12.2020 - High Level Goal - IBC Handlers

[ebuchman]

Summary

Implement IBC handlers and integrate in a rust-abci app. Goal is to improve testing via:

• language agnostic test vectors to test handlers in Go and Rust
• Rust IBC app that can connect to a Gaia testnet
• Rust IBC app that can be used for Rust Relayer integration testing (ie. relaying between two Rust IBC apps built on Tendermint Core)

Proposal

• IBC data structures
  • most (all?) should be handled by High Level Goal - IBC Relayer  #114 as they're already needed by relayer
• IBC handlers
  • ICS02/07 - Create and Update Client cosmos/ibc-rs#128 -- client (ICS02 and ICS07, though much of the ICS07 functionality should come from the tendermint-rs light client)
  • ICS03 - Connection handshake cosmos/ibc-rs#127 -- connection (ICS03)
  • Implement the channel message domain types cosmos/ibc-rs#105, Implement the channel message handlers cosmos/ibc-rs#104 channels and packets (ICS04 - this is the most complex/advanced of the bunch)
  • token transfer (ICS20)
• Minimal ABCI Framework to support IBC (may belong in tendermint-rs once rust-abci is merged in, Absorb rust-abci tendermint-rs#29)
  • transaction verification (copy SDK? get construction/signing for free then)
  • storage (ICS23) - need an abstraction, do we need to implement IAVL+ or can will Gaia understand something simpler as well?
  • port binding (ICS05)
  • host requirements (ICS24, ICS25, ICS26)
  • bank module

Questions:

• How important is the Loopback handler (ICS09) ?
• Can we minimize initial requirements from the ABCI framework, eg. ICS 05,23,24,25,26

[cwgoes]

Note that the SDK implementation already supports generalised Merkle proofs, so it shouldn't be hard to use a simpler (non-IAVL+) store if that would be easier for an initial Rust prototype. Ideally the Rust implementation can support these as well.

The loopback handler is not particularly important, and bears no relevance to cross-implementation testing.

[adizere]

Moved most of the relevant issues from here into #385. For the ABCI framework, some issues are work in progress (signing), some are almost done (host requirements), while others are deferred to a later relayer version (bank module).