/* 
   Unix SMB/CIFS implementation.

   Samba internal messaging functions

   Copyright (C) Andrew Tridgell 2004
   
   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 "includes.h"
#include "lib/events/events.h"
#include "system/filesys.h"
#include "messaging/messaging.h"
#include "../lib/util/dlinklist.h"
#include "lib/socket/socket.h"
#include "librpc/gen_ndr/ndr_irpc.h"
#include "lib/messaging/irpc.h"
#include "tdb_wrap.h"
#include "../lib/util/unix_privs.h"
#include "librpc/rpc/dcerpc.h"
#include "../tdb/include/tdb.h"
#include "../lib/util/util_tdb.h"
#include "cluster/cluster.h"
#include "../lib/util/tevent_ntstatus.h"

/* change the message version with any incompatible changes in the protocol */
#define MESSAGING_VERSION 1

/*
  a pending irpc call
*/
struct irpc_request {
	struct messaging_context *msg_ctx;
	int callid;
	struct {
		void (*handler)(struct irpc_request *irpc, struct irpc_message *m);
		void *private_data;
	} incoming;
};

struct messaging_context {
	struct server_id server_id;
	struct socket_context *sock;
	const char *base_path;
	const char *path;
	struct dispatch_fn **dispatch;
	uint32_t num_types;
	struct idr_context *dispatch_tree;
	struct messaging_rec *pending;
	struct messaging_rec *retry_queue;
	struct irpc_list *irpc;
	struct idr_context *idr;
	const char **names;
	struct timeval start_time;
	struct tevent_timer *retry_te;
	struct {
		struct tevent_context *ev;
		struct tevent_fd *fde;
	} event;
};

/* we have a linked list of dispatch handlers for each msg_type that
   this messaging server can deal with */
struct dispatch_fn {
	struct dispatch_fn *next, *prev;
	uint32_t msg_type;
	void *private_data;
	msg_callback_t fn;
};

/* an individual message */
struct messaging_rec {
	struct messaging_rec *next, *prev;
	struct messaging_context *msg;
	const char *path;

	struct messaging_header {
		uint32_t version;
		uint32_t msg_type;
		struct server_id from;
		struct server_id to;
		uint32_t length;
	} *header;

	DATA_BLOB packet;
	uint32_t retries;
};


static void irpc_handler(struct messaging_context *, void *, 
			 uint32_t, struct server_id, DATA_BLOB *);


/*
 A useful function for testing the message system.
*/
static void ping_message(struct messaging_context *msg, void *private_data,
			 uint32_t msg_type, struct server_id src, DATA_BLOB *data)
{
	DEBUG(1,("INFO: Received PING message from server %u.%u [%.*s]\n",
		 (unsigned int)src.node, (unsigned int)src.id, (int)data->length,
		 data->data?(const char *)data->data:""));
	messaging_send(msg, src, MSG_PONG, data);
}

/*
  return uptime of messaging server via irpc
*/
static NTSTATUS irpc_uptime(struct irpc_message *msg, 
			    struct irpc_uptime *r)
{
	struct messaging_context *ctx = talloc_get_type(msg->private_data, struct messaging_context);
	*r->out.start_time = timeval_to_nttime(&ctx->start_time);
	return NT_STATUS_OK;
}

/* 
   return the path to a messaging socket
*/
static char *messaging_path(struct messaging_context *msg, struct server_id server_id)
{
	TALLOC_CTX *tmp_ctx = talloc_new(msg);
	const char *id = cluster_id_string(tmp_ctx, server_id);
	char *s;
	if (id == NULL) {
		return NULL;
	}
	s = talloc_asprintf(msg, "%s/msg.%s", msg->base_path, id);
	talloc_steal(s, tmp_ctx);
	return s;
}

/*
  dispatch a fully received message

  note that this deliberately can match more than one message handler
  per message. That allows a single messasging context to register
  (for example) a debug handler for more than one piece of code
*/
static void messaging_dispatch(struct messaging_context *msg, struct messaging_rec *rec)
{
	struct dispatch_fn *d, *next;

	/* temporary IDs use an idtree, the rest use a array of pointers */
	if (rec->header->msg_type >= MSG_TMP_BASE) {
		d = (struct dispatch_fn *)idr_find(msg->dispatch_tree, 
						   rec->header->msg_type);
	} else if (rec->header->msg_type < msg->num_types) {
		d = msg->dispatch[rec->header->msg_type];
	} else {
		d = NULL;
	}

	for (; d; d = next) {
		DATA_BLOB data;
		next = d->next;
		data.data = rec->packet.data + sizeof(*rec->header);
		data.length = rec->header->length;
		d->fn(msg, d->private_data, d->msg_type, rec->header->from, &data);
	}
	rec->header->length = 0;
}

/*
  handler for messages that arrive from other nodes in the cluster
*/
static void cluster_message_handler(struct messaging_context *msg, DATA_BLOB packet)
{
	struct messaging_rec *rec;

	rec = talloc(msg, struct messaging_rec);
	if (rec == NULL) {
		smb_panic("Unable to allocate messaging_rec");
	}

	rec->msg           = msg;
	rec->path          = msg->path;
	rec->header        = (struct messaging_header *)packet.data;
	rec->packet        = packet;
	rec->retries       = 0;

	if (packet.length != sizeof(*rec->header) + rec->header->length) {
		DEBUG(0,("messaging: bad message header size %d should be %d\n", 
			 rec->header->length, (int)(packet.length - sizeof(*rec->header))));
		talloc_free(rec);
		return;
	}

	messaging_dispatch(msg, rec);
	talloc_free(rec);
}



/*
  try to send the message
*/
static NTSTATUS try_send(struct messaging_rec *rec)
{
	struct messaging_context *msg = rec->msg;
	size_t nsent;
	void *priv;
	NTSTATUS status;
	struct socket_address *path;

	/* rec->path is the path of the *other* socket, where we want
	 * this to end up */
	path = socket_address_from_strings(msg, msg->sock->backend_name, 
					   rec->path, 0);
	if (!path) {
		return NT_STATUS_NO_MEMORY;
	}

	/* we send with privileges so messages work from any context */
	priv = root_privileges();
	status = socket_sendto(msg->sock, &rec->packet, &nsent, path);
	talloc_free(path);
	talloc_free(priv);

	return status;
}

/*
  retry backed off messages
*/
static void msg_retry_timer(struct tevent_context *ev, struct tevent_timer *te, 
			    struct timeval t, void *private_data)
{
	struct messaging_context *msg = talloc_get_type(private_data,
							struct messaging_context);
	msg->retry_te = NULL;

	/* put the messages back on the main queue */
	while (msg->retry_queue) {
		struct messaging_rec *rec = msg->retry_queue;
		DLIST_REMOVE(msg->retry_queue, rec);
		DLIST_ADD_END(msg->pending, rec, struct messaging_rec *);
	}

	EVENT_FD_WRITEABLE(msg->event.fde);	
}

/*
  handle a socket write event
*/
static void messaging_send_handler(struct messaging_context *msg)
{
	while (msg->pending) {
		struct messaging_rec *rec = msg->pending;
		NTSTATUS status;
		status = try_send(rec);
		if (NT_STATUS_EQUAL(status, STATUS_MORE_ENTRIES)) {
			rec->retries++;
			if (rec->retries > 3) {
				/* we're getting continuous write errors -
				   backoff this record */
				DLIST_REMOVE(msg->pending, rec);
				DLIST_ADD_END(msg->retry_queue, rec, 
					      struct messaging_rec *);
				if (msg->retry_te == NULL) {
					msg->retry_te = 
						event_add_timed(msg->event.ev, msg, 
								timeval_current_ofs(1, 0), 
								msg_retry_timer, msg);
				}
			}
			break;
		}
		rec->retries = 0;
		if (!NT_STATUS_IS_OK(status)) {
			TALLOC_CTX *tmp_ctx = talloc_new(msg);
			DEBUG(1,("messaging: Lost message from %s to %s of type %u - %s\n", 
				 cluster_id_string(tmp_ctx, rec->header->from),
				 cluster_id_string(tmp_ctx, rec->header->to),
				 rec->header->msg_type, 
				 nt_errstr(status)));
			talloc_free(tmp_ctx);
		}
		DLIST_REMOVE(msg->pending, rec);
		talloc_free(rec);
	}
	if (msg->pending == NULL) {
		EVENT_FD_NOT_WRITEABLE(msg->event.fde);
	}
}

/*
  handle a new incoming packet
*/
static void messaging_recv_handler(struct messaging_context *msg)
{
	struct messaging_rec *rec;
	NTSTATUS status;
	DATA_BLOB packet;
	size_t msize;

	/* see how many bytes are in the next packet */
	status = socket_pending(msg->sock, &msize);
	if (!NT_STATUS_IS_OK(status)) {
		DEBUG(0,("socket_pending failed in messaging - %s\n", 
			 nt_errstr(status)));
		return;
	}
	
	packet = data_blob_talloc(msg, NULL, msize);
	if (packet.data == NULL) {
		/* assume this is temporary and retry */
		return;
	}
	    
	status = socket_recv(msg->sock, packet.data, msize, &msize);
	if (!NT_STATUS_IS_OK(status)) {
		data_blob_free(&packet);
		return;
	}

	if (msize < sizeof(*rec->header)) {
		DEBUG(0,("messaging: bad message of size %d\n", (int)msize));
		data_blob_free(&packet);
		return;
	}

	rec = talloc(msg, struct messaging_rec);
	if (rec == NULL) {
		smb_panic("Unable to allocate messaging_rec");
	}

	talloc_steal(rec, packet.data);
	rec->msg           = msg;
	rec->path          = msg->path;
	rec->header        = (struct messaging_header *)packet.data;
	rec->packet        = packet;
	rec->retries       = 0;

	if (msize != sizeof(*rec->header) + rec->header->length) {
		DEBUG(0,("messaging: bad message header size %d should be %d\n", 
			 rec->header->length, (int)(msize - sizeof(*rec->header))));
		talloc_free(rec);
		return;
	}

	messaging_dispatch(msg, rec);
	talloc_free(rec);
}


/*
  handle a socket event
*/
static void messaging_handler(struct tevent_context *ev, struct tevent_fd *fde, 
			      uint16_t flags, void *private_data)
{
	struct messaging_context *msg = talloc_get_type(private_data,
							struct messaging_context);
	if (flags & EVENT_FD_WRITE) {
		messaging_send_handler(msg);
	}
	if (flags & EVENT_FD_READ) {
		messaging_recv_handler(msg);
	}
}


/*
  Register a dispatch function for a particular message type.
*/
NTSTATUS messaging_register(struct messaging_context *msg, void *private_data,
			    uint32_t msg_type, msg_callback_t fn)
{
	struct dispatch_fn *d;

	/* possibly expand dispatch array */
	if (msg_type >= msg->num_types) {
		struct dispatch_fn **dp;
		int i;
		dp = talloc_realloc(msg, msg->dispatch, struct dispatch_fn *, msg_type+1);
		NT_STATUS_HAVE_NO_MEMORY(dp);
		msg->dispatch = dp;
		for (i=msg->num_types;i<=msg_type;i++) {
			msg->dispatch[i] = NULL;
		}
		msg->num_types = msg_type+1;
	}

	d = talloc_zero(msg->dispatch, struct dispatch_fn);
	NT_STATUS_HAVE_NO_MEMORY(d);
	d->msg_type = msg_type;
	d->private_data = private_data;
	d->fn = fn;

	DLIST_ADD(msg->dispatch[msg_type], d);

	return NT_STATUS_OK;
}

/*
  register a temporary message handler. The msg_type is allocated
  above MSG_TMP_BASE
*/
NTSTATUS messaging_register_tmp(struct messaging_context *msg, void *private_data,
				msg_callback_t fn, uint32_t *msg_type)
{
	struct dispatch_fn *d;
	int id;

	d = talloc_zero(msg->dispatch, struct dispatch_fn);
	NT_STATUS_HAVE_NO_MEMORY(d);
	d->private_data = private_data;
	d->fn = fn;

	id = idr_get_new_above(msg->dispatch_tree, d, MSG_TMP_BASE, UINT16_MAX);
	if (id == -1) {
		talloc_free(d);
		return NT_STATUS_TOO_MANY_CONTEXT_IDS;
	}

	d->msg_type = (uint32_t)id;
	(*msg_type) = d->msg_type;

	return NT_STATUS_OK;
}

/*
  De-register the function for a particular message type.
*/
void messaging_deregister(struct messaging_context *msg, uint32_t msg_type, void *private_data)
{
	struct dispatch_fn *d, *next;

	if (msg_type >= msg->num_types) {
		d = (struct dispatch_fn *)idr_find(msg->dispatch_tree, 
						   msg_type);
		if (!d) return;
		idr_remove(msg->dispatch_tree, msg_type);
		talloc_free(d);
		return;
	}

	for (d = msg->dispatch[msg_type]; d; d = next) {
		next = d->next;
		if (d->private_data == private_data) {
			DLIST_REMOVE(msg->dispatch[msg_type], d);
			talloc_free(d);
		}
	}
}

/*
  Send a message to a particular server
*/
NTSTATUS messaging_send(struct messaging_context *msg, struct server_id server, 
			uint32_t msg_type, const DATA_BLOB *data)
{
	struct messaging_rec *rec;
	NTSTATUS status;
	size_t dlength = data?data->length:0;

	rec = talloc(msg, struct messaging_rec);
	if (rec == NULL) {
		return NT_STATUS_NO_MEMORY;
	}

	rec->packet = data_blob_talloc(rec, NULL, sizeof(*rec->header) + dlength);
	if (rec->packet.data == NULL) {
		talloc_free(rec);
		return NT_STATUS_NO_MEMORY;
	}

	rec->retries       = 0;
	rec->msg              = msg;
	rec->header           = (struct messaging_header *)rec->packet.data;
	/* zero padding */
	ZERO_STRUCTP(rec->header);
	rec->header->version  = MESSAGING_VERSION;
	rec->header->msg_type = msg_type;
	rec->header->from     = msg->server_id;
	rec->header->to       = server;
	rec->header->length   = dlength;
	if (dlength != 0) {
		memcpy(rec->packet.data + sizeof(*rec->header), 
		       data->data, dlength);
	}

	if (!cluster_node_equal(&msg->server_id, &server)) {
		/* the destination is on another node - dispatch via
		   the cluster layer */
		status = cluster_message_send(server, &rec->packet);
		talloc_free(rec);
		return status;
	}

	rec->path = messaging_path(msg, server);
	talloc_steal(rec, rec->path);

	if (msg->pending != NULL) {
		status = STATUS_MORE_ENTRIES;
	} else {
		status = try_send(rec);
	}

	if (NT_STATUS_EQUAL(status, STATUS_MORE_ENTRIES)) {
		if (msg->pending == NULL) {
			EVENT_FD_WRITEABLE(msg->event.fde);
		}
		DLIST_ADD_END(msg->pending, rec, struct messaging_rec *);
		return NT_STATUS_OK;
	}

	talloc_free(rec);

	return status;
}

/*
  Send a message to a particular server, with the message containing a single pointer
*/
NTSTATUS messaging_send_ptr(struct messaging_context *msg, struct server_id server, 
			    uint32_t msg_type, void *ptr)
{
	DATA_BLOB blob;

	blob.data = (uint8_t *)&ptr;
	blob.length = sizeof(void *);

	return messaging_send(msg, server, msg_type, &blob);
}


/*
  destroy the messaging context
*/
static int messaging_destructor(struct messaging_context *msg)
{
	unlink(msg->path);
	while (msg->names && msg->names[0]) {
		irpc_remove_name(msg, msg->names[0]);
	}
	return 0;
}

/*
  create the listening socket and setup the dispatcher
*/
struct messaging_context *messaging_init(TALLOC_CTX *mem_ctx, 
					 const char *dir,
					 struct server_id server_id, 
					 struct tevent_context *ev)
{
	struct messaging_context *msg;
	NTSTATUS status;
	struct socket_address *path;

	if (ev == NULL) {
		return NULL;
	}

	msg = talloc_zero(mem_ctx, struct messaging_context);
	if (msg == NULL) {
		return NULL;
	}

	/* setup a handler for messages from other cluster nodes, if appropriate */
	status = cluster_message_init(msg, server_id, cluster_message_handler);
	if (!NT_STATUS_IS_OK(status)) {
		talloc_free(msg);
		return NULL;
	}

	/* create the messaging directory if needed */
	mkdir(dir, 0700);

	msg->base_path     = talloc_reference(msg, dir);
	msg->path          = messaging_path(msg, server_id);
	msg->server_id     = server_id;
	msg->idr           = idr_init(msg);
	msg->dispatch_tree = idr_init(msg);
	msg->start_time    = timeval_current();

	status = socket_create("unix", SOCKET_TYPE_DGRAM, &msg->sock, 0);
	if (!NT_STATUS_IS_OK(status)) {
		talloc_free(msg);
		return NULL;
	}

	/* by stealing here we ensure that the socket is cleaned up (and even 
	   deleted) on exit */
	talloc_steal(msg, msg->sock);

	path = socket_address_from_strings(msg, msg->sock->backend_name, 
					   msg->path, 0);
	if (!path) {
		talloc_free(msg);
		return NULL;
	}

	status = socket_listen(msg->sock, path, 50, 0);
	if (!NT_STATUS_IS_OK(status)) {
		DEBUG(0,("Unable to setup messaging listener for '%s':%s\n", msg->path, nt_errstr(status)));
		talloc_free(msg);
		return NULL;
	}

	/* it needs to be non blocking for sends */
	set_blocking(socket_get_fd(msg->sock), false);

	msg->event.ev   = ev;
	msg->event.fde	= event_add_fd(ev, msg, socket_get_fd(msg->sock), 
				       EVENT_FD_READ, messaging_handler, msg);
	tevent_fd_set_auto_close(msg->event.fde);

	talloc_set_destructor(msg, messaging_destructor);
	
	messaging_register(msg, NULL, MSG_PING, ping_message);
	messaging_register(msg, NULL, MSG_IRPC, irpc_handler);
	IRPC_REGISTER(msg, irpc, IRPC_UPTIME, irpc_uptime, msg);

	return msg;
}

/* 
   A hack, for the short term until we get 'client only' messaging in place 
*/
struct messaging_context *messaging_client_init(TALLOC_CTX *mem_ctx, 
						const char *dir,
						struct tevent_context *ev)
{
	struct server_id id;
	ZERO_STRUCT(id);
	id.id = random() % 0x10000000;
	return messaging_init(mem_ctx, dir, id, ev);
}
/*
  a list of registered irpc server functions
*/
struct irpc_list {
	struct irpc_list *next, *prev;
	struct GUID uuid;
	const struct ndr_interface_table *table;
	int callnum;
	irpc_function_t fn;
	void *private_data;
};


/*
  register a irpc server function
*/
NTSTATUS irpc_register(struct messaging_context *msg_ctx, 
		       const struct ndr_interface_table *table, 
		       int callnum, irpc_function_t fn, void *private_data)
{
	struct irpc_list *irpc;

	/* override an existing handler, if any */
	for (irpc=msg_ctx->irpc; irpc; irpc=irpc->next) {
		if (irpc->table == table && irpc->callnum == callnum) {
			break;
		}
	}
	if (irpc == NULL) {
		irpc = talloc(msg_ctx, struct irpc_list);
		NT_STATUS_HAVE_NO_MEMORY(irpc);
		DLIST_ADD(msg_ctx->irpc, irpc);
	}

	irpc->table   = table;
	irpc->callnum = callnum;
	irpc->fn      = fn;
	irpc->private_data = private_data;
	irpc->uuid = irpc->table->syntax_id.uuid;

	return NT_STATUS_OK;
}


/*
  handle an incoming irpc reply message
*/
static void irpc_handler_reply(struct messaging_context *msg_ctx, struct irpc_message *m)
{
	struct irpc_request *irpc;

	irpc = (struct irpc_request *)idr_find(msg_ctx->idr, m->header.callid);
	if (irpc == NULL) return;

	irpc->incoming.handler(irpc, m);
}

/*
  send a irpc reply
*/
NTSTATUS irpc_send_reply(struct irpc_message *m, NTSTATUS status)
{
	struct ndr_push *push;
	DATA_BLOB packet;
	enum ndr_err_code ndr_err;

	m->header.status = status;

	/* setup the reply */
	push = ndr_push_init_ctx(m->ndr);
	if (push == NULL) {
		status = NT_STATUS_NO_MEMORY;
		goto failed;
	}

	m->header.flags |= IRPC_FLAG_REPLY;

	/* construct the packet */
	ndr_err = ndr_push_irpc_header(push, NDR_SCALARS|NDR_BUFFERS, &m->header);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
		status = ndr_map_error2ntstatus(ndr_err);
		goto failed;
	}

	ndr_err = m->irpc->table->calls[m->irpc->callnum].ndr_push(push, NDR_OUT, m->data);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
		status = ndr_map_error2ntstatus(ndr_err);
		goto failed;
	}

	/* send the reply message */
	packet = ndr_push_blob(push);
	status = messaging_send(m->msg_ctx, m->from, MSG_IRPC, &packet);
	if (!NT_STATUS_IS_OK(status)) goto failed;

failed:
	talloc_free(m);
	return status;
}

/*
  handle an incoming irpc request message
*/
static void irpc_handler_request(struct messaging_context *msg_ctx, 
				 struct irpc_message *m)
{
	struct irpc_list *i;
	void *r;
	enum ndr_err_code ndr_err;

	for (i=msg_ctx->irpc; i; i=i->next) {
		if (GUID_equal(&i->uuid, &m->header.uuid) &&
		    i->table->syntax_id.if_version == m->header.if_version &&
		    i->callnum == m->header.callnum) {
			break;
		}
	}

	if (i == NULL) {
		/* no registered handler for this message */
		talloc_free(m);
		return;
	}

	/* allocate space for the structure */
	r = talloc_zero_size(m->ndr, i->table->calls[m->header.callnum].struct_size);
	if (r == NULL) goto failed;

	/* parse the request data */
	ndr_err = i->table->calls[i->callnum].ndr_pull(m->ndr, NDR_IN, r);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) goto failed;

	/* make the call */
	m->private_data= i->private_data;
	m->defer_reply = false;
	m->no_reply    = false;
	m->msg_ctx     = msg_ctx;
	m->irpc        = i;
	m->data        = r;
	m->ev          = msg_ctx->event.ev;

	m->header.status = i->fn(m, r);

	if (m->no_reply) {
		/* the server function won't ever be replying to this request */
		talloc_free(m);
		return;
	}

	if (m->defer_reply) {
		/* the server function has asked to defer the reply to later */
		talloc_steal(msg_ctx, m);
		return;
	}

	irpc_send_reply(m, m->header.status);
	return;

failed:
	talloc_free(m);
}

/*
  handle an incoming irpc message
*/
static void irpc_handler(struct messaging_context *msg_ctx, void *private_data,
			 uint32_t msg_type, struct server_id src, DATA_BLOB *packet)
{
	struct irpc_message *m;
	enum ndr_err_code ndr_err;

	m = talloc(msg_ctx, struct irpc_message);
	if (m == NULL) goto failed;

	m->from = src;

	m->ndr = ndr_pull_init_blob(packet, m);
	if (m->ndr == NULL) goto failed;

	m->ndr->flags |= LIBNDR_FLAG_REF_ALLOC;

	ndr_err = ndr_pull_irpc_header(m->ndr, NDR_BUFFERS|NDR_SCALARS, &m->header);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) goto failed;

	if (m->header.flags & IRPC_FLAG_REPLY) {
		irpc_handler_reply(msg_ctx, m);
	} else {
		irpc_handler_request(msg_ctx, m);
	}
	return;

failed:
	talloc_free(m);
}


/*
  destroy a irpc request
*/
static int irpc_destructor(struct irpc_request *irpc)
{
	if (irpc->callid != -1) {
		idr_remove(irpc->msg_ctx->idr, irpc->callid);
		irpc->callid = -1;
	}

	return 0;
}

/*
  open the naming database
*/
static struct tdb_wrap *irpc_namedb_open(struct messaging_context *msg_ctx)
{
	struct tdb_wrap *t;
	char *path = talloc_asprintf(msg_ctx, "%s/names.tdb", msg_ctx->base_path);
	if (path == NULL) {
		return NULL;
	}
	t = tdb_wrap_open(msg_ctx, path, 0, 0, O_RDWR|O_CREAT, 0660);
	talloc_free(path);
	return t;
}
	

/*
  add a string name that this irpc server can be called on
*/
NTSTATUS irpc_add_name(struct messaging_context *msg_ctx, const char *name)
{
	struct tdb_wrap *t;
	TDB_DATA rec;
	int count;
	NTSTATUS status = NT_STATUS_OK;

	t = irpc_namedb_open(msg_ctx);
	NT_STATUS_HAVE_NO_MEMORY(t);

	if (tdb_lock_bystring(t->tdb, name) != 0) {
		talloc_free(t);
		return NT_STATUS_LOCK_NOT_GRANTED;
	}
	rec = tdb_fetch_bystring(t->tdb, name);
	count = rec.dsize / sizeof(struct server_id);
	rec.dptr = (unsigned char *)realloc_p(rec.dptr, struct server_id, count+1);
	rec.dsize += sizeof(struct server_id);
	if (rec.dptr == NULL) {
		tdb_unlock_bystring(t->tdb, name);
		talloc_free(t);
		return NT_STATUS_NO_MEMORY;
	}
	((struct server_id *)rec.dptr)[count] = msg_ctx->server_id;
	if (tdb_store_bystring(t->tdb, name, rec, 0) != 0) {
		status = NT_STATUS_INTERNAL_ERROR;
	}
	free(rec.dptr);
	tdb_unlock_bystring(t->tdb, name);
	talloc_free(t);

	msg_ctx->names = str_list_add(msg_ctx->names, name);
	talloc_steal(msg_ctx, msg_ctx->names);

	return status;
}

/*
  return a list of server ids for a server name
*/
struct server_id *irpc_servers_byname(struct messaging_context *msg_ctx,
				      TALLOC_CTX *mem_ctx,
				      const char *name)
{
	struct tdb_wrap *t;
	TDB_DATA rec;
	int count, i;
	struct server_id *ret;

	t = irpc_namedb_open(msg_ctx);
	if (t == NULL) {
		return NULL;
	}

	if (tdb_lock_bystring(t->tdb, name) != 0) {
		talloc_free(t);
		return NULL;
	}
	rec = tdb_fetch_bystring(t->tdb, name);
	if (rec.dptr == NULL) {
		tdb_unlock_bystring(t->tdb, name);
		talloc_free(t);
		return NULL;
	}
	count = rec.dsize / sizeof(struct server_id);
	ret = talloc_array(mem_ctx, struct server_id, count+1);
	if (ret == NULL) {
		tdb_unlock_bystring(t->tdb, name);
		talloc_free(t);
		return NULL;
	}
	for (i=0;i<count;i++) {
		ret[i] = ((struct server_id *)rec.dptr)[i];
	}
	ret[i] = cluster_id(0, 0);
	free(rec.dptr);
	tdb_unlock_bystring(t->tdb, name);
	talloc_free(t);

	return ret;
}

/*
  remove a name from a messaging context
*/
void irpc_remove_name(struct messaging_context *msg_ctx, const char *name)
{
	struct tdb_wrap *t;
	TDB_DATA rec;
	int count, i;
	struct server_id *ids;

	str_list_remove(msg_ctx->names, name);

	t = irpc_namedb_open(msg_ctx);
	if (t == NULL) {
		return;
	}

	if (tdb_lock_bystring(t->tdb, name) != 0) {
		talloc_free(t);
		return;
	}
	rec = tdb_fetch_bystring(t->tdb, name);
	if (rec.dptr == NULL) {
		tdb_unlock_bystring(t->tdb, name);
		talloc_free(t);
		return;
	}
	count = rec.dsize / sizeof(struct server_id);
	if (count == 0) {
		free(rec.dptr);
		tdb_unlock_bystring(t->tdb, name);
		talloc_free(t);
		return;
	}
	ids = (struct server_id *)rec.dptr;
	for (i=0;i<count;i++) {
		if (cluster_id_equal(&ids[i], &msg_ctx->server_id)) {
			if (i < count-1) {
				memmove(ids+i, ids+i+1, 
					sizeof(struct server_id) * (count-(i+1)));
			}
			rec.dsize -= sizeof(struct server_id);
			break;
		}
	}
	tdb_store_bystring(t->tdb, name, rec, 0);
	free(rec.dptr);
	tdb_unlock_bystring(t->tdb, name);
	talloc_free(t);
}

struct server_id messaging_get_server_id(struct messaging_context *msg_ctx)
{
	return msg_ctx->server_id;
}

struct irpc_bh_state {
	struct messaging_context *msg_ctx;
	struct server_id server_id;
	const struct ndr_interface_table *table;
	uint32_t timeout;
};

static bool irpc_bh_is_connected(struct dcerpc_binding_handle *h)
{
	struct irpc_bh_state *hs = dcerpc_binding_handle_data(h,
				   struct irpc_bh_state);

	if (!hs->msg_ctx) {
		return false;
	}

	return true;
}

static uint32_t irpc_bh_set_timeout(struct dcerpc_binding_handle *h,
				    uint32_t timeout)
{
	struct irpc_bh_state *hs = dcerpc_binding_handle_data(h,
				   struct irpc_bh_state);
	uint32_t old = hs->timeout;

	hs->timeout = timeout;

	return old;
}

struct irpc_bh_raw_call_state {
	struct irpc_request *irpc;
	uint32_t opnum;
	DATA_BLOB in_data;
	DATA_BLOB in_packet;
	DATA_BLOB out_data;
};

static void irpc_bh_raw_call_incoming_handler(struct irpc_request *irpc,
					      struct irpc_message *m);

static struct tevent_req *irpc_bh_raw_call_send(TALLOC_CTX *mem_ctx,
						struct tevent_context *ev,
						struct dcerpc_binding_handle *h,
						const struct GUID *object,
						uint32_t opnum,
						uint32_t in_flags,
						const uint8_t *in_data,
						size_t in_length)
{
	struct irpc_bh_state *hs =
		dcerpc_binding_handle_data(h,
		struct irpc_bh_state);
	struct tevent_req *req;
	struct irpc_bh_raw_call_state *state;
	bool ok;
	struct irpc_header header;
	struct ndr_push *ndr;
	NTSTATUS status;
	enum ndr_err_code ndr_err;

	req = tevent_req_create(mem_ctx, &state,
				struct irpc_bh_raw_call_state);
	if (req == NULL) {
		return NULL;
	}
	state->opnum = opnum;
	state->in_data.data = discard_const_p(uint8_t, in_data);
	state->in_data.length = in_length;

	ok = irpc_bh_is_connected(h);
	if (!ok) {
		tevent_req_nterror(req, NT_STATUS_INVALID_CONNECTION);
		return tevent_req_post(req, ev);
	}

	state->irpc = talloc_zero(state, struct irpc_request);
	if (tevent_req_nomem(state->irpc, req)) {
		return tevent_req_post(req, ev);
	}

	state->irpc->msg_ctx  = hs->msg_ctx;
	state->irpc->callid   = idr_get_new(hs->msg_ctx->idr,
					    state->irpc, UINT16_MAX);
	if (state->irpc->callid == -1) {
		tevent_req_nterror(req, NT_STATUS_INSUFFICIENT_RESOURCES);
		return tevent_req_post(req, ev);
	}
	state->irpc->incoming.handler = irpc_bh_raw_call_incoming_handler;
	state->irpc->incoming.private_data = req;

	talloc_set_destructor(state->irpc, irpc_destructor);

	/* setup the header */
	header.uuid = hs->table->syntax_id.uuid;

	header.if_version = hs->table->syntax_id.if_version;
	header.callid     = state->irpc->callid;
	header.callnum    = state->opnum;
	header.flags      = 0;
	header.status     = NT_STATUS_OK;

	/* construct the irpc packet */
	ndr = ndr_push_init_ctx(state->irpc);
	if (tevent_req_nomem(ndr, req)) {
		return tevent_req_post(req, ev);
	}

	ndr_err = ndr_push_irpc_header(ndr, NDR_SCALARS|NDR_BUFFERS, &header);
	status = ndr_map_error2ntstatus(ndr_err);
	if (!NT_STATUS_IS_OK(status)) {
		tevent_req_nterror(req, status);
		return tevent_req_post(req, ev);
	}

	ndr_err = ndr_push_bytes(ndr, in_data, in_length);
	status = ndr_map_error2ntstatus(ndr_err);
	if (!NT_STATUS_IS_OK(status)) {
		tevent_req_nterror(req, status);
		return tevent_req_post(req, ev);
	}

	/* and send it */
	state->in_packet = ndr_push_blob(ndr);
	status = messaging_send(hs->msg_ctx, hs->server_id,
				MSG_IRPC, &state->in_packet);
	if (!NT_STATUS_IS_OK(status)) {
		tevent_req_nterror(req, status);
		return tevent_req_post(req, ev);
	}

	ok = tevent_req_set_endtime(req, ev, timeval_current_ofs(hs->timeout, 0));
	if (!ok) {
		return tevent_req_post(req, ev);
	}

	return req;
}

static void irpc_bh_raw_call_incoming_handler(struct irpc_request *irpc,
					      struct irpc_message *m)
{
	struct tevent_req *req =
		talloc_get_type_abort(irpc->incoming.private_data,
		struct tevent_req);
	struct irpc_bh_raw_call_state *state =
		tevent_req_data(req,
		struct irpc_bh_raw_call_state);

	talloc_steal(state, m);

	if (!NT_STATUS_IS_OK(m->header.status)) {
		tevent_req_nterror(req, m->header.status);
		return;
	}

	state->out_data = data_blob_talloc(state,
		m->ndr->data + m->ndr->offset,
		m->ndr->data_size - m->ndr->offset);
	if ((m->ndr->data_size - m->ndr->offset) > 0 && !state->out_data.data) {
		tevent_req_nomem(NULL, req);
		return;
	}

	tevent_req_done(req);
}

static NTSTATUS irpc_bh_raw_call_recv(struct tevent_req *req,
					TALLOC_CTX *mem_ctx,
					uint8_t **out_data,
					size_t *out_length,
					uint32_t *out_flags)
{
	struct irpc_bh_raw_call_state *state =
		tevent_req_data(req,
		struct irpc_bh_raw_call_state);
	NTSTATUS status;

	if (tevent_req_is_nterror(req, &status)) {
		tevent_req_received(req);
		return status;
	}

	*out_data = talloc_move(mem_ctx, &state->out_data.data);
	*out_length = state->out_data.length;
	*out_flags = 0;
	tevent_req_received(req);
	return NT_STATUS_OK;
}

struct irpc_bh_disconnect_state {
	uint8_t _dummy;
};

static struct tevent_req *irpc_bh_disconnect_send(TALLOC_CTX *mem_ctx,
						struct tevent_context *ev,
						struct dcerpc_binding_handle *h)
{
	struct irpc_bh_state *hs = dcerpc_binding_handle_data(h,
				     struct irpc_bh_state);
	struct tevent_req *req;
	struct irpc_bh_disconnect_state *state;
	bool ok;

	req = tevent_req_create(mem_ctx, &state,
				struct irpc_bh_disconnect_state);
	if (req == NULL) {
		return NULL;
	}

	ok = irpc_bh_is_connected(h);
	if (!ok) {
		tevent_req_nterror(req, NT_STATUS_INVALID_CONNECTION);
		return tevent_req_post(req, ev);
	}

	hs->msg_ctx = NULL;

	tevent_req_done(req);
	return tevent_req_post(req, ev);
}

static NTSTATUS irpc_bh_disconnect_recv(struct tevent_req *req)
{
	NTSTATUS status;

	if (tevent_req_is_nterror(req, &status)) {
		tevent_req_received(req);
		return status;
	}

	tevent_req_received(req);
	return NT_STATUS_OK;
}

static bool irpc_bh_ref_alloc(struct dcerpc_binding_handle *h)
{
	return true;
}

static const struct dcerpc_binding_handle_ops irpc_bh_ops = {
	.name			= "wbint",
	.is_connected		= irpc_bh_is_connected,
	.set_timeout		= irpc_bh_set_timeout,
	.raw_call_send		= irpc_bh_raw_call_send,
	.raw_call_recv		= irpc_bh_raw_call_recv,
	.disconnect_send	= irpc_bh_disconnect_send,
	.disconnect_recv	= irpc_bh_disconnect_recv,

	.ref_alloc		= irpc_bh_ref_alloc,
};

/* initialise a irpc binding handle */
struct dcerpc_binding_handle *irpc_binding_handle(TALLOC_CTX *mem_ctx,
					struct messaging_context *msg_ctx,
					struct server_id server_id,
					const struct ndr_interface_table *table)
{
	struct dcerpc_binding_handle *h;
	struct irpc_bh_state *hs;

	h = dcerpc_binding_handle_create(mem_ctx,
					 &irpc_bh_ops,
					 NULL,
					 table,
					 &hs,
					 struct irpc_bh_state,
					 __location__);
	if (h == NULL) {
		return NULL;
	}
	hs->msg_ctx = msg_ctx;
	hs->server_id = server_id;
	hs->table = table;
	hs->timeout = IRPC_CALL_TIMEOUT;

	dcerpc_binding_handle_set_sync_ev(h, msg_ctx->event.ev);

	return h;
}

struct dcerpc_binding_handle *irpc_binding_handle_by_name(TALLOC_CTX *mem_ctx,
					struct messaging_context *msg_ctx,
					const char *dest_task,
					const struct ndr_interface_table *table)
{
	struct dcerpc_binding_handle *h;
	struct server_id *sids;
	struct server_id sid;

	/* find the server task */
	sids = irpc_servers_byname(msg_ctx, mem_ctx, dest_task);
	if (sids == NULL) {
		errno = EADDRNOTAVAIL;
		return NULL;
	}
	if (sids[0].id == 0) {
		talloc_free(sids);
		errno = EADDRNOTAVAIL;
		return NULL;
	}
	sid = sids[0];
	talloc_free(sids);

	h = irpc_binding_handle(mem_ctx, msg_ctx,
				sid, table);
	if (h == NULL) {
		return NULL;
	}

	return h;
}