Unexpected behaviour when a circuit relay server is also relayed

[marcus-pousette]

• Version:
  0.44.0

• Subsystem:
  Circuit Relay

Severity:

Medium

Description:

I have three nodes running locally (A,B,C) each as a circuit relay server and with circuit transport where discoverRelays: 1

First A is dials and connects B.

Both A and B will obtain an relayed address in .getMultiaddrs() (expected)

Then, when B directly dials C address

Unexpectedly (?), I am receiving "onConnect" events on node A from C after this when observering changes

this.topology = createTopology({
	onConnect: ...
});

The incoming connection event on A is as follows.

remotePeer: 12D3KooWDv7TfQ5Ct8jfQ98Vcs3mNSJYXABnKJvHPe4M1ZiGmqoC   (Node C)
remoteAddr: /ip4/127.0.0.1/tcp/61655

Then, additionally, C recieves an incoming connection from A

remotePeer: 12D3KooWR9JDmVK72ZZNEARjArap8SnFyV2v5Exq1jzANSKdDyrr  (Node  A)
remoteAddr: /ip4/127.0.0.1/tcp/61623/ws/p2p/12D3KooWR9JDmVK72ZZNEARjArap8SnFyV2v5Exq1jzANSKdDyrr

A

"/ip4/127.0.0.1/tcp/61623/ws/p2p/12D3KooWR9JDmVK72ZZNEARjArap8SnFyV2v5Exq1jzANSKdDyrr"
"/ip4/127.0.0.1/tcp/61622/ws/p2p/12D3KooWHw7m2xHFQjJJH3ozx59Z6AWT7yWyMHgfj1x3fELa8Baz/p2p-circuit/p2p/12D3KooWR9JDmVK72ZZNEARjArap8SnFyV2v5Exq1jzANSKdDyrr"```

B

"/ip4/127.0.0.1/tcp/61622/ws/p2p/12D3KooWHw7m2xHFQjJJH3ozx59Z6AWT7yWyMHgfj1x3fELa8Baz"
"/ip4/127.0.0.1/tcp/61623/ws/p2p/12D3KooWR9JDmVK72ZZNEARjArap8SnFyV2v5Exq1jzANSKdDyrr/p2p-circuit/p2p/12D3KooWHw7m2xHFQjJJH3ozx59Z6AWT7yWyMHgfj1x3fELa8Baz"

C

"/ip4/127.0.0.1/tcp/61625/ws/p2p/12D3KooWDv7TfQ5Ct8jfQ98Vcs3mNSJYXABnKJvHPe4M1ZiGmqoC"
"/ip4/127.0.0.1/tcp/61622/ws/p2p/12D3KooWHw7m2xHFQjJJH3ozx59Z6AWT7yWyMHgfj1x3fELa8Baz/p2p-circuit/p2p/12D3KooWDv7TfQ5Ct8jfQ98Vcs3mNSJYXABnKJvHPe4M1ZiGmqoC"

I am not expecting this, and wonder what part of the configuration is wrong?
It seems like if you are dialing a node, are you automatically also dial all relayed connections that starts with the same address?
In this case, if C dials B (/ip4/127.0.0.1/tcp/61622/ws/p2p/12D3KooWHw7m2xHFQjJJH3ozx59Z6AWT7yWyMHgfj1x3fELa8Baz)

It seems like both

/ip4/127.0.0.1/tcp/61622/ws/p2p/12D3KooWHw7m2xHFQjJJH3ozx59Z6AWT7yWyMHgfj1x3fELa8Baz

and

/ip4/127.0.0.1/tcp/61622/ws/p2p/12D3KooWHw7m2xHFQjJJH3ozx59Z6AWT7yWyMHgfj1x3fELa8Baz/p2p-circuit/p2p/12D3KooWR9JDmVK72ZZNEARjArap8SnFyV2v5Exq1jzANSKdDyrr

would receive connection events?

[marcus-pousette]

Doing some digging, I start to understand a little more about this:

On reservation, the server takes all its addresses and forwards them to the node that wants to reserve.

js-libp2p/src/circuit-relay/server/index.ts

Line 285 in 3115786

for (const relayAddr of this.addressManager.getAddresses()) {

According to the specification, the addrs field contains all the public relay addrs. For my case, since the server node is also a client reserved in another server, it will the "addrs" field would look something like

"/ip4/127.0.0.1/tcp/61625/ws/p2p/12D3KooWDv7TfQ5Ct8jfQ98Vcs3mNSJYXABnKJvHPe4M1ZiGmqoC"
"/ip4/127.0.0.1/tcp/61622/ws/p2p/12D3KooWHw7m2xHFQjJJH3ozx59Z6AWT7yWyMHgfj1x3fELa8Baz/p2p-circuit/p2p/12D3KooWDv7TfQ5Ct8jfQ98Vcs3mNSJYXABnKJvHPe4M1ZiGmqoC"

Then the "client" node takes all these addresses and starts to listen on them

js-libp2p/src/circuit-relay/transport/reservation-store.ts

Line 192 in 3115786

await this.transportManager.listen(

Which leads to an connection to be opened to every address that the server sent.

js-libp2p/src/circuit-relay/transport/listener.ts

Line 46 in 3115786

const relayConn = await this.connectionManager.openConnection(ma)

This means, that if B and C connects, C will reserve a slot in B, and obtain all addresses of B in the process. One of these addresses is the relayed address through A, hence C will also connect to A.

Putting a breakpoint at

js-libp2p/src/circuit-relay/transport/reservation-store.ts

Line 192 in 3115786

await this.transportManager.listen(

I see the addresses that are beeing sent to this.transportManager.listen

Is

'/ip4/127.0.0.1/tcp/60025/ws/p2p/12D3KooWQrMumZzLpF6fgmt8vdaCf7dCqKVXuFsr5jrjH5dzRpbX/p2p-circuit'
'/ip4/127.0.0.1/tcp/60024/ws/p2p/12D3KooWBj1WJNmLDwEG7Y6cL3xua367ZsXc5zCuiw3BsRcve6j8/p2p-circuit/p2p/12D3KooWQrMumZzLpF6fgmt8vdaCf7dCqKVXuFsr5jrjH5dzRpbX/p2p-circuit'

The second one looks not quite right (?). I assume here that the issue is that we should not return relayed addresses for the RESERVE response from the relay server.

A fix, perhaps server side to filter out relayed addresses?

- for (const relayAddr of this.addressManager.getAddresses()) {
+ for (const relayAddr of this.addressManager.getAddresses().filter(addr => !addrs.protoCodes().includes(290)) {

js-libp2p/src/circuit-relay/server/index.ts

Line 285 in 3115786

for (const relayAddr of this.addressManager.getAddresses()) {

but according to the specification "all" addresses should be returned.

Another solution is to do the filtering on the client side.

[achingbrain]

This needs some analysis - the spec disallows dialling relays through relays and there are tests for this but perhaps a case has been missed.