Listen by default if user does not specify

Author: AgeManning

beacon_node/src/cli.rs

@@ -156,16 +156,16 @@ pub fn cli_app() -> Command {
                 .long("listen-address")
                 .value_name("ADDRESS")
                 .help("The address lighthouse will listen for UDP and TCP connections. To listen \
-                      over IpV4 and IpV6 set this flag twice with the different values.\n\
+                      over IPv4 and IPv6 set this flag twice with the different values.\n\
                       Examples:\n\
                       - --listen-address '0.0.0.0' will listen over IPv4.\n\
                       - --listen-address '::' will listen over IPv6.\n\
                       - --listen-address '0.0.0.0' --listen-address '::' will listen over both \
                       IPv4 and IPv6. The order of the given addresses is not relevant. However, \
-                      multiple IPv4, or multiple IPv6 addresses will not be accepted.")
+                      multiple IPv4, or multiple IPv6 addresses will not be accepted. \
+                      If omitted, Lighthouse will listen on all interfaces, for both IPv4 and IPv6.")
                 .action(ArgAction::Append)
                 .num_args(0..=2)
-                .default_value("0.0.0.0")
                 .display_order(0)
         )
         .arg(
@@ -224,13 +224,6 @@ pub fn cli_app() -> Command {
                 .action(ArgAction::Set)
                 .display_order(0)
         )
-        .arg(
-            Arg::new("disable-ipv6")
-                .long("disable-ipv6")
-                .help("If 0.0.0.0 is set as the IPv4 listening address and the host has a globally routeable IPv6 address, Lighthouse will listen on :: by default, in dual-stack mode. This flag prevents this.")
-                .action(ArgAction::SetTrue)
-                .display_order(0)
-        )
         .arg(
             Arg::new("target-peers")
                 .long("target-peers")

beacon_node/src/config.rs

@@ -913,37 +913,24 @@ pub fn parse_listening_addresses(
             IpAddr::V4(v4_addr) => match &maybe_ipv4 {
                 Some(first_ipv4_addr) => {
                     return Err(format!(
-                                "When setting the --listen-address option twice, use an IpV4 address and an Ipv6 address. \
-                                Got two IpV4 addresses {first_ipv4_addr} and {v4_addr}"
+                                "When setting the --listen-address option twice, use an IPv4 address and an IPv6 address. \
+                                Got two IPv4 addresses {first_ipv4_addr} and {v4_addr}"
                             ));
                 }
                 None => maybe_ipv4 = Some(v4_addr),
             },
             IpAddr::V6(v6_addr) => match &maybe_ipv6 {
                 Some(first_ipv6_addr) => {
                     return Err(format!(
-                                "When setting the --listen-address option twice, use an IpV4 address and an Ipv6 address. \
-                                Got two IpV6 addresses {first_ipv6_addr} and {v6_addr}"
+                                "When setting the --listen-address option twice, use an IPv4 address and an IPv6 address. \
+                                Got two IPv6 addresses {first_ipv6_addr} and {v6_addr}"
                             ));
                 }
                 None => maybe_ipv6 = Some(v6_addr),
             },
         }
     }
 
-    // If we have specified an IPv4 listen address and not an IPv6 address and the
-    // host has a globally routeable IPv6 address and the CLI doesn't expressly disable IPv6,
-    // then we also listen on IPv6.
-    // Note that we will only listen on all interfaces if the IPv4 counterpart is also listening on
-    // all interfaces, to prevent accidental exposure of ports.
-    if maybe_ipv4 == Some(Ipv4Addr::UNSPECIFIED)
-        && maybe_ipv6.is_none()
-        && !cli_args.get_flag("disable_ipv6")
-        && NetworkConfig::is_ipv6_supported()
-    {
-        maybe_ipv6 = Some(Ipv6Addr::UNSPECIFIED);
-    }
-
     // parse the possible tcp ports
     let port = cli_args
         .get_one::<String>("port")
@@ -991,11 +978,22 @@ pub fn parse_listening_addresses(
             format!("Failed to parse --quic6-port as an integer: {parse_error}")
         })?;
 
+    // Here we specify the default listening addresses for Lighthouse.
+    // By default, we listen on 0.0.0.0.
+    //
+    // IF the host supports a globally routable IPv6 address, we also listen on ::.
+    if matches!((maybe_ipv4, maybe_ipv6), (None, None)) {
+        maybe_ipv4 = Some(Ipv4Addr::UNSPECIFIED);
+
+        if NetworkConfig::is_ipv6_supported() {
+            maybe_ipv6 = Some(Ipv6Addr::UNSPECIFIED);
+        }
+    }
+
     // Now put everything together
     let listening_addresses = match (maybe_ipv4, maybe_ipv6) {
         (None, None) => {
-            // This should never happen unless clap is broken
-            return Err("No listening addresses provided".into());
+            unreachable!("This path is handled above this match statement");
         }
         (None, Some(ipv6)) => {
             // A single ipv6 address was provided. Set the ports