1 use std::io::{Read, Seek, SeekFrom};
2 use std::path::PathBuf;
4 use std::time::Duration;
7 use lightning::chain::chaininterface::{BroadcasterInterface, ConfirmationTarget, FeeEstimator};
8 use lightning::sign::{EntropySource, KeysManager, SpendableOutputDescriptor};
9 use lightning::util::logger::Logger;
10 use lightning::util::persist::KVStore;
11 use lightning::util::ser::{Readable, WithoutLength, Writeable};
13 use lightning_persister::fs_store::FilesystemStore;
15 use bitcoin::blockdata::locktime::absolute::LockTime;
16 use bitcoin::secp256k1::Secp256k1;
17 use rand::{thread_rng, Rng};
20 use crate::BitcoindClient;
21 use crate::ChannelManager;
22 use crate::FilesystemLogger;
24 /// If we have any pending claimable outputs, we should slowly sweep them to our Bitcoin Core
25 /// wallet. We technically don't need to do this - they're ours to spend when we want and can just
26 /// use them to build new transactions instead, but we cannot feed them direclty into Bitcoin
27 /// Core's wallet so we have to sweep.
29 /// Note that this is unececssary for [`SpendableOutputDescriptor::StaticOutput`]s, which *do* have
30 /// an associated secret key we could simply import into Bitcoin Core's wallet, but for consistency
31 /// we don't do that here either.
32 pub(crate) async fn periodic_sweep(
33 ldk_data_dir: String, keys_manager: Arc<KeysManager>, logger: Arc<FilesystemLogger>,
34 persister: Arc<FilesystemStore>, bitcoind_client: Arc<BitcoindClient>,
35 channel_manager: Arc<ChannelManager>,
37 // Regularly claim outputs which are exclusively spendable by us and send them to Bitcoin Core.
38 // Note that if you more tightly integrate your wallet with LDK you may not need to do this -
39 // these outputs can just be treated as normal outputs during coin selection.
40 let pending_spendables_dir =
41 format!("{}/{}", ldk_data_dir, crate::PENDING_SPENDABLE_OUTPUT_DIR);
42 let processing_spendables_dir = format!("{}/processing_spendable_outputs", ldk_data_dir);
43 let spendables_dir = format!("{}/spendable_outputs", ldk_data_dir);
45 // We batch together claims of all spendable outputs generated each day, however only after
46 // batching any claims of spendable outputs which were generated prior to restart. On a mobile
47 // device we likely won't ever be online for more than a minute, so we have to ensure we sweep
48 // any pending claims on startup, but for an always-online node you may wish to sweep even less
49 // frequently than this (or move the interval await to the top of the loop)!
51 // There is no particular rush here, we just have to ensure funds are availably by the time we
52 // need to send funds.
53 let mut interval = tokio::time::interval(Duration::from_secs(60 * 60 * 24));
56 interval.tick().await; // Note that the first tick completes immediately
57 if let Ok(dir_iter) = fs::read_dir(&pending_spendables_dir) {
58 // Move any spendable descriptors from pending folder so that we don't have any
59 // races with new files being added.
60 for file_res in dir_iter {
61 let file = file_res.unwrap();
62 // Only move a file if its a 32-byte-hex'd filename, otherwise it might be a
64 if file.file_name().len() == 64 {
65 fs::create_dir_all(&processing_spendables_dir).unwrap();
66 let mut holding_path = PathBuf::new();
67 holding_path.push(&processing_spendables_dir);
68 holding_path.push(&file.file_name());
69 fs::rename(file.path(), holding_path).unwrap();
72 // Now concatenate all the pending files we moved into one file in the
73 // `spendable_outputs` directory and drop the processing directory.
74 let mut outputs = Vec::new();
75 if let Ok(processing_iter) = fs::read_dir(&processing_spendables_dir) {
76 for file_res in processing_iter {
77 outputs.append(&mut fs::read(file_res.unwrap().path()).unwrap());
80 if !outputs.is_empty() {
81 let key = hex_utils::hex_str(&keys_manager.get_secure_random_bytes());
83 .write("spendable_outputs", "", &key, &WithoutLength(&outputs).encode())
85 fs::remove_dir_all(&processing_spendables_dir).unwrap();
88 // Iterate over all the sets of spendable outputs in `spendables_dir` and try to claim
90 // Note that here we try to claim each set of spendable outputs over and over again
91 // forever, even long after its been claimed. While this isn't an issue per se, in practice
92 // you may wish to track when the claiming transaction has confirmed and remove the
93 // spendable outputs set. You may also wish to merge groups of unspent spendable outputs to
95 if let Ok(dir_iter) = fs::read_dir(&spendables_dir) {
96 for file_res in dir_iter {
97 let mut outputs: Vec<SpendableOutputDescriptor> = Vec::new();
98 let mut file = fs::File::open(file_res.unwrap().path()).unwrap();
100 // Check if there are any bytes left to read, and if so read a descriptor.
101 match file.read_exact(&mut [0; 1]) {
103 file.seek(SeekFrom::Current(-1)).unwrap();
105 Err(e) if e.kind() == io::ErrorKind::UnexpectedEof => break,
106 Err(e) => Err(e).unwrap(),
108 outputs.push(Readable::read(&mut file).unwrap());
110 let destination_address = bitcoind_client.get_new_address().await;
111 let output_descriptors = &outputs.iter().map(|a| a).collect::<Vec<_>>();
112 let tx_feerate = bitcoind_client
113 .get_est_sat_per_1000_weight(ConfirmationTarget::ChannelCloseMinimum);
115 // We set nLockTime to the current height to discourage fee sniping.
116 // Occasionally randomly pick a nLockTime even further back, so
117 // that transactions that are delayed after signing for whatever reason,
118 // e.g. high-latency mix networks and some CoinJoin implementations, have
120 // Logic copied from core: https://github.com/bitcoin/bitcoin/blob/1d4846a8443be901b8a5deb0e357481af22838d0/src/wallet/spend.cpp#L936
121 let mut cur_height = channel_manager.current_best_block().height();
124 if thread_rng().gen_range(0, 10) == 0 {
125 // subtract random number between 0 and 100
126 cur_height = cur_height.saturating_sub(thread_rng().gen_range(0, 100));
130 LockTime::from_height(cur_height).map_or(LockTime::ZERO, |l| l.into());
132 if let Ok(spending_tx) = keys_manager.spend_spendable_outputs(
135 destination_address.script_pubkey(),
140 // Note that, most likely, we've already sweeped this set of outputs
141 // and they're already confirmed on-chain, so this broadcast will fail.
142 bitcoind_client.broadcast_transactions(&[&spending_tx]);
144 lightning::log_error!(
146 "Failed to sweep spendable outputs! This may indicate the outputs are dust. Will try again in a day.");