`/dnsaddr` can not be properly used with secure WebSocket transport

Description

Currently there is no way to properly pass /dnsaddr to WSS transport and work as expected:

1. If you wrap libp2p::websocket::WsConfig with libp2p::dns::Transport then you break secure WebSocket because DNS transport will resolve /dns4 to /ip4.
2. If you wrap libp2p::dns::Transport with libp2p::websocket::WsConfig then you break /dnsaddr because it will never fetch the multiaddresses from DNS.

Currently 2 is the recommended way (link).

Motivation

I want to be able to use /dnsaddr with secure WebSocket.

Requirements

I want to be able to wrap libp2p::websocket::WsConfig with libp2p::dns::Transport which will resolve only /dnsaddr before it passing the multiaddr to WebSocket transport.

For example:

let inner_tcp_transport =
    dns::tokio::Transport::system(tcp::tokio::Transport::new(tcp::Config::default()))
        .unwrap();

let wss_transport = websocket::WsConfig::new(inner_tcp_transport);

let mut dns_opts = dns::ResolverOpts::default();
dns_opts.resolve_dnsaddr_only = true;

let transport =
    dns::tokio::Transport::custom(wss_transport, dns::ResolverConfig::default(), dns_opts);

In case of /dnsaddr the above transport should have the following flow:

1. User dials to /dnsaddr/da-bridge-1.celestia-arabica-11.com/p2p/12D3KooWGqwzdEqM54Dce6LXzfFr97Bnhvm6rN7KM7MFwdomfm4S
2. DNS transport resolves multiaddr to /dns/da-bridge-1.celestia-arabica-11.com/tcp/2122/tls/ws/p2p/12D3KooWGqwzdEqM54Dce6LXzfFr97Bnhvm6rN7KM7MFwdomfm4S
3. DNS transport passes the /dns multiaddr to WebSocket transport.
4. WebSocket transport initializes TLS based on /dns multiaddr and passes multiaddr to TCP transport.
5. TCP transport resolves /dns multiaddr to /ip4 multiaddr and establishes the connection.

In case of /dns the above transport should have the following flow:

1. User dials to /dns/da-bridge-1.celestia-arabica-11.com/tcp/2122/tls/ws/p2p/12D3KooWGqwzdEqM54Dce6LXzfFr97Bnhvm6rN7KM7MFwdomfm4S
2. DNS transport passes the /dns multiaddr to WebSocket transport.
3. WebSocket transport initializes TLS based on /dns multiaddr and passes multiaddr to TCP transport.
4. TCP transport resolves /dns multiaddr to /ip4 multiaddr and establishes the connection.

Open questions

It would be hard to implement this kind of transport combination in SwarmBuilder.

Are you planning to do it yourself in a pull request ?

Maybe

Start with transports/websocket/src/lib.rs, especially the documented transport wrapping order, then inspect the DNS and WebSocket transport entry points. Confirm the composition preserves /dnsaddr and /dns for secure WebSocket while leaving TCP resolution intact; done means both example flows work.