When Jool truncates ICMP error messages, it forgets to update the ICMP checksum.
In practice, this shouldn't be a problem because the original packet would have to have been translated by Jool with no problems, and generating an error message bigger than the packet that caused it makes no sense. Therefore, Jool should never have to slice ICMP errors in the first place.
Still, it better be prepared against weird implementations out there.
Issue #108. Jool was actually forgetting to update Payload Length; Ch…
…ecksum was correct.
Still, I also refactored a lot of checksumming code, to stop sparse's whining.
Merging version 3.2.1 into master, hereby makingthe changes official.
Version 3.2.1 is 3.2.0 with issues #57, #106, #108 and #109 fixed.
Issue #107 has been marked as duplicate and postponed to 3.3.0.
rting with '#' will be ignored, and an empty message aborts