Configure multiple LSPs as liquidity sources

LDK Node's `add_liquidity_source()` registers an LSP generically and
discovers its supported protocols (LSPS1/LSPS2) via bLIP-50 / LSPS0.
Replace the single `[liquidity.lsps2_client]` section with a
`[[liquidity.lsps_client]]` array so several LSPs can be registered. Each
entry is passed to `add_liquidity_source()` on startup, after which LSPS2
JIT invoices select the cheapest fee offer across every LSPS2-capable
LSP.

Surface the per-LSP `trust_peer_0conf` flag, previously hardcoded to
`false`. It is required rather than defaulted, since accepting
0-confirmation channels from an LSP is a trust decision each operator
should make explicitly.

Author: Camillarhi

contrib/ldk-server-config.toml

@@ -66,14 +66,19 @@ server_url = "ssl://electrum.blockstream.info:50002"  # Electrum endpoint
 [esplora]
 server_url = "https://mempool.space/api"      # Esplora endpoint
 
-# LSPS2 Client Support
-[liquidity.lsps2_client]
-# The public key of the LSPS2 LSP we source just-in-time liquidity from.
+# LSPS Client Support
+# Repeat this section to register several LSPs. Supported protocols are discovered per
+# LSP via bLIP-50 / LSPS0 on startup. Only LSPS2 is supported at present.
+[[liquidity.lsps_client]]
+# The public key of the LSP we source inbound liquidity from.
 node_pubkey = "<lsp node pubkey>"
-# Address to connect to the LSPS2 LSP (IPv4:port, IPv6:port, OnionV3:port, or hostname:port).
+# Address to connect to the LSP (IPv4:port, IPv6:port, OnionV3:port, or hostname:port).
 address = "<lsp ip address>:9735"
 # Optional token for authenticating to the LSP.
 # token = ""
+# Accept 0-confirmation channels opened by this LSP. Required for JIT channels to be
+# usable before the funding transaction confirms.
+trust_peer_0conf = true
 
 # Experimental LSPS2 Service Support
 # CAUTION: LSPS2 support is highly experimental and for testing purposes only.

docs/api-guide.md

@@ -118,8 +118,8 @@ These RPCs support a manual claim/fail workflow for held payments. See
 
 ### BOLT11 JIT Channels (LSPS2)
 
-Requires an `[liquidity.lsps2_client]` configuration. The LSP opens a channel just-in-time
-when the invoice is paid.
+Requires at least one `[[liquidity.lsps_client]]` entry for an LSPS2-capable LSP. The LSP opens
+a channel just-in-time when the invoice is paid.
 
 | RPC                                        | Description                                               |
 |--------------------------------------------|-----------------------------------------------------------|

docs/configuration.md

@@ -147,14 +147,22 @@ You must configure **exactly one** of the following sections:
 > against the blockchain. This means a malicious peer could flood your node with fake channel
 > announcements, consuming memory and disk. If your node is publicly reachable, use bitcoind.
 
-### `[liquidity.lsps2_client]`
-
-Connects to an [LSPS2](https://github.com/BitcoinAndLightningLayerSpecs/lsp/blob/main/LSPS2/README.md)
-Liquidity Service Provider for just-in-time (JIT) inbound channel opening. When configured,
-the `Bolt11ReceiveViaJitChannel` and `Bolt11ReceiveVariableAmountViaJitChannel` RPCs become
-available, the LSP will open a channel on the fly when the generated invoice is paid.
-
-Requires the LSP's public key and address. Some LSPs also require an authentication token.
+### `[[liquidity.lsps_client]]`
+
+Registers a Liquidity Service Provider to source inbound liquidity from. Repeat the section
+to register several LSPs. Each LSP's supported protocols are discovered on startup via
+[bLIP-50 / LSPS0](https://github.com/lightning/blips/blob/master/blip-0050.md). LDK Server
+currently supports LSPS2 only, so an LSP that does not advertise it is registered but unused.
+
+When at least one LSPS2-capable LSP is configured, the `Bolt11ReceiveViaJitChannel` and
+`Bolt11ReceiveVariableAmountViaJitChannel` RPCs become available, and the cheapest fee offer
+across all LSPS2-capable LSPs is selected per invoice.
+
+Requires each LSP's public key and address. Some LSPs also require an authentication token.
+`trust_peer_0conf` is required and controls whether 0-confirmation channels from that LSP are
+accepted. Setting it to `true` is generally necessary for JIT channels to be usable before
+the funding transaction confirms. Each entry must name a distinct `node_pubkey` as duplicates
+are rejected at startup.
 
 ### `[liquidity.lsps2_service]`
 

ldk-server-client/src/config.rs

@@ -294,10 +294,11 @@ mod tests {
 				rpc_user = "bitcoind-testuser"
 				rpc_password = "bitcoind-testpassword"
 
-				[liquidity.lsps2_client]
+				[[liquidity.lsps_client]]
 				node_pubkey = "0217890e3aad8d35bc054f43acc00084b25229ecff0ab68debd82883ad65ee8266"
 				address = "127.0.0.1:39735"
 				token = "lsps2-token"
+				trust_peer_0conf = true
 
 				[liquidity.lsps2_service]
 				advertise_service = false

ldk-server/src/main.rs

@@ -220,13 +220,15 @@ fn main() {
 		std::process::exit(-1);
 	}
 
-	if let Some(lsps2_client_config) = config_file.lsps2_client_config {
-		builder.add_liquidity_source(
-			lsps2_client_config.node_id,
-			lsps2_client_config.address,
-			lsps2_client_config.token,
-			false,
-		);
+	if let Some(lsps_client_configs) = config_file.lsps_client_config {
+		for lsps_client_config in lsps_client_configs {
+			builder.add_liquidity_source(
+				lsps_client_config.node_id,
+				lsps_client_config.address,
+				lsps_client_config.token,
+				lsps_client_config.trust_peer_0conf,
+			);
+		}
 	}
 
 	if let Some(tor_config) = config_file.tor_config {