vfs: Add struct vfs_open_how.resolve

This prepares the later introduction of VFS_OPEN_HOW_RESOLVE_NO_SYMLINKS,
which will be used to make use of RESOLVE_NO_SYMLINKS on linux with openat2().

Right now all terminal VFS objects reject any resolve bits with ENOSYS.
So we only prepare the vfs layer for now without any real change.
But this will make backports to 4.17 much easier.

Pair-programmed-with: Stefan Metzmacher <metze@samba.org>

Signed-off-by: Volker Lendecke <vl@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Sat Aug  6 02:39:11 UTC 2022 on sn-devel-184

examples/VFS/skel_opaque.c

@@ -199,6 +199,11 @@ static int skel_openat(struct vfs_handle_struct *handle,
 		       struct files_struct *fsp,
 		       const struct vfs_open_how *how)
 {
+	if (how->resolve != 0) {
+		errno = ENOSYS;
+		return -1;
+	}
+
 	errno = ENOSYS;
 	return -1;
 }

source3/include/vfs.h

@@ -908,6 +908,7 @@ struct vfs_aio_state {
 struct vfs_open_how {
 	int flags;
 	mode_t mode;
+	uint64_t resolve;
 };
 
 /*

source3/modules/vfs_aio_pthread.c

@@ -457,6 +457,11 @@ static int aio_pthread_openat_fn(vfs_handle_struct *handle,
 	bool aio_allow_open = lp_parm_bool(
 		SNUM(handle->conn), "aio_pthread", "aio open", false);
 
+	if (how->resolve != 0) {
+		errno = ENOSYS;
+		return -1;
+	}
+
 	if (is_named_stream(smb_fname)) {
 		/* Don't handle stream opens. */
 		errno = ENOENT;

source3/modules/vfs_ceph.c

@@ -409,6 +409,11 @@ static int cephwrap_openat(struct vfs_handle_struct *handle,
 	bool became_root = false;
 	int result = -ENOENT;
 
+	if (how->resolve != 0) {
+		errno = ENOSYS;
+		return -1;
+	}
+
 	/*
 	 * ceph doesn't have openat().
 	 */

source3/modules/vfs_default.c

@@ -701,6 +701,12 @@ static int vfswrap_openat(vfs_handle_struct *handle,
 
 	START_PROFILE(syscall_openat);
 
+	if (how->resolve != 0) {
+		errno = ENOSYS;
+		result = -1;
+		goto out;
+	}
+
 	if (is_named_stream(smb_fname)) {
 		errno = ENOENT;
 		result = -1;

source3/modules/vfs_fruit.c

@@ -1758,6 +1758,11 @@ static int fruit_openat(vfs_handle_struct *handle,
 					   how);
 	}
 
+	if (how->resolve != 0) {
+		errno = ENOSYS;
+		return -1;
+	}
+
 	SMB_ASSERT(fsp_is_alternate_stream(fsp));
 
 	if (is_afpinfo_stream(smb_fname->stream_name)) {

source3/modules/vfs_glusterfs.c

@@ -772,6 +772,12 @@ static int vfs_gluster_openat(struct vfs_handle_struct *handle,
 
 	START_PROFILE(syscall_openat);
 
+	if (how->resolve != 0) {
+		END_PROFILE(syscall_openat);
+		errno = ENOSYS;
+		return -1;
+	}
+
 	/*
 	 * Looks like glfs API doesn't have openat().
 	 */

source3/modules/vfs_shadow_copy2.c

@@ -1553,6 +1553,11 @@ static int shadow_copy2_openat(vfs_handle_struct *handle,
 	int ret;
 	bool ok;
 
+	if (how.resolve != 0) {
+		errno = ENOSYS;
+		return -1;
+	}
+
 	smb_fname = shadow_copy2_openat_name(
 		talloc_tos(), dirfsp, fsp, smb_fname_in);
 	if (smb_fname == NULL) {

source3/modules/vfs_streams_depot.c

@@ -681,6 +681,11 @@ static int streams_depot_openat(struct vfs_handle_struct *handle,
 					   how);
 	}
 
+	if (how->resolve != 0) {
+		errno = ENOSYS;
+		return -1;
+	}
+
 	SMB_ASSERT(fsp_is_alternate_stream(fsp));
 	SMB_ASSERT(dirfsp == NULL);
 	SMB_ASSERT(VALID_STAT(fsp->base_fsp->fsp_name->st));

source3/modules/vfs_streams_xattr.c

@@ -341,6 +341,11 @@ static int streams_xattr_openat(struct vfs_handle_struct *handle,
 					   how);
 	}
 
+	if (how->resolve != 0) {
+		errno = ENOSYS;
+		return -1;
+	}
+
 	SMB_ASSERT(fsp_is_alternate_stream(fsp));
 	SMB_ASSERT(dirfsp == NULL);