We ignore port when identifying peers - what happens if a peer changes its port?

[antiochp]

Related #2540.
Possibly related #2616?

Scenario -

• We run a node on 10.0.0.1:3414
• Other nodes store our peer address in their db (keyed by ip, ignoring the port - 10.0.0.1)
• We restart our node, changing the port to 4414
• What happens to inbound/outbound connections?
  • We should be able to initiate outbound connections to peers (regardless of our port)
  • But nobody knows we are now running on an updated port (existing nodes cannot connect to us?)

There is no mechanism to let peers and other nodes know about our updated port.

Do new nodes see our updated port? Only if they get our ip:port from us. If they get it from an existing node do they still see the old port?

This is kind of an edge-case but we should think through the implications here.

[nikito7]

It will be an eternal defunct in case of static ip

Since change there are less 100 healthy peers

The another issue is #2616

[nikito7]

Another perspective

If peer is behind NAT port will change alot

If peers are behind a CarrierNAT its worse

Not everybody have a public ip

[antiochp]

@nikito7 I still don't fully understand what you are saying. Can you explain the problem a bit more, specifically around #2616?

[antiochp]

If peer is behind NAT port will change alot.

That's what the NAT is for though, by definition - to provide a stable port forwarding setup, with a "static" port.

To allow "inbound" connections you need to be listening on a known port (by default 3414 but you can advertise a non-standard port).
Even behind a NAT with no port forwarding you can initiate outbound connections fine, its just that nobody will be able to initiate inbound connections to your node.

[nikito7]

But peer identity will change

1.2.3.4:56788
1.2.3.4:45638

If you use only 1.2.3.4 how do you know?
20190222 12:10:14.609 DEBUG grin_servers::grin::seed - monitor_peers: on 0.0.0.0:3414, 28 connected (20 most_work). all 7904 = 107 healthy + 3 banned + 7794 defunct

the other issue #2616
I will test again

[antiochp]

But peer identity will change

1.2.3.4:56788
1.2.3.4:45638

If you use only 1.2.3.4 how do you know?

You don't and you don't need to.

If the peer on 1.2.3.4 allows inbound connections then its listening on 3414 (or whatever it is configured to listen on).
The ports you are displaying there are the ports on the outbound end of an outbound connection. you will never connect to those directly.

Those ports do not (and should not) have any bearing on the identity of a peer.

[nikito7]

My theory:

When I change the port. I am a new node for old nodes x.x.x.x:xxxx

And get "attacked" by them

The problem may be fixed when all nodes update in next release

Sorry for wasted time :) @antiochp

[quentinlesceller]

Is this issue still relevant? @antiochp

[yeastplume]

Have inadvertently tested this on testnet during the course of other testing. With a two nodes running on the same machine on different ports:
-Node on port 1: 6 peers
-Start node on port 2: 0 peers, no peers connect.
-Stop node on port 1
-Wait a bit
-Start node on port 2: 6 peers
-Start node on port 1: no peers connect

Seems to be working as intended,