Support dynamic version strings in ChanOpen handshake [ibc-go v2]

[adizere]

Crate

ibc-relayer

Summary

Add support in Hermes for dynamic channel version negotiation for use in channel open handshakes, with application to ICS-027.

Problem Definition

Whenever Hermes is building one of the first three messages of a channel's handshake (init, try, ack), it must also relay a version parameter which is an application-defined string. The relevant part of the specification is here. The ICA protocol (ics-027) uses the channel version to pass the interchain account between the host chain and the controller chain. Issue cosmos/ibc-go#378 describes accurately what Hermes is supposed to do, in particular:

a relayer will need to query the host chain for an updated version string prior to calling the OnChanOpenAck endpoint

Further details are provided in this comment: cosmos/ibc-go#136 (comment)

The actual implementation of the new query (which Hermes will need to rely on) is in this PR: cosmos/ibc-go#384

Proposal

The changes we need to do are localized here:

https://github.com/informalsystems/ibc-rs/blob/8d4d73bf6aa35a6f9111bf6cfbf08f23f2ffe7c6/relayer/src/chain.rs#L224-L233

There is also a note with respect to this problem at a call site in the relayer's channel object implementation.

https://github.com/informalsystems/ibc-rs/blob/8d4d73bf6aa35a6f9111bf6cfbf08f23f2ffe7c6/relayer/src/channel.rs#L655-L656

Acceptance Criteria

• Modified channel handshake implementation to rely on the new gRPC for supporting dynamic version
• Take note of forward and backwards compatibility
  • Take note that closing this issue will depend (e.g., for testing) on ibc-go v2: https://github.com/cosmos/ibc-go/blob/v2.0.0-beta1/CHANGELOG.md
  • Concrete branch to use for testing: Ibc v2 test cosmos/gaia#1021

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[andynog]

https://github.com/cosmos/ibc-go/blob/release/v2.0.x/docs/migrations/ibc-migration-v100.md#relayers