systemd: Move socket activation to module

crates/radicle-node/src/runtime.rs

@@ -347,7 +347,7 @@ impl Runtime {
     #[cfg(all(feature = "systemd", target_family = "unix"))]
     fn receive_listener() -> Option<UnixListener> {
         use std::os::fd::FromRawFd;
-        match radicle_systemd::listen_fd("control") {
+        match radicle_systemd::listen::fd("control") {
             Ok(Some(fd)) => {
                 // NOTE: Here, we should make a call to [`fstat(2)`](man:fstat(2))
                 // and make sure that the file descriptor we received actually

crates/radicle-systemd/Cargo.toml

@@ -7,3 +7,7 @@ license.workspace = true
 edition.workspace = true
 version = "0.9.0"
 rust-version.workspace = true
+
+[features]
+default = ["listen"]
+listen = []

crates/radicle-systemd/src/lib.rs

@@ -1,41 +1,4 @@
 //! Library for interaction with systemd, specialized for Radicle.
 
-use std::env::{remove_var, var, VarError};
+#[cfg(feature = "listen")]
-use std::os::fd::RawFd;
+pub mod listen;
-use std::process::id;
-
-const LISTEN_PID: &str = "LISTEN_PID";
-const LISTEN_FDS: &str = "LISTEN_FDS";
-const LISTEN_FDNAMES: &str = "LISTEN_FDNAMES";
-
-/// Minimum file descriptor used by systemd.
-/// See <https://github.com/systemd/systemd/blob/v254/src/systemd/sd-daemon.h#L56>.
-const SD_LISTEN_FDS_START: RawFd = 3;
-
-/// Checks whether *at most one* file descriptor with given name was passed, returning it.
-/// systemd sending none, more than one, or a file descriptor with a different name, all
-/// results in [`Option::None`], but errors decoding environment variables or missing
-/// environment variables will error.
-/// This is a specialization of [`sd_listen_fds_with_names(3)`](man:sd_listen_fds_with_names(3)).
-/// See:
-///  - <https://www.freedesktop.org/software/systemd/man/254/sd_listen_fds_with_names.html>
-///  - <https://github.com/systemd/systemd/blob/v254/src/libsystemd/sd-daemon/sd-daemon.c>
-///  - <https://0pointer.de/blog/projects/socket-activation.html>
-///  - <https://0pointer.de/blog/projects/socket-activation2.html>
-pub fn listen_fd(name: &str) -> Result<Option<RawFd>, VarError> {
-    let fd = match var(LISTEN_PID) {
-        Err(VarError::NotPresent) => Ok(None),
-        Err(err) => Err(err),
-        Ok(pid) if pid != id().to_string() => Ok(None),
-        _ if var(LISTEN_FDS)? != "1" || var(LISTEN_FDNAMES).ok() != Some(name.to_string()) => {
-            Ok(None)
-        }
-        _ => Ok(Some(SD_LISTEN_FDS_START)),
-    };
-
-    remove_var(LISTEN_PID);
-    remove_var(LISTEN_FDS);
-    remove_var(LISTEN_FDNAMES);
-
-    fd
-}

crates/radicle-systemd/src/listen.rs

@@ -0,0 +1,39 @@
+use std::env::{remove_var, var, VarError};
+use std::os::fd::RawFd;
+use std::process::id;
+
+const LISTEN_PID: &str = "LISTEN_PID";
+const LISTEN_FDS: &str = "LISTEN_FDS";
+const LISTEN_FDNAMES: &str = "LISTEN_FDNAMES";
+
+/// Minimum file descriptor used by systemd.
+/// See <https://github.com/systemd/systemd/blob/v254/src/systemd/sd-daemon.h#L56>.
+const SD_LISTEN_FDS_START: RawFd = 3;
+
+/// Checks whether *at most one* file descriptor with given name was passed, returning it.
+/// systemd sending none, more than one, or a file descriptor with a different name, all
+/// results in [`Option::None`], but errors decoding environment variables or missing
+/// environment variables will error.
+/// This is a specialization of [`sd_listen_fds_with_names(3)`](man:sd_listen_fds_with_names(3)).
+/// See:
+///  - <https://www.freedesktop.org/software/systemd/man/254/sd_listen_fds_with_names.html>
+///  - <https://github.com/systemd/systemd/blob/v254/src/libsystemd/sd-daemon/sd-daemon.c>
+///  - <https://0pointer.de/blog/projects/socket-activation.html>
+///  - <https://0pointer.de/blog/projects/socket-activation2.html>
+pub fn fd(name: &str) -> Result<Option<RawFd>, VarError> {
+    let fd = match var(LISTEN_PID) {
+        Err(VarError::NotPresent) => Ok(None),
+        Err(err) => Err(err),
+        Ok(pid) if pid != id().to_string() => Ok(None),
+        _ if var(LISTEN_FDS)? != "1" || var(LISTEN_FDNAMES).ok() != Some(name.to_string()) => {
+            Ok(None)
+        }
+        _ => Ok(Some(SD_LISTEN_FDS_START)),
+    };
+
+    remove_var(LISTEN_PID);
+    remove_var(LISTEN_FDS);
+    remove_var(LISTEN_FDNAMES);
+
+    fd
+}