[bug]: syncToChain always false.

[Zhangguiguang]

Background

In an iOS app, LND is unable to fully synchronize, and syncToChain always false.

Your environment

• Version of lnd: 0.18.2-beta
• Device and operating system: iPhone Xs Max, iOS 16.3.1
• Backend: Neutrino
• Network: Tested with VPN, but synchronization still fails

Steps to reproduce

1. Start LND with the following arguments:

let args: [String] = [
    "--logdir=\(libraryPath)/mn/log",
    "--lnddir=\(libraryPath)/mn/lnd",
    "--alias=ComingChat-Bevm-Signet",
    "--color=#301DF5",
    "--tlsdisableautofill",
    "--debuglevel=debug",
    "--maxbackoff=2s",
    "--norest",
    "--sync-freelist",
    "--accept-keysend",
    "--routing.assumechanvalid",
    "--bitcoin.active",
    "--rpclisten=localhost:29735",
    "--listen=localhost:29735",
    "--bitcoin.signet",
    "--bitcoin.node=neutrino",
    "--neutrino.connect=x49.seed.signet.bitcoin.sprovoost.nl",
]
let argString = args.joined(separator: " ")
LndmobileStart(argString, callback)

2. After starting LND, use the BIP39 mnemonic with extendMasterKey and a password to either create or unlock the wallet.

Expected behaviour

LND should quickly synchronize to the latest block height on the Signet network, and syncToChain should update to true.

Actual behaviour

When calling getInfo, the latest block height can be retrieved successfully, but syncToChain remains false. The logs repeatedly output the following types of messages:

// Every second:
2024-12-28 15:54:43.390 [DBG] LTND: Syncing to block timestamp: 2024-12-28 15:29:28 +0000 UTC, is synced=false

// Very high frequency (~40 times per second):
2024-12-29 13:56:51.093 [DBG] BTCN: Received cfilter from 198.18.0.11:38333 (outbound)

// Approximately every 30 seconds:
2024-12-29 13:55:23.760 [DBG] BTCN: Fetching filters for heights=[47297, 48296], stophash=00000059e68fbca13e8473448b981c5aec32b56c42df6fcdd482e19a8173556e

// Error logs:
2024-12-29 13:46:34.290 [ERR] BTCN: Command [addrv2] from 198.18.0.11:38333 does not contain any addresses
2024-12-29 13:55:29.960 [ERR] LNWL: Neutrino rescan ended with error: did not get response before timeout

// Other logs:
2024-12-29 13:56:46.927 [INF] BTCN: Attempting to fetch set of un-checkpointed filters at height=228480, hash=000000d8cf3f39a4de7401053561a48ea943e05769484d

2024-12-29 13:54:10.682 [DBG] LNWL: Adding new batch(38) of 1 queries to work queue
2024-12-29 13:55:23.890 [DBG] LNWL: Adding new batch(40) of 1 queries to work queue

2024-12-29 13:54:37.075 [WRN] LNWL: Query(39) from peer 198.18.0.11:38333 failed, rescheduling: did not get response before timeout
2024-12-29 13:55:29.959 [WRN] LNWL: Query(40) from peer 198.18.0.11:38333 failed and reached maximum number of retries, not rescheduling: did not get response before timeout

2024-12-29 13:28:47.508 [DBG] CMGR: Attempting to connect to 198.18.0.11:38333 (reqid 1)
2024-12-29 13:28:48.515 [DBG] CMGR: Cannot start peer 198.18.0.11:38333 (outbound): EOF
2024-12-29 13:28:48.515 [DBG] CMGR: Reconnecting to 198.18.0.11:38333 (reqid 1)

[guggero]

Don't use --neutrino.connect, that restricts the connection to a single peer. Use --neutrino.addpeer instead, that allows your node to connect out to other peers.

Also, are you sure x49.seed.signet.bitcoin.sprovoost.nl is a valid Neutrino node? That's supposed to be a DNS seed, not a node itself (which might explain why you can't connect). Check the example config here, which has some known valid nodes: https://github.com/alexbosworth/run-lnd?tab=readme-ov-file#install-lnd

[Zhangguiguang]

Thank you for your help. Based on your instructions, I modified the mainnet configuration. After confirming that getInfo can retrieve the latest block height and testing multiple times for over 10 minutes, syncToChain still remains false.

The modified configuration is as follows:

            "--logdir=\(logDirectory)",
            "--lnddir=\(lndDirectory)",
            "--alias=ComingChat-Bevm-Signet",
            "--color=#301DF5",
            "--tlsdisableautofill",
            "--debuglevel=debug",
            "--maxbackoff=2s",
            "--norest",
            "--sync-freelist",
            "--accept-keysend",
            "--routing.assumechanvalid",
            "--bitcoin.active",
            "--fee.url=https://nodes.lightning.computer/fees/v1/btc-fee-estimates.json",
            "--bitcoin.mainnet",
            "--bitcoin.node=neutrino",
            "--neutrino.addpeer=node.blixtwallet.com",
            "--neutrino.addpeer=btcd.lnolymp.us",
            "--neutrino.addpeer=uswest.blixtwallet.com",
            "--neutrino.addpeer=europe.blixtwallet.com",
            "--neutrino.addpeer=asia.blixtwallet.com",
            "--neutrino.addpeer=btcd-mainnet.lightning.computer",
            "--neutrino.broadcasttimeout=11s",
            "--neutrino.persistfilters",

During this period, the following logs were constantly output:

2024-12-30 14:44:46.317 [DBG] BTCN: Sending version (agent /btcwire:0.5.0/neutrino:0.12.0-beta/, pver 70016, block 877054) to 198.18.0.13:8333 (outbound)
2024-12-30 14:44:46.333 [DBG] BTCN: Cannot start peer 198.18.0.13:8333 (outbound): EOF
2024-12-30 14:44:46.333 [DBG] CMGR: Disconnected from 198.18.0.13:8333 (reqid 2)
2024-12-30 14:44:46.384 [DBG] CMGR: Reconnecting to 198.18.0.13:8333 (reqid 2)
2024-12-30 14:44:46.431 [DBG] CMGR: Retrying connection to 198.18.0.13:8333 (reqid 2) in 5s

2024-12-30 14:34:10.720 [DBG] BTCN: Received pong from 198.18.0.32:8333 (outbound)
2024-12-30 14:34:11.398 [DBG] BTCN: Received ping from 198.18.0.33:8333 (outbound)
2024-12-30 14:34:11.399 [DBG] BTCN: Sending pong to 198.18.0.33:8333 (outbound)

[guggero]

Can you try with the latest version (0.18.4) and if the problem persists share a bit more of the logs please? It looks okay as far as I can tell, peers will sometimes just disconnect you. But that's why you can configure multiple ones.