Introduce a check for replayer's can withdraw balance in MessageDispatch trait

[hackfisher]

Another problem here is that, if the relayer have no enough funds for paying to the dispatch origin, and we ignore it here, this message will probably be fail as a result.

But it does not make sense, because the message sender paid enough fees in source chain, the message is unluckily failed just because some relayer's fault.

Solution:

We might need to introduce another check before dispatch, to make sure this relayer have enough funds for this pre_dispatch, otherwise, an invalid ReceivalResult should be returned before dispatch.

https://github.com/darwinia-network/darwinia-messages-substrate/blob/main/modules/messages/src/lib.rs#L461-L471

https://github.com/darwinia-network/darwinia-messages-substrate/blob/main/modules/messages/src/inbound_lane.rs#L134-L142

I'll create an issue in repo darwinia-messages-substrate for fixing before continue.

And here, we should remove if condition, and return Err if transfer failed.

Originally posted by @hackfisher in darwinia-network/darwinia-common#1267 (comment)

[hackfisher]

But one more thing need to note here is that, one single message should not block latter messages.

minimum_required_balance(relayer_on_target_chain) -> Balances { min(MAX_REQUIRED_RELAYER_BALNCE, gas_price * gas_limit / 10 ** 9) }

So the check here for relayer's balance should be

relayer's balance > minimum_required_balance(relayer)

If the gas_price * gas_limit are set too large by message sender, larger than MAX_REQUIRED_RELAYER_BALANCE, then it is not the relayer's fault if this message is failed in validation/pre-dispatch.

[boundless-forest]

#137 Close this.