Announce multiple transports

[daviddias]

When discovery was designed, it was assumed that an IPFS node would be announcing only one transport at a time and so, the mDNS query responses are just announcing one of the multiaddr. We need to announce all of them :) Specially cause even one transport can have several multiaddr:

https://github.com/diasdavid/node-libp2p-mdns-discovery/blob/master/src/index.js#L125-L190

[daviddias]

@lgierth @whyrusleeping thoughts here?

[richardschneider]

Responses are announcing all TCP address, which is what mdns allows.

@diasdavid Can we close this?

[daviddias]

@richardschneider mdns doesn't let us announce transports such as WebSockets?

[richardschneider]

It's because mdns uses DNS records and only ip4/ip6 is supported by A and AAAA records.

However, we are free to define what's in the TXT record. Currently we just add the public ID. However, we can use a key-value, which is recommended. Something like

id=Qm...
ma=/..../ws/ipfs/Qm...
ma=/ip4/127.0.1/tcp/4001/ipfs/Qm

[ghost]

Ideally put dnsaddrs in there -- dnsaddr=/ip4/...

https://github.com/multiformats/go-multiaddr-dns

[richardschneider]

Yes, we can do the above.

But remember MDNS is used to discover an IPFS daemon over UPD. If its discovered then we should be able to use an IPv4/IPv6 TCP port to make a connection.

Also, since MDNS uses UPD, the response payload should be as small as possible.

KISS

[richardschneider]

I must admit, I like the idea of changing the TXT record to contain key pairs. Even if we just change it for id=Qm.... This allows future enhancements to make non-breaking additions,

[whyrusleeping]

The keypairs idea is nice.