Add ldk-server backend support

Add `LdkServerNode` as a new `LightningNode` implementation
ldk-server-client over gRPC-over-HTTPS. Supports keysend via
`spontaneous_send`, payment tracking via polling `get_payment_details`,
graph queries, and channel capacity reporting.

Wire up `NodeConnection::LdkServer` in sim-cli parsing so ldk-server
nodes can be specified in sim.json alongside LND, CLN, and Eclair nodes.

Author: randomlogin

Cargo.lock

@@ -16,7 +16,7 @@ lightning network development. It may be useful to you if you are:
 * LND ✅
 * CLN ✅
 * Eclair ✅️
-* LDK-node 🏗️
+* LDK-Server ✅
 
 See our [tracking issue](https://github.com/bitcoin-dev-project/sim-ln/issues/26)
 for updates on implementation support (contributions welcome!).
@@ -36,6 +36,7 @@ of the simulator uses keysend to execute payments, which must be enabled as foll
 * LND: `--accept-keysend`
 * CLN: enabled by default
 * Eclair: `-Declair.features.keysend=optional` (or `--features.keysend=optional` if you're using Polar)
+* LDK-Server: enabled by default via `spontaneous_send`
 
 NOTE: for CLN `keysend` to work with eclair, you need to add additional config to eclair:
 ```
@@ -98,6 +99,23 @@ The required access details will depend on the node implementation.
   "api_password": <password_to_authorize>
 }
 ```
+* LDK-Server:
+```
+{
+  "address": <ip:port or domain:port>,
+  "api_key": <hex_encoded_api_key>,
+  "cert": <path_to_tls_cert>
+}
+```
+The `api_key` is the raw bytes of `~/.ldk-server/<network>/api_key` hex-encoded.
+Unlike other backends, ldk-server does not require an `id` field — the node's
+public key and network are fetched automatically on startup.
+
+Note: ldk-server channels are **unannounced by default**. Pass `--announce-channel`
+to `open-channel` (and set `announcement_addresses` in the ldk-server config) to
+make channels public and visible to other nodes for routing. Also ldk-server enforces a minimum final CLTV expiry delta
+of **144 blocks** on inbound keysend payments. Ensure that sending nodes are configured with a sufficiently high final
+CLTV delta.
 
 Payment activity can be simulated in two different ways:
 * [Random activity](#setup---random-activity): generate random activity on the `nodes` provided, 
@@ -135,6 +153,11 @@ to send and receive payments when running with random activity.
       "base_url": "127.0.0.1:8286",
       "api_username": "",
       "api_password": "eclairpw"
+    },
+    {
+      "address": "localhost:3536",
+      "api_key": "ldk_server_hex_encoded_api_key",
+      "cert": "/path/tls.crt"
     }
   ]
 }

README.md

@@ -9,9 +9,9 @@ use simln_lib::sim_node::{
     SimGraph, SimNode, SimulatedChannel,
 };
 use simln_lib::{
-    cln, cln::ClnNode, eclair, eclair::EclairNode, lnd, lnd::LndNode, serializers,
-    ActivityDefinition, Amount, Interval, LightningError, LightningNode, NodeId, NodeInfo,
-    Simulation, SimulationCfg, WriteResults,
+    cln, cln::ClnNode, eclair, eclair::EclairNode, ldk_server, ldk_server::LdkServerNode, lnd,
+    lnd::LndNode, serializers, ActivityDefinition, Amount, Interval, LightningError, LightningNode,
+    NodeId, NodeInfo, Simulation, SimulationCfg, WriteResults,
 };
 use simln_lib::{ShortChannelID, SimulationError};
 use std::collections::HashMap;
@@ -160,6 +160,7 @@ pub enum NodeConnection {
     Lnd(lnd::LndConnection),
     Cln(cln::ClnConnection),
     Eclair(eclair::EclairConnection),
+    LdkServer(ldk_server::LdkServerConnection),
 }
 
 /// Data structure that is used to parse information from the simulation file. It is used to
@@ -396,6 +397,7 @@ async fn get_clients(
             NodeConnection::Lnd(c) => Arc::new(Mutex::new(LndNode::new(c).await?)),
             NodeConnection::Cln(c) => Arc::new(Mutex::new(ClnNode::new(c).await?)),
             NodeConnection::Eclair(c) => Arc::new(Mutex::new(EclairNode::new(c).await?)),
+            NodeConnection::LdkServer(c) => Arc::new(Mutex::new(LdkServerNode::new(c).await?)),
         };
 
         let node_info = node.lock().await.get_info().clone();

sim-cli/src/parsing.rs

@@ -33,6 +33,7 @@ rand_distr = "0.4.3"
 rand_chacha = "0.3.1"
 reqwest = { version = "0.12", features = ["json", "multipart"] }
 tokio-util = { version = "0.7.13", features = ["rt"] }
+ldk-server-client = { git = "https://github.com/lightningdevkit/ldk-server", rev = "8163f4fe139368613959bf4f10b19ee6a5b9b4ab" }
 
 [dev-dependencies]
 ntest = "0.9.0"