messaging4: Simplify imessaging_path

[Samba.git] / source4 / lib / messaging / messaging.c

/*
   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 "lib/tdb_wrap/tdb_wrap.h"
#include "../lib/util/unix_privs.h"
#include "librpc/rpc/dcerpc.h"
#include "../lib/tdb_compat/tdb_compat.h"
#include "../lib/util/util_tdb.h"
#include "cluster/cluster.h"
#include "../lib/util/tevent_ntstatus.h"
#include "lib/param/param.h"

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

static struct tdb_wrap *irpc_namedb_open(TALLOC_CTX *mem_ctx, const char *base_path,
                                         struct loadparm_context *lp_ctx);

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

struct imessaging_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 imessaging_rec *pending;
        struct imessaging_rec *retry_queue;
        struct irpc_list *irpc;
        struct idr_context *idr;
        const char **names;
        struct tdb_wrap *names_db;
        struct timeval start_time;
        struct tevent_timer *retry_te;
        struct {
                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 imessaging_rec {
        struct imessaging_rec *next, *prev;
        struct imessaging_context *msg;
        const char *path;

        struct imessaging_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 imessaging_context *, void *,
                         uint32_t, struct server_id, DATA_BLOB *);


/*
 A useful function for testing the message system.
*/
static void ping_message(struct imessaging_context *msg, void *private_data,
                         uint32_t msg_type, struct server_id src, DATA_BLOB *data)
{
        struct server_id_buf idbuf;
        DEBUG(1,("INFO: Received PING message from server %s [%.*s]\n",
                 server_id_str_buf(src, &idbuf), (int)data->length,
                 data->data?(const char *)data->data:""));
        imessaging_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 imessaging_context *ctx = talloc_get_type(msg->private_data, struct imessaging_context);
        *r->out.start_time = timeval_to_nttime(&ctx->start_time);
        return NT_STATUS_OK;
}

/*
   return the path to a messaging socket
*/
static char *imessaging_path(struct imessaging_context *msg, struct server_id server_id)
{
        struct server_id_buf buf;

        return talloc_asprintf(msg, "%s/msg.%s", msg->base_path,
                               server_id_str_buf(server_id, &buf));
}

/*
  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 imessaging_dispatch(struct imessaging_context *msg, struct imessaging_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 imessaging_context *msg, DATA_BLOB packet)
{
        struct imessaging_rec *rec;

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

        rec->msg           = msg;
        rec->path          = msg->path;
        rec->header        = (struct imessaging_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;
        }

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



/*
  try to send the message
*/
static NTSTATUS try_send(struct imessaging_rec *rec)
{
        struct imessaging_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 imessaging_context *msg = talloc_get_type(private_data,
                                                        struct imessaging_context);
        msg->retry_te = NULL;

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

        TEVENT_FD_WRITEABLE(msg->event.fde);
}

/*
  handle a socket write event
*/
static void imessaging_send_handler(struct imessaging_context *msg, struct tevent_context *ev)
{
        while (msg->pending) {
                struct imessaging_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 imessaging_rec *);
                                if (msg->retry_te == NULL) {
                                        msg->retry_te =
                                                tevent_add_timer(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",
                                 server_id_str(tmp_ctx, &rec->header->from),
                                 server_id_str(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) {
                TEVENT_FD_NOT_WRITEABLE(msg->event.fde);
        }
}

/*
  handle a new incoming packet
*/
static void imessaging_recv_handler(struct imessaging_context *msg, struct tevent_context *ev)
{
        struct imessaging_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 imessaging_rec);
        if (rec == NULL) {
                smb_panic("Unable to allocate imessaging_rec");
        }

        talloc_steal(rec, packet.data);
        rec->msg           = msg;
        rec->path          = msg->path;
        rec->header        = (struct imessaging_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;
        }

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


/*
  handle a socket event
*/
static void imessaging_handler(struct tevent_context *ev, struct tevent_fd *fde,
                              uint16_t flags, void *private_data)
{
        struct imessaging_context *msg = talloc_get_type(private_data,
                                                        struct imessaging_context);
        if (flags & TEVENT_FD_WRITE) {
                imessaging_send_handler(msg, ev);
        }
        if (flags & TEVENT_FD_READ) {
                imessaging_recv_handler(msg, ev);
        }
}


/*
  Register a dispatch function for a particular message type.
*/
NTSTATUS imessaging_register(struct imessaging_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 imessaging_register_tmp(struct imessaging_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 imessaging_deregister(struct imessaging_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 imessaging_send(struct imessaging_context *msg, struct server_id server,
                        uint32_t msg_type, const DATA_BLOB *data)
{
        struct imessaging_rec *rec;
        NTSTATUS status;
        size_t dlength = data?data->length:0;

        rec = talloc(msg, struct imessaging_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 imessaging_header *)rec->packet.data;
        /* zero padding */
        ZERO_STRUCTP(rec->header);
        rec->header->version  = IMESSAGING_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 = imessaging_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) {
                        TEVENT_FD_WRITEABLE(msg->event.fde);
                }
                DLIST_ADD_END(msg->pending, rec, struct imessaging_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 imessaging_send_ptr(struct imessaging_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 imessaging_send(msg, server, msg_type, &blob);
}


/*
  remove our messaging socket and database entry
*/
int imessaging_cleanup(struct imessaging_context *msg)
{
        if (!msg) {
                return 0;
        }

        DEBUG(5,("imessaging: cleaning up %s\n", msg->path));
        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

  use auto_remove=true when you want a destructor to remove the
  associated messaging socket and database entry on talloc free. Don't
  use this in processes that may fork and a child may talloc free this
  memory
*/
struct imessaging_context *imessaging_init(TALLOC_CTX *mem_ctx,
                                           struct loadparm_context *lp_ctx,
                                           struct server_id server_id,
                                           struct tevent_context *ev,
                                           bool auto_remove)
{
        struct imessaging_context *msg;
        NTSTATUS status;
        struct socket_address *path;
        bool ok;

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

        msg = talloc_zero(mem_ctx, struct imessaging_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)) {
                goto fail;
        }

        /* create the messaging directory if needed */

        msg->base_path     = lpcfg_imessaging_path(msg, lp_ctx);
        if (msg->base_path == NULL) {
                goto fail;
        }

        ok = directory_create_or_exist_strict(msg->base_path, geteuid(), 0700);
        if (!ok) {
                goto fail;
        }

        msg->path          = imessaging_path(msg, server_id);
        if (msg->path == NULL) {
                goto fail;
        }

        msg->server_id     = server_id;
        msg->idr           = idr_init(msg);
        if (msg->idr == NULL) {
                goto fail;
        }

        msg->dispatch_tree = idr_init(msg);
        if (msg->dispatch_tree == NULL) {
                goto fail;
        }

        msg->start_time    = timeval_current();

        msg->names_db = irpc_namedb_open(msg, msg->base_path, lp_ctx);
        if (msg->names_db == NULL) {
                goto fail;
        }

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

        /* 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) {
                goto fail;
        }

        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)));
                goto fail;
        }

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

        msg->event.fde  = tevent_add_fd(ev, msg, socket_get_fd(msg->sock),
                                        TEVENT_FD_READ, imessaging_handler, msg);
        tevent_fd_set_auto_close(msg->event.fde);

        if (auto_remove) {
                talloc_set_destructor(msg, imessaging_cleanup);
        }

        imessaging_register(msg, NULL, MSG_PING, ping_message);
        imessaging_register(msg, NULL, MSG_IRPC, irpc_handler);
        IRPC_REGISTER(msg, irpc, IRPC_UPTIME, irpc_uptime, msg);

        return msg;
fail:
        talloc_free(msg);
        return NULL;
}

/*
   A hack, for the short term until we get 'client only' messaging in place
*/
struct imessaging_context *imessaging_client_init(TALLOC_CTX *mem_ctx,
                                                  struct loadparm_context *lp_ctx,
                                                struct tevent_context *ev)
{
        struct server_id id;
        ZERO_STRUCT(id);
        id.pid = getpid();
        id.task_id = generate_random();
        id.vnn = NONCLUSTER_VNN;

        /* This is because we are not in the s3 serverid database */
        id.unique_id = SERVERID_UNIQUE_ID_NOT_TO_VERIFY;

        return imessaging_init(mem_ctx, lp_ctx, id, ev, true);
}
/*
  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 imessaging_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 imessaging_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;
        m->header.creds.token= NULL;

        /* 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 = imessaging_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 imessaging_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;

        m->ndr->flags |= LIBNDR_FLAG_REF_ALLOC;

        /* 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->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 imessaging_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(TALLOC_CTX *mem_ctx, const char *base_path,
                                         struct loadparm_context *lp_ctx)
{
        struct tdb_wrap *t;
        char *path = talloc_asprintf(mem_ctx, "%s/names.tdb", base_path);
        if (path == NULL) {
                return NULL;
        }
        t = tdb_wrap_open(mem_ctx, path, lpcfg_tdb_hash_size(lp_ctx, path),
                          lpcfg_tdb_flags(lp_ctx, 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 imessaging_context *msg_ctx, const char *name)
{
        struct tdb_context *t = msg_ctx->names_db->tdb;
        struct server_id pid = msg_ctx->server_id;
        TDB_DATA key, data;
        int ret;

        msg_ctx->names = str_list_add(msg_ctx->names, name);
        if (msg_ctx->names == NULL) {
                return NT_STATUS_NO_MEMORY;
        }
        talloc_steal(msg_ctx, msg_ctx->names);

        key = string_term_tdb_data(name);
        data = (TDB_DATA) { .dptr = (uint8_t *)&pid, .dsize = sizeof(pid) };

        ret = tdb_append(t, key, data);
        if (ret != 0) {
                enum TDB_ERROR err = tdb_error(t);
                str_list_remove(msg_ctx->names, name);
                return map_nt_error_from_tdb(err);
        }

        return NT_STATUS_OK;
}

/*
  return a list of server ids for a server name
*/
NTSTATUS irpc_servers_byname(struct imessaging_context *msg_ctx,
                             TALLOC_CTX *mem_ctx, const char *name,
                             unsigned *num_servers,
                             struct server_id **servers)
{
        struct tdb_wrap *t = msg_ctx->names_db;
        TDB_DATA rec;
        unsigned count;
        struct server_id *ret;

        rec = tdb_fetch_bystring(t->tdb, name);
        if (rec.dptr == NULL) {
                enum TDB_ERROR err = tdb_error(t->tdb);
                return map_nt_error_from_tdb(err);
        }

        count = rec.dsize / sizeof(struct server_id);
        if (count == 0) {
                /*
                 * In a corrupted db we could end up with a record of size
                 * less than a struct server_id. Don't leak in this case.
                 */
                free(rec.dptr);
                return NT_STATUS_NOT_FOUND;
        }

        ret = talloc_array(mem_ctx, struct server_id, count);
        if (ret == NULL) {
                free(rec.dptr);
                return NT_STATUS_NO_MEMORY;
        }
        memcpy(ret, rec.dptr, count * sizeof(struct server_id));
        free(rec.dptr);

        *num_servers = count;
        *servers = ret;
        return NT_STATUS_OK;
}

static int all_servers_func(struct tdb_context *tdb, TDB_DATA key, TDB_DATA data, void *state)
{
        struct irpc_name_records *name_records = talloc_get_type(state, struct irpc_name_records);
        struct irpc_name_record *name_record;
        int i;

        name_records->names
                = talloc_realloc(name_records, name_records->names,
                                 struct irpc_name_record *, name_records->num_records+1);
        if (!name_records->names) {
                return -1;
        }

        name_records->names[name_records->num_records] = name_record
                = talloc(name_records->names,
                         struct irpc_name_record);
        if (!name_record) {
                return -1;
        }

        name_records->num_records++;

        name_record->name
                = talloc_strndup(name_record,
                                 (const char *)key.dptr, key.dsize);
        if (!name_record->name) {
                return -1;
        }

        name_record->count = data.dsize / sizeof(struct server_id);
        name_record->ids = talloc_array(name_record,
                                        struct server_id,
                                        name_record->count);
        if (name_record->ids == NULL) {
                return -1;
        }
        for (i=0;i<name_record->count;i++) {
                name_record->ids[i] = ((struct server_id *)data.dptr)[i];
        }
        return 0;
}

/*
  return a list of server ids for a server name
*/
struct irpc_name_records *irpc_all_servers(struct imessaging_context *msg_ctx,
                                           TALLOC_CTX *mem_ctx)
{
        struct tdb_wrap *t = msg_ctx->names_db;
        int ret;
        struct irpc_name_records *name_records = talloc_zero(mem_ctx, struct irpc_name_records);
        if (name_records == NULL) {
                return NULL;
        }

        ret = tdb_traverse_read(t->tdb, all_servers_func, name_records);
        if (ret == -1) {
                return NULL;
        }

        return name_records;
}

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

        str_list_remove(msg_ctx->names, name);

        if (tdb_lock_bystring(t->tdb, name) != 0) {
                return;
        }
        rec = tdb_fetch_bystring(t->tdb, name);
        if (rec.dptr == NULL) {
                tdb_unlock_bystring(t->tdb, name);
                return;
        }
        count = rec.dsize / sizeof(struct server_id);
        if (count == 0) {
                free(rec.dptr);
                tdb_unlock_bystring(t->tdb, name);
                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);
}

struct server_id imessaging_get_server_id(struct imessaging_context *msg_ctx)
{
        return msg_ctx->server_id;
}

struct irpc_bh_state {
        struct imessaging_context *msg_ctx;
        struct server_id server_id;
        const struct ndr_interface_table *table;
        uint32_t timeout;
        struct security_token *token;
};

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_CONNECTION_DISCONNECTED);
                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;
        header.creds.token= hs->token;

        /* 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 = imessaging_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);
        }

        if (hs->timeout != IRPC_CALL_TIMEOUT_INF) {
                /* set timeout-callback in case caller wants that */
                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_oom(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_CONNECTION_DISCONNECTED);
                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 imessaging_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;

        return h;
}

struct dcerpc_binding_handle *irpc_binding_handle_by_name(TALLOC_CTX *mem_ctx,
                                                          struct imessaging_context *msg_ctx,
                                                          const char *dest_task,
                                                          const struct ndr_interface_table *table)
{
        struct dcerpc_binding_handle *h;
        unsigned num_sids;
        struct server_id *sids;
        struct server_id sid;
        NTSTATUS status;

        /* find the server task */

        status = irpc_servers_byname(msg_ctx, mem_ctx, dest_task,
                                     &num_sids, &sids);
        if (!NT_STATUS_IS_OK(status)) {
                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;
}

void irpc_binding_handle_add_security_token(struct dcerpc_binding_handle *h,
                                            struct security_token *token)
{
        struct irpc_bh_state *hs =
                dcerpc_binding_handle_data(h,
                struct irpc_bh_state);

        hs->token = token;
}