Implement FUSE_SYMLINK

Fixes #3452

2 files changed, 36 insertions, 0 deletions

diff --git a/pkg/abi/linux/fuse.go b/pkg/abi/linux/fuse.go
index 97d960096..ea5a7fd43 100644
--- a/pkg/abi/linux/fuse.go
+++ b/pkg/abi/linux/fuse.go
@@ -456,3 +456,30 @@ func (r *FUSEMknodIn) MarshalUnsafe(buf []byte) {
 func (r *FUSEMknodIn) SizeBytes() int {
 	return r.MknodMeta.SizeBytes() + len(r.Name) + 1
 }
+
+// FUSESymLinkIn is the request sent by the kernel to the daemon,
+// to create a symbolic link.
+//
+// Dynamically-sized objects cannot be marshalled.
+type FUSESymLinkIn struct {
+	marshal.StubMarshallable
+
+	// Name of symlink to create.
+	Name string
+
+	// Target of the symlink.
+	Target string
+}
+
+// MarshalUnsafe serializes r.Name and r.Target to the dst buffer.
+// Left null-termination at end of r.Name and r.Target.
+func (r *FUSESymLinkIn) MarshalUnsafe(buf []byte) {
+	copy(buf, r.Name)
+	copy(buf[len(r.Name)+1:], r.Target)
+}
+
+// SizeBytes is the size of the memory representation of FUSESymLinkIn.
+// 2 extra bytes for null-terminated string.
+func (r *FUSESymLinkIn) SizeBytes() int {
+	return len(r.Name) + len(r.Target) + 2
+}
diff --git a/pkg/sentry/fsimpl/fuse/fusefs.go b/pkg/sentry/fsimpl/fuse/fusefs.go
index 5cef0b94f..0021e2933 100644
--- a/pkg/sentry/fsimpl/fuse/fusefs.go
+++ b/pkg/sentry/fsimpl/fuse/fusefs.go
@@ -362,6 +362,15 @@ func (i *inode) NewNode(ctx context.Context, name string, opts vfs.MknodOptions)
 	return i.newEntry(ctx, name, opts.Mode.FileType(), linux.FUSE_MKNOD, &in)
 }
 
+// NewSymlink implements kernfs.Inode.NewSymlink.
+func (i *inode) NewSymlink(ctx context.Context, name, target string) (*vfs.Dentry, error) {
+	in := linux.FUSESymLinkIn{
+		Name:   name,
+		Target: target,
+	}
+	return i.newEntry(ctx, name, linux.S_IFLNK, linux.FUSE_SYMLINK, &in)
+}
+
 // newEntry calls FUSE server for entry creation and allocates corresponding entry according to response.
 // Shared by FUSE_MKNOD, FUSE_MKDIR, FUSE_SYMLINK, FUSE_LINK and FUSE_LOOKUP.
 func (i *inode) newEntry(ctx context.Context, name string, fileType linux.FileMode, opcode linux.FUSEOpcode, payload marshal.Marshallable) (*vfs.Dentry, error) {