daemon w/ tests PoC

src/daemon.rs

@@ -1,6 +1,7 @@
 use std::{
     env, io,
     os::fd::{AsFd, BorrowedFd, IntoRawFd, OwnedFd, RawFd},
+    process::{Command, Stdio},
     sync::{
         Arc, LazyLock,
         atomic::{AtomicUsize, Ordering},
@@ -12,7 +13,20 @@ use iddqd::{BiHashMap, IdOrdMap};
 
 use mio::{Events, Interest, Poll, Token, event::Event, net::UnixListener, unix::SourceFd};
 
-use rustix::{buffer::spare_capacity, net::SocketFlags, process::Uid};
+use rustix::{
+    buffer::spare_capacity,
+    net::SocketFlags,
+    process::{Pid, PidfdFlags, Uid, WaitId, WaitIdOptions},
+};
+
+mod rustix {
+    pub use rustix::process::{getuid, pidfd_open, waitid};
+    pub use rustix::*;
+}
+
+//mod rustix_prelude {
+//    pub use rustix::process::{getuid, pidfd_open, waitid};
+//}
 
 use serde_json::StreamDeserializer;
 
@@ -21,10 +35,7 @@ use crate::prelude::*;
 pub mod api;
 use api::DaemonCmd;
 
-use crate::{
-    SourceFile, SourceLine,
-    daemon_tokfd::{FdInfo, FdKind},
-};
+use crate::daemon_tokfd::{FdInfo, FdKind};
 
 use crate::{OwnedFdWithFlags, TokenFd};
 
@@ -45,6 +56,22 @@ pub static TMPDIR: LazyLock<&'static Path> = LazyLock::new(|| {
     Box::leak(dir)
 });
 
+pub static NIXOS_REBUILD: LazyLock<&'static Path> = LazyLock::new(|| {
+    which::which("nixos-rebuild")
+        .inspect_err(|e| error!("couldn't find `nixos-rebuild` in PATH: {e}"))
+        .map(PathBuf::into_boxed_path)
+        .map(|boxed| &*Box::leak(boxed))
+        .unwrap_or(Path::new("/run/current-system/sw/bin/nixos-rebuild"))
+});
+
+pub static NIX: LazyLock<&'static Path> = LazyLock::new(|| {
+    which::which("nix")
+        .inspect_err(|e| error!("couldn't find `nix` in PATH: {e}"))
+        .map(PathBuf::into_boxed_path)
+        .map(|boxed| &*Box::leak(boxed))
+        .unwrap_or(Path::new("/run/current-system/sw/bin/nix"))
+});
+
 const TIMEOUT_NEVER: Option<Duration> = None;
 
 static NEXT_TOKEN_NUMBER: AtomicUsize = AtomicUsize::new(1);
@@ -60,6 +87,42 @@ fn next_token() -> Token {
     Token(tok)
 }
 
+trait EventExt {
+    type Display;
+
+    fn display(&self) -> Self::Display;
+}
+
+#[derive(Copy)]
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+struct EventDisplay {
+    token: Token,
+    error: bool,
+    writable: bool,
+    write_closed: bool,
+    readable: bool,
+    read_closed: bool,
+}
+impl EventExt for Event {
+    type Display = EventDisplay;
+
+    fn display(&self) -> Self::Display {
+        EventDisplay {
+            token: self.token(),
+            error: self.is_error(),
+            writable: self.is_writable(),
+            write_closed: self.is_write_closed(),
+            readable: self.is_readable(),
+            read_closed: self.is_read_closed(),
+        }
+    }
+}
+impl Display for EventDisplay {
+    fn fmt(&self, f: &mut Formatter) -> FmtResult {
+        todo!()
+    }
+}
+
 #[derive(Debug)]
 pub struct Daemon {
     config_path: Arc<Path>,
@@ -132,6 +195,32 @@ impl Daemon {
         token
     }
 
+    fn register_with_name<S>(&mut self, fd: RawFd, kind: FdKind, name: Box<OsStr>) -> Token {
+        let token = next_token();
+
+        debug!(
+            "Registering new {} FdInfo for {fd} ({}) with token {token:?}",
+            name.to_string_lossy(),
+            kind.name_str(),
+        );
+
+        self.fd_info
+            .insert_unique(FdInfo::new_with_name(fd, kind, name))
+            .unwrap();
+
+        self.tokfd
+            .insert_unique(TokenFd { token, fd })
+            .unwrap_or_else(|e| todo!("{e}"));
+
+        let mut source = SourceFd(&fd);
+        self.poller
+            .registry()
+            .register(&mut source, token, Interest::READABLE)
+            .unwrap_or_else(|e| unreachable!("registering {fd:?} with poller failed: {e}"));
+
+        token
+    }
+
     fn deregister(&mut self, fd: RawFd) {
         let info = self
             .fd_info
@@ -279,6 +368,32 @@ const DAEMON: Token = Token(0);
 
 /// Private helpers.
 impl Daemon {
+    fn proxy_stdio(&mut self, fd: &BorrowedFd) -> Result<(), IoError> {
+        let info = self.fd_info.get(&fd.as_raw_fd()).unwrap();
+        let label = match info.kind {
+            FdKind::ChildStdout => "stdout",
+            FdKind::ChildStderr => "stderr",
+            other => unreachable!("child stdio cannot have kind {other:?}"),
+        };
+        // FIXME: don't use a new allocation every time.
+        let mut buffer: Vec<u8> = Vec::with_capacity(1024);
+        // FIXME: handle line buffering correctly.
+        loop {
+            let count = rustix::io::read(fd, spare_capacity(&mut buffer))
+                .inspect_err(|e| error!("read() on child stdio fd {fd:?} failed: {e}"))?;
+
+            if count == 0 {
+                break;
+            }
+
+            for line in buffer.lines() {
+                info!("[child {label}]: {}", line.as_bstr())
+            }
+        }
+
+        Ok(())
+    }
+
     fn read_cmd(&mut self, fd: &BorrowedFd) -> Result<(), IoError> {
         // FIXME: don't use a new allocation every time.
         let mut cmd_buffer: Vec<u8> = Vec::with_capacity(1024);
@@ -317,42 +432,82 @@ impl Daemon {
     }
 
     fn dispatch_cmd(&mut self, cmd: DaemonCmd) -> Result<(), IoError> {
+        // Write the new file...
         let (name, value) = match cmd {
             DaemonCmd::Append { name, value } => (name, value),
         };
-        let mut opts = File::options();
-        opts.read(true)
-            .write(true)
-            .create(false)
-            .custom_flags(libc::O_CLOEXEC);
-        let source_file = SourceFile::open_from(self.config_path.clone(), opts)?;
+        let source_file = crate::open_source_file(self.config_path.clone())?;
         let pri = crate::get_where(source_file.clone()).unwrap_or_else(|e| todo!("{e}"));
         let new_pri = pri - 1;
-        //let new_pri_line =
-        //    crate::get_next_prio_line(source_file.clone(), Arc::from(name), Arc::from(value));
         // Get next priority line.
-        let source_lines = source_file.lines()?;
-        let penultimate = source_lines.get(source_lines.len() - 2);
-        // FIXME: don't rely on whitespace lol
-        debug_assert_eq!(penultimate.map(SourceLine::text).as_deref(), Some("  ];"));
-        let penultimate = penultimate.unwrap();
-        let new_generation = 0 - new_pri;
-        let new_line = SourceLine {
-            line: penultimate.line,
-            path: source_file.path(),
-            text: Arc::from(format!(
-                "      {} = lib.mkOverride ({}) ({}); # DYNIX GENERATION {}",
-                name.to_nix_decl(),
-                new_pri,
-                value,
-                new_generation,
-            )),
-        };
-
-        drop(source_lines);
+        let opt_name = name.to_nix_decl();
+        let new_line = crate::get_next_prio_line(
+            source_file.clone(),
+            &opt_name,
+            new_pri,
+            &value.to_nix_source(),
+        )
+        .unwrap_or_else(|e| panic!("someone is holding a reference to source.lines(): {e}"));
 
         crate::write_next_prio(source_file, new_line).unwrap_or_else(|e| todo!("{e}"));
 
+        // Rebuild and switch.
+        // FIXME: allow passing additional args.
+        //let child = Command::new(*NIXOS_REBUILD)
+        //    .arg("switch")
+        //    .arg("--log-format")
+        //    .arg("raw-with-logs")
+        //    .arg("--no-reexec")
+        //    .arg("-v")
+        //    .stdout(Stdio::piped())
+        //    .stderr(Stdio::piped())
+        //    .spawn()
+        //    .inspect_err(|e| {
+        //        error!("failed to spawn `nixos-rebuild` command: {e}");
+        //    })?;
+
+        let expr = "(import <nixpkgs/nixos> { }).config.dynamicism.applyDynamicConfiguration { }";
+        let child = Command::new(*NIX)
+            .arg("run")
+            .arg("--show-trace")
+            .arg("--log-format")
+            .arg("raw-with-logs")
+            .arg("--impure")
+            .arg("-E")
+            .arg(expr)
+            .stdout(Stdio::piped())
+            .stderr(Stdio::piped())
+            .spawn()
+            .inspect_err(|e| error!("failed to spawn `nix run` command: {e}"))?;
+
+        debug!("Spanwed child process {}", child.id());
+
+        let pid = Pid::from_child(&child);
+
+        let stdout = child.stdout.unwrap_or_else(|| {
+            unreachable!("`child` is given `.stdout(Stdio::piped())`");
+        });
+        let stderr = child.stderr.unwrap_or_else(|| {
+            unreachable!("`child` is given `.stderr(Stdio::piped())`");
+        });
+
+        let _token = self.register(stdout.into_raw_fd(), FdKind::ChildStdout);
+        let _token = self.register(stderr.into_raw_fd(), FdKind::ChildStderr);
+
+        match rustix::process::pidfd_open(pid, PidfdFlags::NONBLOCK) {
+            Ok(pidfd) => {
+                debug!("Opened pidfd {pidfd:?}, for process {pid}");
+                self.register(pidfd.into_raw_fd(), FdKind::Pid(pid));
+            },
+            Err(e) if e.kind() == IoErrorKind::NotFound => {
+                warn!("child {pid} not found; died before we could open it?");
+            },
+            Err(e) => {
+                error!("Error opening pidfd for child {pid}: {e}");
+                return Err(e)?;
+            },
+        }
+
         Ok(())
     }
 
@@ -386,9 +541,9 @@ impl Daemon {
 
         loop {
             if tracing::enabled!(tracing::Level::DEBUG) {
-                trace!("Daemon loop iteration, with file descriptors: ");
+                debug!("Daemon loop iteration, with file descriptors: ");
                 for info in &self.fd_info {
-                    trace!("- {}", info.display());
+                    debug!("- {}", info.display());
                 }
             }
 
@@ -441,7 +596,7 @@ impl Daemon {
     }
 
     fn handle_event(&mut self, event: &Event) -> Result<(), IoError> {
-        trace!("Handling event {event:?}");
+        trace!("Handling event {event:#?}");
 
         match event.token() {
             DAEMON => {
@@ -487,16 +642,92 @@ impl Daemon {
             },
             other_token => {
                 // This must be a stream fd.
-                let stream_fd = self.fd_for_token(other_token).unwrap_or_else(|| {
+                let fd = self.fd_for_token(other_token).unwrap_or_else(|| {
                     unreachable!("tried to get fd for non-existent token? {other_token:?}")
                 });
+                let Some(info) = self.fd_info.get(&fd) else {
+                    panic!("Received an event on an unregistered fd {fd}; IO-safety violation?");
+                };
+
+                let either_available = event.is_readable() || event.is_writable();
+                if !either_available {
+                    info!(
+                        "File descriptor {} r:{}, w:{}",
+                        info.display(),
+                        event.is_readable(),
+                        event.is_writable(),
+                    );
+                    // FIXME: code duplication
+                    if event.is_read_closed() {
+                        self.deregister(fd);
+                        return Ok(());
+                    }
+                }
+
+                match info.kind {
+                    FdKind::Pid(pid) => {
+                        debug!("Reaping child process {pid}");
+                        // SAFETY: `fd` cannot have been closed yet, since that's what we do here.
+                        let pidfd = unsafe { BorrowedFd::borrow_raw(fd) };
+                        let status = rustix::waitid(WaitId::PidFd(pidfd), WaitIdOptions::EXITED)
+                            .unwrap_or_else(|e| {
+                                todo!("waitid() can fail? on pid {pid}: {e}");
+                            })
+                            .unwrap_or_else(|| {
+                                todo!("waitid() returned None? for pid {pid}");
+                            });
+
+                        debug!("waitid() for pid {pid} returned status: {status:?}");
+                        let is_dead = status.exited() || status.killed() || status.dumped();
+                        if !is_dead {
+                            todo!("Handle process {pid} events that aren't death: {status:?}");
+                        }
+                        let Some(exit_code) = status.exit_status() else {
+                            unreachable!("Process {pid} died with no exit code at all? {status:?}");
+                        };
+                        debug!("Child process {pid} exited with code {exit_code}");
+
+                        // Close the pidfd.
+                        self.deregister(fd);
+
+                        let stream = self
+                            .fd_info
+                            .iter()
+                            .find_map(|info| (info.kind == FdKind::SockStream).then_some(info));
+                        if let Some(stream) = stream {
+                            // SAFETY: fixme.
+                            let stream_fd = unsafe { BorrowedFd::borrow_raw(stream.fd) };
+                            let payload = format!("{{ \"status\": {exit_code} }}\n");
+                            if let Err(e) = rustix::io::write(stream_fd, payload.as_bytes()) {
+                                error!("couldn't write reply to stream fd {stream_fd:?}: {e}");
+                            }
+                        }
+                    },
+                    FdKind::ChildStdout => {
+                        warn!("got stdout");
+                        // SAFETY: oh boy.
+                        let stdout = unsafe { BorrowedFd::borrow_raw(fd) };
+                        self.proxy_stdio(&stdout)
+                            .unwrap_or_else(|e| error!("failed to proxy child stdout: {e}"));
+                    },
+                    FdKind::ChildStderr => {
+                        warn!("got stderr");
+                        // SAFETY: oh boy.
+                        let stderr = unsafe { BorrowedFd::borrow_raw(fd) };
+                        self.proxy_stdio(&stderr)
+                            .unwrap_or_else(|e| error!("failed to proxy child stderr: {e}"));
+                    },
+                    FdKind::SockStream => {
+                        // SAFETY: oh boy.
+                        let stream_fd = unsafe { BorrowedFd::borrow_raw(fd) };
+                        self.read_cmd(&stream_fd).unwrap();
+                    },
+                    kind => todo!("{kind:?}"),
+                };
 
                 if event.is_read_closed() {
-                    self.deregister(stream_fd);
-                } else {
-                    // SAFETY: oh boy.
-                    let stream_fd = unsafe { BorrowedFd::borrow_raw(stream_fd) };
-                    self.read_cmd(&stream_fd).unwrap();
+                    self.deregister(fd);
+                    return Ok(());
                 }
             },
         }

src/daemon/api.rs

@@ -47,6 +47,24 @@ impl ConvenientAttrPath {
     }
 }
 
+#[derive(Debug, Clone, PartialEq)]
+#[derive(Deserialize, Serialize)]
+#[serde(untagged)]
+pub enum NixLiteral {
+    String(String),
+    Number(f64),
+    // FIXME: add the rest =P
+}
+
+impl NixLiteral {
+    pub fn to_nix_source(&self) -> String {
+        match self {
+            NixLiteral::String(s) => format!("\"{s}\""),
+            NixLiteral::Number(n) => n.to_string(),
+        }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq)]
 #[derive(serde::Deserialize, serde::Serialize)]
 #[serde(tag = "action", content = "args", rename_all = "snake_case")]
@@ -54,6 +72,6 @@ impl ConvenientAttrPath {
 pub enum DaemonCmd {
     Append {
         name: ConvenientAttrPath,
-        value: Box<str>,
+        value: Box<NixLiteral>,
     },
 }

src/daemon_tokfd.rs

@@ -3,6 +3,7 @@ use std::{os::fd::RawFd, sync::OnceLock};
 use circular_buffer::CircularBuffer;
 use iddqd::{BiHashItem, IdOrdItem};
 use mio::Token;
+use rustix::process::Pid;
 
 use crate::prelude::*;
 
@@ -76,11 +77,11 @@ impl FdInfo {
 impl IdOrdItem for FdInfo {
     type Key<'a> = &'a RawFd;
 
+    iddqd::id_upcast!();
+
     fn key(&self) -> &RawFd {
         &self.fd
     }
-
-    iddqd::id_upcast!();
 }
 
 #[derive(Debug)]
@@ -105,13 +106,16 @@ impl<'a> Display for FdInfoDisplay<'a> {
 }
 
 #[derive(Copy)]
-#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Default)]
 #[non_exhaustive]
 pub enum FdKind {
     File,
     Socket,
     SockStream,
     Poller,
+    ChildStdout,
+    ChildStderr,
+    Pid(Pid),
     #[default]
     Unknown,
 }
@@ -124,6 +128,9 @@ impl FdKind {
             Socket => "socket",
             SockStream => "socket stream",
             Poller => "poller",
+            ChildStdout => "child stdout",
+            ChildStderr => "child stderr",
+            Pid(_) => "pidfd",
             Unknown => "«unknown»",
         }
     }
@@ -140,6 +147,8 @@ impl BiHashItem for TokenFd {
     type K1<'a> = Token;
     type K2<'a> = RawFd;
 
+    iddqd::bi_upcast!();
+
     fn key1(&self) -> Token {
         self.token
     }
@@ -147,8 +156,6 @@ impl BiHashItem for TokenFd {
     fn key2(&self) -> RawFd {
         self.fd
     }
-
-    iddqd::bi_upcast!();
 }
 
 impl From<TokenFd> for (Token, RawFd) {

src/lib.rs

@@ -99,6 +99,22 @@ static MK_OVERRIDE_RE: LazyLock<Regex> = LazyLock::new(|| {
     Regex::new(r"(?-u)\bmkOverride\s+\((?<priority>[\d-]+)\)").unwrap()
 });
 
+pub(crate) fn open_source_file(path: Arc<Path>) -> Result<SourceFile, IoError> {
+    let mut opts = File::options();
+    opts.read(true)
+        .write(true)
+        .create(false)
+        .custom_flags(libc::O_CLOEXEC);
+
+    SourceFile::open_from(Arc::clone(&path), opts)
+        .tap_err(|e| error!("couldn't open source file at {}: {e}", path.display()))
+}
+
+pub(crate) fn get_line_to_insert() -> SourceLine {
+    //
+    todo!();
+}
+
 #[tracing::instrument(level = "debug")]
 pub fn do_append(args: Arc<Args>, append_args: AppendCmd) -> Result<(), BoxDynError> {
     let filepath = Path::new(&args.file);
@@ -110,22 +126,16 @@ pub fn do_append(args: Arc<Args>, append_args: AppendCmd) -> Result<(), BoxDynEr
         filepath.to_path_buf()
     };
 
-    let mut opts = File::options();
-    opts.read(true)
-        .write(true)
-        .create(false)
-        .custom_flags(libc::O_CLOEXEC);
-
-    let source_file = SourceFile::open_from(Arc::from(filepath), opts)?;
+    let source_file = open_source_file(Arc::from(filepath))?;
     let pri = get_where(source_file.clone())?;
 
     let new_pri = pri - 1;
 
     let new_pri_line = get_next_prio_line(
         source_file.clone(),
-        append_args.name,
+        &append_args.name,
         new_pri,
-        append_args.value,
+        &append_args.value,
     )?;
 
     debug!("new_pri_line={new_pri_line}");
@@ -210,9 +220,9 @@ pub fn get_where(dynamic_nix: SourceFile) -> Result<i64, BoxDynError> {
 
 pub fn get_next_prio_line(
     source: SourceFile,
-    option_name: Arc<str>,
+    option_name: &str,
     new_prio: i64,
-    new_value: Arc<str>,
+    new_value: &str,
 ) -> Result<SourceLine, BoxDynError> {
     let source_lines = source.lines()?;
     let penultimate = source_lines.get(source_lines.len() - 2);
@@ -246,6 +256,8 @@ pub fn write_next_prio(mut source: SourceFile, new_line: SourceLine) -> Result<(
         text: Arc::from("    }"),
     };
 
+    debug!("writing new source line: {new_line}");
+
     source.insert_lines(&[new_mod_start, new_line, new_mod_end])?;
 
     Ok(())

src/source.rs

@@ -6,6 +6,7 @@ use std::{
     cell::{Ref, RefCell},
     hash::Hash,
     io::{BufRead, BufReader, BufWriter},
+    mem::{self, MaybeUninit},
     ops::Deref,
     ptr,
     sync::{Arc, Mutex, OnceLock},
@@ -103,6 +104,28 @@ pub struct SourceFile {
     lines: Arc<OnceLock<RefCell<Vec<SourceLine>>>>,
 }
 
+#[derive(Debug)]
+#[repr(transparent)]
+pub struct OpaqueDerefSourceLines<'s>(Ref<'s, [SourceLine]>);
+impl<'s> Deref for OpaqueDerefSourceLines<'s> {
+    type Target = [SourceLine];
+
+    fn deref(&self) -> &[SourceLine] {
+        &*self.0
+    }
+}
+
+#[derive(Debug)]
+#[repr(transparent)]
+pub struct OpaqueDerefSourceLine<'s>(Ref<'s, SourceLine>);
+impl<'s> Deref for OpaqueDerefSourceLine<'s> {
+    type Target = SourceLine;
+
+    fn deref(&self) -> &SourceLine {
+        &*self.0
+    }
+}
+
 impl SourceFile {
     /// Panics if `path` is a directory path instead of a file path.
     pub fn open_from(path: Arc<Path>, options: OpenOptions) -> Result<Self, IoError> {
@@ -159,15 +182,17 @@ impl SourceFile {
         Ok(self._lines_slice())
     }
 
-    pub fn lines(&self) -> Result<impl Deref<Target = [SourceLine]> + '_, IoError> {
-        self._lines()
+    pub fn lines(&self) -> Result<OpaqueDerefSourceLines<'_>, IoError> {
+        let lines = self._lines()?;
+
+        Ok(OpaqueDerefSourceLines(lines))
     }
 
-    pub fn line(&self, line: Line) -> Result<impl Deref<Target = SourceLine> + '_, IoError> {
+    pub fn line(&self, line: Line) -> Result<OpaqueDerefSourceLine<'_>, IoError> {
         let lines_lock = self._lines()?;
         let line = Ref::map(lines_lock, |lines| &lines[line.index() as usize]);
 
-        Ok(line)
+        Ok(OpaqueDerefSourceLine(line))
     }
 
     /// `lines` but already be initialized.