How can i implement re-entrancy in ink! smart contracts?

Question

I am trying to solve the following problem statement:- Contract A(func1) -> Contract A(func2) -> Contract B(funcB)

so, func1 will call func2 and then func2 will invoke multiple calls on different B contracts as per the payload. If any contract B call will revert, I need to revert all previous execution happened on contract B'. But at the same time some acknowledgement needs to be updated on Contract A.

So, Just like in solidity I am reverting from func2 and receiving that success flag in func1 and then performing the business logic. So, How can i implement same func1 to func2 implementation in ink smart contracts?

Answer 1

pallet-contract has a build in re-entrancy detection and re-entrancy is prevented by default. Indeed, you can allow for re-entrancy by setting the correct CallFlags, see:

https://paritytech.github.io/ink/ink_env/struct.CallFlags.html

I'd advise you to check how cross contract calls are build in the upgradable contracts example:

https://github.com/paritytech/ink/blob/master/examples/upgradeable-contracts/forward-calls/lib.rs#L72

Just that you need to set .allow_reentry(true) flag in addition when building the cross-contract call.

Answer 2

You can use call_builder to allow reentrancy