ibc-go v.7.5.0 (and v7.6.0) breaks ICS27 backwards compatibility by default

[AmitPr]

Summary of Bug

7.5.0 introduces channel ordering options in the interchain accounts controller module. Older versions of ibc-go will fail to create the ICA channel if the ordering is not ORDER_ORDERED. However, the default ordering in NewMsgRegisterInterchainAccount is ORDER_UNORDERED, meaning that existing code that has been upgraded to ibc-go >=7.5.0 will no longer be compatible with older chains.

Relevant code:

ibc-go/modules/apps/27-interchain-accounts/controller/types/msgs.go

Lines 34 to 41 in b605529

	func NewMsgRegisterInterchainAccount(connectionID, owner, version string) *MsgRegisterInterchainAccount {
	return &MsgRegisterInterchainAccount{
	ConnectionId: connectionID,
	Owner: owner,
	Version: version,
	Ordering: channeltypes.UNORDERED,
	}
	}

Expected Behaviour

Channels are ORDER_ORDERED by default, to preserve compatibility with older ibc-go versions

Version

Observed on ibc-go 7.6.0 (Kujira)

Steps to Reproduce

N/A

[AmitPr]

Note: I haven't taken a look at ibc-go v8 and beyond, as we are not yet using it on Kujira.

[crodriguezvega]

Hi @AmitPr. This change was documented in the release notes of v7.5.0 and in the documentation (here and here). You can keep the previous behaviour by setting the ordering to UNORDERED in the MsgRegisterInterchainAccount, or if you are using the legacy API, you can also use the RegisterInterchainAccountWithOrdering function to explicitly set the ordering to UNORDERED. Does this help?

[AmitPr]

@crodriguezvega the issue is that the default method for creating MsgRegisterInterchainAccount creates an UNORDERED channel, which is not backwards compatible, since previous versions of ibc-go are only compatible with ORDERED.

A module we have creates ICAs, and this default behavior silently broke the functionality and backwards compatibility of this module because of the change in default behavior. I will also note that this breakage was implemented in a minor semver upgrade.

[crodriguezvega]

Hi @AmitPr. Sorry for the late reply. We discussed this internally and we agree that we should probably not have introduced this change in a minor release, but the reason why we did it is because reopening ordered channels that close due to timeouts was one of the biggest complaints about ICA, so we decided to address it as soon as possible. We realise that this change in the default behaviour might be a bit surprising for existing users of ICA, but using unordered channels as the default for new ICA channels provides a better experience. We take for the future the learning point that we shouldn't make behavioural changes in minor releases, but we will not make a new minor release now to change back the ordering, since it would potentially make things even more confusing for our users.

I will close the issue now, but thanks for raising this problem. Feel free still to leave a comment if you have any more thoughts.