I'm dealing with kind of a weird situation that's uncovered a small corner case in c-ares. An SRV query from an upstream DNS server is replying with Server Failed. I'm planning on getting to the bottom of that later, but for now, I'm considering it expected behavior. When I instead point c-ares at my linksys router, which is running dnsmasq, the response I get back changes Format Error. I'm not sure if this is a bug in dnsmasq, or if there is something else weird/unique to my setup.
Anyways, when I get the Format Error response, ares simply times out waiting for a response rather than detecting the error and invoking the callback with status = ARES_EFORMERR. Looking into it, the crux of the problem is in process_answer, where we require that both the query id's and the questions match, so as to handle the case of query ids wrapping with sufficient oustanding requests. In the case of format error, however, we get no questions in the response, and so we never find the match. I'm not positive what the correct fix is in this case (or if any action is necessary). Does it seem reasonable to match the response in the event that it's a format error and there's only a single outstanding query with the given id? I'm mostly just trying to avoid an annoying timeout that could otherwise be avoided. Thanks, --Jeremy
