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findnode(self) should return multiple peers #968

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Apr 3, 2024
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findnode(self) should return multiple peers #968

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40 changes: 18 additions & 22 deletions handlers.go
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Original file line number Diff line number Diff line change
Expand Up @@ -262,30 +262,26 @@ func (dht *IpfsDHT) handleFindPeer(ctx context.Context, from peer.ID, pmes *pb.M

// if looking for self... special case where we send it on CloserPeers.
targetPid := peer.ID(pmes.GetKey())
if targetPid == dht.self {
closest = []peer.ID{dht.self}
} else {
closest = dht.betterPeersToQuery(pmes, from, dht.bucketSize)

// Never tell a peer about itself.
if targetPid != from {
// Add the target peer to the set of closest peers if
// not already present in our routing table.
//
// Later, when we lookup known addresses for all peers
// in this set, we'll prune this peer if we don't
// _actually_ know where it is.
found := false
for _, p := range closest {
if targetPid == p {
found = true
break
}
}
if !found {
closest = append(closest, targetPid)
closest = dht.betterPeersToQuery(pmes, from, dht.bucketSize)
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dht.betterPeersToQuery errors if the list contains self.
https://github.com/libp2p/go-libp2p-kad-dht/blob/master/dht.go#L765-L769

		if clp == dht.self {
			logger.Error("BUG betterPeersToQuery: attempted to return self! this shouldn't happen...")
			return nil
		}
		// Dont send a peer back themselves
		if clp == from {
			continue
		}

It also handles the case that we don't inform the peer about itself.

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This snippet handles the output of routingTable.NearestPeers, which never contains itself.

The peer adds it own peer id, only if its own peer id is the target of the FIND_NODE request at

go-libp2p-kad-dht/handlers.go

Lines 263 to 285 in 7d6120f

// if looking for self... special case where we send it on CloserPeers.
targetPid := peer.ID(pmes.GetKey())
closest = dht.betterPeersToQuery(pmes, from, dht.bucketSize)
// Never tell a peer about itself.
if targetPid != from {
// Add the target peer to the set of closest peers if
// not already present in our routing table.
//
// Later, when we lookup known addresses for all peers
// in this set, we'll prune this peer if we don't
// _actually_ know where it is.
found := false
for _, p := range closest {
if targetPid == p {
found = true
break
}
}
if !found {
closest = append(closest, targetPid)
}
}


// Never tell a peer about itself.
if targetPid != from {
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// Add the target peer to the set of closest peers if
// not already present in our routing table.
//
// Later, when we lookup known addresses for all peers
// in this set, we'll prune this peer if we don't
// _actually_ know where it is.
found := false
for _, p := range closest {
if targetPid == p {
found = true
break
}
}
if !found {
closest = append(closest, targetPid)
}
Comment on lines +282 to +284
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Why do we do this? If the peerID isn't found, should we return it in findPeer?

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dht.betterPeersToQuery never includes itself (nor from) in the results.

Currently if A sends FIND_NODE(B) to B, B will reply [B], and we now want it to return [B, C, D, ...]. In this case targetPid is our own peer id, it wasn't returned by dht.betterPeersToQuery, so we need to add it at this step.

We will be able to get rid of this when the response to FIND_NODE(self) will be not include self.

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But if the target node doesnt exist we will include it in the output, right?

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Peers without addresses are excluded from the response

go-libp2p-kad-dht/handlers.go

Lines 292 to 301 in 7d6120f

closestinfos := pstore.PeerInfos(dht.peerstore, closest)
// possibly an over-allocation but this array is temporary anyways.
withAddresses := make([]peer.AddrInfo, 0, len(closestinfos))
for _, pi := range closestinfos {
if len(pi.Addrs) > 0 {
withAddresses = append(withAddresses, pi)
}
}
resp.CloserPeers = pb.PeerInfosToPBPeers(dht.host.Network(), withAddresses)

}

if closest == nil {
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