s3-vfs: add copy_chunk vfs hooks

copy_chunk copies n bytes from a source file at a specific offset to a
destination file at a given offset. This interface will be used in
handling smb2 FSCTL_SRV_COPYCHUNK ioctl requests.

Use a pread/pwrite loop in vfs_default, so that requests referring to
the same src and dest file are possible.

Provide send and receive hooks for copy chunk VFS interface, allowing
asynchronous behaviour.

Check whether the request source offset + length exceeds the current
size. Return STATUS_INVALID_VIEW_SIZE under such a condition, matching
Windows server behaviour.

Reviewed by: Jeremy Allison <jra@samba.org>

1 files changed, 111 insertions, 0 deletions

diff --git a/source3/modules/vfs_default.c b/source3/modules/vfs_default.c
index 0f651dca51..d937c4a862 100644
--- a/source3/modules/vfs_default.c
+++ b/source3/modules/vfs_default.c
@@ -31,6 +31,7 @@
 #include "librpc/gen_ndr/ndr_dfsblobs.h"
 #include "lib/util/tevent_unix.h"
 #include "lib/asys/asys.h"
+#include "lib/util/tevent_ntstatus.h"
 
 #undef DBGC_CLASS
 #define DBGC_CLASS DBGC_VFS
@@ -1323,6 +1324,114 @@ static NTSTATUS vfswrap_fsctl(struct vfs_handle_struct *handle,
 	return NT_STATUS_NOT_SUPPORTED;
 }
 
+struct vfs_cc_state {
+	off_t copied;
+	uint8_t buf[65536];
+};
+
+static struct tevent_req *vfswrap_copy_chunk_send(struct vfs_handle_struct *handle,
+						  TALLOC_CTX *mem_ctx,
+						  struct tevent_context *ev,
+						  struct files_struct *src_fsp,
+						  off_t src_off,
+						  struct files_struct *dest_fsp,
+						  off_t dest_off,
+						  off_t num)
+{
+	struct tevent_req *req;
+	struct vfs_cc_state *vfs_cc_state;
+	NTSTATUS status;
+
+	DEBUG(10, ("performing server side copy chunk of length %lu\n",
+		   (unsigned long)num));
+
+	req = tevent_req_create(mem_ctx, &vfs_cc_state, struct vfs_cc_state);
+	if (req == NULL) {
+		return NULL;
+	}
+
+	status = vfs_stat_fsp(src_fsp);
+	if (tevent_req_nterror(req, status)) {
+		return tevent_req_post(req, ev);
+	}
+
+	if (src_fsp->fsp_name->st.st_ex_size < src_off + num) {
+		/*
+		 * [MS-SMB2] 3.3.5.15.6 Handling a Server-Side Data Copy Request
+		 *   If the SourceOffset or SourceOffset + Length extends beyond
+		 *   the end of file, the server SHOULD<240> treat this as a
+		 *   STATUS_END_OF_FILE error.
+		 * ...
+		 *   <240> Section 3.3.5.15.6: Windows servers will return
+		 *   STATUS_INVALID_VIEW_SIZE instead of STATUS_END_OF_FILE.
+		 */
+		tevent_req_nterror(req, NT_STATUS_INVALID_VIEW_SIZE);
+		return tevent_req_post(req, ev);
+	}
+
+	/* could use 2.6.33+ sendfile here to do this in kernel */
+	while (vfs_cc_state->copied < num) {
+		ssize_t ret;
+		off_t this_num = MIN(sizeof(vfs_cc_state->buf),
+				     num - vfs_cc_state->copied);
+
+		ret = SMB_VFS_PREAD(src_fsp, vfs_cc_state->buf,
+				    this_num, src_off);
+		if (ret == -1) {
+			tevent_req_nterror(req, map_nt_error_from_unix(errno));
+			return tevent_req_post(req, ev);
+		}
+		if (ret != this_num) {
+			/* zero tolerance for short reads */
+			tevent_req_nterror(req, NT_STATUS_IO_DEVICE_ERROR);
+			return tevent_req_post(req, ev);
+		}
+		src_off += ret;
+
+		ret = SMB_VFS_PWRITE(dest_fsp, vfs_cc_state->buf,
+				     this_num, dest_off);
+		if (ret == -1) {
+			tevent_req_nterror(req, map_nt_error_from_unix(errno));
+			return tevent_req_post(req, ev);
+		}
+		if (ret != this_num) {
+			/* zero tolerance for short writes */
+			tevent_req_nterror(req, NT_STATUS_IO_DEVICE_ERROR);
+			return tevent_req_post(req, ev);
+		}
+		dest_off += ret;
+
+		vfs_cc_state->copied += this_num;
+	}
+
+	tevent_req_done(req);
+	return tevent_req_post(req, ev);
+}
+
+static NTSTATUS vfswrap_copy_chunk_recv(struct vfs_handle_struct *handle,
+					struct tevent_req *req,
+					off_t *copied)
+{
+	struct vfs_cc_state *vfs_cc_state = tevent_req_data(req,
+							struct vfs_cc_state);
+	NTSTATUS status;
+
+	if (tevent_req_is_nterror(req, &status)) {
+		DEBUG(2, ("server side copy chunk failed: %s\n",
+			  nt_errstr(status)));
+		*copied = 0;
+		tevent_req_received(req);
+		return status;
+	}
+
+	*copied = vfs_cc_state->copied;
+	DEBUG(10, ("server side copy chunk copied %lu\n",
+		   (unsigned long)*copied));
+	tevent_req_received(req);
+
+	return NT_STATUS_OK;
+}
+
 /********************************************************************
  Given a stat buffer return the allocated size on disk, taking into
  account sparse files.
@@ -2367,6 +2476,8 @@ static struct vfs_fn_pointers vfs_default_fns = {
 	.strict_unlock_fn = vfswrap_strict_unlock,
 	.translate_name_fn = vfswrap_translate_name,
 	.fsctl_fn = vfswrap_fsctl,
+	.copy_chunk_send_fn = vfswrap_copy_chunk_send,
+	.copy_chunk_recv_fn = vfswrap_copy_chunk_recv,
 
 	/* NT ACL operations. */