[PATCH v3 1/3] tools/router: use socket activation

[Alyssa Ross <hi@alyssa.is>]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 13458 bytes --]

This means we can use readiness notification to wait until the sockets
are created without having to add special functionality for that to
the router program, and also means we can do extra system-specific
setup to the sockets, like changing their owners, outside of the
router.

Since the socket paths were the only arguments taken by the router,
this also lets us drop the clap dependency entirely.

Signed-off-by: Alyssa Ross <hi@alyssa.is>
---
v3: • use anyhow::bail
    • set sockets to non-blocking in router
v2: https://spectrum-os.org/lists/archives/spectrum-devel/20251209110503.674499-2-hi@alyssa.is/

 host/rootfs/file-list.mk                      |   1 +
 .../service/spectrum-router/notification-fd   |   1 +
 .../spectrum-router/notification-fd.license   |   2 +
 .../template/data/service/spectrum-router/run |  21 ++-
 tools/router/Cargo.lock                       | 148 ++++++++++++------
 tools/router/Cargo.toml                       |   2 +-
 tools/router/src/main.rs                      |  40 +++--
 7 files changed, 141 insertions(+), 74 deletions(-)
 create mode 100644 host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/notification-fd
 create mode 100644 host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/notification-fd.license

diff --git a/host/rootfs/file-list.mk b/host/rootfs/file-list.mk
index df22bce8..5a043b7b 100644
--- a/host/rootfs/file-list.mk
+++ b/host/rootfs/file-list.mk
@@ -28,6 +28,7 @@ FILES = \
 	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/dbus/notification-fd \
 	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/dbus/run \
 	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/down \
+	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/notification-fd \
 	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/run \
 	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-fs/notification-fd \
 	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-fs/run \
diff --git a/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/notification-fd b/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/notification-fd
new file mode 100644
index 00000000..7ed6ff82
--- /dev/null
+++ b/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/notification-fd
@@ -0,0 +1 @@
+5
diff --git a/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/notification-fd.license b/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/notification-fd.license
new file mode 100644
index 00000000..0d3d47ca
--- /dev/null
+++ b/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/notification-fd.license
@@ -0,0 +1,2 @@
+SPDX-License-Identifier: CC0-1.0
+SPDX-FileCopyrightText: 2025 Alyssa Ross <hi@alyssa.is>
diff --git a/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/run b/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/run
index 3ba35def..dc1ef900 100755
--- a/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/run
+++ b/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/run
@@ -1,14 +1,30 @@
 #!/bin/execlineb -P
 # SPDX-License-Identifier: EUPL-1.2+
 # SPDX-FileCopyrightText: 2025 Yureka Lilian <yureka@cyberchaos.dev>
+# SPDX-FileCopyrightText: 2025 Alyssa Ross <hi@alyssa.is>
 
 importas -i VM VM
 
+s6-ipcserver-socketbinder -a 0770 /run/vm/by-id/${VM}/router-driver.sock
+fdmove -c 3 0
+
+s6-ipcserver-socketbinder -a 0770 /run/vm/by-id/${VM}/router-app.sock
+fdmove -c 4 0
+
+# Notify readiness.
+if {
+  fdmove -c 5 1
+  echo
+}
+
+redirfd -r 0 /dev/null
+
 bwrap
   --unshare-all
   --unshare-user
   --dev-bind / /
   --setenv RUST_LOG spectrum-router=debug,info
+  --setenv LISTEN_FDS 2
   --tmpfs /tmp
   --dev /dev
   --tmpfs /dev/shm
@@ -19,6 +35,7 @@ bwrap
   --ro-bind /lib /lib
   --bind /run/vm/by-id/${VM} /run/vm/by-id/${VM}
   --
+
+getpid LISTEN_PID
+
 spectrum-router
-  --app-listen-path /run/vm/by-id/${VM}/router-app.sock
-  --driver-listen-path /run/vm/by-id/${VM}/router-driver.sock
diff --git a/tools/router/Cargo.lock b/tools/router/Cargo.lock
index 60d7657b..d0d105aa 100644
--- a/tools/router/Cargo.lock
+++ b/tools/router/Cargo.lock
@@ -113,6 +113,12 @@ dependencies = [
  "wyz",
 ]
 
+[[package]]
+name = "bumpalo"
+version = "3.19.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "46c5e41b57b8bba42a04676d81cb89e9ee8e859a1a66f80a5a72e1cb76b34d43"
+
 [[package]]
 name = "bytes"
 version = "1.11.0"
@@ -120,44 +126,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b35204fbdc0b3f4446b89fc1ac2cf84a8a68971995d0bf2e925ec7cd960f9cb3"
 
 [[package]]
-name = "clap"
-version = "4.5.53"
+name = "cfg-if"
+version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c9e340e012a1bf4935f5282ed1436d1489548e8f72308207ea5df0e23d2d03f8"
-dependencies = [
- "clap_builder",
- "clap_derive",
-]
-
-[[package]]
-name = "clap_builder"
-version = "4.5.53"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d76b5d13eaa18c901fd2f7fca939fefe3a0727a953561fefdf3b2922b8569d00"
-dependencies = [
- "anstream",
- "anstyle",
- "clap_lex",
- "strsim",
-]
-
-[[package]]
-name = "clap_derive"
-version = "4.5.49"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2a0b5487afeab2deb2ff4e03a807ad1a03ac532ff5a2cee5d86884440c7f7671"
-dependencies = [
- "heck",
- "proc-macro2",
- "quote",
- "syn",
-]
-
-[[package]]
-name = "clap_lex"
-version = "0.7.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a1d728cc89cf3aee9ff92b05e62b19ee65a02b5702cff7d5a377e32c6ae29d8d"
+checksum = "9330f8b2ff13f34540b44e946ef35111825727b38d33286ef986142615121801"
 
 [[package]]
 name = "colorchoice"
@@ -263,12 +235,6 @@ dependencies = [
  "slab",
 ]
 
-[[package]]
-name = "heck"
-version = "0.5.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2304e00983f87ffb38b55b444b5e3b60a884b5d30c0fca7d82fe33449bbe55ea"
-
 [[package]]
 name = "is_terminal_polyfill"
 version = "1.70.2"
@@ -299,12 +265,33 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "js-sys"
+version = "0.3.83"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "464a3709c7f55f1f721e5389aa6ea4e3bc6aba669353300af094b29ffbdde1d8"
+dependencies = [
+ "once_cell",
+ "wasm-bindgen",
+]
+
 [[package]]
 name = "libc"
 version = "0.2.177"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2874a2af47a2325c2001a6e6fad9b16a53b802102b528163885171cf92b15976"
 
+[[package]]
+name = "listenfd"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b87bc54a4629b4294d0b3ef041b64c40c611097a677d9dc07b2c67739fe39dba"
+dependencies = [
+ "libc",
+ "uuid",
+ "winapi",
+]
+
 [[package]]
 name = "log"
 version = "0.4.28"
@@ -328,6 +315,12 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "once_cell"
+version = "1.21.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "42f5e15c9953c5e4ccceeb2e7382a716482c34515315f7b03532b8b4e8393d2d"
+
 [[package]]
 name = "once_cell_polyfill"
 version = "1.70.2"
@@ -420,6 +413,12 @@ version = "0.8.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7a2d987857b319362043e95f5353c0535c1f58eec5336fdfcf626430af7def58"
 
+[[package]]
+name = "rustversion"
+version = "1.0.22"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b39cdef0fa800fc44525c84ccb54a029961a8215f9619753635a9c0d2538d46d"
+
 [[package]]
 name = "serde_core"
 version = "1.0.228"
@@ -462,9 +461,9 @@ version = "0.1.0"
 dependencies = [
  "anyhow",
  "arrayvec",
- "clap",
  "env_logger",
  "futures-util",
+ "listenfd",
  "log",
  "tokio",
  "tokio-stream",
@@ -474,12 +473,6 @@ dependencies = [
  "zerocopy",
 ]
 
-[[package]]
-name = "strsim"
-version = "0.11.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7da8b5736845d9f2fcb837ea5d9e2628564b3b043a70948a3f0b778838c5fb4f"
-
 [[package]]
 name = "syn"
 version = "2.0.111"
@@ -608,6 +601,16 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "06abde3611657adf66d383f00b093d7faecc7fa57071cce2578660c9f1010821"
 
+[[package]]
+name = "uuid"
+version = "1.19.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2e054861b4bd027cd373e18e8d8d8e6548085000e41290d95ce0c373a654b4a"
+dependencies = [
+ "js-sys",
+ "wasm-bindgen",
+]
+
 [[package]]
 name = "vhost-device-net"
 version = "0.1.1"
@@ -666,6 +669,51 @@ version = "0.11.1+wasi-snapshot-preview1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ccf3ec651a847eb01de73ccad15eb7d99f80485de043efb2f370cd654f4ea44b"
 
+[[package]]
+name = "wasm-bindgen"
+version = "0.2.106"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0d759f433fa64a2d763d1340820e46e111a7a5ab75f993d1852d70b03dbb80fd"
+dependencies = [
+ "cfg-if",
+ "once_cell",
+ "rustversion",
+ "wasm-bindgen-macro",
+ "wasm-bindgen-shared",
+]
+
+[[package]]
+name = "wasm-bindgen-macro"
+version = "0.2.106"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "48cb0d2638f8baedbc542ed444afc0644a29166f1595371af4fecf8ce1e7eeb3"
+dependencies = [
+ "quote",
+ "wasm-bindgen-macro-support",
+]
+
+[[package]]
+name = "wasm-bindgen-macro-support"
+version = "0.2.106"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cefb59d5cd5f92d9dcf80e4683949f15ca4b511f4ac0a6e14d4e1ac60c6ecd40"
+dependencies = [
+ "bumpalo",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "wasm-bindgen-shared",
+]
+
+[[package]]
+name = "wasm-bindgen-shared"
+version = "0.2.106"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cbc538057e648b67f72a982e708d485b2efa771e1ac05fec311f9f63e5800db4"
+dependencies = [
+ "unicode-ident",
+]
+
 [[package]]
 name = "winapi"
 version = "0.3.9"
diff --git a/tools/router/Cargo.toml b/tools/router/Cargo.toml
index 0b969113..cfdf3527 100644
--- a/tools/router/Cargo.toml
+++ b/tools/router/Cargo.toml
@@ -8,7 +8,6 @@ edition = "2024"
 
 [dependencies]
 anyhow = "1.0.100"
-clap = { version = "4.5.45", features = ["derive"] }
 env_logger = "0.11.8"
 log = { version = "0.4.27", features = ["release_max_level_debug"] }
 vhost-device-net = "0.1.0"
@@ -19,3 +18,4 @@ tokio-stream = "0.1.17"
 arrayvec = "0.7.6"
 vm-memory = "0.16"
 tokio-util = "0.7.17"
+listenfd = "1.0.2"
diff --git a/tools/router/src/main.rs b/tools/router/src/main.rs
index e3aca65a..3b26ddb0 100644
--- a/tools/router/src/main.rs
+++ b/tools/router/src/main.rs
@@ -1,47 +1,45 @@
 // SPDX-License-Identifier: EUPL-1.2+
 // SPDX-FileCopyrightText: 2025 Yureka Lilian <yureka@cyberchaos.dev>
+// SPDX-FileCopyrightText: 2025 Alyssa Ross <hi@alyssa.is>
 
 pub(crate) mod packet;
 pub(crate) mod protocol;
 mod router;
 mod upstream;
 
-use std::path::PathBuf;
-
 use packet::*;
 use router::{InterfaceId, Router};
 use upstream::Upstream;
 
-use clap::Parser;
+use anyhow::bail;
 use futures_util::{SinkExt, TryStreamExt};
+use listenfd::ListenFd;
 use log::{error, info};
 use tokio::net::UnixListener;
 use vhost_device_net::{IncomingPacket, VhostDeviceNet};
 use vm_memory::GuestMemoryMmap;
 
-#[derive(Parser, Debug)]
-#[command()] //version = None, about = None, long_about = None)]
-struct Args {
-    #[arg(long)]
-    driver_listen_path: PathBuf,
-    #[arg(long)]
-    app_listen_path: PathBuf,
-}
-
 fn main() -> anyhow::Result<()> {
     env_logger::init();
-    let args = Args::parse();
 
-    for path in [&args.driver_listen_path, &args.app_listen_path] {
-        let _ = std::fs::remove_file(path);
-    }
-
-    run_router(args)
+    run_router()
 }
 #[tokio::main(flavor = "current_thread")]
-async fn run_router(args: Args) -> anyhow::Result<()> {
-    let app_listener = UnixListener::bind(&args.app_listen_path)?;
-    let driver_listener = UnixListener::bind(&args.driver_listen_path)?;
+async fn run_router() -> anyhow::Result<()> {
+    let mut listenfd = ListenFd::from_env();
+
+    let Some(driver_listener) = listenfd.take_unix_listener(0)? else {
+        bail!("not activated with driver socket");
+    };
+    let Some(app_listener) = listenfd.take_unix_listener(1)? else {
+        bail!("not activated with app socket");
+    };
+
+    driver_listener.set_nonblocking(true)?;
+    app_listener.set_nonblocking(true)?;
+
+    let driver_listener = UnixListener::from_std(driver_listener)?;
+    let app_listener = UnixListener::from_std(app_listener)?;
 
     let mut router = Router::<GuestMemoryMmap>::new(InterfaceId::Upstream);
 
-- 
2.51.0