kad: FIND_NODE not conform to specs

[guillaumemichel]

kad: FIND_NODE not conform to specs

[achingbrain]

Sorry - I missed this. It copies the go-libp2p-kad-dht behaviour as that was what was understood to be correct at the time.

This issue has an analogue here: libp2p/js-libp2p#2450 - the fix is here: libp2p/js-libp2p#2499

[dennis-tra]

It would be silly, because the requester already know the peer it is sending the request to.

As mentioned above, I think there could be a valid reason why you would want the latest peer record

[mxinden]

I don't unfortunately @guillaumemichel.

[dariusc93]

This was discussed here and here. I think if the latter was discussed more that could provide more clarification not just to rust-libp2p but other implementations as well but in my opinion, I dont believe it really make much sense to be able to find one self when calling FIND_NODE. I havent tested it recently but i know in go-libp2p i was not able to do the same when I tried it so did something change in the go implementation for this?

[dennis-tra]

IMO it can make sense that the peer returns itself. The response could include additional multiaddresses that the requestor isn't aware of yet. For example, the peer record could include a multiaddress that allows a direct connection while the requestor and requestee are connected through a relay.

You could argue that this is already covered by the identify protocol though 🤷‍♂️ personally I don't find this implicit dependency on another protocol a super compelling argument to not do the suggested change.

[guillaumemichel]

Currently go-libp2p-kad-dht is returning only itself when its own key is requested through FIND_NODE, which isn't either conform to the libp2p kad specs.

The question isn't: should the node return itself to such queries. It would be silly, because the requester already know the peer it is sending the request to.

My main concern here is that nodes should return the closest nodes to the requested key (excluding themselves, and the requester). FIND_NODE should never return an empty response, unless the routing table of the node is empty.

So both rust-libp2p and go-libp2p-kad-dht should should return the list of their closest peers, when receiving a FIND_NODE request for their own id.

[guillaumemichel]

@mxinden do you know why the empty response was introduced in ef9cb05?

[guillaumemichel]

The spec says:

The libp2p Kademlia DHT offers the following types of operations:

• Peer routing
  • Finding the closest nodes to a given key via FIND_NODE.

3. Upon a response:
   1. If successful the response will contain the k closest nodes the peer knows to the key Key. Add them to the candidate list Pn, except for those that have already been queried.

So the response should contain k peers (including/excluding self). An empty response isn't conform to specs

[dhuseby]

@achingbrain did you check the js-libp2p behavior to see how it behaves?