Introduction

Reference

Technical reference for the GMP module

The GMP (General Message Passing) module is an IBC middleware that processes messages embedded in IBC transfer packet memo fields.

Message Format

GMP messages are embedded in IBC transfer memo fields as JSON:

{
  "source_chain": "string",
  "source_address": "string", 
  "payload": "base64-encoded-bytes",
  "type": "integer"
}

Field	Type	Required	Description
`source_chain`	string	Yes	Originating blockchain identifier (informational)
`source_address`	string	Yes	Original sender address (informational)
`payload`	string	Yes	Base64-encoded message payload (cannot be empty)
`type`	integer	Yes	Message type: 1 (GeneralMessage) or 2 (GeneralMessageWithToken)

Standard message passing without specific token coordination.

Processing: Payload replaces memo, transfer proceeds normally.

Message passing that coordinates with token transfers.

Processing: Payload replaces memo, indicates atomic message-token processing.

Invalid message type.

Processing: Returns error acknowledgment, packet fails.

Extract packet data from IBC transfer packet
Parse GMP message from memo field (if valid JSON with non-empty payload)
Process by type:
- Types 1 & 2: Replace memo with payload, forward to transfer module
- Other types: Return error acknowledgment
Pass through if not a valid GMP message

Invalid packet data: "cannot unmarshal ICS-20 transfer packet data"
Unrecognized message type: "unrecognized message type: X"
Packet remarshaling error: "cannot marshal ICS-20 post-processed transfer packet data"

All channel lifecycle methods pass through to underlying transfer module without modification.

Middleware: Sits between IBC core and transfer module
Memo Processing: Extracts and processes messages from transfer memos
Pass-through: Non-GMP transfers work normally
Error Recovery: Invalid GMP messages return error acknowledgments
Payload Replacement: GMP payload becomes the new memo for downstream processing