Did the musl people never get around to implementing EDNS0? There's lots of talk here about not implementing DNS/TCP, but the musl people could have ameliorated that, and side-stepped the years of complaints to an extent, by implementing EDNS0 and allowing up to 64KiB datagrams.
Yes, some (I hope more rare now than when I wrote the FGA on it almost 20 years ago) firewalls cannot handle large DNS/UDP datagrams, but this code isn't for traffic that crosses firewalls. It's for traffic that goes only as far as the local resolving proxy, or at least goes somewhere "nearby" like 9.9.9.9. EDNS0 firewall worries are a lot less here.
And EDNS0, at least for the bit that enables >512 byte datagram sizes, is a lot less complex to implement than full DNS/TCP fallback. It's just proper buffer size handling and an extra resource record set.
Yes, some (I hope more rare now than when I wrote the FGA on it almost 20 years ago) firewalls cannot handle large DNS/UDP datagrams, but this code isn't for traffic that crosses firewalls. It's for traffic that goes only as far as the local resolving proxy, or at least goes somewhere "nearby" like 9.9.9.9. EDNS0 firewall worries are a lot less here.
And EDNS0, at least for the bit that enables >512 byte datagram sizes, is a lot less complex to implement than full DNS/TCP fallback. It's just proper buffer size handling and an extra resource record set.