In-protocol liquidity probing and channel jamming mitigation

However, a concern was raised about the possibility of malicious routing nodes succeeding in the probe and then failing the payment to collect the failed payment fee. In response, a proposal by ZmnSCPxj was mentioned which suggested reusing the mechanism of sending an onion and getting back an "error" reply, but only accepting a "everything is OK" result from the destination and a "sorry cannot forward" from any node along the path. This way, a malicious node cannot succeed the probe if it has to reach the destination, and a malicious forwarding node would have no incentive to cooperate with the destination to fail the actual payment later just to extract a tiny failure fee.