/* 
   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
   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 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 server_id dest;
	struct server_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 server_id pid, void *buf, size_t len,
		   void *private_data);
	void *private_data;
} *dispatch_fns;

static void message_register(int msg_type, 
			     void (*fn)(int msg_type, struct server_id pid,
					void *buf, size_t len,
					void *private_data),
			     void *private_data);

/****************************************************************************
 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);
}

static NTSTATUS message_send_pid(struct server_id pid, int msg_type,
				 const void *buf, size_t len);

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

static void ping_message(int msg_type, struct server_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);
}

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

static BOOL message_init(struct messaging_context *msg_ctx)
{
	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(msg_ctx);
	register_dmalloc_msgs(msg_ctx);
	debug_register_msgs(msg_ctx);

	return True;
}

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

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

	slprintf(key, sizeof(key)-1, "PID/%s", procid_str_static(&pid));
	
	kbuf.dptr = (uint8 *)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 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
	 */

	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;
}

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

static NTSTATUS message_send_pid(struct server_id pid, int msg_type,
				 const void *buf, size_t len)
{
	TDB_DATA dbuf;
	struct message_rec rec;
	int ret;

	/* 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;

	dbuf.dptr = (uint8 *)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);

	ret = tdb_append(tdb, message_key_pid(pid), dbuf);

	SAFE_FREE(dbuf.dptr);

	if (ret == -1) {
		return NT_STATUS_INTERNAL_ERROR;
	}

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

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

unsigned int messages_pending_for_pid(struct server_id pid)
{
	TDB_DATA dbuf;
	uint8 *buf;
	unsigned int message_count = 0;

	dbuf = tdb_fetch(tdb, message_key_pid(pid));
	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(procid_self());

	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 = (char *)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 server_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 server_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.
****************************************************************************/

static void message_register(int msg_type, 
			     void (*fn)(int msg_type, struct server_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;
		}
	}

	if (!(dfn = SMB_MALLOC_P(struct dispatch_fns))) {
		DEBUG(0,("message_register: Not enough memory. malloc "
			 "failed!\n"));
		return;
	}

	ZERO_STRUCTPN(dfn);

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

	DLIST_ADD(dispatch_fns, dfn);
}

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

static 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);

	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(struct messaging_context *msg_ctx,
		      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;

	connections_traverse(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 event_context *event_ctx;
	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 event_context *messaging_event_context(struct messaging_context *msg_ctx)
{
	return msg_ctx->event_ctx;
}

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;
	ctx->event_ctx = ev;
	talloc_set_destructor(ctx, messaging_context_destructor);

	if (!message_init(ctx)) {
		DEBUG(0, ("message_init failed: %s\n", strerror(errno)));
		TALLOC_FREE(ctx);
	}

	return ctx;
}

static void messaging_callback(int msg_type, struct server_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;

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

			cb->fn(ctx, cb->private_data, msg_type, pid, &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_ctx,
			struct server_id server, 
			uint32_t msg_type, const DATA_BLOB *data)
{
	return message_send_pid(server, msg_type, data->data, data->length);
}

NTSTATUS messaging_send_buf(struct messaging_context *msg_ctx,
			    struct server_id server, uint32_t msg_type,
			    const uint8 *buf, size_t len)
{
	DATA_BLOB blob = data_blob_const(buf, len);
	return messaging_send(msg_ctx, server, msg_type, &blob);
}

/** @} **/