host/start-vm: implement shared directories

Signed-off-by: Alyssa Ross <hi@alyssa.is>
Message-Id: <20221010232909.1953738-3-hi@alyssa.is>

3 files changed, 69 insertions, 0 deletions

diff --git a/host/start-vm/lib.rs b/host/start-vm/lib.rs
index 9a92ab7..3959566 100644
--- a/host/start-vm/lib.rs
+++ b/host/start-vm/lib.rs
@@ -112,6 +112,32 @@ pub fn vm_command(dir: PathBuf, config_root: &Path) -> Result<Command, String> {
         return Err("no block devices specified".to_string());
     }
 
+    let shared_dirs_dir = config_dir.join("shared-dirs");
+    match shared_dirs_dir.read_dir().map(Iterator::peekable) {
+        Ok(mut entries) => {
+            if entries.peek().is_some() {
+                command.arg("--fs");
+            }
+
+            for result in entries {
+                let entry = result
+                    .map_err(|e| format!("examining directory entry: {}", e))?
+                    .file_name();
+
+                let mut arg = OsString::from("tag=");
+                arg.push(&entry);
+                arg.push(",socket=../");
+                arg.push(vm_name);
+                arg.push("-fs-");
+                arg.push(&entry);
+                arg.push("/env/virtiofsd.sock");
+                command.arg(arg);
+            }
+        }
+        Err(e) if e.kind() == ErrorKind::NotFound => {}
+        Err(e) => return Err(format!("reading directory {:?}: {}", shared_dirs_dir, e)),
+    }
+
     command.arg("--serial").arg({
         let mut serial = OsString::from("file=/run/");
         serial.push(&vm_name);
diff --git a/host/start-vm/tests/meson.build b/host/start-vm/tests/meson.build
index 00bd33d..857414b 100644
--- a/host/start-vm/tests/meson.build
+++ b/host/start-vm/tests/meson.build
@@ -31,3 +31,5 @@ test('tap_open (name too long)', executable('tap_open-name-too-long',
 
 test('vm_command-basic', executable('vm_command-basic',
   'vm_command-basic.rs', link_with : [rust_lib, rust_helper]))
+test('vm_command-shared-dir', executable('vm_command-shared-dir',
+  'vm_command-shared-dir.rs', link_with : [rust_lib, rust_helper]))
diff --git a/host/start-vm/tests/vm_command-shared-dir.rs b/host/start-vm/tests/vm_command-shared-dir.rs
new file mode 100644
index 0000000..2b13663
--- /dev/null
+++ b/host/start-vm/tests/vm_command-shared-dir.rs
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: EUPL-1.2+
+// SPDX-FileCopyrightText: 2022 Alyssa Ross <hi@alyssa.is>
+
+use std::fs::{create_dir, create_dir_all, File};
+use std::os::unix::fs::symlink;
+
+use start_vm::vm_command;
+use test_helper::TempDir;
+
+fn contains_seq<H: PartialEq<N>, N>(haystack: &[H], needle: &[N]) -> bool {
+    let start_indexes = 0..=(haystack.len() - needle.len());
+    let mut candidates = start_indexes.map(|i| &haystack[i..][..needle.len()]);
+    candidates.any(|c| c == needle)
+}
+
+fn main() -> std::io::Result<()> {
+    let tmp_dir = TempDir::new()?;
+
+    let service_dir = tmp_dir.path().join("testvm");
+    let vm_config = tmp_dir.path().join("svc/data/testvm");
+
+    create_dir(&service_dir)?;
+    create_dir_all(&vm_config)?;
+    File::create(vm_config.join("vmlinux"))?;
+    create_dir(vm_config.join("blk"))?;
+    symlink("/dev/null", vm_config.join("blk/root.img"))?;
+
+    create_dir(vm_config.join("shared-dirs"))?;
+    create_dir(vm_config.join("shared-dirs/root"))?;
+    symlink("/", vm_config.join("shared-dirs/root/dir"))?;
+
+    let expected_args = [
+        "--fs",
+        "tag=root,socket=../testvm-fs-root/env/virtiofsd.sock",
+    ];
+
+    let command = vm_command(service_dir, &tmp_dir.path().join("svc/data")).unwrap();
+    let args: Box<[_]> = command.get_args().collect();
+    assert!(contains_seq(&args, &expected_args));
+    Ok(())
+}