feat: add --advertise-false-custody-group-count flag for PeerDAS testing

Author: startup-dreamer

beacon_node/lighthouse_network/src/config.rs

@@ -148,6 +148,10 @@ pub struct Config {
     /// Configuration for the minimum message size for which IDONTWANT messages are send in the mesh.
     /// Lower the value reduces the optimization effect of the IDONTWANT messages.
     pub idontwant_message_size_threshold: usize,
+
+    /// Advertise a false custody group count in metadata.
+    /// Makes peers think this node custodies more columns than it actually does.
+    pub advertise_false_custody_group_count: Option<u64>,
 }
 
 impl Config {
@@ -372,6 +376,7 @@ impl Default for Config {
             invalid_block_storage: None,
             inbound_rate_limiter_config: None,
             idontwant_message_size_threshold: DEFAULT_IDONTWANT_MESSAGE_SIZE_THRESHOLD,
+            advertise_false_custody_group_count: None,
         }
     }
 }

beacon_node/lighthouse_network/src/service/mod.rs

@@ -198,8 +198,23 @@ impl<E: EthSpec> Network<E> {
 
         // Construct the metadata
         let custody_group_count = ctx.chain_spec.is_peer_das_scheduled().then(|| {
-            ctx.chain_spec
-                .custody_group_count(config.subscribe_all_data_column_subnets)
+            // Use the false custody group count if specified, otherwise use the normal one
+            if let Some(false_count) = config.advertise_false_custody_group_count {
+                // Ensure the false count is within valid range
+                if (ctx.chain_spec.custody_requirement..=ctx.chain_spec.number_of_custody_groups).contains(&false_count) {
+                    warn!(log, "Using false custody group count for testing"; "count" => false_count);
+                    false_count
+                } else {
+                    warn!(log, "Specified false custody group count is out of valid range, using normal count"; 
+                        "false_count" => false_count,
+                        "min" => ctx.chain_spec.custody_requirement,
+                        "max" => ctx.chain_spec.number_of_custody_groups
+                    );
+                    ctx.chain_spec.custody_group_count(config.subscribe_all_data_column_subnets)
+                }
+            } else {
+                ctx.chain_spec.custody_group_count(config.subscribe_all_data_column_subnets)
+            }
         });
         let meta_data =
             utils::load_or_build_metadata(&config.network_dir, custody_group_count, &log);

beacon_node/src/cli.rs

@@ -68,6 +68,20 @@ pub fn cli_app() -> Command {
                 .hide(true)
                 .display_order(0)
         )
+        .arg(
+            // TODO(das): remove this before PeerDAS release
+            Arg::new("advertise-false-custody-group-count")
+                .long("advertise-false-custody-group-count")
+                .action(ArgAction::Set)
+                .help_heading(FLAG_HEADER)
+                .help("TESTING ONLY: Advertise a false custody group count in metadata. Makes \
+                        peers think this node custodies more columns than it actually does. \
+                        It's used to override the actual custody group count when building node metadata, \
+                        but only when PeerDAS is scheduled and the value is within valid range.
+                        DO NOT USE IN PRODUCTION.")
+                .hide(true)
+                .display_order(0)
+        )
         .arg(
             Arg::new("enable-sampling")
                 .long("enable-sampling")

beacon_node/src/config.rs

@@ -1180,6 +1180,12 @@ pub fn set_network_config(
         config.shutdown_after_sync = true;
     }
 
+    if let Some(false_custody_group_count) =
+        clap_utils::parse_optional(cli_args, "advertise-false-custody-group-count")?
+    {
+        config.advertise_false_custody_group_count = Some(false_custody_group_count);
+    }
+
     config.set_listening_addr(parse_listening_addresses(cli_args, log)?);
 
     // A custom target-peers command will overwrite the --proposer-only default.

lighthouse/tests/beacon_node.rs

@@ -2033,6 +2033,20 @@ fn malicious_withhold_count_flag() {
         .with_config(|config| assert_eq!(config.chain.malicious_withhold_count, 128));
 }
 
+#[test]
+fn advertise_false_custody_group_count_flag() {
+    CommandLineTest::new()
+        .flag("advertise-false-custody-group-count", Some("128"))
+        .run_with_zero_port()
+        .with_config(|config| {
+            let network_config = &config.network;
+            assert_eq!(
+                network_config.advertise_false_custody_group_count,
+                Some(128)
+            );
+        });
+}
+
 // Tests for Slasher flags.
 // Using `--slasher-max-db-size` to work around https://github.com/sigp/lighthouse/issues/2342
 #[test]