messages.c

samba-3.0.22.tar.gz 编译smb服务器的源码

/* 
   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);
} *dispatch_fns;

/****************************************************************************
 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)
{
	const char *msg = buf ? 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)
{
	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;
	}

	CatchSignal(SIGUSR1, SIGNAL_CAST sig_usr1);

	message_register(MSG_PING, ping_message);

	/* 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 BOOL message_notify(struct process_id procid)
{
	pid_t pid = procid.pid;
	/*
	 * Doing kill with a non-positive pid causes messages to be
	 * sent to places we don't want.
	 */

	SMB_ASSERT(pid > 0);

	if (kill(pid, SIGUSR1) == -1) {
		if (errno == ESRCH) {
			DEBUG(2,("pid %d doesn't exist - deleting messages record\n", (int)pid));
			tdb_delete(tdb, message_key_pid(procid));
		} else {
			DEBUG(2,("message to process %d failed - %s\n", (int)pid, strerror(errno)));
		}
		return False;
	}
	return True;
}

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

static BOOL 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;

	/*
	 * 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 = len;

	kbuf = message_key_pid(pid);

	dbuf.dptr = (void *)SMB_MALLOC(len + sizeof(rec));
	if (!dbuf.dptr)
		return False;

	memcpy(dbuf.dptr, &rec, sizeof(rec));
	if (len > 0)
		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));
				return False;
			}
		} else {
			if (tdb_chainlock(tdb, kbuf) == -1) {
				DEBUG(0,("message_send_pid_internal: failed to get chainlock.\n"));
				return False;
			}
		}	
		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));
			return False;
		}
	} else {
		if (tdb_chainlock(tdb, kbuf) == -1) {
			DEBUG(0,("message_send_pid_internal: failed to get chainlock.\n"));
			return False;
		}
	}	

	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 True;
			}
		}
		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.
****************************************************************************/

BOOL 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.
****************************************************************************/