Wrong port is gossiped, in addition to correct one

[laanwj]

I'm having an issue where the gossiped port is wrong, possibly part of the time. It's supposed to be 9736, but 9735 ends up in the list too:

% lcli listnodes [M]
{
   "nodes": [
      {
         "nodeid": "[M]",
…
         "addresses": [
            {
               "type": "ipv4",
               "address": "[A]",
               "port": 9735
            },
            {
               "type": "ipv4",
               "address": "[A]",
               "port": 9736
            },
            {
               "type": "ipv6",
               "address": "[B]",
               "port": 9736
            },
            {
               "type": "torv3",
               "address": "[C].onion",
               "port": 9736
            }
         ]
      }
   ]
}

I not only see this in my own listnodes, other nodes and services do, as well. I do not have anything running on port 9735, FWIW, there's only one lightningd on this system. I've only ever seen it happen for IPv4.

Relevant configuration is:

    --proxy 127.0.0.1:9050 \
    --addr '0.0.0.0:9736' \
    --addr '[::]:9736' \
    --announce-addr '[C].onion:9736' \

getinfo output shows, correctly:

{
   "id": "[M]",
…
   "address": [
      {
         "type": "ipv4",
         "address": "[A]",
         "port": 9736
      },
      {
         "type": "ipv6",
         "address": "[B]",
         "port": 9736
      },
      {
         "type": "torv3",
         "address": "[C].onion",
         "port": 9736
      }
   ],
   "binding": [
      {
         "type": "ipv4",
         "address": "0.0.0.0",
         "port": 9736
      },
      {
         "type": "ipv6",
         "address": "::",
         "port": 9736
      }
   ],
   "version": "v0.11.0.1-36-g74ddc15",
…
}

[laanwj]

amboss.space has a history for the node that shows 9735 appearing and disappearing, it's really strange:

None of these are intentional configuration changes.

Edit: looks like they correlate roughly with server restarts:

2022-03-31T15:19:33.974Z INFO    lightningd: Server started with public key —
2022-04-07T17:54:35.409Z INFO    lightningd: Server started with public key —
2022-04-08T16:07:24.407Z INFO    lightningd: Server started with public key —
2022-05-02T18:02:38.327Z INFO    lightningd: Server started with public key —
2022-06-03T14:52:29.719Z INFO    lightningd: Server started with public key —

(it's only a subset though, there were more restarts in this time period)

Edit.2: Just found this option:

--autolisten <arg>                      If true, listen on default port and
                                        announce if it seems to be a public
                                        interface (default: true)

Will try setting it to false, as it seems what is happening here except for the actual binding.

[kroese]

Maybe you can also try if setting disable-ip-discovery makes any difference. Because it only is able to discover the IP and not the port, so if will automaticly append 9735.

[vincenzopalazzo]

Mh! I did not debug it, and I put here only a pointer that we had changed somethings in the default port but there was some refusal that this PR will remove #5242

Maybe can help

[laanwj]

Thanks @kroese and @vincenzopalazzo .

It doesn't look like -autolisten false solved the issue. Will try with disable-ip-discovery. I'll have to pass in all addresses with --announce-addr in that case, I suppose. This is okay, they're all static.

Edit: uhm, I now announce the IPv4 and IPv6 addresses twice, scrap that.

[kroese]

The manual for disable-ip-discovery says:

Turn off public IP discovery to send node_announcement updates that contain the discovered IP with TCP port 9735 as announced address.

So it seems it just adds port 9735 to the external IP without checking if that is really the port you are listening on. It would be better if it used that port instead.

[rustyrussell]

Hmm, @m-schmoock ? This shouldn't happen; we can't really tell what port is exposed, so we guess. But obviously we should not add anything if that IP is already advertized!

[m-schmoock]

Yes. I'll open up an PR.
Maybe disable discovery at all when something is announced manually.

[m-schmoock]

Or maybe only do discovery on IP protocols that are not configured manually.