test/internal/mountinfo: move from sandbox

This also improves its API.

Signed-off-by: Ophestra <cat@gensokyo.uk>

5 files changed, 229 insertions, 189 deletions

diff --git a/test/internal/mountinfo/mountinfo.go b/test/internal/mountinfo/mountinfo.go
new file mode 100644
index 00000000..19892cd2
--- /dev/null
+++ b/test/internal/mountinfo/mountinfo.go
@@ -0,0 +1,177 @@
+// Package mountinfo provides util-linux bindings for parsing
+// proc_pid_mountinfo(5).
+//
+// This package must never be used outside integration tests, a much better
+// implementation can be found in package vfs.
+//
+// Attempting to import this package outside testing causes the resulting
+// program to panic.
+package mountinfo
+
+/*
+#cgo linux pkg-config: --static mount
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <libmount.h>
+
+const char *HAKUREI_MOUNTINFO_PATH = "/proc/self/mountinfo";
+*/
+import "C"
+
+import (
+	"errors"
+	"fmt"
+	"runtime"
+	"unsafe"
+)
+
+var (
+	// ErrParse is returned by [Open] when encountering a bad record.
+	ErrParse = errors.New("invalid mountinfo record")
+	// ErrIter is returned by [Open] if an iterator cannot be allocated.
+	ErrIter = errors.New("cannot allocate iterator")
+	// ErrIterAdvance is stored when the iterator is unable to advance.
+	ErrIterAdvance = errors.New("unable to advance iterator")
+)
+
+type (
+	// Iter refers to libmnt iterator state.
+	Iter struct {
+		// Last stored error.
+		err error
+		// Whether iteration has concluded.
+		ok bool
+		// Whether Close had already been called.
+		closed bool
+
+		tb  *C.struct_libmnt_table
+		itr *C.struct_libmnt_iter
+
+		fs *C.struct_libmnt_fs
+	}
+
+	// Entry represents deterministic mountinfo parts of a libmnt_fs entry.
+	Entry struct {
+		// mount ID: a unique ID for the mount (may be reused after umount(2)).
+		ID int `json:"id"`
+		// parent ID: the ID of the parent mount (or of self for the root of
+		// this mount namespace's mount tree).
+		Parent int `json:"parent"`
+		// root: the pathname of the directory in the filesystem which forms the
+		// root of this mount.
+		Root string `json:"root"`
+		// mount point: the pathname of the mount point relative to the
+		// process's root directory.
+		Target string `json:"target"`
+		// mount options: per-mount options (see mount(2)).
+		VfsOptstr string `json:"vfs_optstr"`
+		// filesystem type: the filesystem type in the form "type[.subtype]".
+		FsType string `json:"fstype"`
+		// mount source: filesystem-specific information or "none".
+		Source string `json:"source"`
+		// super options: per-superblock options (see mount(2)).
+		FsOptstr string `json:"fs_optstr"`
+	}
+)
+
+// Copy populates v with the current record.
+func (m *Iter) Copy(v *Entry) {
+	if m.fs == nil {
+		panic("invalid entry")
+	}
+	v.ID = int(C.mnt_fs_get_id(m.fs))
+	v.Parent = int(C.mnt_fs_get_parent_id(m.fs))
+	v.Root = C.GoString(C.mnt_fs_get_root(m.fs))
+	v.Target = C.GoString(C.mnt_fs_get_target(m.fs))
+	v.VfsOptstr = C.GoString(C.mnt_fs_get_vfs_options(m.fs))
+	v.FsType = C.GoString(C.mnt_fs_get_fstype(m.fs))
+	v.Source = C.GoString(C.mnt_fs_get_source(m.fs))
+	v.FsOptstr = C.GoString(C.mnt_fs_get_fs_options(m.fs))
+}
+
+// Err returns the saved iterator error.
+func (m *Iter) Err() error { return m.err }
+
+// Open opens a mountinfo document. If name is an empty string, the mountinfo
+// document of the current process is opened instead.
+func Open(name string) (*Iter, error) {
+	var m Iter
+	if name == "" {
+		m.tb = C.mnt_new_table_from_file(C.HAKUREI_MOUNTINFO_PATH)
+	} else {
+		_name := C.CString(name)
+		m.tb = C.mnt_new_table_from_file(_name)
+		C.free(unsafe.Pointer(_name))
+	}
+	if m.tb == nil {
+		return nil, ErrParse
+	}
+	m.itr = C.mnt_new_iter(C.MNT_ITER_FORWARD)
+	if m.itr == nil {
+		C.mnt_unref_table(m.tb)
+		return nil, ErrIter
+	}
+	m.ok = true
+
+	runtime.SetFinalizer(&m, (*Iter).Close)
+	return &m, nil
+}
+
+// Close frees the iterator.
+func (m *Iter) Close() {
+	if m.closed {
+		return
+	}
+	if m.tb == nil {
+		panic("unref called before open")
+	}
+
+	C.mnt_unref_table(m.tb)
+	C.mnt_free_iter(m.itr)
+	m.closed = true
+	runtime.SetFinalizer(m, nil)
+}
+
+// Reset resets the iterator to the first record for reuse.
+func (m *Iter) Reset() {
+	if m.err != nil {
+		panic("attempting to reset a faulted iterator")
+	}
+	m.ok = true
+	C.mnt_reset_iter(m.itr, -1)
+}
+
+// Next advances the iterator to the next record. The record may be copied if
+// Next returns true.
+func (m *Iter) Next() bool {
+	if !m.ok || m.err != nil {
+		return false
+	}
+
+	r := C.mnt_table_next_fs(m.tb, m.itr, &m.fs)
+	if r < 0 {
+		m.err = ErrIterAdvance
+	}
+	m.ok = r == 0
+	return m.ok
+}
+
+// EqualWithIgnore compares e with want, ignoring fields with the specified
+// ignore value.
+func (e *Entry) EqualWithIgnore(want *Entry, ignore string) bool {
+	return (e.ID == want.ID || want.ID == -1) &&
+		(e.Parent == want.Parent || want.Parent == -1) &&
+		(e.Root == want.Root || want.Root == ignore) &&
+		(e.Target == want.Target || want.Target == ignore) &&
+		(e.VfsOptstr == want.VfsOptstr || want.VfsOptstr == ignore) &&
+		(e.FsType == want.FsType || want.FsType == ignore) &&
+		(e.Source == want.Source || want.Source == ignore) &&
+		(e.FsOptstr == want.FsOptstr || want.FsOptstr == ignore)
+}
+
+// String returns a text representation of e loosely following the kernel format.
+func (e *Entry) String() string {
+	return fmt.Sprintf("%d %d %s %s %s %s %s %s",
+		e.ID, e.Parent, e.Root, e.Target, e.VfsOptstr, e.FsType, e.Source, e.FsOptstr)
+}
diff --git a/test/internal/mountinfo/mountinfo_guard.go b/test/internal/mountinfo/mountinfo_guard.go
new file mode 100644
index 00000000..aaf63ac4
--- /dev/null
+++ b/test/internal/mountinfo/mountinfo_guard.go
@@ -0,0 +1,15 @@
+//go:build !testsuite && !tester
+
+package mountinfo
+
+import (
+	"os"
+	"testing"
+)
+
+func init() {
+	if !testing.Testing() {
+		println("package mountinfo imported in non-testsuite program")
+		os.Exit(1)
+	}
+}
diff --git a/test/internal/sandbox/mount_test.go b/test/internal/mountinfo/mountinfo_test.go
index a565b0a0..45cfdf5f 100644
--- a/test/internal/sandbox/mount_test.go
+++ b/test/internal/mountinfo/mountinfo_test.go
@@ -1,13 +1,11 @@
-//go:build testtool
-
-package sandbox_test
+package mountinfo_test
 
 import (
 	"os"
 	"path/filepath"
 	"testing"
 
-	"hakurei.app/test/internal/sandbox"
+	"hakurei.app/test/internal/mountinfo"
 )
 
 func TestMountinfo(t *testing.T) {
@@ -15,7 +13,7 @@ func TestMountinfo(t *testing.T) {
 		name string
 
 		sample string
-		want   []*sandbox.MountinfoEntry
+		want   []*mountinfo.Entry
 	}{
 		{"util-linux", `15 20 0:3 / /proc rw,relatime - proc /proc rw
 16 20 0:15 / /sys rw,relatime - sysfs /sys rw
@@ -49,7 +47,7 @@ func TestMountinfo(t *testing.T) {
 44 41 0:36 / /home/kzak/.gvfs rw,nosuid,nodev,relatime - fuse.gvfs-fuse-daemon gvfs-fuse-daemon rw,user_id=500,group_id=500
 45 20 0:37 / /var/lib/nfs/rpc_pipefs rw,relatime - rpc_pipefs sunrpc rw
 47 20 0:38 / /mnt/sounds rw,relatime - cifs //foo.home/bar/ rw,unc=\\foo.home\bar,username=kzak,domain=SRGROUP,uid=0,noforceuid,gid=0,noforcegid,addr=192.168.111.1,posixpaths,serverino,acl,rsize=16384,wsize=57344
-49 20 0:56 / /mnt/test/foobar rw,relatime,nosymfollow shared:323 - tmpfs tmpfs rw`, []*sandbox.MountinfoEntry{
+49 20 0:56 / /mnt/test/foobar rw,relatime,nosymfollow shared:323 - tmpfs tmpfs rw`, []*mountinfo.Entry{
 			e(15, 20, "/", "/proc", "rw,relatime", "proc", "/proc", "rw"),
 			e(16, 20, "/", "/sys", "rw,relatime", "sysfs", "/sys", "rw"),
 			e(17, 20, "/", "/dev", "rw,relatime", "devtmpfs", "udev", "rw,size=1983516k,nr_inodes=495879,mode=755"),
@@ -93,33 +91,35 @@ func TestMountinfo(t *testing.T) {
 		}
 
 		t.Run(tc.name, func(t *testing.T) {
-			m := sandbox.NewMountinfo(name)
-			if err := m.Parse(); err != nil {
-				t.Fatalf("Parse: error = %v", err)
+			m, err := mountinfo.Open(name)
+			if err != nil {
+				t.Fatalf("Open: error = %v", err)
 			}
+			t.Cleanup(m.Close)
 
 			i := 0
-			for ent := range m.Entries() {
+			var ent mountinfo.Entry
+			for m.Next() {
+				m.Copy(&ent)
+
 				if i == len(tc.want) {
-					t.Errorf("Entries: got more than %d entries", i)
+					t.Errorf("Next: got more than %d entries", i)
 					t.FailNow()
 				}
 				if !ent.EqualWithIgnore(tc.want[i], "\x00") {
-					t.Errorf("Entries: entry %d\n got: %#v\nwant: %#v", i,
+					t.Errorf("Next: entry %d\n got: %#v\nwant: %#v", i,
 						ent, &tc.want[i])
 					t.FailNow()
 				} else {
-					t.Logf("%s", ent)
+					t.Logf("%s", &ent)
 				}
 
 				i++
 			}
 
-			if err := m.Err(); err != nil {
-				t.Fatalf("Mountinfo: error = %v", err)
+			if err = m.Err(); err != nil {
+				t.Fatalf("Err: %v", err)
 			}
-
-			m.Unref()
 		})
 
 		if err := os.Remove(name); err != nil {
@@ -129,9 +129,11 @@ func TestMountinfo(t *testing.T) {
 }
 
 func e(
-	id, parent int, root, target, vfsOptstr string, fsType, source, fsOptstr string,
-) *sandbox.MountinfoEntry {
-	return &sandbox.MountinfoEntry{
+	id, parent int,
+	root, target, vfsOptstr string,
+	fsType, source, fsOptstr string,
+) *mountinfo.Entry {
+	return &mountinfo.Entry{
 		ID:        id,
 		Parent:    parent,
 		Root:      root,
diff --git a/test/internal/sandbox/assert.go b/test/internal/sandbox/assert.go
index e6fe926b..2125419b 100644
--- a/test/internal/sandbox/assert.go
+++ b/test/internal/sandbox/assert.go
@@ -19,6 +19,8 @@ import (
 	"os"
 	"path/filepath"
 	"syscall"
+
+	"hakurei.app/test/internal/mountinfo"
 )
 
 var (
@@ -31,10 +33,10 @@ func printf(format string, v ...any) { printfFunc(format, v...) }
 func fatalf(format string, v ...any) { fatalfFunc(format, v...) }
 
 type TestCase struct {
-	Env     []string          `json:"env"`
-	FS      *FS               `json:"fs"`
-	Mount   []*MountinfoEntry `json:"mount"`
-	Seccomp bool              `json:"seccomp"`
+	Env     []string           `json:"env"`
+	FS      *FS                `json:"fs"`
+	Mount   []*mountinfo.Entry `json:"mount"`
+	Seccomp bool               `json:"seccomp"`
 
 	TrySocket      string `json:"try_socket,omitempty"`
 	SocketAbstract bool   `json:"socket_abstract,omitempty"`
@@ -120,15 +122,18 @@ func (t *T) MustCheck(want *TestCase) {
 		var fail bool
 		m := mustParseMountinfo(t.MountsPath)
 		i := 0
-		for ent := range m.Entries() {
+		var ent mountinfo.Entry
+		for m.Next() {
+			m.Copy(&ent)
+
 			if i == len(want.Mount) {
 				fatalf("got more than %d entries", i)
 			}
 			if !ent.EqualWithIgnore(want.Mount[i], "//ignore") {
 				fail = true
-				printf("[FAIL] %s", ent)
+				printf("[FAIL] %s", &ent)
 			} else {
-				printf("[ OK ] %s", ent)
+				printf("[ OK ] %s", &ent)
 			}
 
 			i++
@@ -262,9 +267,9 @@ func mustDecode(wantFilePath string, v any) {
 	}
 }
 
-func mustParseMountinfo(name string) *Mountinfo {
-	m := NewMountinfo(name)
-	if err := m.Parse(); err != nil {
+func mustParseMountinfo(name string) *mountinfo.Iter {
+	m, err := mountinfo.Open(name)
+	if err != nil {
 		fatalf("%v", err)
 		panic("unreachable")
 	}
diff --git a/test/internal/sandbox/mount.go b/test/internal/sandbox/mount.go
deleted file mode 100644
index 791a68b9..00000000
--- a/test/internal/sandbox/mount.go
+++ /dev/null
@@ -1,159 +0,0 @@
-//go:build testtool
-
-package sandbox
-
-/*
-#cgo linux pkg-config: --static mount
-
-#include <stdlib.h>
-#include <stdio.h>
-#include <libmount.h>
-
-const char *HAKUREI_MOUNTINFO_PATH = "/proc/self/mountinfo";
-*/
-import "C"
-
-import (
-	"errors"
-	"fmt"
-	"iter"
-	"runtime"
-	"sync"
-	"unsafe"
-)
-
-var (
-	ErrMountinfoParse = errors.New("invalid mountinfo records")
-	ErrMountinfoIter  = errors.New("cannot allocate iterator")
-	ErrMountinfoFault = errors.New("cannot iterate on filesystems")
-)
-
-type (
-	Mountinfo struct {
-		mu  sync.RWMutex
-		p   string
-		err error
-
-		tb  *C.struct_libmnt_table
-		itr *C.struct_libmnt_iter
-
-		fs *C.struct_libmnt_fs
-	}
-
-	// MountinfoEntry represents deterministic mountinfo parts of a libmnt_fs entry.
-	MountinfoEntry struct {
-		// mount ID: a unique ID for the mount (may be reused after umount(2)).
-		ID int `json:"id"`
-		// parent ID: the ID of the parent mount (or of self for the root of this mount namespace's mount tree).
-		Parent int `json:"parent"`
-		// root: the pathname of the directory in the filesystem which forms the root of this mount.
-		Root string `json:"root"`
-		// mount point: the pathname of the mount point relative to the process's root directory.
-		Target string `json:"target"`
-		// mount options: per-mount options (see mount(2)).
-		VfsOptstr string `json:"vfs_optstr"`
-		// filesystem type: the filesystem type in the form "type[.subtype]".
-		FsType string `json:"fstype"`
-		// mount source: filesystem-specific information or "none".
-		Source string `json:"source"`
-		// super options: per-superblock options (see mount(2)).
-		FsOptstr string `json:"fs_optstr"`
-	}
-)
-
-func (m *Mountinfo) copy(v *MountinfoEntry) {
-	if m.fs == nil {
-		panic("invalid entry")
-	}
-	v.ID = int(C.mnt_fs_get_id(m.fs))
-	v.Parent = int(C.mnt_fs_get_parent_id(m.fs))
-	v.Root = C.GoString(C.mnt_fs_get_root(m.fs))
-	v.Target = C.GoString(C.mnt_fs_get_target(m.fs))
-	v.VfsOptstr = C.GoString(C.mnt_fs_get_vfs_options(m.fs))
-	v.FsType = C.GoString(C.mnt_fs_get_fstype(m.fs))
-	v.Source = C.GoString(C.mnt_fs_get_source(m.fs))
-	v.FsOptstr = C.GoString(C.mnt_fs_get_fs_options(m.fs))
-}
-
-func NewMountinfo(p string) *Mountinfo { m := new(Mountinfo); m.p = p; return m }
-
-func (m *Mountinfo) Err() error { m.mu.RLock(); defer m.mu.RUnlock(); return m.err }
-
-func (m *Mountinfo) Parse() error {
-	m.mu.Lock()
-	defer m.mu.Unlock()
-
-	if m.tb != nil {
-		panic("open called twice")
-	}
-
-	if m.p == "" {
-		m.tb = C.mnt_new_table_from_file(C.HAKUREI_MOUNTINFO_PATH)
-	} else {
-		name := C.CString(m.p)
-		m.tb = C.mnt_new_table_from_file(name)
-		C.free(unsafe.Pointer(name))
-	}
-	if m.tb == nil {
-		return ErrMountinfoParse
-	}
-	m.itr = C.mnt_new_iter(C.MNT_ITER_FORWARD)
-	if m.itr == nil {
-		C.mnt_unref_table(m.tb)
-		return ErrMountinfoIter
-	}
-
-	runtime.SetFinalizer(m, (*Mountinfo).Unref)
-	return nil
-}
-
-func (m *Mountinfo) Unref() {
-	m.mu.Lock()
-	defer m.mu.Unlock()
-
-	if m.tb == nil {
-		panic("unref called before parse")
-	}
-
-	C.mnt_unref_table(m.tb)
-	C.mnt_free_iter(m.itr)
-	runtime.SetFinalizer(m, nil)
-}
-
-func (m *Mountinfo) Entries() iter.Seq[*MountinfoEntry] {
-	return func(yield func(*MountinfoEntry) bool) {
-		m.mu.Lock()
-		defer m.mu.Unlock()
-
-		C.mnt_reset_iter(m.itr, -1)
-
-		var rc C.int
-		ent := new(MountinfoEntry)
-		for rc = C.mnt_table_next_fs(m.tb, m.itr, &m.fs); rc == 0; rc = C.mnt_table_next_fs(m.tb, m.itr, &m.fs) {
-			m.copy(ent)
-			if !yield(ent) {
-				return
-			}
-		}
-		if rc < 0 {
-			m.err = ErrMountinfoFault
-			return
-		}
-	}
-}
-
-func (e *MountinfoEntry) EqualWithIgnore(want *MountinfoEntry, ignore string) bool {
-	return (e.ID == want.ID || want.ID == -1) &&
-		(e.Parent == want.Parent || want.Parent == -1) &&
-		(e.Root == want.Root || want.Root == ignore) &&
-		(e.Target == want.Target || want.Target == ignore) &&
-		(e.VfsOptstr == want.VfsOptstr || want.VfsOptstr == ignore) &&
-		(e.FsType == want.FsType || want.FsType == ignore) &&
-		(e.Source == want.Source || want.Source == ignore) &&
-		(e.FsOptstr == want.FsOptstr || want.FsOptstr == ignore)
-}
-
-func (e *MountinfoEntry) String() string {
-	return fmt.Sprintf("%d %d %s %s %s %s %s %s",
-		e.ID, e.Parent, e.Root, e.Target, e.VfsOptstr, e.FsType, e.Source, e.FsOptstr)
-}