src/tools/daemon.rs

   1 //! Helpers for daemons/services.
   2
   3 use std::ffi::CString;
   4 use std::future::Future;
   5 use std::io::{Read, Write};
   6 use std::os::raw::{c_char, c_uchar, c_int};
   7 use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
   8 use std::os::unix::ffi::OsStrExt;
   9 use std::panic::UnwindSafe;
  10 use std::pin::Pin;
  11 use std::task::{Context, Poll};
  12 use std::path::PathBuf;
  13
  14 use anyhow::{bail, format_err, Error};
  15
  16 use proxmox::tools::io::{ReadExt, WriteExt};
  17
  18 use crate::server;
  19 use crate::tools::{fd_change_cloexec, self};
  20
  21 #[link(name = "systemd")]
  22 extern "C" {
  23     fn sd_journal_stream_fd(identifier: *const c_uchar, priority: c_int, level_prefix: c_int) -> c_int;
  24 }
  25
  26 // Unfortunately FnBox is nightly-only and Box<FnOnce> is unusable, so just use Box<Fn>...
  27 pub type BoxedStoreFunc = Box<dyn FnMut() -> Result<String, Error> + UnwindSafe + Send>;
  28
  29 /// Helper trait to "store" something in the environment to be re-used after re-executing the
  30 /// service on a reload.
  31 pub trait Reloadable: Sized {
  32     fn restore(var: &str) -> Result<Self, Error>;
  33     fn get_store_func(&self) -> Result<BoxedStoreFunc, Error>;
  34 }
  35
  36 /// Manages things to be stored and reloaded upon reexec.
  37 /// Anything which should be restorable should be instantiated via this struct's `restore` method,
  38 #[derive(Default)]
  39 pub struct Reloader {
  40     pre_exec: Vec<PreExecEntry>,
  41     self_exe: PathBuf,
  42 }
  43
  44 // Currently we only need environment variables for storage, but in theory we could also add
  45 // variants which need temporary files or pipes...
  46 struct PreExecEntry {
  47     name: &'static str, // Feel free to change to String if necessary...
  48     store_fn: BoxedStoreFunc,
  49 }
  50
  51 impl Reloader {
  52     pub fn new() -> Result<Self, Error> {
  53         Ok(Self {
  54             pre_exec: Vec::new(),
  55
  56             // Get the path to our executable as PathBuf
  57             self_exe: std::fs::read_link("/proc/self/exe")?,
  58         })
  59     }
  60
  61     /// Restore an object from an environment variable of the given name, or, if none exists, uses
  62     /// the function provided in the `or_create` parameter to instantiate the new "first" instance.
  63     ///
  64     /// Values created via this method will be remembered for later re-execution.
  65     pub async fn restore<T, F, U>(&mut self, name: &'static str, or_create: F) -> Result<T, Error>
  66     where
  67         T: Reloadable,
  68         F: FnOnce() -> U,
  69         U: Future<Output = Result<T, Error>>,
  70     {
  71         let res = match std::env::var(name) {
  72             Ok(varstr) => T::restore(&varstr)?,
  73             Err(std::env::VarError::NotPresent) => or_create().await?,
  74             Err(_) => bail!("variable {} has invalid value", name),
  75         };
  76
  77         self.pre_exec.push(PreExecEntry {
  78             name,
  79             store_fn: res.get_store_func()?,
  80         });
  81         Ok(res)
  82     }
  83
  84     fn pre_exec(self) -> Result<(), Error> {
  85         for mut item in self.pre_exec {
  86             std::env::set_var(item.name, (item.store_fn)()?);
  87         }
  88         Ok(())
  89     }
  90
  91     pub fn fork_restart(self) -> Result<(), Error> {
  92         // Get our parameters as Vec<CString>
  93         let args = std::env::args_os();
  94         let mut new_args = Vec::with_capacity(args.len());
  95         for arg in args {
  96             new_args.push(CString::new(arg.as_bytes())?);
  97         }
  98
  99         // Synchronisation pipe:
 100         let (pold, pnew) = super::socketpair()?;
 101
 102         // Start ourselves in the background:
 103         use nix::unistd::{fork, ForkResult};
 104         match fork() {
 105             Ok(ForkResult::Child) => {
 106                 // Double fork so systemd can supervise us without nagging...
 107                 match fork() {
 108                     Ok(ForkResult::Child) => {
 109                         std::mem::drop(pold);
 110                         // At this point we call pre-exec helpers. We must be certain that if they fail for
 111                         // whatever reason we can still call `_exit()`, so use catch_unwind.
 112                         match std::panic::catch_unwind(move || {
 113                             let mut pnew = unsafe {
 114                                 std::fs::File::from_raw_fd(pnew.into_raw_fd())
 115                             };
 116                             let pid = nix::unistd::Pid::this();
 117                             if let Err(e) = unsafe { pnew.write_host_value(pid.as_raw()) } {
 118                                 log::error!("failed to send new server PID to parent: {}", e);
 119                                 unsafe {
 120                                     libc::_exit(-1);
 121                                 }
 122                             }
 123
 124                             let mut ok = [0u8];
 125                             if let Err(e) = pnew.read_exact(&mut ok) {
 126                                 log::error!("parent vanished before notifying systemd: {}", e);
 127                                 unsafe {
 128                                     libc::_exit(-1);
 129                                 }
 130                             }
 131                             assert_eq!(ok[0], 1, "reload handshake should have sent a 1 byte");
 132
 133                             std::mem::drop(pnew);
 134
 135                             // Try to reopen STDOUT/STDERR journald streams to get correct PID in logs
 136                             let ident = CString::new(self.self_exe.file_name().unwrap().as_bytes()).unwrap();
 137                             let ident = ident.as_bytes();
 138                             let fd = unsafe { sd_journal_stream_fd(ident.as_ptr(), libc::LOG_INFO, 1) };
 139                             if fd >= 0 && fd != 1 {
 140                                 let fd = proxmox::tools::fd::Fd(fd); // add drop handler
 141                                 nix::unistd::dup2(fd.as_raw_fd(), 1)?;
 142                             } else {
 143                                 log::error!("failed to update STDOUT journal redirection ({})", fd);
 144                             }
 145                             let fd = unsafe { sd_journal_stream_fd(ident.as_ptr(), libc::LOG_ERR, 1) };
 146                             if fd >= 0 && fd != 2 {
 147                                 let fd = proxmox::tools::fd::Fd(fd); // add drop handler
 148                                 nix::unistd::dup2(fd.as_raw_fd(), 2)?;
 149                             } else {
 150                                 log::error!("failed to update STDERR journal redirection ({})", fd);
 151                             }
 152
 153                             self.do_reexec(new_args)
 154                         })
 155                         {
 156                             Ok(Ok(())) => eprintln!("do_reexec returned!"),
 157                             Ok(Err(err)) => eprintln!("do_reexec failed: {}", err),
 158                             Err(_) => eprintln!("panic in re-exec"),
 159                         }
 160                     }
 161                     Ok(ForkResult::Parent { child }) => {
 162                         std::mem::drop((pold, pnew));
 163                         log::debug!("forked off a new server (second pid: {})", child);
 164                     }
 165                     Err(e) => log::error!("fork() failed, restart delayed: {}", e),
 166                 }
 167                 // No matter how we managed to get here, this is the time where we bail out quickly:
 168                 unsafe {
 169                     libc::_exit(-1)
 170                 }
 171             }
 172             Ok(ForkResult::Parent { child }) => {
 173                 log::debug!("forked off a new server (first pid: {}), waiting for 2nd pid", child);
 174                 std::mem::drop(pnew);
 175                 let mut pold = unsafe {
 176                     std::fs::File::from_raw_fd(pold.into_raw_fd())
 177                 };
 178                 let child = nix::unistd::Pid::from_raw(match unsafe { pold.read_le_value() } {
 179                     Ok(v) => v,
 180                     Err(e) => {
 181                         log::error!("failed to receive pid of double-forked child process: {}", e);
 182                         // systemd will complain but won't kill the service...
 183                         return Ok(());
 184                     }
 185                 });
 186
 187                 if let Err(e) = systemd_notify(SystemdNotify::MainPid(child)) {
 188                     log::error!("failed to notify systemd about the new main pid: {}", e);
 189                 }
 190
 191                 // notify child that it is now the new main process:
 192                 if let Err(e) = pold.write_all(&[1u8]) {
 193                     log::error!("child vanished during reload: {}", e);
 194                 }
 195
 196                 Ok(())
 197             }
 198             Err(e) => {
 199                 log::error!("fork() failed, restart delayed: {}", e);
 200                 Ok(())
 201             }
 202         }
 203     }
 204
 205     fn do_reexec(self, args: Vec<CString>) -> Result<(), Error> {
 206         let exe = CString::new(self.self_exe.as_os_str().as_bytes())?;
 207         self.pre_exec()?;
 208         nix::unistd::setsid()?;
 209         let args: Vec<&std::ffi::CStr> = args.iter().map(|s| s.as_ref()).collect();
 210         nix::unistd::execvp(&exe, &args)?;
 211         panic!("exec misbehaved");
 212     }
 213 }
 214
 215 // For now all we need to do is store and reuse a tcp listening socket:
 216 impl Reloadable for tokio::net::TcpListener {
 217     // NOTE: The socket must not be closed when the store-function is called:
 218     // FIXME: We could become "independent" of the TcpListener and its reference to the file
 219     // descriptor by `dup()`ing it (and check if the listener still exists via kcmp()?)
 220     fn get_store_func(&self) -> Result<BoxedStoreFunc, Error> {
 221         let mut fd_opt = Some(tools::Fd(
 222             nix::fcntl::fcntl(self.as_raw_fd(), nix::fcntl::FcntlArg::F_DUPFD_CLOEXEC(0))?
 223         ));
 224         Ok(Box::new(move || {
 225             let fd = fd_opt.take().unwrap();
 226             fd_change_cloexec(fd.as_raw_fd(), false)?;
 227             Ok(fd.into_raw_fd().to_string())
 228         }))
 229     }
 230
 231     fn restore(var: &str) -> Result<Self, Error> {
 232         let fd = var.parse::<u32>()
 233             .map_err(|e| format_err!("invalid file descriptor: {}", e))?
 234             as RawFd;
 235         fd_change_cloexec(fd, true)?;
 236         Ok(Self::from_std(
 237             unsafe { std::net::TcpListener::from_raw_fd(fd) },
 238         )?)
 239     }
 240 }
 241
 242 pub struct NotifyReady;
 243
 244 impl Future for NotifyReady {
 245     type Output = Result<(), Error>;
 246
 247     fn poll(self: Pin<&mut Self>, _cx: &mut Context) -> Poll<Result<(), Error>> {
 248         systemd_notify(SystemdNotify::Ready)?;
 249         Poll::Ready(Ok(()))
 250     }
 251 }
 252
 253 /// This creates a future representing a daemon which reloads itself when receiving a SIGHUP.
 254 /// If this is started regularly, a listening socket is created. In this case, the file descriptor
 255 /// number will be remembered in `PROXMOX_BACKUP_LISTEN_FD`.
 256 /// If the variable already exists, its contents will instead be used to restore the listening
 257 /// socket.  The finished listening socket is then passed to the `create_service` function which
 258 /// can be used to setup the TLS and the HTTP daemon.
 259 pub async fn create_daemon<F, S>(
 260     address: std::net::SocketAddr,
 261     create_service: F,
 262 ) -> Result<(), Error>
 263 where
 264     F: FnOnce(tokio::net::TcpListener, NotifyReady) -> Result<S, Error>,
 265     S: Future<Output = ()>,
 266 {
 267     let mut reloader = Reloader::new()?;
 268
 269     let listener: tokio::net::TcpListener = reloader.restore(
 270         "PROXMOX_BACKUP_LISTEN_FD",
 271         move || async move { Ok(tokio::net::TcpListener::bind(&address).await?) },
 272     ).await?;
 273
 274     create_service(listener, NotifyReady)?.await;
 275
 276     let mut reloader = Some(reloader);
 277
 278     crate::tools::request_shutdown(); // make sure we are in shutdown mode
 279     if server::is_reload_request() {
 280         log::info!("daemon reload...");
 281         if let Err(e) = systemd_notify(SystemdNotify::Reloading) {
 282             log::error!("failed to notify systemd about the state change: {}", e);
 283         }
 284         if let Err(e) = reloader.take().unwrap().fork_restart() {
 285             log::error!("error during reload: {}", e);
 286             let _ = systemd_notify(SystemdNotify::Status("error during reload".to_string()));
 287         }
 288     } else {
 289         log::info!("daemon shutting down...");
 290     }
 291     Ok(())
 292 }
 293
 294 #[link(name = "systemd")]
 295 extern "C" {
 296     fn sd_notify(unset_environment: c_int, state: *const c_char) -> c_int;
 297 }
 298
 299 pub enum SystemdNotify {
 300     Ready,
 301     Reloading,
 302     Stopping,
 303     Status(String),
 304     MainPid(nix::unistd::Pid),
 305 }
 306
 307 pub fn systemd_notify(state: SystemdNotify) -> Result<(), Error> {
 308     let message = match state {
 309         SystemdNotify::Ready => CString::new("READY=1"),
 310         SystemdNotify::Reloading => CString::new("RELOADING=1"),
 311         SystemdNotify::Stopping => CString::new("STOPPING=1"),
 312         SystemdNotify::Status(msg) => CString::new(format!("STATUS={}", msg)),
 313         SystemdNotify::MainPid(pid) => CString::new(format!("MAINPID={}", pid)),
 314     }?;
 315     let rc = unsafe { sd_notify(0, message.as_ptr()) };
 316     if rc < 0 {
 317         bail!(
 318             "systemd_notify failed: {}",
 319             std::io::Error::from_raw_os_error(-rc),
 320         );
 321     }
 322     Ok(())
 323 }