source: vendor/3.6.23/source3/lib/messages_local.c

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

   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/>.
*/

/**
  @defgroup messages Internal messaging framework
  @{
  @file messages.c

  @brief  Module for internal messaging between Samba daemons. 

   The idea is that if a part of Samba wants to do communication with
   another Samba process then it will do a message_register() of a
   dispatch function, and use message_send_pid() to send messages to
   that process.

   The dispatch function is given the pid of the sender, and it can
   use that to reply by message_send_pid().  See ping_message() for a
   simple example.

   @caution Dispatch functions must be able to cope with incoming
   messages on an *odd* byte boundary.

   This system doesn't have any inherent size limitations but is not
   very efficient for large messages or when messages are sent in very
   quick succession.

*/

#include "includes.h"
#include "system/filesys.h"
#include "messages.h"
#include "lib/util/tdb_wrap.h"

struct messaging_tdb_context {
        struct messaging_context *msg_ctx;
        struct tdb_wrap *tdb;
        struct tevent_signal *se;
        int received_messages;
};

static NTSTATUS messaging_tdb_send(struct messaging_context *msg_ctx,
                                   struct server_id pid, int msg_type,
                                   const DATA_BLOB *data,
                                   struct messaging_backend *backend);
static void message_dispatch(struct messaging_context *msg_ctx);

static void messaging_tdb_signal_handler(struct tevent_context *ev_ctx,
                                         struct tevent_signal *se,
                                         int signum, int count,
                                         void *_info, void *private_data)
{
        struct messaging_tdb_context *ctx = talloc_get_type(private_data,
                                            struct messaging_tdb_context);

        ctx->received_messages++;

        DEBUG(10, ("messaging_tdb_signal_handler: sig[%d] count[%d] msgs[%d]\n",
                   signum, count, ctx->received_messages));

        message_dispatch(ctx->msg_ctx);
}

/****************************************************************************
 Initialise the messaging functions. 
****************************************************************************/

NTSTATUS messaging_tdb_init(struct messaging_context *msg_ctx,
                            TALLOC_CTX *mem_ctx,
                            struct messaging_backend **presult)
{
        struct messaging_backend *result;
        struct messaging_tdb_context *ctx;

        if (!(result = TALLOC_P(mem_ctx, struct messaging_backend))) {
                DEBUG(0, ("talloc failed\n"));
                return NT_STATUS_NO_MEMORY;
        }

        ctx = TALLOC_ZERO_P(result, struct messaging_tdb_context);
        if (!ctx) {
                DEBUG(0, ("talloc failed\n"));
                TALLOC_FREE(result);
                return NT_STATUS_NO_MEMORY;
        }
        result->private_data = ctx;
        result->send_fn = messaging_tdb_send;

        ctx->msg_ctx = msg_ctx;

        ctx->tdb = tdb_wrap_open(ctx, lock_path("messages.tdb"), 0,
                                 TDB_CLEAR_IF_FIRST|TDB_DEFAULT|TDB_VOLATILE|TDB_INCOMPATIBLE_HASH,
                                 O_RDWR|O_CREAT,0600);

        if (!ctx->tdb) {
                NTSTATUS status = map_nt_error_from_unix(errno);
                DEBUG(2, ("ERROR: Failed to initialise messages database: "
                          "%s\n", strerror(errno)));
                TALLOC_FREE(result);
                return status;
        }

        ctx->se = tevent_add_signal(msg_ctx->event_ctx,
                                    ctx,
                                    SIGUSR1, 0,
                                    messaging_tdb_signal_handler,
                                    ctx);
        if (!ctx->se) {
                NTSTATUS status = map_nt_error_from_unix(errno);
                DEBUG(0, ("ERROR: Failed to initialise messages signal handler: "
                          "%s\n", strerror(errno)));
                TALLOC_FREE(result);
                return status;
        }

        sec_init();

        *presult = result;
        return NT_STATUS_OK;
}

bool messaging_tdb_parent_init(TALLOC_CTX *mem_ctx)
{
        struct tdb_wrap *db;

        /*
         * Open the tdb in the parent process (smbd) so that our
         * CLEAR_IF_FIRST optimization in tdb_reopen_all can properly
         * work.
         */

        db = tdb_wrap_open(mem_ctx, lock_path("messages.tdb"), 0,
                           TDB_CLEAR_IF_FIRST|TDB_DEFAULT|TDB_VOLATILE|TDB_INCOMPATIBLE_HASH,
                           O_RDWR|O_CREAT,0600);
        if (db == NULL) {
                DEBUG(1, ("could not open messaging.tdb: %s\n",
                          strerror(errno)));
                return false;
        }
        return true;
}

/*******************************************************************
 Form a static tdb key from a pid.
******************************************************************/

static TDB_DATA message_key_pid(TALLOC_CTX *mem_ctx, struct server_id pid)
{
        char *key;
        TDB_DATA kbuf;

        key = talloc_asprintf(talloc_tos(), "PID/%s", procid_str_static(&pid));

        SMB_ASSERT(key != NULL);

        kbuf.dptr = (uint8 *)key;
        kbuf.dsize = strlen(key)+1;
        return kbuf;
}

/*
  Fetch the messaging array for a process
 */

static NTSTATUS messaging_tdb_fetch(TDB_CONTEXT *msg_tdb,
                                    TDB_DATA key,
                                    TALLOC_CTX *mem_ctx,
                                    struct messaging_array **presult)
{
        struct messaging_array *result;
        TDB_DATA data;
        DATA_BLOB blob;
        enum ndr_err_code ndr_err;

        if (!(result = TALLOC_ZERO_P(mem_ctx, struct messaging_array))) {
                return NT_STATUS_NO_MEMORY;
        }

        data = tdb_fetch(msg_tdb, key);

        if (data.dptr == NULL) {
                *presult = result;
                return NT_STATUS_OK;
        }

        blob = data_blob_const(data.dptr, data.dsize);

        ndr_err = ndr_pull_struct_blob(
                &blob, result, result,
                (ndr_pull_flags_fn_t)ndr_pull_messaging_array);

        SAFE_FREE(data.dptr);

        if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
                TALLOC_FREE(result);
                return ndr_map_error2ntstatus(ndr_err);
        }

        if (DEBUGLEVEL >= 10) {
                DEBUG(10, ("messaging_tdb_fetch:\n"));
                NDR_PRINT_DEBUG(messaging_array, result);
        }

        *presult = result;
        return NT_STATUS_OK;
}

/*
  Store a messaging array for a pid
*/

static NTSTATUS messaging_tdb_store(TDB_CONTEXT *msg_tdb,
                                    TDB_DATA key,
                                    struct messaging_array *array)
{
        TDB_DATA data;
        DATA_BLOB blob;
        enum ndr_err_code ndr_err;
        TALLOC_CTX *mem_ctx;
        int ret;

        if (array->num_messages == 0) {
                tdb_delete(msg_tdb, key);
                return NT_STATUS_OK;
        }

        if (!(mem_ctx = talloc_new(array))) {
                return NT_STATUS_NO_MEMORY;
        }

        ndr_err = ndr_push_struct_blob(&blob, mem_ctx, array,
                (ndr_push_flags_fn_t)ndr_push_messaging_array);

        if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
                talloc_free(mem_ctx);
                return ndr_map_error2ntstatus(ndr_err);
        }

        if (DEBUGLEVEL >= 10) {
                DEBUG(10, ("messaging_tdb_store:\n"));
                NDR_PRINT_DEBUG(messaging_array, array);
        }

        data.dptr = blob.data;
        data.dsize = blob.length;

        ret = tdb_store(msg_tdb, key, data, TDB_REPLACE);
        TALLOC_FREE(mem_ctx);

        return (ret == 0) ? NT_STATUS_OK : NT_STATUS_INTERNAL_DB_CORRUPTION;
}

/****************************************************************************
 Notify a process that it has a message. If the process doesn't exist 
 then delete its record in the database.
****************************************************************************/

static NTSTATUS message_notify(struct server_id procid)
{
        pid_t pid = procid.pid;
        int ret;
        uid_t euid = geteuid();

        /*
         * Doing kill with a non-positive pid causes messages to be
         * sent to places we don't want.
         */

        SMB_ASSERT(pid > 0);

        if (euid != 0) {
                /* If we're not root become so to send the message. */
                save_re_uid();
                set_effective_uid(0);
        }

        ret = kill(pid, SIGUSR1);

        if (euid != 0) {
                /* Go back to who we were. */
                int saved_errno = errno;
                restore_re_uid_fromroot();
                errno = saved_errno;
        }

        if (ret == 0) {
                return NT_STATUS_OK;
        }

        /*
         * Something has gone wrong
         */

        DEBUG(2,("message to process %d failed - %s\n", (int)pid,
                 strerror(errno)));

        /*
         * No call to map_nt_error_from_unix -- don't want to link in
         * errormap.o into lots of utils.
         */

        if (errno == ESRCH)  return NT_STATUS_INVALID_HANDLE;
        if (errno == EINVAL) return NT_STATUS_INVALID_PARAMETER;
        if (errno == EPERM)  return NT_STATUS_ACCESS_DENIED;
        return NT_STATUS_UNSUCCESSFUL;
}

/****************************************************************************
 Send a message to a particular pid.
****************************************************************************/

static NTSTATUS messaging_tdb_send(struct messaging_context *msg_ctx,
                                   struct server_id pid, int msg_type,
                                   const DATA_BLOB *data,
                                   struct messaging_backend *backend)
{
        struct messaging_tdb_context *ctx = talloc_get_type(backend->private_data,
                                            struct messaging_tdb_context);
        struct messaging_array *msg_array;
        struct messaging_rec *rec;
        NTSTATUS status;
        TDB_DATA key;
        struct tdb_wrap *tdb = ctx->tdb;
        TALLOC_CTX *frame = talloc_stackframe();

        /* NULL pointer means implicit length zero. */
        if (!data->data) {
                SMB_ASSERT(data->length == 0);
        }

        /*
         * Doing kill with a non-positive pid causes messages to be
         * sent to places we don't want.
         */

        SMB_ASSERT(procid_to_pid(&pid) > 0);

        key = message_key_pid(frame, pid);

        if (tdb_chainlock(tdb->tdb, key) == -1) {
                TALLOC_FREE(frame);
                return NT_STATUS_LOCK_NOT_GRANTED;
        }

        status = messaging_tdb_fetch(tdb->tdb, key, talloc_tos(), &msg_array);

        if (!NT_STATUS_IS_OK(status)) {
                goto done;
        }

        if ((msg_type & MSG_FLAG_LOWPRIORITY)
            && (msg_array->num_messages > 1000)) {
                DEBUG(5, ("Dropping message for PID %s\n",
                          procid_str_static(&pid)));
                status = NT_STATUS_INSUFFICIENT_RESOURCES;
                goto done;
        }

        if (!(rec = TALLOC_REALLOC_ARRAY(talloc_tos(), msg_array->messages,
                                         struct messaging_rec,
                                         msg_array->num_messages+1))) {
                status = NT_STATUS_NO_MEMORY;
                goto done;
        }

        rec[msg_array->num_messages].msg_version = MESSAGE_VERSION;
        rec[msg_array->num_messages].msg_type = msg_type & MSG_TYPE_MASK;
        rec[msg_array->num_messages].dest = pid;
        rec[msg_array->num_messages].src = msg_ctx->id;
        rec[msg_array->num_messages].buf = *data;

        msg_array->messages = rec;
        msg_array->num_messages += 1;

        status = messaging_tdb_store(tdb->tdb, key, msg_array);

        if (!NT_STATUS_IS_OK(status)) {
                goto done;
        }

        status = message_notify(pid);

        if (NT_STATUS_EQUAL(status, NT_STATUS_INVALID_HANDLE)) {
                DEBUG(2, ("pid %s doesn't exist - deleting messages record\n",
                          procid_str_static(&pid)));
                tdb_delete(tdb->tdb, message_key_pid(talloc_tos(), pid));
        }

 done:
        tdb_chainunlock(tdb->tdb, key);
        TALLOC_FREE(frame);
        return status;
}

/****************************************************************************
 Retrieve all messages for a process.
****************************************************************************/

static NTSTATUS retrieve_all_messages(TDB_CONTEXT *msg_tdb,
                                      struct server_id id,
                                      TALLOC_CTX *mem_ctx,
                                      struct messaging_array **presult)
{
        struct messaging_array *result;
        TDB_DATA key = message_key_pid(mem_ctx, id);
        NTSTATUS status;

        if (tdb_chainlock(msg_tdb, key) == -1) {
                TALLOC_FREE(key.dptr);
                return NT_STATUS_LOCK_NOT_GRANTED;
        }

        status = messaging_tdb_fetch(msg_tdb, key, mem_ctx, &result);

        /*
         * We delete the record here, tdb_set_max_dead keeps it around
         */
        tdb_delete(msg_tdb, key);
        tdb_chainunlock(msg_tdb, key);

        if (NT_STATUS_IS_OK(status)) {
                *presult = result;
        }

        TALLOC_FREE(key.dptr);

        return status;
}

/****************************************************************************
 Receive and dispatch any messages pending for this process.
 JRA changed Dec 13 2006. Only one message handler now permitted per type.
 *NOTE*: Dispatch functions must be able to cope with incoming
 messages on an *odd* byte boundary.
****************************************************************************/

static void message_dispatch(struct messaging_context *msg_ctx)
{
        struct messaging_tdb_context *ctx = talloc_get_type(msg_ctx->local->private_data,
                                            struct messaging_tdb_context);
        struct messaging_array *msg_array = NULL;
        struct tdb_wrap *tdb = ctx->tdb;
        NTSTATUS status;
        uint32 i;

        if (ctx->received_messages == 0) {
                return;
        }

        DEBUG(10, ("message_dispatch: received_messages = %d\n",
                   ctx->received_messages));

        status = retrieve_all_messages(tdb->tdb, msg_ctx->id, NULL, &msg_array);
        if (!NT_STATUS_IS_OK(status)) {
                DEBUG(0, ("message_dispatch: failed to retrieve messages: %s\n",
                           nt_errstr(status)));
                return;
        }

        ctx->received_messages = 0;

        for (i=0; i<msg_array->num_messages; i++) {
                messaging_dispatch_rec(msg_ctx, &msg_array->messages[i]);
        }

        TALLOC_FREE(msg_array);
}

/** @} **/