devtools: Allow specifiying an address to listen to and default to localhost (#42502)

Previously we listened to 0.0.0.0. which means any connection coming to
a specific port. That seems a bit ill advised as not everybody has a
good firewall setup. Now we default listen only on 127.0.0.1 but
optionally can describe a full SocketAddr such as "192.168.1.23:1234".

Side note: Cleaned up the ipc-channel syntax.

Signed-off-by: Narfinger <Narfinger@users.noreply.github.com>

Testing: Currently we don't have an automatic way to test this. Manually
run devtools and it connects.

---------

Signed-off-by: Narfinger <Narfinger@users.noreply.github.com>

Cargo.toml

@@ -111,7 +111,7 @@ icu_segmenter = "1.5.0"
 image = { version = "0.25", default-features = false, features = ["avif", "rayon", "bmp", "gif", "ico", "jpeg", "png", "webp"] }
 imsz = "0.4"
 indexmap = { version = "2.11.4", features = ["std"] }
-ipc-channel = { version = "0.21" }
+ipc-channel = "0.21"
 itertools = "0.14"
 js = { package = "mozjs", version = "=0.15.0", default-features = false, features = ["libz-sys", "intl"] }
 keyboard-types = { version = "0.8.3", features = ["serde", "webdriver"] }

components/config/prefs.rs

@@ -87,9 +87,8 @@ pub struct Preferences {
     pub css_animations_testing_enabled: bool,
     /// Start the devtools server at startup
     pub devtools_server_enabled: bool,
-    /// Port number to start a server to listen to remote Firefox devtools connections.
-    /// 0 for random port.
-    pub devtools_server_port: i64,
+    /// The address +port the devtools server listens to, default to 127.0.0.1:7000.
+    pub devtools_server_listen_address: String,
     // feature: WebGPU | #24706 | Web/API/WebGPU_API
     pub dom_webgpu_enabled: bool,
     /// List of comma-separated backends to be used by wgpu.
@@ -342,7 +341,7 @@ impl Preferences {
         Self {
             css_animations_testing_enabled: false,
             devtools_server_enabled: false,
-            devtools_server_port: 0,
+            devtools_server_listen_address: String::new(),
             dom_abort_controller_enabled: true,
             dom_adoptedstylesheet_enabled: false,
             dom_allow_scripts_to_close_windows: false,

components/devtools/lib.rs

@@ -14,7 +14,8 @@
 use std::borrow::ToOwned;
 use std::collections::HashMap;
 use std::io::Read;
-use std::net::{Shutdown, TcpListener, TcpStream};
+use std::net::{Ipv4Addr, Shutdown, SocketAddr, TcpListener, TcpStream};
+use std::str::FromStr;
 use std::sync::{Arc, Mutex};
 use std::thread;
 
@@ -36,6 +37,7 @@ use rand::{RngCore, rng};
 use resource::{ResourceArrayType, ResourceAvailable};
 use rustc_hash::FxHashMap;
 use serde::Serialize;
+use servo_config::pref;
 
 use crate::actor::{Actor, ActorError, ActorRegistry};
 use crate::actors::browsing_context::BrowsingContextActor;
@@ -110,7 +112,6 @@ pub(crate) struct ActorMsg {
 
 /// Spin up a devtools server that listens for connections on the specified port.
 pub fn start_server(
-    port: u16,
     embedder: EmbedderProxy,
     mem_profiler_chan: ProfilerChan,
 ) -> Sender<DevtoolsControlMsg> {
@@ -123,8 +124,7 @@ pub fn start_server(
             .spawn(move || {
                 mem_profiler_chan.run_with_memory_reporting(
                     || {
-                        if let Some(instance) =
-                            DevtoolsInstance::create(sender, receiver, port, embedder)
+                        if let Some(instance) = DevtoolsInstance::create(sender, receiver, embedder)
                         {
                             instance.run()
                         }
@@ -172,10 +172,20 @@ impl DevtoolsInstance {
     fn create(
         sender: Sender<DevtoolsControlMsg>,
         receiver: Receiver<DevtoolsControlMsg>,
-        port: u16,
         embedder: EmbedderProxy,
     ) -> Option<Self> {
-        let bound = TcpListener::bind(("0.0.0.0", port)).ok().and_then(|l| {
+        let address = if pref!(devtools_server_listen_address).is_empty() {
+            SocketAddr::new(Ipv4Addr::new(127, 0, 0, 1).into(), 7000)
+        } else if let Ok(addr) = SocketAddr::from_str(&pref!(devtools_server_listen_address)) {
+            addr
+        } else if let Ok(port) = pref!(devtools_server_listen_address).parse() {
+            SocketAddr::new(Ipv4Addr::new(127, 0, 0, 1).into(), port)
+        } else {
+            SocketAddr::new(Ipv4Addr::new(127, 0, 0, 1).into(), 7000)
+        };
+        println!("Binding devtools to {address}");
+
+        let bound = TcpListener::bind(address).ok().and_then(|l| {
             l.local_addr()
                 .map(|addr| addr.port())
                 .ok()
@@ -183,7 +193,11 @@ impl DevtoolsInstance {
         });
 
         // A token shared with the embedder to bypass permission prompt.
-        let port = if bound.is_some() { Ok(port) } else { Err(()) };
+        let port = if bound.is_some() {
+            Ok(address.port())
+        } else {
+            Err(())
+        };
         let token = format!("{:X}", rng().next_u32());
         embedder.send(EmbedderMsg::OnDevtoolsStarted(port, token.clone()));
 

components/servo/servo.rs

@@ -769,7 +769,6 @@ impl Servo {
 
         let devtools_sender = if pref!(devtools_server_enabled) {
             Some(devtools::start_server(
-                pref!(devtools_server_port) as u16,
                 embedder_proxy.clone(),
                 mem_profiler_chan.clone(),
             ))

ports/servoshell/prefs.rs

@@ -407,9 +407,9 @@ struct CmdArgs {
     #[bpaf(argument("1.0"))]
     device_pixel_ratio: Option<f32>,
 
-    /// Start remote devtools server on port.
-    #[bpaf(argument("0"))]
-    devtools: Option<u16>,
+    /// Start remote devtools server on port listening on this address. <address>:<port> and <port> are valid values.
+    #[bpaf(argument("127.0.0.1:7000"))]
+    devtools: Option<String>,
 
     ///
     ///  Whether or not to enable experimental web platform features.
@@ -569,9 +569,9 @@ fn update_preferences_from_command_line_arguemnts(
     preferences: &mut Preferences,
     cmd_args: &CmdArgs,
 ) {
-    if let Some(port) = cmd_args.devtools {
+    if let Some(listen_address) = &cmd_args.devtools {
         preferences.devtools_server_enabled = true;
-        preferences.devtools_server_port = port as i64;
+        preferences.devtools_server_listen_address = listen_address.clone();
     }
 
     if cmd_args.enable_experimental_web_platform_features {