librpc: Shorten dcerpc_binding_handle_call a bit

[Samba/vl.git] / source3 / rpc_server / rpc_ncacn_np.c

/*
 *  Unix SMB/CIFS implementation.
 *  RPC Pipe client / server routines
 *  Copyright (C) Andrew Tridgell              1992-1998,
 *  Largely re-written : 2005
 *  Copyright (C) Jeremy Allison                1998 - 2005
 *  Copyright (C) Simo Sorce                    2010
 *  Copyright (C) Andrew Bartlett               2011
 *
 *  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 "rpc_client/cli_pipe.h"
#include "rpc_server/srv_pipe_internal.h"
#include "rpc_dce.h"
#include "../libcli/named_pipe_auth/npa_tstream.h"
#include "rpc_server/rpc_ncacn_np.h"
#include "librpc/gen_ndr/netlogon.h"
#include "librpc/gen_ndr/auth.h"
#include "../auth/auth_sam_reply.h"
#include "auth.h"
#include "rpc_server/rpc_pipes.h"
#include "../lib/tsocket/tsocket.h"
#include "../lib/util/tevent_ntstatus.h"
#include "rpc_contexts.h"
#include "rpc_server/rpc_config.h"

#undef DBGC_CLASS
#define DBGC_CLASS DBGC_RPC_SRV

/****************************************************************************
 Make an internal namedpipes structure
****************************************************************************/

struct pipes_struct *make_internal_rpc_pipe_p(TALLOC_CTX *mem_ctx,
                                              const struct ndr_syntax_id *syntax,
                                              const struct tsocket_address *remote_address,
                                              const struct auth_session_info *session_info,
                                              struct messaging_context *msg_ctx)
{
        struct pipes_struct *p;
        struct pipe_rpc_fns *context_fns;
        const char *pipe_name;
        int ret;

        pipe_name = get_pipe_name_from_syntax(talloc_tos(), syntax);

        DEBUG(4,("Create pipe requested %s\n", pipe_name));

        ret = make_base_pipes_struct(mem_ctx, msg_ctx, pipe_name,
                                     NCALRPC, RPC_LITTLE_ENDIAN, false,
                                     remote_address, NULL, &p);
        if (ret) {
                DEBUG(0,("ERROR! no memory for pipes_struct!\n"));
                return NULL;
        }

        if (!init_pipe_handles(p, syntax)) {
                DEBUG(0,("open_rpc_pipe_p: init_pipe_handles failed.\n"));
                TALLOC_FREE(p);
                return NULL;
        }

        p->session_info = copy_session_info(p, session_info);
        if (p->session_info == NULL) {
                DEBUG(0, ("open_rpc_pipe_p: copy_serverinfo failed\n"));
                close_policy_by_pipe(p);
                TALLOC_FREE(p);
                return NULL;
        }

        context_fns = talloc(p, struct pipe_rpc_fns);
        if (context_fns == NULL) {
                DEBUG(0,("talloc() failed!\n"));
                TALLOC_FREE(p);
                return NULL;
        }

        context_fns->next = context_fns->prev = NULL;
        context_fns->n_cmds = rpc_srv_get_pipe_num_cmds(syntax);
        context_fns->cmds = rpc_srv_get_pipe_cmds(syntax);
        context_fns->context_id = 0;
        context_fns->syntax = *syntax;

        /* add to the list of open contexts */
        DLIST_ADD(p->contexts, context_fns);

        DEBUG(4,("Created internal pipe %s\n", pipe_name));

        return p;
}

static NTSTATUS rpcint_dispatch(struct pipes_struct *p,
                                TALLOC_CTX *mem_ctx,
                                uint32_t opnum,
                                const DATA_BLOB *in_data,
                                DATA_BLOB *out_data)
{
        struct pipe_rpc_fns *fns = find_pipe_fns_by_context(p->contexts, 0);
        uint32_t num_cmds = fns->n_cmds;
        const struct api_struct *cmds = fns->cmds;
        uint32_t i;
        bool ok;

        /* set opnum */
        p->opnum = opnum;

        for (i = 0; i < num_cmds; i++) {
                if (cmds[i].opnum == opnum && cmds[i].fn != NULL) {
                        break;
                }
        }

        if (i == num_cmds) {
                return NT_STATUS_RPC_PROCNUM_OUT_OF_RANGE;
        }

        p->in_data.data = *in_data;
        p->out_data.rdata = data_blob_null;

        ok = cmds[i].fn(p);
        p->in_data.data = data_blob_null;
        if (!ok) {
                data_blob_free(&p->out_data.rdata);
                talloc_free_children(p->mem_ctx);
                return NT_STATUS_RPC_CALL_FAILED;
        }

        if (p->fault_state) {
                NTSTATUS status;

                status = NT_STATUS(p->fault_state);
                p->fault_state = 0;
                data_blob_free(&p->out_data.rdata);
                talloc_free_children(p->mem_ctx);
                return status;
        }

        *out_data = p->out_data.rdata;
        talloc_steal(mem_ctx, out_data->data);
        p->out_data.rdata = data_blob_null;

        talloc_free_children(p->mem_ctx);
        return NT_STATUS_OK;
}

struct rpcint_bh_state {
        struct pipes_struct *p;
};

static bool rpcint_bh_is_connected(struct dcerpc_binding_handle *h)
{
        struct rpcint_bh_state *hs = dcerpc_binding_handle_data(h,
                                     struct rpcint_bh_state);

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

        return true;
}

static uint32_t rpcint_bh_set_timeout(struct dcerpc_binding_handle *h,
                                      uint32_t timeout)
{
        /* TODO: implement timeouts */
        return UINT32_MAX;
}

struct rpcint_bh_raw_call_state {
        DATA_BLOB in_data;
        DATA_BLOB out_data;
        uint32_t out_flags;
};

static struct tevent_req *rpcint_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 rpcint_bh_state *hs =
                dcerpc_binding_handle_data(h,
                struct rpcint_bh_state);
        struct tevent_req *req;
        struct rpcint_bh_raw_call_state *state;
        bool ok;
        NTSTATUS status;

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

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

        /* TODO: allow async */
        status = rpcint_dispatch(hs->p, state, opnum,
                                 &state->in_data,
                                 &state->out_data);
        if (!NT_STATUS_IS_OK(status)) {
                tevent_req_nterror(req, status);
                return tevent_req_post(req, ev);
        }

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

static NTSTATUS rpcint_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 rpcint_bh_raw_call_state *state =
                tevent_req_data(req,
                struct rpcint_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 rpcint_bh_disconnect_state {
        uint8_t _dummy;
};

static struct tevent_req *rpcint_bh_disconnect_send(TALLOC_CTX *mem_ctx,
                                                struct tevent_context *ev,
                                                struct dcerpc_binding_handle *h)
{
        struct rpcint_bh_state *hs = dcerpc_binding_handle_data(h,
                                     struct rpcint_bh_state);
        struct tevent_req *req;
        struct rpcint_bh_disconnect_state *state;
        bool ok;

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

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

        /*
         * TODO: do a real async disconnect ...
         *
         * For now the caller needs to free pipes_struct
         */
        hs->p = NULL;

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

static NTSTATUS rpcint_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 rpcint_bh_ref_alloc(struct dcerpc_binding_handle *h)
{
        return true;
}

static void rpcint_bh_do_ndr_print(struct dcerpc_binding_handle *h,
                                   int ndr_flags,
                                   const void *_struct_ptr,
                                   const struct ndr_interface_call *call)
{
        void *struct_ptr = discard_const(_struct_ptr);

        if (DEBUGLEVEL < 11) {
                return;
        }

        if (ndr_flags & NDR_IN) {
                ndr_print_function_debug(call->ndr_print,
                                         call->name,
                                         ndr_flags,
                                         struct_ptr);
        }
        if (ndr_flags & NDR_OUT) {
                ndr_print_function_debug(call->ndr_print,
                                         call->name,
                                         ndr_flags,
                                         struct_ptr);
        }
}

static const struct dcerpc_binding_handle_ops rpcint_bh_ops = {
        .name                   = "rpcint",
        .is_connected           = rpcint_bh_is_connected,
        .set_timeout            = rpcint_bh_set_timeout,
        .raw_call_send          = rpcint_bh_raw_call_send,
        .raw_call_recv          = rpcint_bh_raw_call_recv,
        .disconnect_send        = rpcint_bh_disconnect_send,
        .disconnect_recv        = rpcint_bh_disconnect_recv,

        .ref_alloc              = rpcint_bh_ref_alloc,
        .do_ndr_print           = rpcint_bh_do_ndr_print,
};

static NTSTATUS rpcint_binding_handle_ex(TALLOC_CTX *mem_ctx,
                        const struct ndr_syntax_id *abstract_syntax,
                        const struct ndr_interface_table *ndr_table,
                        const struct tsocket_address *remote_address,
                        const struct auth_session_info *session_info,
                        struct messaging_context *msg_ctx,
                        struct dcerpc_binding_handle **binding_handle)
{
        struct dcerpc_binding_handle *h;
        struct rpcint_bh_state *hs;

        if (ndr_table) {
                abstract_syntax = &ndr_table->syntax_id;
        }

        h = dcerpc_binding_handle_create(mem_ctx,
                                         &rpcint_bh_ops,
                                         NULL,
                                         ndr_table,
                                         &hs,
                                         struct rpcint_bh_state,
                                         __location__);
        if (h == NULL) {
                return NT_STATUS_NO_MEMORY;
        }
        hs->p = make_internal_rpc_pipe_p(hs,
                                         abstract_syntax,
                                         remote_address,
                                         session_info,
                                         msg_ctx);
        if (hs->p == NULL) {
                TALLOC_FREE(h);
                return NT_STATUS_NO_MEMORY;
        }

        *binding_handle = h;
        return NT_STATUS_OK;
}
/**
 * @brief Create a new DCERPC Binding Handle which uses a local dispatch function.
 *
 * @param[in]  mem_ctx  The memory context to use.
 *
 * @param[in]  ndr_table Normally the ndr_table_<name>.
 *
 * @param[in]  remote_address The info about the connected client.
 *
 * @param[in]  serversupplied_info The server supplied authentication function.
 *
 * @param[in]  msg_ctx   The messaging context that can be used by the server
 *
 * @param[out] binding_handle  A pointer to store the connected
 *                             dcerpc_binding_handle
 *
 * @return              NT_STATUS_OK on success, a corresponding NT status if an
 *                      error occured.
 *
 * @code
 *   struct dcerpc_binding_handle *winreg_binding;
 *   NTSTATUS status;
 *
 *   status = rpcint_binding_handle(tmp_ctx,
 *                                  &ndr_table_winreg,
 *                                  p->remote_address,
 *                                  p->session_info,
 *                                  p->msg_ctx
 *                                  &winreg_binding);
 * @endcode
 */
NTSTATUS rpcint_binding_handle(TALLOC_CTX *mem_ctx,
                               const struct ndr_interface_table *ndr_table,
                               const struct tsocket_address *remote_address,
                               const struct auth_session_info *session_info,
                               struct messaging_context *msg_ctx,
                               struct dcerpc_binding_handle **binding_handle)
{
        return rpcint_binding_handle_ex(mem_ctx, NULL, ndr_table, remote_address,
                                        session_info, msg_ctx, binding_handle);
}

/**
 * @internal
 *
 * @brief Create a new RPC client context which uses a local transport.
 *
 * This creates a local transport. It is a shortcut to directly call the server
 * functions and avoid marshalling.
 * NOTE: this function should be used only by rpc_pipe_open_interface()
 *
 * @param[in]  mem_ctx  The memory context to use.
 *
 * @param[in]  abstract_syntax Normally the syntax_id of the autogenerated
 *                             ndr_table_<name>.
 *
 * @param[in]  serversupplied_info The server supplied authentication function.
 *
 * @param[in]  remote_address The client address information.
 *
 * @param[in]  msg_ctx  The messaging context to use.
 *
 * @param[out] presult  A pointer to store the connected rpc client pipe.
 *
 * @return              NT_STATUS_OK on success, a corresponding NT status if an
 *                      error occured.
 */
NTSTATUS rpc_pipe_open_internal(TALLOC_CTX *mem_ctx,
                                const struct ndr_syntax_id *abstract_syntax,
                                const struct auth_session_info *session_info,
                                const struct tsocket_address *remote_address,
                                struct messaging_context *msg_ctx,
                                struct rpc_pipe_client **presult)
{
        struct rpc_pipe_client *result;
        NTSTATUS status;

        result = talloc_zero(mem_ctx, struct rpc_pipe_client);
        if (result == NULL) {
                return NT_STATUS_NO_MEMORY;
        }

        result->abstract_syntax = *abstract_syntax;
        result->transfer_syntax = ndr_transfer_syntax_ndr;

        if (remote_address == NULL) {
                struct tsocket_address *local;
                int rc;

                rc = tsocket_address_inet_from_strings(mem_ctx,
                                                       "ip",
                                                       "127.0.0.1",
                                                       0,
                                                       &local);
                if (rc < 0) {
                        TALLOC_FREE(result);
                        return NT_STATUS_NO_MEMORY;
                }

                remote_address = local;
        }

        result->max_xmit_frag = -1;
        result->max_recv_frag = -1;

        status = rpcint_binding_handle_ex(result,
                                          abstract_syntax,
                                          NULL,
                                          remote_address,
                                          session_info,
                                          msg_ctx,
                                          &result->binding_handle);
        if (!NT_STATUS_IS_OK(status)) {
                TALLOC_FREE(result);
                return status;
        }

        *presult = result;
        return NT_STATUS_OK;
}

/****************************************************************************
 * External pipes functions
 ***************************************************************************/


struct np_proxy_state *make_external_rpc_pipe_p(TALLOC_CTX *mem_ctx,
                                const char *pipe_name,
                                const struct tsocket_address *local_address,
                                const struct tsocket_address *remote_address,
                                const struct auth_session_info *session_info)
{
        struct np_proxy_state *result;
        char *socket_np_dir;
        const char *socket_dir;
        struct tevent_context *ev;
        struct tevent_req *subreq;
        struct auth_session_info_transport *session_info_t;
        bool ok;
        int ret;
        int sys_errno;

        result = talloc(mem_ctx, struct np_proxy_state);
        if (result == NULL) {
                DEBUG(0, ("talloc failed\n"));
                return NULL;
        }

        result->read_queue = tevent_queue_create(result, "np_read");
        if (result->read_queue == NULL) {
                DEBUG(0, ("tevent_queue_create failed\n"));
                goto fail;
        }

        result->write_queue = tevent_queue_create(result, "np_write");
        if (result->write_queue == NULL) {
                DEBUG(0, ("tevent_queue_create failed\n"));
                goto fail;
        }

        ev = s3_tevent_context_init(talloc_tos());
        if (ev == NULL) {
                DEBUG(0, ("s3_tevent_context_init failed\n"));
                goto fail;
        }

        socket_dir = lp_parm_const_string(
                GLOBAL_SECTION_SNUM, "external_rpc_pipe", "socket_dir",
                lp_ncalrpc_dir());
        if (socket_dir == NULL) {
                DEBUG(0, ("externan_rpc_pipe:socket_dir not set\n"));
                goto fail;
        }
        socket_np_dir = talloc_asprintf(talloc_tos(), "%s/np", socket_dir);
        if (socket_np_dir == NULL) {
                DEBUG(0, ("talloc_asprintf failed\n"));
                goto fail;
        }

        session_info_t = talloc_zero(talloc_tos(), struct auth_session_info_transport);
        if (session_info_t == NULL) {
                DEBUG(0, ("talloc failed\n"));
                goto fail;
        }

        session_info_t->session_info = copy_session_info(session_info_t,
                                                         session_info);
        if (session_info_t->session_info == NULL) {
                DEBUG(0, ("copy_session_info failed\n"));
                goto fail;
        }

        become_root();
        subreq = tstream_npa_connect_send(talloc_tos(), ev,
                                          socket_np_dir,
                                          pipe_name,
                                          remote_address, /* client_addr */
                                          NULL, /* client_name */
                                          local_address, /* server_addr */
                                          NULL, /* server_name */
                                          session_info_t);
        if (subreq == NULL) {
                unbecome_root();
                DEBUG(0, ("tstream_npa_connect_send to %s for pipe %s and "
                          "user %s\\%s failed\n",
                          socket_np_dir, pipe_name, session_info_t->session_info->info->domain_name,
                          session_info_t->session_info->info->account_name));
                goto fail;
        }
        ok = tevent_req_poll(subreq, ev);
        unbecome_root();
        if (!ok) {
                DEBUG(0, ("tevent_req_poll to %s for pipe %s and user %s\\%s "
                          "failed for tstream_npa_connect: %s\n",
                          socket_np_dir, pipe_name, session_info_t->session_info->info->domain_name,
                          session_info_t->session_info->info->account_name,
                          strerror(errno)));
                goto fail;

        }
        ret = tstream_npa_connect_recv(subreq, &sys_errno,
                                       result,
                                       &result->npipe,
                                       &result->file_type,
                                       &result->device_state,
                                       &result->allocation_size);
        TALLOC_FREE(subreq);
        if (ret != 0) {
                int l = 1;
                if (errno == ENOENT) {
                        l = 2;
                }
                DEBUG(l, ("tstream_npa_connect_recv  to %s for pipe %s and "
                          "user %s\\%s failed: %s\n",
                          socket_np_dir, pipe_name, session_info_t->session_info->info->domain_name,
                          session_info_t->session_info->info->account_name,
                          strerror(sys_errno)));
                goto fail;
        }

        return result;

 fail:
        TALLOC_FREE(result);
        return NULL;
}

static NTSTATUS rpc_pipe_open_external(TALLOC_CTX *mem_ctx,
                                const char *pipe_name,
                                const struct ndr_syntax_id *abstract_syntax,
                                const struct auth_session_info *session_info,
                                struct rpc_pipe_client **_result)
{
        struct tsocket_address *local, *remote;
        struct rpc_pipe_client *result = NULL;
        struct np_proxy_state *proxy_state = NULL;
        struct pipe_auth_data *auth;
        NTSTATUS status;
        int ret;

        /* this is an internal connection, fake up ip addresses */
        ret = tsocket_address_inet_from_strings(talloc_tos(), "ip",
                                                NULL, 0, &local);
        if (ret) {
                return NT_STATUS_NO_MEMORY;
        }
        ret = tsocket_address_inet_from_strings(talloc_tos(), "ip",
                                                NULL, 0, &remote);
        if (ret) {
                return NT_STATUS_NO_MEMORY;
        }

        proxy_state = make_external_rpc_pipe_p(mem_ctx, pipe_name,
                                                local, remote, session_info);
        if (!proxy_state) {
                return NT_STATUS_UNSUCCESSFUL;
        }

        result = talloc_zero(mem_ctx, struct rpc_pipe_client);
        if (result == NULL) {
                status = NT_STATUS_NO_MEMORY;
                goto done;
        }

        result->abstract_syntax = *abstract_syntax;
        result->transfer_syntax = ndr_transfer_syntax_ndr;

        result->desthost = get_myname(result);
        result->srv_name_slash = talloc_asprintf_strupper_m(
                result, "\\\\%s", result->desthost);
        if ((result->desthost == NULL) || (result->srv_name_slash == NULL)) {
                status = NT_STATUS_NO_MEMORY;
                goto done;
        }

        result->max_xmit_frag = RPC_MAX_PDU_FRAG_LEN;
        result->max_recv_frag = RPC_MAX_PDU_FRAG_LEN;

        status = rpc_transport_tstream_init(result,
                                            &proxy_state->npipe,
                                            &result->transport);
        if (!NT_STATUS_IS_OK(status)) {
                goto done;
        }

        result->binding_handle = rpccli_bh_create(result);
        if (result->binding_handle == NULL) {
                status = NT_STATUS_NO_MEMORY;
                DEBUG(0, ("Failed to create binding handle.\n"));
                goto done;
        }

        result->auth = talloc_zero(result, struct pipe_auth_data);
        if (!result->auth) {
                status = NT_STATUS_NO_MEMORY;
                goto done;
        }
        result->auth->auth_type = DCERPC_AUTH_TYPE_NONE;
        result->auth->auth_level = DCERPC_AUTH_LEVEL_NONE;

        status = rpccli_anon_bind_data(result, &auth);
        if (!NT_STATUS_IS_OK(status)) {
                DEBUG(0, ("Failed to initialize anonymous bind.\n"));
                goto done;
        }

        status = rpc_pipe_bind(result, auth);
        if (!NT_STATUS_IS_OK(status)) {
                DEBUG(0, ("Failed to bind external pipe.\n"));
                goto done;
        }

done:
        if (!NT_STATUS_IS_OK(status)) {
                TALLOC_FREE(result);
        }
        TALLOC_FREE(proxy_state);
        *_result = result;
        return status;
}

/**
 * @brief Create a new RPC client context which uses a local dispatch function
 *        or a remote transport, depending on rpc_server configuration for the
 *        specific service.
 *
 * @param[in]  mem_ctx  The memory context to use.
 *
 * @param[in]  abstract_syntax Normally the syntax_id of the autogenerated
 *                             ndr_table_<name>.
 *
 * @param[in]  serversupplied_info The server supplied authentication function.
 *
 * @param[in]  remote_address The client address information.
 *
 * @param[in]  msg_ctx  The messaging context to use.
 *
 * @param[out] presult  A pointer to store the connected rpc client pipe.
 *
 * @return              NT_STATUS_OK on success, a corresponding NT status if an
 *                      error occured.
 *
 * @code
 *   struct rpc_pipe_client *winreg_pipe;
 *   NTSTATUS status;
 *
 *   status = rpc_pipe_open_interface(tmp_ctx,
 *                                    &ndr_table_winreg.syntax_id,
 *                                    p->session_info,
 *                                    remote_address,
 *                                    &winreg_pipe);
 * @endcode
 */

NTSTATUS rpc_pipe_open_interface(TALLOC_CTX *mem_ctx,
                                 const struct ndr_syntax_id *syntax,
                                 const struct auth_session_info *session_info,
                                 const struct tsocket_address *remote_address,
                                 struct messaging_context *msg_ctx,
                                 struct rpc_pipe_client **cli_pipe)
{
        struct rpc_pipe_client *cli = NULL;
        enum rpc_service_mode_e pipe_mode;
        const char *pipe_name;
        NTSTATUS status;
        TALLOC_CTX *tmp_ctx;

        if (cli_pipe != NULL) {
                if (rpccli_is_connected(*cli_pipe)) {
                        return NT_STATUS_OK;
                } else {
                        TALLOC_FREE(*cli_pipe);
                }
        }

        tmp_ctx = talloc_stackframe();
        if (tmp_ctx == NULL) {
                return NT_STATUS_NO_MEMORY;
        }

        pipe_name = get_pipe_name_from_syntax(tmp_ctx, syntax);
        if (pipe_name == NULL) {
                status = NT_STATUS_INVALID_PARAMETER;
                goto done;
        }

        while (pipe_name[0] == '\\') {
                pipe_name++;
        }

        DEBUG(5, ("Connecting to %s pipe.\n", pipe_name));

        pipe_mode = rpc_service_mode(pipe_name);

        switch (pipe_mode) {
        case RPC_SERVICE_MODE_EMBEDDED:
                status = rpc_pipe_open_internal(tmp_ctx,
                                                syntax, session_info,
                                                remote_address, msg_ctx,
                                                &cli);
                if (!NT_STATUS_IS_OK(status)) {
                        goto done;
                }
                break;
        case RPC_SERVICE_MODE_EXTERNAL:
                /* It would be nice to just use rpc_pipe_open_ncalrpc() but
                 * for now we need to use the special proxy setup to connect
                 * to spoolssd. */

                status = rpc_pipe_open_external(tmp_ctx,
                                                pipe_name, syntax,
                                                session_info,
                                                &cli);
                if (!NT_STATUS_IS_OK(status)) {
                        goto done;
                }
                break;
        case RPC_SERVICE_MODE_DISABLED:
                status = NT_STATUS_NOT_IMPLEMENTED;
                DEBUG(0, ("Service pipe %s is disabled in config file: %s",
                          pipe_name, nt_errstr(status)));
                goto done;
        }

        status = NT_STATUS_OK;
done:
        if (NT_STATUS_IS_OK(status) && cli_pipe != NULL) {
                *cli_pipe = talloc_move(mem_ctx, &cli);
        }
        TALLOC_FREE(tmp_ctx);
        return status;
}