curl dns 2026, part III, async

In part I and part II I talked about the changes to DNS resolution in curl and why we do them. In this post I cover the difference and changes in synchronous vs asynchronous resolution. Which matter for Happy Eyeballs v3 (HEv3) and Encrypted Client Hellos (ECH). Sync/Async, Old and New Out of all the DNS options I described in part II, the most compatible and most deployed one is getaddrinfo(). Sync, no threads or c-ares