HTTP/3 with IPv6

[anuraaga]

When trying out HTTP/3 support, I noticed on a typical macOS laptop, that it seems IPv6 is used even when configuring the client to IPv4. Following the advice in #584, to force IPv4

builder = builder
      .http3_prior_knowledge()
      .local_address(IpAddr::from([0, 0, 0, 0]));

It seems to still try IPv6 and fail hard. Presumably it should be using IPv4 from the beginning.

E       RuntimeError: Request failed: error sending request for url (https://localhost:8081/echo): error sending request: invalid remote address: [::1]:8081

Besides that, if not forcing IPv4 like that, when issuing a request to localhost, it will first try IPv6 before IPv4. This should generally be fine but AFAICT, on macOS IPv6 can't be used with quic - when trying with curl --http3, I get the below output which confirms it tries with IPv6 and quickly falls back to IPv4. This is not noticable. However, when using reqwest, it seems to finally succeed after 30s - I'm guessing there is a 30s timeout on trying to connect with IPv6 before falling back to IPv4 and succeeding. If I change the URL to 127.0.0.1, no issues - I guess the IPv6 -> v4 fallback has to be configured somehow to fail faster.

* Host localhost:8081 was resolved.
* IPv6: ::1
* IPv4: 127.0.0.1
*   Trying [::1]:8081...
* SSL Trust: peer verification disabled
* QUIC: connection to ::1 port 8081 refused
* QUIC connect to ::1 port 8081 failed: Could not connect to server
*   Trying 127.0.0.1:8081...

[anuraaga]

Noticed one somewhat related but much less impactful issue, it seems http:// URLs are used without checking the scheme

error sending request for url (http://127.0.0.1:49304/echo): error sending request: timed out

This is because the URL was pointing to the plaintext port - if I change to http:// with the quic port, the request actually succeeds but it should probably fail hard and fast instead as a validation error.

[seanmonstar]

Ah, I think local address needs to be piped through in the internals.