Resolv::DNS::Message.decode hangs after detecting truncation in UDP messages
ruby-core:32407 introduced support for a TCP requestor in fetch_resource if Resolv::DNS::Message.decode returned RCode::NoError and a reply tc of 1.
Unfortunately Resolv::DNS::Message.decode proceeds to attempt to unpack all answers based upon the answer count from the message regardless of truncation which causes exception behaviour which is then silently retried as this is seen as the response to the request never being seen (see begin, ensure).
To avoid this issue I add a return to Message.decode once the truncation is detected.
To patch this in a portable fashion I use the attached monkey patch which causes the truncation to propagate correctly back to fetch_resource and allows it to proceed correctly with the TCP based query.