-axner]

Summary

With #6941, we will add a SendPacket rpc which can be called by users/actors in the same fashion that relayers invoke other ibc messages. This will result in a OnSendPacket callback which will replace the ics4wrapper interface function. This will allow middleware applications to provide their own packet data.

Problem Definition

See #6941 and #7008 for reasoning

Proposal

Both #6941 and #6985 require this, so I am opening an issue to agree on the api.

Currently we have the following:

service Msg {
  ...
  // SendPacket defines a rpc handler method for MsgSendPacket.
  rpc SendPacket(MsgSendPacket) returns (MsgSendPacketResponse);
  ...
}

// MsgSendPacket sends an outgoing IBC packet
message MsgSendPacket {
  option (cosmos.msg.v1.signer) = "signer";

  option (gogoproto.goproto_getters) = false;

  string                    port_id           = 1;
  string                    channel_id        = 2;
  ibc.core.client.v1.Height timeout_height    = 3 [(gogoproto.nullable) = false];
  uint64                    timeout_timestamp = 4;
  bytes                     data              = 5;
  string                    signer            = 6;
}

// MsgSendPacketReponse defines the Msg/SendPacket response type.
message MsgSendPacketResponse {
  option (gogoproto.goproto_getters) = false;

  uint64 sequence = 1;
}

But given that Eureka is breaking the correlation between src_channel, src_port <> dest_channel, dest_port, all the packet information (except the sequence) should be provided.

Thus we can start with MsgSendPacket:

// MsgSendPacket sends an outgoing IBC packet
message MsgSendPacket {
  option (cosmos.msg.v1.signer) = "signer";

  option (gogoproto.goproto_getters) = false;

  string                    source_channel    = 1;
  string                    source_port       = 2;
  string                    dest_channel      = 3;
  string                    dest_port         = 4;
  ibc.core.client.v1.Height timeout_height    = 5;
  uint64                    timeout_timestamp = 6;
  bytes                     data              = 7;
  string                    signer            = 8;
}

The decision of #7008 will also decide the type for data.

In addition we will need to add a OnSendPacket callback. We have started with:

type IBCModule interface {
...
OnSendPacket(
		ctx sdk.Context,
		portID string,
		channelID string,
		sequence uint64,
		timeoutHeight clienttypes.Height,
		timeoutTimestamp uint64,
		data []byte,
		signer sdk.AccAddress,
	) error
...
}

I believe we could simplify this to:

type IBCModule interface {
...
OnSendPacket(
		ctx sdk.Context,
		packetID types.PacketID,
		data []byte,
		signer sdk.AccAddress,
	) error
...
}

This should likely mirror the api decided in #7008

---

Now I am going off the deep end a little and hypothesizing what the MsgSendPacketV2 could look like after #7008 and #6985 adoption and no concern for backwards compatibility 😄

// MsgSendPacket sends an outgoing IBC packet
message MsgSendPacketV2 {
  option (cosmos.msg.v1.signer) = "signer";

  option (gogoproto.goproto_getters) = false;

  string                    source_client     = 1; // GetCounterparty would fill in dest_client in packet
  repeated PacketData       data              = 2; // port routing information included in packet data
  string                    timeout           = 3;
  string                    signer            = 4;
}

---

For Admin Use

• Not duplicate issue
• Appropriate labels applied
• Appropriate contributors tagged/assigned