Add setdomainname function (#1244)

* Add setdomainname function

* Use `libc::setdomainname` where possible

Use weak `setdomainname` only for android; remove this special case
once [libc#4212] is merged.

[libc#4212]: rust-lang/libc#4212

* Disable setdomainname on illumos and solaris

Author: yuki0iq

src/backend/libc/system/syscalls.rs

@@ -63,6 +63,44 @@ pub(crate) fn sethostname(name: &[u8]) -> io::Result<()> {
     }
 }
 
+#[cfg(not(any(
+    target_os = "android",
+    target_os = "emscripten",
+    target_os = "espidf",
+    target_os = "illumos",
+    target_os = "haiku",
+    target_os = "redox",
+    target_os = "solaris",
+    target_os = "vita",
+    target_os = "wasi"
+)))]
+pub(crate) fn setdomainname(name: &[u8]) -> io::Result<()> {
+    unsafe {
+        ret(c::setdomainname(
+            name.as_ptr().cast(),
+            name.len().try_into().map_err(|_| io::Errno::INVAL)?,
+        ))
+    }
+}
+
+// https://github.com/rust-lang/libc/pull/4212
+#[cfg(target_os = "android")]
+pub(crate) fn setdomainname(name: &[u8]) -> io::Result<()> {
+    syscall! {
+        fn setdomainname(
+            name: *const c::c_char,
+            len: c::size_t
+        ) via SYS_setdomainname -> c::c_int
+    }
+
+    unsafe {
+        ret(setdomainname(
+            name.as_ptr().cast(),
+            name.len().try_into().map_err(|_| io::Errno::INVAL)?,
+        ))
+    }
+}
+
 #[cfg(target_os = "linux")]
 pub(crate) fn reboot(cmd: RebootCommand) -> io::Result<()> {
     unsafe { ret(c::reboot(cmd as i32)) }

src/backend/linux_raw/system/syscalls.rs

@@ -39,6 +39,12 @@ pub(crate) fn sethostname(name: &[u8]) -> io::Result<()> {
     unsafe { ret(syscall_readonly!(__NR_sethostname, ptr, len)) }
 }
 
+#[inline]
+pub(crate) fn setdomainname(name: &[u8]) -> io::Result<()> {
+    let (ptr, len) = slice(name);
+    unsafe { ret(syscall_readonly!(__NR_setdomainname, ptr, len)) }
+}
+
 #[inline]
 pub(crate) fn reboot(cmd: RebootCommand) -> io::Result<()> {
     unsafe {

src/system.rs

@@ -168,6 +168,29 @@ pub fn sethostname(name: &[u8]) -> io::Result<()> {
     backend::system::syscalls::sethostname(name)
 }
 
+/// `setdomain(name)`—Sets the system NIS domain name.
+///
+/// # References
+///  - [Linux]
+///  - [FreeBSD]
+///
+/// [Linux]: https://man7.org/linux/man-pages/man2/setdomainname.2.html
+/// [FreeBSD]: https://man.freebsd.org/cgi/man.cgi?query=setdomainname&sektion=3
+#[cfg(not(any(
+    target_os = "emscripten",
+    target_os = "espidf",
+    target_os = "haiku",
+    target_os = "illumos",
+    target_os = "redox",
+    target_os = "solaris",
+    target_os = "vita",
+    target_os = "wasi"
+)))]
+#[inline]
+pub fn setdomainname(name: &[u8]) -> io::Result<()> {
+    backend::system::syscalls::setdomainname(name)
+}
+
 /// Reboot command for use with [`reboot`].
 #[cfg(target_os = "linux")]
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]