basic setup for unix socket comms

1 files changed, 136 insertions, 0 deletions

diff --git a/src/unix.rs b/src/unix.rs
new file mode 100644
index 0000000..f26dc8c
--- /dev/null
+++ b/src/unix.rs
@@ -0,0 +1,136 @@
+//! allow sub-programs to invoke arbitrary user-defined functions via a unix socket
+
+use std::ffi::OsStr;
+use std::fs;
+use std::io;
+use std::io::Write;
+use std::os::unix::ffi::OsStrExt;
+use std::os::unix::net::SocketAncillary;
+use std::os::unix::net::UnixListener;
+use std::os::unix::net::UnixStream;
+use std::path::PathBuf;
+use std::process::exit;
+use std::sync::Arc;
+use std::sync::Mutex;
+use std::thread;
+
+use libc::socket;
+
+use crate::BString;
+use crate::Session;
+
+fn user_function_res(sock: &OsStr) -> io::Result<()> {
+    let sock = UnixStream::connect(sock)?;
+
+    let mut ancillary_buffer = [0; 128];
+    let mut ancillary = SocketAncillary::new(&mut ancillary_buffer[..]);
+    ancillary.add_fds(&[0, 1, 2]);
+
+    let buf = [0; 8];
+    let mut bufs = &mut [io::IoSlice::new(&buf[..])][..];
+    sock.send_vectored_with_ancillary(bufs, &mut ancillary)?;
+
+    todo!()
+}
+
+pub fn maybe_run_defined_function() {
+    if let Some(program_name) = std::env::args_os().next() {
+        let program_name = program_name.as_bytes();
+        if !program_name.contains(&b'/') && program_name != b"pish" {
+            if let Some(socket) = std::env::var_os("PISH_SOCKET") {
+                let _ = user_function_res(&socket);
+                exit(-1);
+            }
+        }
+    }
+}
+
+fn unique_string() -> String {
+    use std::collections::hash_map::DefaultHasher;
+    use std::hash::{Hash, Hasher};
+    use std::process;
+    use std::time::{SystemTime, UNIX_EPOCH};
+
+    let pid = process::id();
+    let now = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .unwrap()
+        .as_nanos();
+
+    let mut hasher = DefaultHasher::new();
+    pid.hash(&mut hasher);
+    now.hash(&mut hasher);
+
+    let hash = hasher.finish();
+    let hex = format!("{:016x}", hash);
+
+    hex[..12.min(hex.len())].to_string()
+}
+
+fn unique_socket_path() -> PathBuf {
+    let mut socket_name = b"pish-cmd-".to_vec();
+    socket_name.extend_from_slice(&unique_string().as_bytes());
+    socket_name.extend_from_slice(b".sock");
+    let socket_path = crate::basedir::data_dir().join(OsStr::from_bytes(&socket_name));
+    socket_path
+}
+
+pub struct SocketRunning {
+    path: PathBuf,
+}
+
+#[must_use]
+pub struct SocketDropper {
+    session: Arc<Mutex<Session>>,
+}
+
+impl Drop for SocketDropper {
+    fn drop(&mut self) {
+        // mark socket for closing by `take`ing the socket_running value
+        let session = &self.session;
+        let Ok(mut se) = session.lock() else { return };
+        let Some(sr) = se.socket_running.take() else {
+            return;
+        };
+
+        // connect to the socket for a brief moment to make it check that it should terminate
+        if let Ok(mut con) = UnixStream::connect(&sr.path) {
+            let _ = write!(con, "please shut down :))");
+        };
+    }
+}
+
+pub fn listen(session: Arc<Mutex<Session>>) -> SocketDropper {
+    let path = unique_socket_path();
+
+    {
+        let mut se = session.lock().unwrap();
+        assert!(se.socket_running.is_none());
+        se.socket_running = Some(SocketRunning { path: path.clone() });
+    }
+
+    let se = session.clone();
+    thread::spawn(move || {
+        struct SocketRemover(PathBuf);
+        impl Drop for SocketRemover {
+            fn drop(&mut self) {
+                let _ = fs::remove_file(&self.0);
+            }
+        }
+        let _socket_remover = SocketRemover(path.clone());
+        let listener = UnixListener::bind(path).unwrap();
+        let mut it = listener.incoming();
+        while let Some(stream) = it.next() {
+            match se.lock() {
+                Err(_) => break,
+                Ok(se) if se.socket_running.is_none() => break,
+                _ => (),
+            }
+            if let Ok(_stream) = stream {
+                todo!("handle client")
+            }
+        }
+    });
+
+    SocketDropper { session }
+}