1 files changed, 160 insertions, 0 deletions
diff --git a/src/fuse/mount.rs b/src/fuse/mount.rs
new file mode 100644
index 0000000..ebf7e5d
--- /dev/null
+++ b/src/fuse/mount.rs
@@ -0,0 +1,160 @@
+use std::{
+    ffi::{OsStr, OsString},
+    os::unix::{
+        ffi::OsStrExt,
+        io::{AsRawFd, IntoRawFd, RawFd},
+        net::UnixStream,
+    },
+    process::Command,
+};
+
+use nix::{
+    self, cmsg_space,
+    fcntl::{fcntl, FcntlArg, FdFlag},
+    sys::socket::{recvmsg, ControlMessageOwned, MsgFlags},
+};
+
+use quick_error::quick_error;
+
+use super::Start;
+use crate::util::{from_nix_error, DumbFd};
+
+quick_error! {
+    #[derive(Debug)]
+    pub enum MountError {
+        Io(err: std::io::Error) { from() }
+        Fusermount { display("fusermount failed") }
+    }
+}
+
+#[derive(Default)]
+pub struct Options(OsString);
+
+impl Options {
+    pub fn fs_name<O: AsRef<OsStr>>(&mut self, fs_name: O) -> &mut Self {
+        self.push_key_value("fsname", fs_name)
+    }
+
+    pub fn read_only(&mut self) -> &mut Self {
+        self.push("ro")
+    }
+
+    pub fn push<O: AsRef<OsStr>>(&mut self, option: O) -> &mut Self {
+        self.push_parts(&[option.as_ref()])
+    }
+
+    pub fn push_key_value<K, V>(&mut self, key: K, value: V) -> &mut Self
+    where
+        K: AsRef<OsStr>,
+        V: AsRef<OsStr>,
+    {
+        let (key, value) = (key.as_ref(), value.as_ref());
+
+        let assert_valid = |part: &OsStr| {
+            let bytes = part.as_bytes();
+            assert!(
+                !bytes.is_empty() && bytes.iter().all(|b| !matches!(*b, b',' | b'=')),
+                "invalid key or value: {}",
+                part.to_string_lossy()
+            );
+        };
+
+        assert_valid(key);
+        assert_valid(value);
+
+        self.push_parts(&[key, OsStr::new("="), value])
+    }
+
+    fn push_parts(&mut self, segment: &[&OsStr]) -> &mut Self {
+        if !self.0.is_empty() {
+            self.0.push(",");
+        }
+
+        let start = self.0.as_bytes().len();
+        segment.iter().for_each(|part| self.0.push(part));
+
+        let bytes = self.0.as_bytes();
+        let last = bytes.len() - 1;
+
+        assert!(
+            last >= start && bytes[start] != b',' && bytes[last] != b',',
+            "invalid option string: {}",
+            OsStr::from_bytes(&bytes[start..]).to_string_lossy()
+        );
+
+        self
+    }
+}
+
+impl<O: AsRef<OsStr>> Extend<O> for Options {
+    fn extend<I: IntoIterator<Item = O>>(&mut self, iter: I) {
+        iter.into_iter().for_each(|option| {
+            self.push(option);
+        });
+    }
+}
+
+pub fn mount_sync<M>(mountpoint: M, options: &Options) -> Result<Start, MountError>
+where
+    M: AsRef<OsStr>,
+{
+    let (left_side, right_side) = UnixStream::pair()?;
+
+    // The fusermount protocol requires us to preserve right_fd across execve()
+    let right_fd = right_side.as_raw_fd();
+    fcntl(
+        right_fd,
+        FcntlArg::F_SETFD(
+            FdFlag::from_bits(fcntl(right_fd, FcntlArg::F_GETFD).unwrap()).unwrap()
+                & !FdFlag::FD_CLOEXEC,
+        ),
+    )
+    .unwrap();
+
+    let mut command = Command::new("fusermount3");
+    if !options.0.is_empty() {
+        command.args(&[OsStr::new("-o"), &options.0, mountpoint.as_ref()]);
+    } else {
+        command.arg(mountpoint);
+    };
+
+    let mut fusermount = command.env("_FUSE_COMMFD", right_fd.to_string()).spawn()?;
+
+    // recvmsg() should fail if fusermount exits (last open fd is closed)
+    drop(right_side);
+
+    let session_fd = (|| {
+        let mut buffer = cmsg_space!(RawFd);
+        let message = recvmsg(
+            left_side.as_raw_fd(),
+            &[],
+            Some(&mut buffer),
+            MsgFlags::empty(),
+        )
+        .map_err(from_nix_error)?;
+
+        let session_fd = match message.cmsgs().next() {
+            Some(ControlMessageOwned::ScmRights(fds)) => fds.into_iter().next(),
+            _ => None,
+        };
+
+        session_fd.ok_or(MountError::Fusermount)
+    })();
+
+    match session_fd {
+        Ok(session_fd) => {
+            let fusermount_fd = DumbFd(left_side.into_raw_fd());
+            let session_fd = DumbFd(session_fd);
+            Ok(Start {
+                fusermount_fd,
+                session_fd,
+            })
+        }
+
+        Err(error) => {
+            drop(left_side);
+            fusermount.wait()?;
+            Err(error)
+        }
+    }
+}