cosmos-sdk/docs/spec/ibc/mvp2.md

IBC Spec

This is a living document and should be edited as the IBC spec and implementation change

MVP2

IBC module will store its own router for handling custom incoming msgs. IBCPush are made for inter-module communication. IBCRegisterMsg adds a handler in the router of the module.

IBC Module

// User facing API

type IBCTransferPacket struct {
    DestAddr sdk.Address
    Coins    sdk.Coins
    SrcChain string
    DestChain string
}

// Implements sdk.Msg
type IBCTransferMsg struct {
    IBCTransferPacket
}

// Implements sdk.Msg
type IBCReceiveMsg struct {
    IBCTransferPacket
}

// Internal API

func NewHandler(dispatcher Dispatcher, ibcm IBCMapper) sdk.Handler

type IBCMapper struct {
    ingressKey sdk.StoreKey // Source Chain ID            => last income msg's sequence
    egressKey  sdk.StoreKey // (Dest chain ID, Msg index) => length / indexed msg
}

type IngressKey struct {
    SourceChain string
}

type EgressKey struct {
    DestChain   string
    Index       int64
}

// Used by other modules
func (ibcm IBCMapper) PushPacket(ctx sdk.Context, dest string, data PacketData)

egressKey stores the outgoing IBCTransfers as a list. Its getter takes an EgressKey and returns the length if egressKey.Index == -1, an element if egressKey.Index > 0.

ingressKey stores the last income IBCTransfer's sequence. Its getter takes an IngressKey.

Relayer

Packets

• Connect to 2 Tendermint RPC endpoints
• Query for IBC outgoing IBCOutMsg queue (can poll on a certain time interval, or check after each new block, etc)
• For any new IBCOutMsg, build IBCInMsg and post to destination chain

CLI

• Load relay process
• Execute IBCOutMsg