edns-udp-size docs not updated for Flag Day changes
In chapter 5 of the ARM, the documentation for the
edns-udp-size option says:
If the initial response times out, named will try again with plain DNS, and if that is successful, it will be taken as evidence that the server does not support EDNS. After enough failures using EDNS and successes using plain DNS, named will default to plain DNS for future communications with that server. (Periodically, named will send an EDNS query to see if the situation has improved.)
I believe this is wrong. That section of the documentation has been the same since at least 2014, but with the DNS Flag Day 2019 changes from #150 (closed)/!555 (merged), named's behavior should be different now.
I'm not sure what named's behavior is now, but the !555 (merged) documentation changes say that the "named will try again with plain DNS" part is no longer true, at least. (I think the size negotiation remains.)