XUD doesn't update LND's pubkey

[offerm]

Looks like XUD keeps in its database the identity pubkeys of LND.
As such, replacing LND creates a problem since peers are still using the old identities.

for example:

on test3 I now have this:

xud@xud-test-3:~/scripts$ lndbtc-lncli getinfo
{
	"version": "0.6.1-beta commit=v0.6.1-beta-rc2-dirty",
	"identity_pubkey": "02043a2b3414e0a4ba8b1426e5a33b7368cd6bdfb2bce97f00d78fb5e18af6003f",
	"alias": "LND for BTC on 10002/10012",
	"num_pending_channels": 0,
	"num_active_channels": 0,
	"num_inactive_channels": 0,
	"num_peers": 0,
	"block_height": 1981,
	"block_hash": "05910bfd7c95bd052ac6d68e0876b80190d3ff7ffde33e04d083540ad46f6588",
	"best_header_timestamp": 1560093417,
	"synced_to_chain": true,
	"testnet": false,
	"chains": [
		{
			"chain": "bitcoin",
			"network": "simnet"
		}
	],
	"uris": null
}

but on test2 I see this

xud@xud-test-2:~$ xucli listpeers
{
  "peersList": [
    {
      "address": "xud1.test.exchangeunion.com:8885",
      "nodePubKey": "02b66438730d1fcdf4a4ae5d3d73e847a272f160fee2938e132b52cab0a0d9cfc6",
      "lndPubKeysMap": [
        [
          "BTC",
          "038c0ea7e0dd31103fb16888a1afb5f046785a0e3b2f5f51f082bd961838212eb3"
        ],
        [
          "LTC",
          "027cd7ac85c2196a2002420f1316f0e3b9b5a73920cb21874fd63bb28fe778101b"
        ]
      ],
      "inbound": false,
      "pairsList": [
        "LTC/BTC",
        "WETH/BTC"
      ],
      "xudVersion": "1.0.0-alpha.11",
      "secondsConnected": 191,
      "raidenAddress": "0x7ed0299Fa1ADA71D10536B866231D447cDFa48b9"
    },
    {
      "address": "xud3.test.exchangeunion.com:8885",
      "nodePubKey": "03fd337659e99e628d0487e4f87acf93e353db06f754dccc402f2de1b857a319d0",
      "lndPubKeysMap": [
        [
          "BTC",
          "030c2ffd29a92e2dd2fb6fb046b0d9157e0eda8b11caa0e439d0dd6a46a444381c"
        ],
        [
          "LTC",
          "03301fd51f87728426918f284174d7d8d324585106f190276f4546f85ed6de123e"
        ]
      ],
      "inbound": false,
      "pairsList": [
        "LTC/BTC",
        "WETH/BTC"
      ],
      "xudVersion": "1.0.0-alpha.11",
      "secondsConnected": 191,
      "raidenAddress": "0x283EAD0338f8C202b996146d77a542fDfB60d437"
    },
    {
      "address": "92.191.159.161:56294",
      "nodePubKey": "025598976b93fd07c30ff5e98ae3ff593098068cb9c921a799956914f4a593bfb2",
      "lndPubKeysMap": [],
      "inbound": true,
      "pairsList": [
        "LTC/BTC",
        "BTC/LTC"
      ],
      "xudVersion": "1.0.0-alpha.11",
      "secondsConnected": 189,
      "raidenAddress": ""
    }
  ]
}

[offerm]

Might be that an old XUD process was still running.

[kilrau]

Very good point! I believe "caching" swap client addresses (lnd URIs and raiden addresses) locally is legit, but we definitely need a (pull) update mechanism:

These are the situations I can think of where we should pull new swap client addresses from a peer:

• on every connect <node_uri>
• on openchannel (Channel management #909)
• on swaps failing because swap client can't be reached, but peers are connected on xud level

Which ones are missing? Which ones are we doing already? @sangaman @erkarl

I'd categorize this as post-1.0.0 hardening though.

[sangaman]

We don't actually store or cache lnd pub keys between sessions. We request them anew each time we connect (or reconnect). I'm thinking this is probably indeed a case of an old xud process or something along those lines.

I think we can close this issues unless there are any lingering concerns.

[offerm]

I had this problem again.

@sangaman please have another look:

• are we keeping LND pubkey in database?
• do we refresh them on every LND connection?

[sangaman]

We definitely don't keep lnd pubkeys anywhere in the database. Can you describe exactly what is happening? When did the lnd pubkey change? While xud was running?

Every time xud verifies a connection to lnd it calls GetInfo and saves the lnd pub key to share with peers it connects to. It should refresh (and notify its peers of the new pub key) if lnd is shuts down and restarts with a different pub key, but this is not something I've personally tested in a while and there is no simulation test for it currently.

[kilrau]

if lnd is shuts down and restarts with a different pub key, but this is not something I've personally tested in a while and there is no simulation test for it currently.

added issue to add this to the simulation tests: #1040

[kilrau]

I'd say we have to invest some time trying to reproduce this, if not close.

[kilrau]

Check for TODO in code to broadcast node state update packet if nodepubkey is detected

[kilrau]

Will be handled by #1040 (comment) in future.