DNSAddr does not respect transport-specific DNS resolution

[aschmahmann]

Problem

Dialing a DNSAddr multiaddr that somewhere down the recursion chain forwards to an address type that handles DNS specially (e.g. WSS) does not work because the host over-resolves the address.

Example:

• Dial /dnsaddr/bootstrap.libp2p.io/p2p/QmbLHAnMoJPWSCR5Zhtx6BHJX9KiKNN6tpvbUcqanj75Nb (but only have WSS as a supported transport)
• This will resolve to /dns4/am6.bootstrap.libp2p.io/tcp/443/wss/p2p/QmbLHAnMoJPWSCR5Zhtx6BHJX9KiKNN6tpvbUcqanj75Nb
• Which will resolve to /ip4/147.75.87.27/tcp/443/wss/p2p/QmbLHAnMoJPWSCR5Zhtx6BHJX9KiKNN6tpvbUcqanj75Nb
• Which will fail due to an invalid TLS certificate

However: dialing /dns4/am6.bootstrap.libp2p.io/tcp/443/wss/p2p/QmbLHAnMoJPWSCR5Zhtx6BHJX9KiKNN6tpvbUcqanj75Nb directly works fine.

Potential Fix

This is effectively a continuation of #1597, but accounting for DNSAddr recursion. I suspect the fix that will help here is to keep doing the type of check we do in

go-libp2p/p2p/net/swarm/swarm_dial.go

Lines 305 to 318 in 0509445

	for _, a := range peerAddrs {
	tpt := s.TransportForDialing(a)
	resolver, ok := tpt.(transport.Resolver)
	if ok {
	resolvedAddrs, err := resolver.Resolve(ctx, a)
	if err != nil {
	log.Warnf("Failed to resolve multiaddr %s by transport %v: %v", a, tpt, err)
	continue
	}
	peerAddrsAfterTransportResolved = append(peerAddrsAfterTransportResolved, resolvedAddrs...)
	} else {
	peerAddrsAfterTransportResolved = append(peerAddrsAfterTransportResolved, a)
	}
	}

not just at the top layer of address resolution, but also in the recursive DNSAddr resolution function

go-libp2p/p2p/net/swarm/swarm_dial.go

Line 344 in 0509445

func (s *Swarm) resolveAddrs(ctx context.Context, pi peer.AddrInfo) ([]ma.Multiaddr, error) {

cc @dennis-tra (thanks for finding out something was going wrong here 😄)

[marten-seemann]

Very interesting. Looks like the transport-specific name resolution is bypassed altogehter, since looking at /dnsaddr/..., we don't know it will resolve to a wss address. We'll need to do that check recursively.

Fix incoming.

[marten-seemann]

Getting the fix merged took us a while, but it's merged now, and will be included in the v0.32 release later this week.