Add ioctl example

This matches libfuse's example:

https://github.com/libfuse/libfuse/blob/d30247c36dadd386b994cd47ad84351ae68cc94c/example/ioctl.c

Author: colinmarc

examples/ioctl.rs

@@ -0,0 +1,201 @@
+use clap::{crate_version, Arg, ArgAction, Command};
+use fuser::{
+    FileAttr, FileType, Filesystem, MountOption, ReplyAttr, ReplyData, ReplyDirectory, ReplyEntry,
+    Request,
+};
+use libc::{EINVAL, ENOENT};
+use std::ffi::OsStr;
+use std::time::{Duration, UNIX_EPOCH};
+
+const TTL: Duration = Duration::from_secs(1); // 1 second
+
+struct FiocFS {
+    content: Vec<u8>,
+    root_attr: FileAttr,
+    fioc_file_attr: FileAttr,
+}
+
+impl FiocFS {
+    fn new() -> Self {
+        let uid = unsafe { libc::getuid() };
+        let gid = unsafe { libc::getgid() };
+
+        let root_attr = FileAttr {
+            ino: 1,
+            size: 0,
+            blocks: 0,
+            atime: UNIX_EPOCH, // 1970-01-01 00:00:00
+            mtime: UNIX_EPOCH,
+            ctime: UNIX_EPOCH,
+            crtime: UNIX_EPOCH,
+            kind: FileType::Directory,
+            perm: 0o755,
+            nlink: 2,
+            uid,
+            gid,
+            rdev: 0,
+            flags: 0,
+            blksize: 512,
+        };
+
+        let fioc_file_attr = FileAttr {
+            ino: 2,
+            size: 0,
+            blocks: 1,
+            atime: UNIX_EPOCH, // 1970-01-01 00:00:00
+            mtime: UNIX_EPOCH,
+            ctime: UNIX_EPOCH,
+            crtime: UNIX_EPOCH,
+            kind: FileType::RegularFile,
+            perm: 0o644,
+            nlink: 1,
+            uid,
+            gid,
+            rdev: 0,
+            flags: 0,
+            blksize: 512,
+        };
+
+        Self {
+            content: vec![],
+            root_attr,
+            fioc_file_attr,
+        }
+    }
+}
+
+impl Filesystem for FiocFS {
+    fn lookup(&mut self, _req: &Request, parent: u64, name: &OsStr, reply: ReplyEntry) {
+        if parent == 1 && name.to_str() == Some("fioc") {
+            reply.entry(&TTL, &self.fioc_file_attr, 0);
+        } else {
+            reply.error(ENOENT);
+        }
+    }
+
+    fn getattr(&mut self, _req: &Request, ino: u64, _fh: Option<u64>, reply: ReplyAttr) {
+        match ino {
+            1 => reply.attr(&TTL, &self.root_attr),
+            2 => reply.attr(&TTL, &self.fioc_file_attr),
+            _ => reply.error(ENOENT),
+        }
+    }
+
+    fn read(
+        &mut self,
+        _req: &Request,
+        ino: u64,
+        _fh: u64,
+        offset: i64,
+        _size: u32,
+        _flags: i32,
+        _lock: Option<u64>,
+        reply: ReplyData,
+    ) {
+        if ino == 2 {
+            reply.data(&self.content[offset as usize..])
+        } else {
+            reply.error(ENOENT);
+        }
+    }
+
+    fn readdir(
+        &mut self,
+        _req: &Request,
+        ino: u64,
+        _fh: u64,
+        offset: i64,
+        mut reply: ReplyDirectory,
+    ) {
+        if ino != 1 {
+            reply.error(ENOENT);
+            return;
+        }
+
+        let entries = vec![
+            (1, FileType::Directory, "."),
+            (1, FileType::Directory, ".."),
+            (2, FileType::RegularFile, "fioc"),
+        ];
+
+        for (i, entry) in entries.into_iter().enumerate().skip(offset as usize) {
+            // i + 1 means the index of the next entry
+            if reply.add(entry.0, (i + 1) as i64, entry.1, entry.2) {
+                break;
+            }
+        }
+        reply.ok();
+    }
+
+    fn ioctl(
+        &mut self,
+        _req: &Request<'_>,
+        ino: u64,
+        _fh: u64,
+        _flags: u32,
+        cmd: u32,
+        in_data: &[u8],
+        _out_size: u32,
+        reply: fuser::ReplyIoctl,
+    ) {
+        if ino != 2 {
+            reply.error(EINVAL);
+            return;
+        }
+
+        const FIOC_GET_SIZE: u32 = 0;
+        const FIOC_SET_SIZE: u32 = 1;
+
+        match cmd {
+            FIOC_GET_SIZE => {
+                let size_bytes = (self.content.len() as u32).to_ne_bytes();
+                reply.ioctl(0, &size_bytes);
+            }
+            FIOC_SET_SIZE => {
+                let new_size = u32::from_ne_bytes(in_data.try_into().unwrap());
+                self.content = vec![0_u8; new_size as usize];
+                reply.ioctl(0, &[]);
+            }
+            _ => reply.error(EINVAL),
+        }
+    }
+}
+
+fn main() {
+    let matches = Command::new("hello")
+        .version(crate_version!())
+        .author("Colin Marc")
+        .arg(
+            Arg::new("MOUNT_POINT")
+                .required(true)
+                .index(1)
+                .help("Act as a client, and mount FUSE at given path"),
+        )
+        .arg(
+            Arg::new("auto_unmount")
+                .long("auto_unmount")
+                .action(ArgAction::SetTrue)
+                .help("Automatically unmount on process exit"),
+        )
+        .arg(
+            Arg::new("allow-root")
+                .long("allow-root")
+                .action(ArgAction::SetTrue)
+                .help("Allow root user to access filesystem"),
+        )
+        .get_matches();
+
+    env_logger::init();
+
+    let mountpoint = matches.get_one::<String>("MOUNT_POINT").unwrap();
+    let mut options = vec![MountOption::FSName("fioc".to_string())];
+    if matches.get_flag("auto_unmount") {
+        options.push(MountOption::AutoUnmount);
+    }
+    if matches.get_flag("allow-root") {
+        options.push(MountOption::AllowRoot);
+    }
+
+    let fs = FiocFS::new();
+    fuser::mount2(fs, mountpoint, &options).unwrap();
+}