samba-mirror/source3/lib/ctdbd_conn.c

/* 
   Unix SMB/CIFS implementation.
   Samba internal messaging functions
   Copyright (C) 2007 by Volker Lendecke
   Copyright (C) 2007 by Andrew Tridgell

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "replace.h"
#include <tevent.h>
#include "util_tdb.h"
#include "serverid.h"
#include "ctdbd_conn.h"
#include "system/select.h"
#include "lib/util/sys_rw_data.h"
#include "lib/util/iov_buf.h"
#include "lib/util/select.h"
#include "lib/util/debug.h"
#include "lib/util/talloc_stack.h"
#include "lib/util/genrand.h"
#include "lib/util/fault.h"
#include "lib/util/dlinklist.h"
#include "lib/util/tevent_unix.h"
#include "lib/util/sys_rw.h"
#include "lib/util/blocking.h"
#include "ctdb/include/ctdb_protocol.h"
#include "lib/async_req/async_sock.h"

/* paths to these include files come from --with-ctdb= in configure */

struct ctdbd_srvid_cb {
	uint64_t srvid;
	int (*cb)(struct tevent_context *ev,
		  uint32_t src_vnn, uint32_t dst_vnn,
		  uint64_t dst_srvid,
		  const uint8_t *msg, size_t msglen,
		  void *private_data);
	void *private_data;
};

struct ctdbd_connection {
	uint32_t reqid;
	uint32_t our_vnn;
	uint64_t rand_srvid;
	struct ctdbd_srvid_cb *callbacks;
	int fd;
	int timeout;

	/*
	 * Outgoing queue for writev_send of asynchronous ctdb requests
	 */
	struct tevent_queue *outgoing;
	struct tevent_req **pending;
	struct tevent_req *read_req;
};

static bool ctdbd_conn_has_async_reqs(struct ctdbd_connection *conn)
{
	size_t len = talloc_array_length(conn->pending);
	return (len != 0);
}

static uint32_t ctdbd_next_reqid(struct ctdbd_connection *conn)
{
	conn->reqid += 1;
	if (conn->reqid == 0) {
		conn->reqid += 1;
	}
	return conn->reqid;
}

static int ctdbd_control(struct ctdbd_connection *conn,
			 uint32_t vnn, uint32_t opcode,
			 uint64_t srvid, uint32_t flags,
			 TDB_DATA data,
			 TALLOC_CTX *mem_ctx, TDB_DATA *outdata,
			 int32_t *cstatus);

/*
 * exit on fatal communications errors with the ctdbd daemon
 */
static void cluster_fatal(const char *why)
{
	DEBUG(0,("cluster fatal event: %s - exiting immediately\n", why));
	/* we don't use smb_panic() as we don't want to delay to write
	   a core file. We need to release this process id immediately
	   so that someone else can take over without getting sharing
	   violations */
	_exit(1);
}

/*
 *
 */
static void ctdb_packet_dump(struct ctdb_req_header *hdr)
{
	if (DEBUGLEVEL < 11) {
		return;
	}
	DEBUGADD(11, ("len=%"PRIu32", magic=%"PRIu32", vers=%"PRIu32", "
		      "gen=%"PRIu32", op=%"PRIu32", reqid=%"PRIu32"\n",
		      hdr->length,
		      hdr->ctdb_magic,
		      hdr->ctdb_version,
		      hdr->generation,
		      hdr->operation,
		      hdr->reqid));
}

/*
 * Register a srvid with ctdbd
 */
int register_with_ctdbd(struct ctdbd_connection *conn, uint64_t srvid,
			int (*cb)(struct tevent_context *ev,
				  uint32_t src_vnn, uint32_t dst_vnn,
				  uint64_t dst_srvid,
				  const uint8_t *msg, size_t msglen,
				  void *private_data),
			void *private_data)
{

	int ret;
	int32_t cstatus;
	size_t num_callbacks;
	struct ctdbd_srvid_cb *tmp;

	ret = ctdbd_control_local(conn, CTDB_CONTROL_REGISTER_SRVID, srvid, 0,
				  tdb_null, NULL, NULL, &cstatus);
	if (ret != 0) {
		return ret;
	}

	num_callbacks = talloc_array_length(conn->callbacks);

	tmp = talloc_realloc(conn, conn->callbacks, struct ctdbd_srvid_cb,
			     num_callbacks + 1);
	if (tmp == NULL) {
		return ENOMEM;
	}
	conn->callbacks = tmp;

	conn->callbacks[num_callbacks] = (struct ctdbd_srvid_cb) {
		.srvid = srvid, .cb = cb, .private_data = private_data
	};

	return 0;
}

static int ctdbd_msg_call_back(struct tevent_context *ev,
			       struct ctdbd_connection *conn,
			       struct ctdb_req_message_old *msg)
{
	uint32_t msg_len;
	size_t i, num_callbacks;

	msg_len = msg->hdr.length;
	if (msg_len < offsetof(struct ctdb_req_message_old, data)) {
		DBG_DEBUG("len %"PRIu32" too small\n", msg_len);
		return 0;
	}
	msg_len -= offsetof(struct ctdb_req_message_old, data);

	if (msg_len < msg->datalen) {
		DBG_DEBUG("msg_len=%"PRIu32" < msg->datalen=%"PRIu32"\n",
			  msg_len, msg->datalen);
		return 0;
	}

	num_callbacks = talloc_array_length(conn->callbacks);

	for (i=0; i<num_callbacks; i++) {
		struct ctdbd_srvid_cb *cb = &conn->callbacks[i];

		if ((cb->srvid == msg->srvid) && (cb->cb != NULL)) {
			int ret;

			ret = cb->cb(ev,
				     msg->hdr.srcnode, msg->hdr.destnode,
				     msg->srvid, msg->data, msg->datalen,
				     cb->private_data);
			if (ret != 0) {
				return ret;
			}
		}
	}
	return 0;
}

/*
 * get our vnn from the cluster
 */
static int get_cluster_vnn(struct ctdbd_connection *conn, uint32_t *vnn)
{
	int32_t cstatus=-1;
	int ret;
	ret = ctdbd_control_local(conn, CTDB_CONTROL_GET_PNN, 0, 0,
				  tdb_null, NULL, NULL, &cstatus);
	if (ret != 0) {
		DEBUG(1, ("ctdbd_control failed: %s\n", strerror(ret)));
		return ret;
	}
	*vnn = (uint32_t)cstatus;
	return ret;
}

/*
 * Are we active (i.e. not banned or stopped?)
 */
static bool ctdbd_working(struct ctdbd_connection *conn, uint32_t vnn)
{
	int32_t cstatus=-1;
	TDB_DATA outdata = {0};
	struct ctdb_node_map_old *m;
	bool ok = false;
	uint32_t i;
	int ret;

	ret = ctdbd_control_local(conn, CTDB_CONTROL_GET_NODEMAP, 0, 0,
				  tdb_null, talloc_tos(), &outdata, &cstatus);
	if (ret != 0) {
		DEBUG(1, ("ctdbd_control failed: %s\n", strerror(ret)));
		return false;
	}
	if ((cstatus != 0) || (outdata.dptr == NULL)) {
		DEBUG(2, ("Received invalid ctdb data\n"));
		goto fail;
	}

	m = (struct ctdb_node_map_old *)outdata.dptr;

	for (i=0; i<m->num; i++) {
		if (vnn == m->nodes[i].pnn) {
			break;
		}
	}

	if (i == m->num) {
		DEBUG(2, ("Did not find ourselves (node %d) in nodemap\n",
			  (int)vnn));
		goto fail;
	}

	if ((m->nodes[i].flags & NODE_FLAGS_INACTIVE) != 0) {
		DEBUG(2, ("Node has status %x, not active\n",
			  (int)m->nodes[i].flags));
		goto fail;
	}

	ok = true;
fail:
	TALLOC_FREE(outdata.dptr);
	return ok;
}

uint32_t ctdbd_vnn(const struct ctdbd_connection *conn)
{
	return conn->our_vnn;
}

/*
 * Get us a ctdb connection
 */

static int ctdbd_connect(const char *sockname, int *pfd)
{
	struct sockaddr_un addr = { 0, };
	int fd;
	socklen_t salen;
	size_t namelen;

	fd = socket(AF_UNIX, SOCK_STREAM, 0);
	if (fd == -1) {
		int err = errno;
		DEBUG(3, ("Could not create socket: %s\n", strerror(err)));
		return err;
	}

	addr.sun_family = AF_UNIX;

	namelen = strlcpy(addr.sun_path, sockname, sizeof(addr.sun_path));
	if (namelen >= sizeof(addr.sun_path)) {
		DEBUG(3, ("%s: Socket name too long: %s\n", __func__,
			  sockname));
		close(fd);
		return ENAMETOOLONG;
	}

	salen = sizeof(struct sockaddr_un);

	if (connect(fd, (struct sockaddr *)(void *)&addr, salen) == -1) {
		int err = errno;
		DEBUG(1, ("connect(%s) failed: %s\n", sockname,
			  strerror(err)));
		close(fd);
		return err;
	}

	*pfd = fd;
	return 0;
}

static int ctdb_read_packet(int fd, int timeout, TALLOC_CTX *mem_ctx,
			    struct ctdb_req_header **result)
{
	struct ctdb_req_header *req;
	uint32_t msglen;
	ssize_t nread;

	if (timeout != -1) {
		struct pollfd pfd = { .fd = fd, .events = POLLIN };
		int ret;

		ret = sys_poll_intr(&pfd, 1, timeout);
		if (ret == -1) {
			return errno;
		}
		if (ret == 0) {
			return ETIMEDOUT;
		}
		if (ret != 1) {
			return EIO;
		}
	}

	nread = read_data(fd, &msglen, sizeof(msglen));
	if (nread == -1) {
		return errno;
	}
	if (nread == 0) {
		return EIO;
	}

	if (msglen < sizeof(struct ctdb_req_header)) {
		return EIO;
	}

	req = talloc_size(mem_ctx, msglen);
	if (req == NULL) {
		return ENOMEM;
	}
	talloc_set_name_const(req, "struct ctdb_req_header");

	req->length = msglen;

	nread = read_data(fd, ((char *)req) + sizeof(msglen),
			  msglen - sizeof(msglen));
	if (nread == -1) {
		TALLOC_FREE(req);
		return errno;
	}
	if (nread == 0) {
		TALLOC_FREE(req);
		return EIO;
	}

	*result = req;
	return 0;
}

/*
 * Read a full ctdbd request. If we have a messaging context, defer incoming
 * messages that might come in between.
 */

static int ctdb_read_req(struct ctdbd_connection *conn, uint32_t reqid,
			 TALLOC_CTX *mem_ctx, struct ctdb_req_header **result)
{
	struct ctdb_req_header *hdr = NULL;
	int ret;

 next_pkt:

	ret = ctdb_read_packet(conn->fd, conn->timeout, mem_ctx, &hdr);
	if (ret != 0) {
		DBG_ERR("ctdb_read_packet failed: %s\n", strerror(ret));
		cluster_fatal("failed to read data from ctdbd\n");
		return -1;
	}
	SMB_ASSERT(hdr != NULL);

	DEBUG(11, ("Received ctdb packet\n"));
	ctdb_packet_dump(hdr);

	if (hdr->operation == CTDB_REQ_MESSAGE) {
		struct ctdb_req_message_old *msg = (struct ctdb_req_message_old *)hdr;

		ret = ctdbd_msg_call_back(NULL, conn, msg);
		if (ret != 0) {
			TALLOC_FREE(hdr);
			return ret;
		}

		TALLOC_FREE(hdr);
		goto next_pkt;
	}

	if ((reqid != 0) && (hdr->reqid != reqid)) {
		/* we got the wrong reply */
		DEBUG(0,("Discarding mismatched ctdb reqid %u should have "
			 "been %u\n", hdr->reqid, reqid));
		TALLOC_FREE(hdr);
		goto next_pkt;
	}

	*result = talloc_move(mem_ctx, &hdr);

	return 0;
}

static int ctdbd_connection_destructor(struct ctdbd_connection *c);

/*
 * Get us a ctdbd connection
 */

static int ctdbd_init_connection_internal(TALLOC_CTX *mem_ctx,
					  const char *sockname, int timeout,
					  struct ctdbd_connection *conn)
{
	int ret;

	conn->timeout = timeout;
	if (conn->timeout == 0) {
		conn->timeout = -1;
	}

	ret = ctdbd_connect(sockname, &conn->fd);
	if (ret != 0) {
		DEBUG(1, ("ctdbd_connect failed: %s\n", strerror(ret)));
		return ret;
	}
	talloc_set_destructor(conn, ctdbd_connection_destructor);

	ret = get_cluster_vnn(conn, &conn->our_vnn);
	if (ret != 0) {
		DEBUG(10, ("get_cluster_vnn failed: %s\n", strerror(ret)));
		return ret;
	}

	if (!ctdbd_working(conn, conn->our_vnn)) {
		DEBUG(2, ("Node is not working, can not connect\n"));
		return EIO;
	}

	generate_random_buffer((unsigned char *)&conn->rand_srvid,
			       sizeof(conn->rand_srvid));

	ret = register_with_ctdbd(conn, conn->rand_srvid, NULL, NULL);
	if (ret != 0) {
		DEBUG(5, ("Could not register random srvid: %s\n",
			  strerror(ret)));
		return ret;
	}

	return 0;
}

int ctdbd_init_connection(TALLOC_CTX *mem_ctx,
			  const char *sockname, int timeout,
			  struct ctdbd_connection **pconn)
{
	struct ctdbd_connection *conn;
	int ret;

	if (!(conn = talloc_zero(mem_ctx, struct ctdbd_connection))) {
		DEBUG(0, ("talloc failed\n"));
		return ENOMEM;
	}

	ret = ctdbd_init_connection_internal(mem_ctx,
					     sockname,
					     timeout,
					     conn);
	if (ret != 0) {
		DBG_ERR("ctdbd_init_connection_internal failed (%s)\n",
			strerror(ret));
		goto fail;
	}

	*pconn = conn;
	return 0;

 fail:
	TALLOC_FREE(conn);
	return ret;
}

int ctdbd_reinit_connection(TALLOC_CTX *mem_ctx,
			    const char *sockname, int timeout,
			    struct ctdbd_connection *conn)
{
	int ret;

	ret = ctdbd_connection_destructor(conn);
	if (ret != 0) {
		DBG_ERR("ctdbd_connection_destructor failed\n");
		return ret;
	}

	ret = ctdbd_init_connection_internal(mem_ctx,
					     sockname,
					     timeout,
					     conn);
	if (ret != 0) {
		DBG_ERR("ctdbd_init_connection_internal failed (%s)\n",
			strerror(ret));
		return ret;
	}

	return 0;
}

int ctdbd_init_async_connection(
	TALLOC_CTX *mem_ctx,
	const char *sockname,
	int timeout,
	struct ctdbd_connection **pconn)
{
	struct ctdbd_connection *conn = NULL;
	int ret;

	ret = ctdbd_init_connection(mem_ctx, sockname, timeout, &conn);
	if (ret != 0) {
		return ret;
	}

	ret = set_blocking(conn->fd, false);
	if (ret == -1) {
		int err = errno;
		TALLOC_FREE(conn);
		return err;
	}

	conn->outgoing = tevent_queue_create(conn, "ctdb async outgoing");
	if (conn->outgoing == NULL) {
		TALLOC_FREE(conn);
		return ENOMEM;
	}

	*pconn = conn;
	return 0;
}

int ctdbd_conn_get_fd(struct ctdbd_connection *conn)
{
	return conn->fd;
}

/*
 * Packet handler to receive and handle a ctdb message
 */
static int ctdb_handle_message(struct tevent_context *ev,
			       struct ctdbd_connection *conn,
			       struct ctdb_req_header *hdr)
{
	struct ctdb_req_message_old *msg;

	if (hdr->operation != CTDB_REQ_MESSAGE) {
		DEBUG(0, ("Received async msg of type %u, discarding\n",
			  hdr->operation));
		return EINVAL;
	}

	msg = (struct ctdb_req_message_old *)hdr;

	ctdbd_msg_call_back(ev, conn, msg);

	return 0;
}

void ctdbd_socket_readable(struct tevent_context *ev,
			   struct ctdbd_connection *conn)
{
	struct ctdb_req_header *hdr = NULL;
	int ret;

	ret = ctdb_read_packet(conn->fd, conn->timeout, talloc_tos(), &hdr);
	if (ret != 0) {
		DBG_ERR("ctdb_read_packet failed: %s\n", strerror(ret));
		cluster_fatal("failed to read data from ctdbd\n");
	}
	SMB_ASSERT(hdr != NULL);

	ret = ctdb_handle_message(ev, conn, hdr);

	TALLOC_FREE(hdr);

	if (ret != 0) {
		DEBUG(10, ("could not handle incoming message: %s\n",
			   strerror(ret)));
	}
}

int ctdbd_messaging_send_iov(struct ctdbd_connection *conn,
			     uint32_t dst_vnn, uint64_t dst_srvid,
			     const struct iovec *iov, int iovlen)
{
	struct ctdb_req_message_old r;
	struct iovec iov2[iovlen+1];
	size_t buflen = iov_buflen(iov, iovlen);
	ssize_t nwritten;

	r.hdr.length = offsetof(struct ctdb_req_message_old, data) + buflen;
	r.hdr.ctdb_magic = CTDB_MAGIC;
	r.hdr.ctdb_version = CTDB_PROTOCOL;
	r.hdr.generation = 1;
	r.hdr.operation  = CTDB_REQ_MESSAGE;
	r.hdr.destnode   = dst_vnn;
	r.hdr.srcnode    = conn->our_vnn;
	r.hdr.reqid      = 0;
	r.srvid          = dst_srvid;
	r.datalen        = buflen;

	DEBUG(10, ("ctdbd_messaging_send: Sending ctdb packet\n"));
	ctdb_packet_dump(&r.hdr);

	iov2[0].iov_base = &r;
	iov2[0].iov_len = offsetof(struct ctdb_req_message_old, data);
	memcpy(&iov2[1], iov, iovlen * sizeof(struct iovec));

	nwritten = write_data_iov(conn->fd, iov2, iovlen+1);
	if (nwritten == -1) {
		DEBUG(3, ("write_data_iov failed: %s\n", strerror(errno)));
		cluster_fatal("cluster dispatch daemon msg write error\n");
	}

	return 0;
}

/*
 * send/recv a generic ctdb control message
 */
static int ctdbd_control(struct ctdbd_connection *conn,
			 uint32_t vnn, uint32_t opcode,
			 uint64_t srvid, uint32_t flags,
			 TDB_DATA data,
			 TALLOC_CTX *mem_ctx, TDB_DATA *outdata,
			 int32_t *cstatus)
{
	struct ctdb_req_control_old req;
	struct ctdb_req_header *hdr;
	struct ctdb_reply_control_old *reply = NULL;
	struct iovec iov[2];
	ssize_t nwritten;
	int ret;

	if (ctdbd_conn_has_async_reqs(conn)) {
		/*
		 * Can't use sync call while an async call is in flight. Adding
		 * this check as a safety net. We'll be using different
		 * connections for sync and async requests, so this shouldn't
		 * happen, but who knows...
		 */
		DBG_ERR("Async ctdb req on sync connection\n");
		return EINVAL;
	}

	ZERO_STRUCT(req);
	req.hdr.length = offsetof(struct ctdb_req_control_old, data) + data.dsize;
	req.hdr.ctdb_magic   = CTDB_MAGIC;
	req.hdr.ctdb_version = CTDB_PROTOCOL;
	req.hdr.operation    = CTDB_REQ_CONTROL;
	req.hdr.reqid        = ctdbd_next_reqid(conn);
	req.hdr.destnode     = vnn;
	req.opcode           = opcode;
	req.srvid            = srvid;
	req.datalen          = data.dsize;
	req.flags            = flags;

	DBG_DEBUG("Sending ctdb packet reqid=%"PRIu32", vnn=%"PRIu32", "
		  "opcode=%"PRIu32", srvid=%"PRIu64"\n", req.hdr.reqid,
		  req.hdr.destnode, req.opcode, req.srvid);
	ctdb_packet_dump(&req.hdr);

	iov[0].iov_base = &req;
	iov[0].iov_len = offsetof(struct ctdb_req_control_old, data);
	iov[1].iov_base = data.dptr;
	iov[1].iov_len = data.dsize;

	nwritten = write_data_iov(conn->fd, iov, ARRAY_SIZE(iov));
	if (nwritten == -1) {
		DEBUG(3, ("write_data_iov failed: %s\n", strerror(errno)));
		cluster_fatal("cluster dispatch daemon msg write error\n");
	}

	if (flags & CTDB_CTRL_FLAG_NOREPLY) {
		if (cstatus) {
			*cstatus = 0;
		}
		return 0;
	}

	ret = ctdb_read_req(conn, req.hdr.reqid, NULL, &hdr);
	if (ret != 0) {
		DEBUG(10, ("ctdb_read_req failed: %s\n", strerror(ret)));
		return ret;
	}

	if (hdr->operation != CTDB_REPLY_CONTROL) {
		DEBUG(0, ("received invalid reply\n"));
		TALLOC_FREE(hdr);
		return EIO;
	}
	reply = (struct ctdb_reply_control_old *)hdr;

	if (outdata) {
		if (!(outdata->dptr = (uint8_t *)talloc_memdup(
			      mem_ctx, reply->data, reply->datalen))) {
			TALLOC_FREE(reply);
			return ENOMEM;
		}
		outdata->dsize = reply->datalen;
	}
	if (cstatus) {
		(*cstatus) = reply->status;
	}

	TALLOC_FREE(reply);
	return ret;
}

/*
 * see if a remote process exists
 */
bool ctdbd_process_exists(struct ctdbd_connection *conn, uint32_t vnn,
			  pid_t pid, uint64_t unique_id)
{
	uint8_t buf[sizeof(pid)+sizeof(unique_id)];
	int32_t cstatus = 0;
	int ret;

	if (unique_id == SERVERID_UNIQUE_ID_NOT_TO_VERIFY) {
		ret = ctdbd_control(conn, vnn, CTDB_CONTROL_PROCESS_EXISTS,
				    0, 0,
				    (TDB_DATA) { .dptr = (uint8_t *)&pid,
						    .dsize = sizeof(pid) },
				    NULL, NULL, &cstatus);
		if (ret != 0) {
			return false;
		}
		return (cstatus == 0);
	}

	memcpy(buf, &pid, sizeof(pid));
	memcpy(buf+sizeof(pid), &unique_id, sizeof(unique_id));

	ret = ctdbd_control(conn, vnn, CTDB_CONTROL_CHECK_PID_SRVID, 0, 0,
			    (TDB_DATA) { .dptr = buf, .dsize = sizeof(buf) },
			    NULL, NULL, &cstatus);
	if (ret != 0) {
		return false;
	}
	return (cstatus == 0);
}

/*
 * Get a db path
 */
char *ctdbd_dbpath(struct ctdbd_connection *conn,
		   TALLOC_CTX *mem_ctx, uint32_t db_id)
{
	int ret;
	TDB_DATA data;
	TDB_DATA rdata = {0};
	int32_t cstatus = 0;

	data.dptr = (uint8_t*)&db_id;
	data.dsize = sizeof(db_id);

	ret = ctdbd_control_local(conn, CTDB_CONTROL_GETDBPATH, 0, 0, data,
				  mem_ctx, &rdata, &cstatus);
	if ((ret != 0) || cstatus != 0) {
		DEBUG(0, (__location__ " ctdb_control for getdbpath failed: %s\n",
			  strerror(ret)));
		TALLOC_FREE(rdata.dptr);
	}

	return (char *)rdata.dptr;
}

/*
 * attach to a ctdb database
 */
int ctdbd_db_attach(struct ctdbd_connection *conn,
		    const char *name, uint32_t *db_id, bool persistent)
{
	int ret;
	TDB_DATA data = {0};
	int32_t cstatus;

	data = string_term_tdb_data(name);

	ret = ctdbd_control_local(conn,
				  persistent
				  ? CTDB_CONTROL_DB_ATTACH_PERSISTENT
				  : CTDB_CONTROL_DB_ATTACH,
				  0, 0, data, NULL, &data, &cstatus);
	if (ret != 0) {
		DEBUG(0, (__location__ " ctdb_control for db_attach "
			  "failed: %s\n", strerror(ret)));
		return ret;
	}

	if (cstatus != 0 || data.dsize != sizeof(uint32_t)) {
		DEBUG(0,(__location__ " ctdb_control for db_attach failed\n"));
		TALLOC_FREE(data.dptr);
		return EIO;
	}

	*db_id = *(uint32_t *)data.dptr;
	talloc_free(data.dptr);

	return 0;
}

/*
 * force the migration of a record to this node
 */
int ctdbd_migrate(struct ctdbd_connection *conn, uint32_t db_id, TDB_DATA key)
{
	struct ctdb_req_call_old req;
	struct ctdb_req_header *hdr = NULL;
	struct iovec iov[2];
	ssize_t nwritten;
	int ret;

	if (ctdbd_conn_has_async_reqs(conn)) {
		/*
		 * Can't use sync call while an async call is in flight. Adding
		 * this check as a safety net. We'll be using different
		 * connections for sync and async requests, so this shouldn't
		 * happen, but who knows...
		 */
		DBG_ERR("Async ctdb req on sync connection\n");
		return EINVAL;
	}

	ZERO_STRUCT(req);

	req.hdr.length = offsetof(struct ctdb_req_call_old, data) + key.dsize;
	req.hdr.ctdb_magic   = CTDB_MAGIC;
	req.hdr.ctdb_version = CTDB_PROTOCOL;
	req.hdr.operation    = CTDB_REQ_CALL;
	req.hdr.reqid        = ctdbd_next_reqid(conn);
	req.flags            = CTDB_IMMEDIATE_MIGRATION;
	req.callid           = CTDB_NULL_FUNC;
	req.db_id            = db_id;
	req.keylen           = key.dsize;

	DEBUG(10, ("ctdbd_migrate: Sending ctdb packet\n"));
	ctdb_packet_dump(&req.hdr);

	iov[0].iov_base = &req;
	iov[0].iov_len = offsetof(struct ctdb_req_call_old, data);
	iov[1].iov_base = key.dptr;
	iov[1].iov_len = key.dsize;

	nwritten = write_data_iov(conn->fd, iov, ARRAY_SIZE(iov));
	if (nwritten == -1) {
		DEBUG(3, ("write_data_iov failed: %s\n", strerror(errno)));
		cluster_fatal("cluster dispatch daemon msg write error\n");
	}

	ret = ctdb_read_req(conn, req.hdr.reqid, NULL, &hdr);
	if (ret != 0) {
		DEBUG(10, ("ctdb_read_req failed: %s\n", strerror(ret)));
		goto fail;
	}

	if (hdr->operation != CTDB_REPLY_CALL) {
		if (hdr->operation == CTDB_REPLY_ERROR) {
			DBG_ERR("received error from ctdb\n");
		} else {
			DBG_ERR("received invalid reply\n");
		}
		ret = EIO;
		goto fail;
	}

 fail:

	TALLOC_FREE(hdr);
	return ret;
}

/*
 * Fetch a record and parse it
 */
int ctdbd_parse(struct ctdbd_connection *conn, uint32_t db_id,
		TDB_DATA key, bool local_copy,
		void (*parser)(TDB_DATA key, TDB_DATA data,
			       void *private_data),
		void *private_data)
{
	struct ctdb_req_call_old req;
	struct ctdb_req_header *hdr = NULL;
	struct ctdb_reply_call_old *reply;
	struct iovec iov[2];
	ssize_t nwritten;
	uint32_t flags;
	int ret;

	if (ctdbd_conn_has_async_reqs(conn)) {
		/*
		 * Can't use sync call while an async call is in flight. Adding
		 * this check as a safety net. We'll be using different
		 * connections for sync and async requests, so this shouldn't
		 * happen, but who knows...
		 */
		DBG_ERR("Async ctdb req on sync connection\n");
		return EINVAL;
	}

	flags = local_copy ? CTDB_WANT_READONLY : 0;

	ZERO_STRUCT(req);

	req.hdr.length = offsetof(struct ctdb_req_call_old, data) + key.dsize;
	req.hdr.ctdb_magic   = CTDB_MAGIC;
	req.hdr.ctdb_version = CTDB_PROTOCOL;
	req.hdr.operation    = CTDB_REQ_CALL;
	req.hdr.reqid        = ctdbd_next_reqid(conn);
	req.flags            = flags;
	req.callid           = CTDB_FETCH_FUNC;
	req.db_id            = db_id;
	req.keylen           = key.dsize;

	iov[0].iov_base = &req;
	iov[0].iov_len = offsetof(struct ctdb_req_call_old, data);
	iov[1].iov_base = key.dptr;
	iov[1].iov_len = key.dsize;

	nwritten = write_data_iov(conn->fd, iov, ARRAY_SIZE(iov));
	if (nwritten == -1) {
		DEBUG(3, ("write_data_iov failed: %s\n", strerror(errno)));
		cluster_fatal("cluster dispatch daemon msg write error\n");
	}

	ret = ctdb_read_req(conn, req.hdr.reqid, NULL, &hdr);
	if (ret != 0) {
		DEBUG(10, ("ctdb_read_req failed: %s\n", strerror(ret)));
		goto fail;
	}

	if ((hdr == NULL) || (hdr->operation != CTDB_REPLY_CALL)) {
		DEBUG(0, ("received invalid reply\n"));
		ret = EIO;
		goto fail;
	}
	reply = (struct ctdb_reply_call_old *)hdr;

	if (reply->datalen == 0) {
		/*
		 * Treat an empty record as non-existing
		 */
		ret = ENOENT;
		goto fail;
	}

	parser(key, make_tdb_data(&reply->data[0], reply->datalen),
	       private_data);

	ret = 0;
 fail:
	TALLOC_FREE(hdr);
	return ret;
}

/*
  Traverse a ctdb database. "conn" must be an otherwise unused
  ctdb_connection where no other messages but the traverse ones are
  expected.
*/

int ctdbd_traverse(struct ctdbd_connection *conn, uint32_t db_id,
			void (*fn)(TDB_DATA key, TDB_DATA data,
				   void *private_data),
			void *private_data)
{
	int ret;
	TDB_DATA key, data;
	struct ctdb_traverse_start t;
	int32_t cstatus = 0;

	if (ctdbd_conn_has_async_reqs(conn)) {
		/*
		 * Can't use sync call while an async call is in flight. Adding
		 * this check as a safety net. We'll be using different
		 * connections for sync and async requests, so this shouldn't
		 * happen, but who knows...
		 */
		DBG_ERR("Async ctdb req on sync connection\n");
		return EINVAL;
	}

	t.db_id = db_id;
	t.srvid = conn->rand_srvid;
	t.reqid = ctdbd_next_reqid(conn);

	data.dptr = (uint8_t *)&t;
	data.dsize = sizeof(t);

	ret = ctdbd_control_local(conn, CTDB_CONTROL_TRAVERSE_START,
				  conn->rand_srvid,
				  0, data, NULL, NULL, &cstatus);

	if ((ret != 0) || (cstatus != 0)) {
		DEBUG(0,("ctdbd_control failed: %s, %d\n", strerror(ret),
			 cstatus));

		if (ret == 0) {
			/*
			 * We need a mapping here
			 */
			ret = EIO;
		}
		return ret;
	}

	while (true) {
		struct ctdb_req_header *hdr = NULL;
		struct ctdb_req_message_old *m;
		struct ctdb_rec_data_old *d;

		ret = ctdb_read_packet(conn->fd, conn->timeout, conn, &hdr);
		if (ret != 0) {
			DBG_ERR("ctdb_read_packet failed: %s\n", strerror(ret));
			cluster_fatal("failed to read data from ctdbd\n");
		}
		SMB_ASSERT(hdr != NULL);

		if (hdr->operation != CTDB_REQ_MESSAGE) {
			DEBUG(0, ("Got operation %u, expected a message\n",
				  (unsigned)hdr->operation));
			return EIO;
		}

		m = (struct ctdb_req_message_old *)hdr;
		d = (struct ctdb_rec_data_old *)&m->data[0];
		if (m->datalen < sizeof(uint32_t) || m->datalen != d->length) {
			DEBUG(0, ("Got invalid traverse data of length %d\n",
				  (int)m->datalen));
			return EIO;
		}

		key.dsize = d->keylen;
		key.dptr  = &d->data[0];
		data.dsize = d->datalen;
		data.dptr = &d->data[d->keylen];

		if (key.dsize == 0 && data.dsize == 0) {
			/* end of traverse */
			return 0;
		}

		if (data.dsize < sizeof(struct ctdb_ltdb_header)) {
			DEBUG(0, ("Got invalid ltdb header length %d\n",
				  (int)data.dsize));
			return EIO;
		}
		data.dsize -= sizeof(struct ctdb_ltdb_header);
		data.dptr += sizeof(struct ctdb_ltdb_header);

		if (fn != NULL) {
			fn(key, data, private_data);
		}
	}
	return 0;
}

/*
   This is used to canonicalize a ctdb_sock_addr structure.
*/
static void smbd_ctdb_canonicalize_ip(const struct sockaddr_storage *in,
				      struct sockaddr_storage *out)
{
	memcpy(out, in, sizeof (*out));

#ifdef HAVE_IPV6
	if (in->ss_family == AF_INET6) {
		const char prefix[12] = { 0,0,0,0,0,0,0,0,0,0,0xff,0xff };
		const struct sockaddr_in6 *in6 =
			(const struct sockaddr_in6 *)in;
		struct sockaddr_in *out4 = (struct sockaddr_in *)out;
		if (memcmp(&in6->sin6_addr, prefix, 12) == 0) {
			memset(out, 0, sizeof(*out));
#ifdef HAVE_SOCK_SIN_LEN
			out4->sin_len = sizeof(*out);
#endif
			out4->sin_family = AF_INET;
			out4->sin_port   = in6->sin6_port;
			memcpy(&out4->sin_addr, &in6->sin6_addr.s6_addr[12], 4);
		}
	}
#endif
}

/*
 * Register us as a server for a particular tcp connection
 */

int ctdbd_register_ips(struct ctdbd_connection *conn,
		       const struct sockaddr_storage *_server,
		       const struct sockaddr_storage *_client,
		       int (*cb)(struct tevent_context *ev,
				 uint32_t src_vnn, uint32_t dst_vnn,
				 uint64_t dst_srvid,
				 const uint8_t *msg, size_t msglen,
				 void *private_data),
		       void *private_data)
{
	struct ctdb_connection p;
	TDB_DATA data = { .dptr = (uint8_t *)&p, .dsize = sizeof(p) };
	int ret;
	struct sockaddr_storage client;
	struct sockaddr_storage server;

	/*
	 * Only one connection so far
	 */

	smbd_ctdb_canonicalize_ip(_client, &client);
	smbd_ctdb_canonicalize_ip(_server, &server);

	switch (client.ss_family) {
	case AF_INET:
		memcpy(&p.dst.ip, &server, sizeof(p.dst.ip));
		memcpy(&p.src.ip, &client, sizeof(p.src.ip));
		break;
	case AF_INET6:
		memcpy(&p.dst.ip6, &server, sizeof(p.dst.ip6));
		memcpy(&p.src.ip6, &client, sizeof(p.src.ip6));
		break;
	default:
		return EIO;
	}

	/*
	 * We want to be told about IP releases
	 */

	ret = register_with_ctdbd(conn, CTDB_SRVID_RELEASE_IP,
				  cb, private_data);
	if (ret != 0) {
		return ret;
	}

	/*
	 * inform ctdb of our tcp connection, so if IP takeover happens ctdb
	 * can send an extra ack to trigger a reset for our client, so it
	 * immediately reconnects
	 */
	ret = ctdbd_control(conn, CTDB_CURRENT_NODE,
			    CTDB_CONTROL_TCP_CLIENT, 0,
			    CTDB_CTRL_FLAG_NOREPLY, data, NULL, NULL,
			    NULL);
	if (ret != 0) {
		return ret;
	}
	return 0;
}

/*
  call a control on the local node
 */
int ctdbd_control_local(struct ctdbd_connection *conn, uint32_t opcode,
			uint64_t srvid, uint32_t flags, TDB_DATA data,
			TALLOC_CTX *mem_ctx, TDB_DATA *outdata,
			int32_t *cstatus)
{
	return ctdbd_control(conn, CTDB_CURRENT_NODE, opcode, srvid, flags, data,
			     mem_ctx, outdata, cstatus);
}

int ctdb_watch_us(struct ctdbd_connection *conn)
{
	struct ctdb_notify_data_old reg_data;
	size_t struct_len;
	int ret;
	int32_t cstatus;

	reg_data.srvid = CTDB_SRVID_SAMBA_NOTIFY;
	reg_data.len = 1;
	reg_data.notify_data[0] = 0;

	struct_len = offsetof(struct ctdb_notify_data_old,
			      notify_data) + reg_data.len;

	ret = ctdbd_control_local(
		conn, CTDB_CONTROL_REGISTER_NOTIFY, conn->rand_srvid, 0,
		make_tdb_data((uint8_t *)&reg_data, struct_len),
		NULL, NULL, &cstatus);
	if (ret != 0) {
		DEBUG(1, ("ctdbd_control_local failed: %s\n",
			  strerror(ret)));
	}
	return ret;
}

int ctdb_unwatch(struct ctdbd_connection *conn)
{
	uint64_t srvid = CTDB_SRVID_SAMBA_NOTIFY;
	int ret;
	int32_t cstatus;

	ret = ctdbd_control_local(
		conn, CTDB_CONTROL_DEREGISTER_NOTIFY, conn->rand_srvid, 0,
		make_tdb_data((uint8_t *)&srvid, sizeof(srvid)),
		NULL, NULL, &cstatus);
	if (ret != 0) {
		DEBUG(1, ("ctdbd_control_local failed: %s\n",
			  strerror(ret)));
	}
	return ret;
}

int ctdbd_probe(const char *sockname, int timeout)
{
	/*
	 * Do a very early check if ctdbd is around to avoid an abort and core
	 * later
	 */
	struct ctdbd_connection *conn = NULL;
	int ret;

	ret = ctdbd_init_connection(talloc_tos(), sockname, timeout,
				    &conn);

	/*
	 * We only care if we can connect.
	 */
	TALLOC_FREE(conn);

	return ret;
}

static int ctdbd_connection_destructor(struct ctdbd_connection *c)
{
	if (c->fd != -1) {
		close(c->fd);
		c->fd = -1;
	}
	return 0;
}

void ctdbd_prep_hdr_next_reqid(
	struct ctdbd_connection *conn, struct ctdb_req_header *hdr)
{
	*hdr = (struct ctdb_req_header) {
		.ctdb_magic = CTDB_MAGIC,
		.ctdb_version = CTDB_PROTOCOL,
		.reqid = ctdbd_next_reqid(conn),
		.destnode = CTDB_CURRENT_NODE,
	};
}

struct ctdbd_pkt_read_state {
	uint8_t *pkt;
};

static ssize_t ctdbd_pkt_read_more(
	uint8_t *buf, size_t buflen, void *private_data);
static void ctdbd_pkt_read_done(struct tevent_req *subreq);

static struct tevent_req *ctdbd_pkt_read_send(
	TALLOC_CTX *mem_ctx, struct tevent_context *ev, int fd)
{
	struct tevent_req *req = NULL, *subreq = NULL;
	struct ctdbd_pkt_read_state *state = NULL;

	req = tevent_req_create(mem_ctx, &state, struct ctdbd_pkt_read_state);
	if (req == NULL) {
		return NULL;
	}
	subreq = read_packet_send(state, ev, fd, 4, ctdbd_pkt_read_more, NULL);
	if (tevent_req_nomem(subreq, req)) {
		return tevent_req_post(req, ev);
	}
	tevent_req_set_callback(subreq, ctdbd_pkt_read_done, req);
	return req;
}

static ssize_t ctdbd_pkt_read_more(
	uint8_t *buf, size_t buflen, void *private_data)
{
	uint32_t msglen;
	if (buflen < 4) {
		return -1;
	}
	if (buflen > 4) {
		return 0; 	/* Been here, done */
	}
	memcpy(&msglen, buf, 4);

	if (msglen < sizeof(struct ctdb_req_header)) {
		return -1;
	}
	return msglen - sizeof(msglen);
}

static void ctdbd_pkt_read_done(struct tevent_req *subreq)
{
	struct tevent_req *req = tevent_req_callback_data(
		subreq, struct tevent_req);
	struct ctdbd_pkt_read_state *state = tevent_req_data(
		req, struct ctdbd_pkt_read_state);
	ssize_t nread;
	int err;

	nread = read_packet_recv(subreq, state, &state->pkt, &err);
	TALLOC_FREE(subreq);
	if (nread == -1) {
		tevent_req_error(req, err);
		return;
	}
	tevent_req_done(req);
}

static int ctdbd_pkt_read_recv(
	struct tevent_req *req, TALLOC_CTX *mem_ctx, uint8_t **pkt)
{
	struct ctdbd_pkt_read_state *state = tevent_req_data(
		req, struct ctdbd_pkt_read_state);
	int err;

	if (tevent_req_is_unix_error(req, &err)) {
		return err;
	}
	*pkt = talloc_move(mem_ctx, &state->pkt);
	tevent_req_received(req);
	return 0;
}

static bool ctdbd_conn_receive_next(struct ctdbd_connection *conn);
static void ctdbd_conn_received(struct tevent_req *subreq);

struct ctdbd_req_state {
	struct ctdbd_connection *conn;
	struct tevent_context *ev;
	uint32_t reqid;
	struct ctdb_req_header *reply;
};

static void ctdbd_req_unset_pending(struct tevent_req *req)
{
	struct ctdbd_req_state *state = tevent_req_data(
		req, struct ctdbd_req_state);
	struct ctdbd_connection *conn = state->conn;
	size_t num_pending = talloc_array_length(conn->pending);
	size_t i, num_after;

	tevent_req_set_cleanup_fn(req, NULL);

	if (num_pending == 1) {
		/*
		 * conn->read_req is a child of conn->pending
		 */
		TALLOC_FREE(conn->pending);
		conn->read_req = NULL;
		return;
	}

	for (i=0; i<num_pending; i++) {
		if (req == conn->pending[i]) {
			break;
		}
	}
	if (i == num_pending) {
		/*
		 * Something's seriously broken. Just returning here is the
		 * right thing nevertheless, the point of this routine is to
		 * remove ourselves from conn->pending.
		 */
		return;
	}

	num_after = num_pending - i - 1;
	if (num_after > 0) {
		memmove(&conn->pending[i],
			&conn->pending[i] + 1,
			sizeof(*conn->pending) * num_after);
	}
	conn->pending = talloc_realloc(
		NULL, conn->pending, struct tevent_req *, num_pending - 1);
}

static void ctdbd_req_cleanup(
	struct tevent_req *req, enum tevent_req_state req_state)
{
	ctdbd_req_unset_pending(req);
}

static bool ctdbd_req_set_pending(struct tevent_req *req)
{
	struct ctdbd_req_state *state = tevent_req_data(
		req, struct ctdbd_req_state);
	struct ctdbd_connection *conn = state->conn;
	struct tevent_req **pending = NULL;
	size_t num_pending = talloc_array_length(conn->pending);
	bool ok;

	pending = talloc_realloc(
		conn, conn->pending, struct tevent_req *, num_pending + 1);
	if (pending == NULL) {
		return false;
	}
	pending[num_pending] = req;
	conn->pending = pending;

	tevent_req_set_cleanup_fn(req, ctdbd_req_cleanup);

	ok = ctdbd_conn_receive_next(conn);
	if (!ok) {
		ctdbd_req_unset_pending(req);
		return false;
	}

	return true;
}

static bool ctdbd_conn_receive_next(struct ctdbd_connection *conn)
{
	size_t num_pending = talloc_array_length(conn->pending);
	struct tevent_req *req = NULL;
	struct ctdbd_req_state *state = NULL;

	if (conn->read_req != NULL) {
		return true;
	}
	if (num_pending == 0) {
		/*
		 * done for now
		 */
		return true;
	}

	req = conn->pending[0];
	state = tevent_req_data(req, struct ctdbd_req_state);

	conn->read_req = ctdbd_pkt_read_send(
		conn->pending, state->ev, conn->fd);
	if (conn->read_req == NULL) {
		return false;
	}
	tevent_req_set_callback(conn->read_req, ctdbd_conn_received, conn);
	return true;
}

static void ctdbd_conn_received(struct tevent_req *subreq)
{
	struct ctdbd_connection *conn = tevent_req_callback_data(
		subreq, struct ctdbd_connection);
	TALLOC_CTX *frame = talloc_stackframe();
	uint8_t *pkt = NULL;
	int ret;
	struct ctdb_req_header *hdr = NULL;
	uint32_t reqid;
	struct tevent_req *req = NULL;
	struct ctdbd_req_state *state = NULL;
	size_t i, num_pending;
	bool ok;

	SMB_ASSERT(subreq == conn->read_req);
	conn->read_req = NULL;

	ret = ctdbd_pkt_read_recv(subreq, frame, &pkt);
	TALLOC_FREE(subreq);
	if (ret != 0) {
		cluster_fatal("ctdbd_pkt_read failed\n");
	}

	hdr = (struct ctdb_req_header *)pkt;
	reqid = hdr->reqid;
	num_pending = talloc_array_length(conn->pending);

	for (i=0; i<num_pending; i++) {
		req = conn->pending[i];
		state = tevent_req_data(req, struct ctdbd_req_state);
		if (state->reqid == reqid) {
			break;
		}
	}

	if (i == num_pending) {
		/* not found */
		TALLOC_FREE(frame);
		return;
	}

	state->reply = talloc_move(state, &hdr);
	tevent_req_defer_callback(req, state->ev);
	tevent_req_done(req);

	TALLOC_FREE(frame);

	ok = ctdbd_conn_receive_next(conn);
	if (!ok) {
		cluster_fatal("ctdbd_conn_receive_next failed\n");
	}
}

static void ctdbd_req_written(struct tevent_req *subreq);

struct tevent_req *ctdbd_req_send(
	TALLOC_CTX *mem_ctx,
	struct tevent_context *ev,
	struct ctdbd_connection *conn,
	struct iovec *iov,
	size_t num_iov)
{
	struct tevent_req *req = NULL, *subreq = NULL;
	struct ctdbd_req_state *state = NULL;
	struct ctdb_req_header *hdr = NULL;
	bool ok;

	req = tevent_req_create(mem_ctx, &state, struct ctdbd_req_state);
	if (req == NULL) {
		return NULL;
	}
	state->conn = conn;
	state->ev = ev;

	if ((num_iov == 0) ||
	    (iov[0].iov_len < sizeof(struct ctdb_req_header))) {
		tevent_req_error(req, EINVAL);
		return tevent_req_post(req, ev);
	}
	hdr = iov[0].iov_base;
	state->reqid = hdr->reqid;

	ok = ctdbd_req_set_pending(req);
	if (!ok) {
		tevent_req_oom(req);
		return tevent_req_post(req, ev);
	}

	subreq = writev_send(
		state, ev, conn->outgoing, conn->fd, false, iov, num_iov);
	if (tevent_req_nomem(subreq, req)) {
		return tevent_req_post(req, ev);
	}
	tevent_req_set_callback(subreq, ctdbd_req_written, req);

	return req;
}

static void ctdbd_req_written(struct tevent_req *subreq)
{
	struct tevent_req *req = tevent_req_callback_data(
		subreq, struct tevent_req);
	ssize_t nwritten;
	int err;

	nwritten = writev_recv(subreq, &err);
	TALLOC_FREE(subreq);
	if (nwritten == -1) {
		tevent_req_error(req, err);
		return;
	}
}

int ctdbd_req_recv(
	struct tevent_req *req,
	TALLOC_CTX *mem_ctx,
	struct ctdb_req_header **reply)
{
	struct ctdbd_req_state *state = tevent_req_data(
		req, struct ctdbd_req_state);
	int err;

	if (tevent_req_is_unix_error(req, &err)) {
		return err;
	}
	*reply = talloc_move(mem_ctx, &state->reply);
	tevent_req_received(req);
	return 0;
}

struct ctdbd_parse_state {
	struct tevent_context *ev;
	struct ctdbd_connection *conn;
	uint32_t reqid;
	TDB_DATA key;
	uint8_t _keybuf[64];
	struct ctdb_req_call_old ctdb_req;
	struct iovec iov[2];
	void (*parser)(TDB_DATA key,
		       TDB_DATA data,
		       void *private_data);
	void *private_data;
};

static void ctdbd_parse_done(struct tevent_req *subreq);

struct tevent_req *ctdbd_parse_send(TALLOC_CTX *mem_ctx,
				    struct tevent_context *ev,
				    struct ctdbd_connection *conn,
				    uint32_t db_id,
				    TDB_DATA key,
				    bool local_copy,
				    void (*parser)(TDB_DATA key,
						   TDB_DATA data,
						   void *private_data),
				    void *private_data,
				    enum dbwrap_req_state *req_state)
{
	struct tevent_req *req = NULL;
	struct ctdbd_parse_state *state = NULL;
	uint32_t flags;
	uint32_t packet_length;
	struct tevent_req *subreq = NULL;

	req = tevent_req_create(mem_ctx, &state, struct ctdbd_parse_state);
	if (req == NULL) {
		*req_state = DBWRAP_REQ_ERROR;
		return NULL;
	}

	*req_state = DBWRAP_REQ_DISPATCHED;

	*state = (struct ctdbd_parse_state) {
		.ev = ev,
		.conn = conn,
		.reqid = ctdbd_next_reqid(conn),
		.parser = parser,
		.private_data = private_data,
	};

	flags = local_copy ? CTDB_WANT_READONLY : 0;
	packet_length = offsetof(struct ctdb_req_call_old, data) + key.dsize;

	/*
	 * Copy the key into our state, as ctdb_pkt_send_cleanup() requires that
	 * all passed iov elements have a lifetime longer that the tevent_req
	 * returned by ctdb_pkt_send_send(). This is required continue sending a
	 * the low level request into the ctdb socket, if a higher level
	 * ('this') request is canceled (or talloc free'd) by the application
	 * layer, without sending invalid packets to ctdb.
	 */
	if (key.dsize > sizeof(state->_keybuf)) {
		state->key.dptr = talloc_memdup(state, key.dptr, key.dsize);
		if (tevent_req_nomem(state->key.dptr, req)) {
			return tevent_req_post(req, ev);
		}
	} else {
		memcpy(state->_keybuf, key.dptr, key.dsize);
		state->key.dptr = state->_keybuf;
	}
	state->key.dsize = key.dsize;

	state->ctdb_req.hdr.length       = packet_length;
	state->ctdb_req.hdr.ctdb_magic   = CTDB_MAGIC;
	state->ctdb_req.hdr.ctdb_version = CTDB_PROTOCOL;
	state->ctdb_req.hdr.operation    = CTDB_REQ_CALL;
	state->ctdb_req.hdr.reqid        = state->reqid;
	state->ctdb_req.flags            = flags;
	state->ctdb_req.callid           = CTDB_FETCH_FUNC;
	state->ctdb_req.db_id            = db_id;
	state->ctdb_req.keylen           = state->key.dsize;

	state->iov[0].iov_base = &state->ctdb_req;
	state->iov[0].iov_len = offsetof(struct ctdb_req_call_old, data);
	state->iov[1].iov_base = state->key.dptr;
	state->iov[1].iov_len = state->key.dsize;

	subreq = ctdbd_req_send(
		state, ev, conn, state->iov, ARRAY_SIZE(state->iov));
	if (tevent_req_nomem(subreq, req)) {
		*req_state = DBWRAP_REQ_ERROR;
		return tevent_req_post(req, ev);
	}
	tevent_req_set_callback(subreq, ctdbd_parse_done, req);

	return req;
}

static void ctdbd_parse_done(struct tevent_req *subreq)
{
	struct tevent_req *req = tevent_req_callback_data(
		subreq, struct tevent_req);
	struct ctdbd_parse_state *state = tevent_req_data(
		req, struct ctdbd_parse_state);
	struct ctdb_req_header *hdr = NULL;
	struct ctdb_reply_call_old *reply = NULL;
	int ret;

	ret = ctdbd_req_recv(subreq, state, &hdr);
	TALLOC_FREE(subreq);
	if (tevent_req_error(req, ret)) {
		DBG_DEBUG("ctdb_req_recv failed %s\n", strerror(ret));
		return;
	}
	SMB_ASSERT(hdr != NULL);

	if (hdr->operation != CTDB_REPLY_CALL) {
		DBG_ERR("received invalid reply\n");
		ctdb_packet_dump(hdr);
		tevent_req_error(req, EIO);
		return;
	}

	reply = (struct ctdb_reply_call_old *)hdr;

	if (reply->datalen == 0) {
		/*
		 * Treat an empty record as non-existing
		 */
		tevent_req_error(req, ENOENT);
		return;
	}

	state->parser(state->key,
		      make_tdb_data(&reply->data[0], reply->datalen),
		      state->private_data);

	tevent_req_done(req);
	return;
}

int ctdbd_parse_recv(struct tevent_req *req)
{
	return tevent_req_simple_recv_unix(req);
}