NAT, P2P AnnounceAddresses

[cryptovestor21]

My understanding is that there is no feature as of today to automatically announce listen addresses against WAN addresses, for example in a scenario where nodes are behind NAT with port forwarding for ingress.

In order for a NAT'd DA node's P2P services to be reachable over the internet, an operator needs to manually add addresses to AnnounceAddresses in config.toml. This assumes they have set up the prerequisite port forwarding on their firewalls.

Can you please confirm that in the case of achieving connectivity for ipv4 this is a matter of adding the following addresses to AnnounceAddresses ? Testing shows that this works but I would like to be certain that we are not broadcasting and making available something we should not expose, before making this change in production.

AnnounceAddresses = ["/ip4/[wanip]/udp/2121/quic-v1/webtransport",  "/ip4/[wanip]/udp/2121/quic-v1",  "/ip4/[wanip]/udp/2121/webrtc-direct", "/ip4/[wanip]/tcp/2121"]

It would be good to know if there are any plans to add features for less common requirements such as NAT in the future.

[Wondertan]

Hey @cryptovestor21. For a NATed node to announce its WAN address, the node should somehow learn about it. By default, the node can only know the addresses of the network interfaces accessible through kernel, which are only aware of LAN addresses. The AnnounceAddress config field feeds the information about the address as early as possible to the node, although manually. The automatic approach would require UPNP or STUN-like protocols to be enabled. Both of these are available with libp2p toolbox and its a matter of enabling them with good enough motivation.

[cryptovestor21]

Hey, thanks for the explainer, sounds as much as I had expected given experiences with libp2p elsewhere.

My remaining concern is broadcasting something I should not - the four components I suggested are just the ipv4 addresses define in ListenAddresses against all interfaces 0.0.0.0 so i am presuming that is safe - it certainly returns public when running celestia p2p nat-status

[Wondertan]

Listing out all the components allows you to specify which transports exactly you want to announce. It doesn't broadcast unnecessary information