[cmeacham98]

This is literally the opposite of true. The OS-supplied resolver supports TCP DNS on all of the most popular desktop and mobile OSes and has for ages. I'd estimate a minimum of 90% of users have setups that support it, and I'm only hedging the 10% because I'm not sure how prevalent horribly misconfigured corporate firewalls are.

By not supporting TCP DNS you are the odd one out.

[toast0]

The OS supplied resolver may support it, but many networks block TCP DNS.

[tptacek]

Many networks also block AAAA DNS, because middleboxes are stupid. That doesn't mean it's OK for libc not to implement AAAA.