move src/tools/daemon.rs to proxmox-rest-server workspace

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

proxmox-rest-server/src/lib.rs

@@ -1,4 +1,10 @@
-use anyhow::{bail, Error};
+use std::os::unix::io::RawFd;
+
+use anyhow::{bail, format_err, Error};
+
+use proxmox::tools::fd::Fd;
+
+pub mod daemon;
 
 mod state;
 pub use state::*;
@@ -52,3 +58,26 @@ pub fn fail_on_shutdown() -> Result<(), Error> {
     Ok(())
 }
 
+/// Helper to set/clear the FD_CLOEXEC flag on file descriptors
+pub fn fd_change_cloexec(fd: RawFd, on: bool) -> Result<(), Error> {
+    use nix::fcntl::{fcntl, FdFlag, F_GETFD, F_SETFD};
+    let mut flags = FdFlag::from_bits(fcntl(fd, F_GETFD)?)
+        .ok_or_else(|| format_err!("unhandled file flags"))?; // nix crate is stupid this way...
+    flags.set(FdFlag::FD_CLOEXEC, on);
+    fcntl(fd, F_SETFD(flags))?;
+    Ok(())
+}
+
+/// safe wrapper for `nix::sys::socket::socketpair` defaulting to `O_CLOEXEC` and guarding the file
+/// descriptors.
+pub fn socketpair() -> Result<(Fd, Fd), Error> {
+    use nix::sys::socket;
+    let (pa, pb) = socket::socketpair(
+        socket::AddressFamily::Unix,
+        socket::SockType::Stream,
+        None,
+        socket::SockFlag::SOCK_CLOEXEC,
+    )?;
+    Ok((Fd(pa), Fd(pb)))
+}
+