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 Packet struct {
    Data      Payload
    SrcChain  string
    DestChain string
}

type Payload interface {
    Type() string
    ValidateBasic() sdk.Error
}

type TransferPayload struct {
    SrcAddr  sdk.Address
    DestAddr sdk.Address
    Coins    sdk.Coins
}

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

// Implements sdk.Msg
type IBCReceiveMsg struct {
    Packet
    Relayer  sdk.Address
    Sequence int64
}

// Internal API

type rule struct {
    r string
    f func(sdk.Context, IBCPacket) sdk.Result
}

type Dispatcher struct {
    rules []rule
}

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

type IBCMapper struct {
    ibcKey sdk.StoreKey // IngressKey / EgressKey             => Value
                        // Ingress: Source Chain ID           => last income msg's sequence
                        // Egress: (Dest chain ID, Msg index) => length / indexed msg
}

type IngressKey struct {
    SrcChain string
}

type EgressKey struct {
    DestChain   string
    Index       int64
}

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

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