Add syslog supports (nix-rust#2537)

* Stub for wrap syslog.h

Signed-off-by: tison <wander4096@gmail.com>

* Wrap openlog

Signed-off-by: tison <wander4096@gmail.com>

* Make it work

Signed-off-by: tison <wander4096@gmail.com>

* lib_enums and docs

Signed-off-by: tison <wander4096@gmail.com>

* wrap priority

Signed-off-by: tison <wander4096@gmail.com>

* reduce error handle noise and add docs

Signed-off-by: tison <wander4096@gmail.com>

* try add setlogmask

Signed-off-by: tison <wander4096@gmail.com>

* Revert "try add setlogmask"

This reverts commit 98289d5.

* fixup tests

Signed-off-by: tison <wander4096@gmail.com>

* fixup all

Signed-off-by: tison <wander4096@gmail.com>

* add changelog

Signed-off-by: tison <wander4096@gmail.com>

* turn on syslog for tests

Signed-off-by: tison <wander4096@gmail.com>

* revert irrelevant format

Signed-off-by: tison <wander4096@gmail.com>

* add new feature flags

Signed-off-by: tison <wander4096@gmail.com>

* Add back closelog

Signed-off-by: tison <wander4096@gmail.com>

* Use AsRef<OsStr> for openlog.ident

Signed-off-by: tison <wander4096@gmail.com>

* polish APIs

Signed-off-by: tison <wander4096@gmail.com>

* fixup

Signed-off-by: tison <wander4096@gmail.com>

* test on linux

Signed-off-by: tison <wander4096@gmail.com>

* test on unix

Signed-off-by: tison <wander4096@gmail.com>

* fixup flags

Signed-off-by: tison <wander4096@gmail.com>

* fixup all

Signed-off-by: tison <wander4096@gmail.com>

* Update src/syslog.rs

Co-authored-by: SteveLauC <stevelauc@outlook.com>

* refactor: use AsRef<OsStr> on non-Linux and &'static CStr on Linux for ident arg of openlog

* style: fmt

* fix: Linux build by importing CStr

---------

Signed-off-by: tison <wander4096@gmail.com>
Co-authored-by: SteveLauC <stevelauc@outlook.com>

Cargo.toml

@@ -64,6 +64,7 @@ resource = []
 sched = ["process"]
 signal = ["process"]
 socket = ["memoffset"]
+syslog = []
 term = []
 time = []
 ucontext = ["signal"]
@@ -80,7 +81,7 @@ semver = "1.0.7"
 nix = { path = ".", features = ["acct", "aio", "dir", "env", "event", "fanotify",
     "feature", "fs", "hostname", "inotify", "ioctl", "kmod", "mman", "mount", "mqueue",
     "net", "personality", "poll", "pthread", "ptrace", "quota", "process", "reboot",
-    "resource", "sched", "signal", "socket", "term", "time", "ucontext", "uio",
+    "resource", "sched", "signal", "socket", "syslog", "term", "time", "ucontext", "uio",
     "user", "zerocopy"] }
 
 [target.'cfg(any(target_os = "android", target_os = "linux"))'.dev-dependencies]

changelog/2537.added.md

@@ -0,0 +1 @@
+Add support for `syslog`, `openlog`, `closelog` on all `unix`.

src/lib.rs

@@ -34,6 +34,7 @@
 //! * `sched` - Manipulate process's scheduling
 //! * `socket` - Sockets, whether for networking or local use
 //! * `signal` - Send and receive signals to processes
+//! * `syslog` - System logging
 //! * `term` - Terminal control APIs
 //! * `time` - Query the operating system's clocks
 //! * `ucontext` - User thread context
@@ -79,6 +80,7 @@
         feature = "sched",
         feature = "socket",
         feature = "signal",
+        feature = "syslog",
         feature = "term",
         feature = "time",
         feature = "ucontext",
@@ -200,6 +202,11 @@ feature! {
     pub mod spawn;
 }
 
+feature! {
+    #![feature = "syslog"]
+    pub mod syslog;
+}
+
 use std::ffi::{CStr, CString, OsStr};
 use std::mem::MaybeUninit;
 use std::os::unix::ffi::OsStrExt;

src/syslog.rs

@@ -0,0 +1,216 @@
+//! Interfaces for controlling system log.
+
+use crate::{NixPath, Result};
+use std::ffi::OsStr;
+use std::ptr;
+
+/// Logging options of subsequent [`syslog`] calls can be set by calling [`openlog`].
+///
+/// The parameter `ident` is a string that will be prepended to every message. The `logopt`
+/// argument specifies logging options. The `facility` parameter encodes a default facility to be
+/// assigned to all messages that do not have an explicit facility encoded.
+//
+// On Linux, the `ident` argument needs to have static lifetime according to the
+// man page:
+//
+// The argument ident in the call of openlog() is probably stored as-is. Thus,
+// if the string it points to is changed, syslog() may start prepending the changed
+// string, and if the string it points to ceases to exist, the results are
+// undefined.  Most portable is to use a string constant.
+#[cfg(target_os = "linux")]
+pub fn openlog(
+    ident: Option<&'static std::ffi::CStr>,
+    logopt: LogFlags,
+    facility: Facility,
+) -> Result<()> {
+    let logopt = logopt.bits();
+    let facility = facility as libc::c_int;
+    match ident {
+        None => unsafe {
+            libc::openlog(ptr::null(), logopt, facility);
+        },
+        Some(ident) => ident.with_nix_path(|ident| unsafe {
+            libc::openlog(ident.as_ptr(), logopt, facility);
+        })?,
+    }
+
+    Ok(())
+}
+
+/// Logging options of subsequent [`syslog`] calls can be set by calling [`openlog`].
+///
+/// The parameter `ident` is a string that will be prepended to every message. The `logopt`
+/// argument specifies logging options. The `facility` parameter encodes a default facility to be
+/// assigned to all messages that do not have an explicit facility encoded.
+#[cfg(not(target_os = "linux"))]
+pub fn openlog<S: AsRef<OsStr> + ?Sized>(
+    ident: Option<&S>,
+    logopt: LogFlags,
+    facility: Facility,
+) -> Result<()> {
+    let logopt = logopt.bits();
+    let facility = facility as libc::c_int;
+    match ident.map(OsStr::new) {
+        None => unsafe {
+            libc::openlog(ptr::null(), logopt, facility);
+        },
+        Some(ident) => ident.with_nix_path(|ident| unsafe {
+            libc::openlog(ident.as_ptr(), logopt, facility);
+        })?,
+    }
+
+    Ok(())
+}
+
+/// Writes message to the system message logger.
+///
+/// The message is then written to the system console, log files, logged-in users, or forwarded
+/// to other machines as appropriate.
+///
+/// # Examples
+///
+/// ```rust
+/// use nix::syslog::{openlog, syslog, Facility, LogFlags, Severity, Priority};
+///
+/// let priority = Priority::new(Severity::LOG_EMERG, Facility::LOG_USER);
+/// syslog(priority, "Hello, nix!").unwrap();
+///
+/// // use `format!` to format the message
+/// let name = "syslog";
+/// syslog(priority, &format!("Hello, {name}!")).unwrap();
+/// ```
+pub fn syslog<P, S>(priority: P, message: &S) -> Result<()>
+where
+    P: Into<Priority>,
+    S: AsRef<OsStr> + ?Sized,
+{
+    let priority = priority.into();
+    let formatter = OsStr::new("%s");
+    let message = OsStr::new(message);
+    formatter.with_nix_path(|formatter| {
+        message.with_nix_path(|message| unsafe {
+            libc::syslog(priority.0, formatter.as_ptr(), message.as_ptr())
+        })
+    })??;
+    Ok(())
+}
+
+/// Closes the log file.
+pub fn closelog() {
+    unsafe { libc::closelog() }
+}
+
+/// The priority for a log message.
+#[derive(Debug, Clone, Copy)]
+pub struct Priority(libc::c_int);
+
+impl Priority {
+    /// Create a new priority from a facility and severity level.
+    pub fn new(severity: Severity, facility: Facility) -> Self {
+        let priority = (facility as libc::c_int) | (severity as libc::c_int);
+        Priority(priority)
+    }
+}
+
+impl From<Severity> for Priority {
+    fn from(severity: Severity) -> Self {
+        let priority = severity as libc::c_int;
+        Priority(priority)
+    }
+}
+
+libc_bitflags! {
+    /// Options for system logging.
+    pub struct LogFlags: libc::c_int {
+        /// Log the process id with each message: useful for identifying instantiations of
+        /// daemons.
+        LOG_PID;
+        /// If syslog() cannot pass the message to syslogd(8) it will attempt to write the
+        /// message to the console ("/dev/console").
+        LOG_CONS;
+        /// The converse of [`LOG_NDELAY`][LogFlags::LOG_NDELAY]; opening of the connection is
+        /// delayed until `syslog` is called.
+        ///
+        /// This is the default, and need not be specified.
+        LOG_ODELAY;
+        /// Open the connection to syslogd(8) immediately. Normally the open is delayed until
+        /// the first message is logged. Useful for programs that need to manage the order in
+        /// which file descriptors are allocated.
+        LOG_NDELAY;
+        /// Write the message to standard error output as well to the system log.
+        #[cfg(not(any(target_os = "redox", target_os = "illumos")))]
+        LOG_PERROR;
+    }
+}
+
+libc_enum! {
+    /// Severity levels for log messages.
+    #[repr(i32)]
+    #[non_exhaustive]
+    pub enum Severity {
+        /// A panic condition.
+        ///
+        /// This is normally broadcast to all users.
+        LOG_EMERG,
+        /// A condition that should be corrected immediately, such as a corrupted system database.
+        LOG_ALERT,
+        /// Critical conditions, e.g., hard device errors.
+        LOG_CRIT,
+        /// Errors.
+        LOG_ERR,
+        /// Warning messages.
+        LOG_WARNING,
+        /// Conditions that are not error conditions, but should possibly be handled specially.
+        LOG_NOTICE,
+        /// Informational messages.
+        LOG_INFO,
+        /// Messages that contain information normally of use only when debugging a program.
+        LOG_DEBUG,
+    }
+}
+
+libc_enum! {
+    /// Facilities for log messages.
+    #[repr(i32)]
+    #[non_exhaustive]
+    pub enum Facility {
+        /// Messages generated by the kernel.
+        ///
+        /// These cannot be generated by any user processes.
+        LOG_KERN,
+        /// Messages generated by random user processes.
+        ///
+        /// This is the default facility identifier if none is specified.
+        LOG_USER,
+        /// The mail system.
+        LOG_MAIL,
+        /// System daemons, such as routed(8), that are not provided for explicitly by other facilities.
+        LOG_DAEMON,
+        /// The authorization system: login(1), su(1), getty(8), etc.
+        LOG_AUTH,
+        /// Messages generated internally by syslogd(8).
+        LOG_SYSLOG,
+        /// The line printer spooling system: cups-lpd(8), cupsd(8), etc.
+        LOG_LPR,
+        /// The network news system.
+        LOG_NEWS,
+        /// The uucp system.
+        LOG_UUCP,
+        /// Reserved for local use.
+        LOG_LOCAL0,
+        /// Reserved for local use.
+        LOG_LOCAL1,
+        /// Reserved for local use.
+        LOG_LOCAL2,
+        /// Reserved for local use.
+        LOG_LOCAL3,
+        /// Reserved for local use.
+        LOG_LOCAL4,
+        /// Reserved for local use.
+        LOG_LOCAL5,
+        /// Reserved for local use.
+        LOG_LOCAL6,
+        /// Reserved for local use.
+        LOG_LOCAL7,
+    }
+}

test/test.rs

@@ -42,6 +42,8 @@ mod test_sendfile;
 ))]
 mod test_spawn;
 
+mod test_syslog;
+
 mod test_time;
 mod test_unistd;
 

test/test_syslog.rs

@@ -0,0 +1,38 @@
+use nix::syslog::{openlog, syslog, Facility, LogFlags, Severity};
+
+#[test]
+fn test_syslog_hello_world() {
+    let flags = LogFlags::LOG_PID;
+
+    #[cfg(not(target_os = "linux"))]
+    openlog(None::<&str>, flags, Facility::LOG_USER).unwrap();
+    #[cfg(target_os = "linux")]
+    openlog(None, flags, Facility::LOG_USER).unwrap();
+
+    syslog(Severity::LOG_EMERG, "Hello, nix!").unwrap();
+    let name = "syslog";
+    syslog(Severity::LOG_NOTICE, &format!("Hello, {name}!")).unwrap();
+}
+
+#[test]
+#[cfg(target_os = "linux")]
+fn test_openlog_with_ident() {
+    use std::ffi::CStr;
+
+    const IDENT: &CStr = unsafe {
+        CStr::from_bytes_with_nul_unchecked(b"test_openlog_with_ident\0")
+    };
+
+    let flags = LogFlags::LOG_PID;
+    openlog(Some(IDENT), flags, Facility::LOG_USER).unwrap();
+    syslog(Severity::LOG_EMERG, "Hello, ident!").unwrap();
+}
+
+#[test]
+#[cfg(not(target_os = "linux"))]
+fn test_openlog_with_ident() {
+    let flags = LogFlags::LOG_PID;
+    openlog(Some("test_openlog_with_ident"), flags, Facility::LOG_USER)
+        .unwrap();
+    syslog(Severity::LOG_EMERG, "Hello, ident!").unwrap();
+}