lib/messages.c

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/* 
   Unix SMB/CIFS implementation.
   Samba internal messaging functions
   Copyright (C) Andrew Tridgell 2000
   Copyright (C) 2001 by Martin Pool
   Copyright (C) 2002 by Jeremy Allison
   
   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 2 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, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

/**
  @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"

/* the locking database handle */
static TDB_CONTEXT *tdb;
static int received_signal;

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

struct message_rec {
        int msg_version;
        int msg_type;
        struct process_id dest;
        struct process_id src;
        size_t len;
};

/* we have a linked list of dispatch handlers */
static struct dispatch_fns {
        struct dispatch_fns *next, *prev;
        int msg_type;
        void (*fn)(int msg_type, struct process_id pid, void *buf, size_t len,
                   void *private_data);
        void *private_data;
} *dispatch_fns;

/****************************************************************************
 Free global objects.
****************************************************************************/

void gfree_messages(void)
{
        struct dispatch_fns *dfn, *next;

        /* delete the dispatch_fns list */
        dfn = dispatch_fns;
        while( dfn ) {
                next = dfn->next;
                DLIST_REMOVE(dispatch_fns, dfn);
                SAFE_FREE(dfn);
                dfn = next;
        }
}

/****************************************************************************
 Notifications come in as signals.
****************************************************************************/

static void sig_usr1(void)
{
        received_signal = 1;
        sys_select_signal(SIGUSR1);
}

/****************************************************************************
 A useful function for testing the message system.
****************************************************************************/

static void ping_message(int msg_type, struct process_id src,
                         void *buf, size_t len, void *private_data)
{
        const char *msg = buf ? (const char *)buf : "none";

        DEBUG(1,("INFO: Received PING message from PID %s [%s]\n",
                 procid_str_static(&src), msg));
        message_send_pid(src, MSG_PONG, buf, len, True);
}

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

BOOL message_init(void)
{
        sec_init();

        if (tdb)
                return True;

        tdb = tdb_open_log(lock_path("messages.tdb"), 
                       0, TDB_CLEAR_IF_FIRST|TDB_DEFAULT, 
                       O_RDWR|O_CREAT,0600);

        if (!tdb) {
                DEBUG(0,("ERROR: Failed to initialise messages database\n"));
                return False;
        }

        /* Activate the per-hashchain freelist */
        tdb_set_max_dead(tdb, 5);

        CatchSignal(SIGUSR1, SIGNAL_CAST sig_usr1);

        message_register(MSG_PING, ping_message, NULL);

        /* Register some debugging related messages */

        register_msg_pool_usage();
        register_dmalloc_msgs();

        return True;
}

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

static TDB_DATA message_key_pid(struct process_id pid)
{
        static char key[20];
        TDB_DATA kbuf;

        slprintf(key, sizeof(key)-1, "PID/%s", procid_str_static(&pid));
        
        kbuf.dptr = (char *)key;
        kbuf.dsize = strlen(key)+1;
        return kbuf;
}

/****************************************************************************
 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 process_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 == -1) {
                if (errno == ESRCH) {
                        DEBUG(2,("pid %d doesn't exist - deleting messages record\n",
                                 (int)pid));
                        tdb_delete(tdb, message_key_pid(procid));

                        /*
                         * INVALID_HANDLE is the closest I can think of -- vl
                         */
                        return NT_STATUS_INVALID_HANDLE;
                }

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

        return NT_STATUS_OK;
}

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

static NTSTATUS message_send_pid_internal(struct process_id pid, int msg_type,
                                          const void *buf, size_t len,
                                          BOOL duplicates_allowed,
                                          unsigned int timeout)
{
        TDB_DATA kbuf;
        TDB_DATA dbuf;
        TDB_DATA old_dbuf;
        struct message_rec rec;
        char *ptr;
        struct message_rec prec;

        /* NULL pointer means implicit length zero. */
        if (!buf) {
                SMB_ASSERT(len == 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);

        rec.msg_version = MESSAGE_VERSION;
        rec.msg_type = msg_type;
        rec.dest = pid;
        rec.src = procid_self();
        rec.len = buf ? len : 0;

        kbuf = message_key_pid(pid);

        dbuf.dptr = (char *)SMB_MALLOC(len + sizeof(rec));
        if (!dbuf.dptr) {
                return NT_STATUS_NO_MEMORY;
        }

        memcpy(dbuf.dptr, &rec, sizeof(rec));
        if (len > 0 && buf)
                memcpy((void *)((char*)dbuf.dptr+sizeof(rec)), buf, len);

        dbuf.dsize = len + sizeof(rec);

        if (duplicates_allowed) {

                /* If duplicates are allowed we can just append the message and return. */

                /* lock the record for the destination */
                if (timeout) {
                        if (tdb_chainlock_with_timeout(tdb, kbuf, timeout) == -1) {
                                DEBUG(0,("message_send_pid_internal: failed to get "
                                         "chainlock with timeout %ul.\n", timeout));
                                SAFE_FREE(dbuf.dptr);
                                return NT_STATUS_IO_TIMEOUT;
                        }
                } else {
                        if (tdb_chainlock(tdb, kbuf) == -1) {
                                DEBUG(0,("message_send_pid_internal: failed to get "
                                         "chainlock.\n"));
                                SAFE_FREE(dbuf.dptr);
                                return NT_STATUS_LOCK_NOT_GRANTED;
                        }
                }       
                tdb_append(tdb, kbuf, dbuf);
                tdb_chainunlock(tdb, kbuf);

                SAFE_FREE(dbuf.dptr);
                errno = 0;                    /* paranoia */
                return message_notify(pid);
        }

        /* lock the record for the destination */
        if (timeout) {
                if (tdb_chainlock_with_timeout(tdb, kbuf, timeout) == -1) {
                        DEBUG(0,("message_send_pid_internal: failed to get chainlock "
                                 "with timeout %ul.\n", timeout));
                        SAFE_FREE(dbuf.dptr);
                        return NT_STATUS_IO_TIMEOUT;
                }
        } else {
                if (tdb_chainlock(tdb, kbuf) == -1) {
                        DEBUG(0,("message_send_pid_internal: failed to get "
                                 "chainlock.\n"));
                        SAFE_FREE(dbuf.dptr);
                        return NT_STATUS_LOCK_NOT_GRANTED;
                }
        }       

        old_dbuf = tdb_fetch(tdb, kbuf);

        if (!old_dbuf.dptr) {
                /* its a new record */

                tdb_store(tdb, kbuf, dbuf, TDB_REPLACE);
                tdb_chainunlock(tdb, kbuf);

                SAFE_FREE(dbuf.dptr);
                errno = 0;                    /* paranoia */
                return message_notify(pid);
        }

        /* Not a new record. Check for duplicates. */

        for(ptr = (char *)old_dbuf.dptr; ptr < old_dbuf.dptr + old_dbuf.dsize; ) {
                /*
                 * First check if the message header matches, then, if it's a non-zero
                 * sized message, check if the data matches. If so it's a duplicate and
                 * we can discard it. JRA.
                 */

                if (!memcmp(ptr, &rec, sizeof(rec))) {
                        if (!len || (len && !memcmp( ptr + sizeof(rec), buf, len))) {
                                tdb_chainunlock(tdb, kbuf);
                                DEBUG(10,("message_send_pid_internal: discarding "
                                          "duplicate message.\n"));
                                SAFE_FREE(dbuf.dptr);
                                SAFE_FREE(old_dbuf.dptr);
                                return NT_STATUS_OK;
                        }
                }
                memcpy(&prec, ptr, sizeof(prec));
                ptr += sizeof(rec) + prec.len;
        }

        /* we're adding to an existing entry */

        tdb_append(tdb, kbuf, dbuf);
        tdb_chainunlock(tdb, kbuf);

        SAFE_FREE(old_dbuf.dptr);
        SAFE_FREE(dbuf.dptr);

        errno = 0;                    /* paranoia */
        return message_notify(pid);
}

/****************************************************************************
 Send a message to a particular pid - no timeout.
****************************************************************************/

NTSTATUS message_send_pid(struct process_id pid, int msg_type, const void *buf,
                          size_t len, BOOL duplicates_allowed)
{
        return message_send_pid_internal(pid, msg_type, buf, len,
                                         duplicates_allowed, 0);
}

/****************************************************************************
 Send a message to a particular pid, with timeout in seconds.
****************************************************************************/

NTSTATUS message_send_pid_with_timeout(struct process_id pid, int msg_type,
                                       const void *buf, size_t len,
                                       BOOL duplicates_allowed, unsigned int timeout)
{
        return message_send_pid_internal(pid, msg_type, buf, len, duplicates_allowed,
                                         timeout);
}

/****************************************************************************
 Count the messages pending for a particular pid. Expensive....
****************************************************************************/

unsigned int messages_pending_for_pid(struct process_id pid)
{
        TDB_DATA kbuf;
        TDB_DATA dbuf;
        char *buf;
        unsigned int message_count = 0;

        kbuf = message_key_pid(pid);

        dbuf = tdb_fetch(tdb, kbuf);
        if (dbuf.dptr == NULL || dbuf.dsize == 0) {
                SAFE_FREE(dbuf.dptr);
                return 0;
        }

        for (buf = dbuf.dptr; dbuf.dsize > sizeof(struct message_rec);) {
                struct message_rec rec;
                memcpy(&rec, buf, sizeof(rec));
                buf += (sizeof(rec) + rec.len);
                dbuf.dsize -= (sizeof(rec) + rec.len);
                message_count++;
        }

        SAFE_FREE(dbuf.dptr);
        return message_count;
}

/****************************************************************************
 Retrieve all messages for the current process.
****************************************************************************/

static BOOL retrieve_all_messages(char **msgs_buf, size_t *total_len)
{
        TDB_DATA kbuf;
        TDB_DATA dbuf;
        TDB_DATA null_dbuf;

        ZERO_STRUCT(null_dbuf);

        *msgs_buf = NULL;
        *total_len = 0;

        kbuf = message_key_pid(pid_to_procid(sys_getpid()));

        if (tdb_chainlock(tdb, kbuf) == -1)
                return False;

        dbuf = tdb_fetch(tdb, kbuf);
        /*
         * Replace with an empty record to keep the allocated
         * space in the tdb.
         */
        tdb_store(tdb, kbuf, null_dbuf, TDB_REPLACE);
        tdb_chainunlock(tdb, kbuf);

        if (dbuf.dptr == NULL || dbuf.dsize == 0) {
                SAFE_FREE(dbuf.dptr);
                return False;
        }

        *msgs_buf = dbuf.dptr;
        *total_len = dbuf.dsize;

        return True;
}

/****************************************************************************
 Parse out the next message for the current process.
****************************************************************************/

static BOOL message_recv(char *msgs_buf, size_t total_len, int *msg_type,
                         struct process_id *src, char **buf, size_t *len)
{
        struct message_rec rec;
        char *ret_buf = *buf;

        *buf = NULL;
        *len = 0;

        if (total_len - (ret_buf - msgs_buf) < sizeof(rec))
                return False;

        memcpy(&rec, ret_buf, sizeof(rec));
        ret_buf += sizeof(rec);

        if (rec.msg_version != MESSAGE_VERSION) {
                DEBUG(0,("message version %d received (expected %d)\n", rec.msg_version, MESSAGE_VERSION));
                return False;
        }

        if (rec.len > 0) {
                if (total_len - (ret_buf - msgs_buf) < rec.len)
                        return False;
        }

        *len = rec.len;
        *msg_type = rec.msg_type;
        *src = rec.src;
        *buf = ret_buf;

        return True;
}

/****************************************************************************
 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.
****************************************************************************/

void message_dispatch(void)
{
        int msg_type;
        struct process_id src;
        char *buf;
        char *msgs_buf;
        size_t len, total_len;
        int n_handled;

        if (!received_signal)
                return;

        DEBUG(10,("message_dispatch: received_signal = %d\n", received_signal));

        received_signal = 0;

        if (!retrieve_all_messages(&msgs_buf, &total_len))
                return;

        for (buf = msgs_buf; message_recv(msgs_buf, total_len, &msg_type, &src, &buf, &len); buf += len) {
                struct dispatch_fns *dfn;

                DEBUG(10,("message_dispatch: received msg_type=%d "
                          "src_pid=%u\n", msg_type,
                          (unsigned int) procid_to_pid(&src)));

                n_handled = 0;
                for (dfn = dispatch_fns; dfn; dfn = dfn->next) {
                        if (dfn->msg_type == msg_type) {
                                DEBUG(10,("message_dispatch: processing message of type %d.\n", msg_type));
                                dfn->fn(msg_type, src,
                                        len ? (void *)buf : NULL, len,
                                        dfn->private_data);
                                n_handled++;
                                break;
                        }
                }
                if (!n_handled) {
                        DEBUG(5,("message_dispatch: warning: no handler registed for "
                                 "msg_type %d in pid %u\n",
                                 msg_type, (unsigned int)sys_getpid()));
                }
        }
        SAFE_FREE(msgs_buf);
}

/****************************************************************************
 Register/replace a dispatch function for a particular message type.
 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.
****************************************************************************/

void message_register(int msg_type, 
                      void (*fn)(int msg_type, struct process_id pid,
                                 void *buf, size_t len,
                                 void *private_data),
                      void *private_data)
{
        struct dispatch_fns *dfn;

        for (dfn = dispatch_fns; dfn; dfn = dfn->next) {
                if (dfn->msg_type == msg_type) {
                        dfn->fn = fn;
                        return;
                }
        }

        dfn = SMB_MALLOC_P(struct dispatch_fns);

        if (dfn != NULL) {

                ZERO_STRUCTPN(dfn);

                dfn->msg_type = msg_type;
                dfn->fn = fn;
                dfn->private_data = private_data;

                DLIST_ADD(dispatch_fns, dfn);
        }
        else {
        
                DEBUG(0,("message_register: Not enough memory. malloc failed!\n"));
        }
}

/****************************************************************************
 De-register the function for a particular message type.
****************************************************************************/

void message_deregister(int msg_type)
{
        struct dispatch_fns *dfn, *next;

        for (dfn = dispatch_fns; dfn; dfn = next) {
                next = dfn->next;
                if (dfn->msg_type == msg_type) {
                        DLIST_REMOVE(dispatch_fns, dfn);
                        SAFE_FREE(dfn);
                        return;
                }
        }       
}

struct msg_all {
        int msg_type;
        uint32 msg_flag;
        const void *buf;
        size_t len;
        BOOL duplicates;
        int n_sent;
};

/****************************************************************************
 Send one of the messages for the broadcast.
****************************************************************************/

static int traverse_fn(TDB_CONTEXT *the_tdb, TDB_DATA kbuf, TDB_DATA dbuf, void *state)
{
        struct connections_data crec;
        struct msg_all *msg_all = (struct msg_all *)state;
        NTSTATUS status;

        if (dbuf.dsize != sizeof(crec))
                return 0;

        memcpy(&crec, dbuf.dptr, sizeof(crec));

        if (crec.cnum != -1)
                return 0;

        /* Don't send if the receiver hasn't registered an interest. */

        if(!(crec.bcast_msg_flags & msg_all->msg_flag))
                return 0;

        /* If the msg send fails because the pid was not found (i.e. smbd died), 
         * the msg has already been deleted from the messages.tdb.*/

        status = message_send_pid(crec.pid, msg_all->msg_type,
                                  msg_all->buf, msg_all->len,
                                  msg_all->duplicates);

        if (NT_STATUS_EQUAL(status, NT_STATUS_INVALID_HANDLE)) {
                
                /* If the pid was not found delete the entry from connections.tdb */

                DEBUG(2,("pid %s doesn't exist - deleting connections %d [%s]\n",
                         procid_str_static(&crec.pid), crec.cnum, crec.servicename));
                tdb_delete(the_tdb, kbuf);
        }
        msg_all->n_sent++;
        return 0;
}

/**
 * Send a message to all smbd processes.
 *
 * It isn't very efficient, but should be OK for the sorts of
 * applications that use it. When we need efficient broadcast we can add
 * it.
 *
 * @param n_sent Set to the number of messages sent.  This should be
 * equal to the number of processes, but be careful for races.
 *
 * @retval True for success.
 **/
BOOL message_send_all(TDB_CONTEXT *conn_tdb, int msg_type,
                      const void *buf, size_t len,
                      BOOL duplicates_allowed,
                      int *n_sent)
{
        struct msg_all msg_all;

        msg_all.msg_type = msg_type;
        if (msg_type < 1000)
                msg_all.msg_flag = FLAG_MSG_GENERAL;
        else if (msg_type > 1000 && msg_type < 2000)
                msg_all.msg_flag = FLAG_MSG_NMBD;
        else if (msg_type > 2000 && msg_type < 2100)
                msg_all.msg_flag = FLAG_MSG_PRINT_NOTIFY;
        else if (msg_type > 2100 && msg_type < 3000)
                msg_all.msg_flag = FLAG_MSG_PRINT_GENERAL;
        else if (msg_type > 3000 && msg_type < 4000)
                msg_all.msg_flag = FLAG_MSG_SMBD;
        else
                return False;

        msg_all.buf = buf;
        msg_all.len = len;
        msg_all.duplicates = duplicates_allowed;
        msg_all.n_sent = 0;

        tdb_traverse(conn_tdb, traverse_fn, &msg_all);
        if (n_sent)
                *n_sent = msg_all.n_sent;
        return True;
}

/*
 * Block and unblock receiving of messages. Allows removal of race conditions
 * when doing a fork and changing message disposition.
 */

void message_block(void)
{
        BlockSignals(True, SIGUSR1);
}

void message_unblock(void)
{
        BlockSignals(False, SIGUSR1);
}

/*
 * Samba4 API wrapper around the Samba3 implementation. Yes, I know, we could
 * import the whole Samba4 thing, but I want notify.c from Samba4 in first.
 */

struct messaging_callback {
        struct messaging_callback *prev, *next;
        uint32 msg_type;
        void (*fn)(struct messaging_context *msg, void *private_data, 
                   uint32_t msg_type, 
                   struct server_id server_id, DATA_BLOB *data);
        void *private_data;
};

struct messaging_context {
        struct server_id id;
        struct messaging_callback *callbacks;
};

static int messaging_context_destructor(struct messaging_context *ctx)
{
        struct messaging_callback *cb;

        for (cb = ctx->callbacks; cb; cb = cb->next) {
                /*
                 * We unconditionally remove all instances of our callback
                 * from the tdb basis.
                 */
                message_deregister(cb->msg_type);
        }
        return 0;
}

struct messaging_context *messaging_init(TALLOC_CTX *mem_ctx, 
                                         struct server_id server_id, 
                                         struct event_context *ev)
{
        struct messaging_context *ctx;

        if (!(ctx = TALLOC_ZERO_P(mem_ctx, struct messaging_context))) {
                return NULL;
        }

        ctx->id = server_id;
        talloc_set_destructor(ctx, messaging_context_destructor);
        return ctx;
}

static void messaging_callback(int msg_type, struct process_id pid,
                               void *buf, size_t len, void *private_data)
{
        struct messaging_context *ctx = talloc_get_type_abort(
                private_data, struct messaging_context);
        struct messaging_callback *cb, *next;

        for (cb = ctx->callbacks; cb; cb = next) {
                /*
                 * Allow a callback to remove itself
                 */
                next = cb->next;

                if (msg_type == cb->msg_type) {
                        DATA_BLOB blob;
                        struct server_id id;

                        blob.data = (uint8 *)buf;
                        blob.length = len;
                        id.id = pid;

                        cb->fn(ctx, cb->private_data, msg_type, id, &blob);
                }
        }
}

/*
 * Register a dispatch function for a particular message type. Allow multiple
 * registrants
*/
NTSTATUS messaging_register(struct messaging_context *ctx, void *private_data,
                            uint32_t msg_type,
                            void (*fn)(struct messaging_context *msg,
                                       void *private_data, 
                                       uint32_t msg_type, 
                                       struct server_id server_id,
                                       DATA_BLOB *data))
{
        struct messaging_callback *cb;

        if (!(cb = talloc(ctx, struct messaging_callback))) {
                return NT_STATUS_NO_MEMORY;
        }

        cb->msg_type = msg_type;
        cb->fn = fn;
        cb->private_data = private_data;

        DLIST_ADD(ctx->callbacks, cb);
        message_register(msg_type, messaging_callback, ctx);
        return NT_STATUS_OK;
}

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

        for (cb = ctx->callbacks; cb; cb = next) {
                next = cb->next;
                if ((cb->msg_type == msg_type)
                    && (cb->private_data == private_data)) {
                        DLIST_REMOVE(ctx->callbacks, cb);
                        TALLOC_FREE(cb);
                }
        }
}

/*
  Send a message to a particular server
*/
NTSTATUS messaging_send(struct messaging_context *msg,
                        struct server_id server, 
                        uint32_t msg_type, DATA_BLOB *data)
{
        return message_send_pid_internal(server.id, msg_type, data->data,
                                         data->length, True, 0);
}

/** @} **/

---