DL102 Invalid host

400. The proxy cannot tell which hostname the request is for. It comes from hand-written requests, HTTP/1.0 clients and misconfigured proxies in front of devlanes.

• No Host header and no absolute URL.
• Two Host headers.
• In HTTP/2, Host disagrees with :authority. In HTTP/1.1, an absolute URL wins over Host, as RFC 9112 requires.
• The host contains user information (user@acme.localhost) or a port that is not a number.

Send one Host header that matches the URL. curl resolves *.localhost to loopback itself:

curl http://acme.localhost/
curl -H 'Host: acme.localhost' http://127.0.0.1/