Submitted by cmichel
Some ERC20 tokens like USDT require resetting the approval to 0 first before being able to reset it to another value. (See Line 201)
The LIibERC20.approve function does not do this - unlike OpenZeppelins safeApprove implementation.
The impact of this, is that repeated USDT cross-chain transfers to the same user on receiving chain = ETH mainnet can fail due to this line not resetting the approval to zero first:
Recommend that LiibERC20.approve should do two approve calls, one setting it to 0 first, then the real one.
Check OpenZeppelins safeApprove.
LayneHaber (Connext) confirmed and patched:
