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/*
Unix SMB/Netbios implementation.
Version 3.0
Samba internal messaging functions
Copyright (C) Andrew Tridgell 2000
Copyright (C) 2001 by Martin Pool
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.
*/
/**
@defgroups messages Internal messaging framework
@{
@file messages.c
This module is used 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.
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;
pid_t dest;
pid_t 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, pid_t pid, void *buf, size_t len);
} *dispatch_fns;
/****************************************************************************
Notifications come in as signals.
****************************************************************************/
static void sig_usr1(void)
{
received_signal = 1;
sys_select_signal();
}
/****************************************************************************
A useful function for testing the message system.
****************************************************************************/
void ping_message(int msg_type, pid_t src, void *buf, size_t len)
{
char *msg = buf ? buf : "none";
DEBUG(1,("INFO: Received PING message from PID %u [%s]\n",(unsigned int)src, msg));
message_send_pid(src, MSG_PONG, buf, len, True);
}
/****************************************************************************
Return current debug level.
****************************************************************************/
void debuglevel_message(int msg_type, pid_t src, void *buf, size_t len)
{
DEBUG(1,("INFO: Received REQ_DEBUGLEVEL message from PID %u\n",(unsigned int)src));
message_send_pid(src, MSG_DEBUGLEVEL, DEBUGLEVEL_CLASS, sizeof(DEBUGLEVEL_CLASS), 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);
message_register(MSG_REQ_DEBUGLEVEL, debuglevel_message);
return True;
}
/*******************************************************************
Form a static tdb key from a pid.
******************************************************************/
static TDB_DATA message_key_pid(pid_t pid)
{
static char key[20];
TDB_DATA kbuf;
slprintf(key, sizeof(key)-1, "PID/%d", (int)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(pid_t pid)
{
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(pid));
} 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.
****************************************************************************/
BOOL message_send_pid(pid_t pid, int msg_type, const void *buf, size_t len,
BOOL duplicates_allowed)
{
TDB_DATA kbuf;
TDB_DATA dbuf;
struct message_rec rec;
void *p;
rec.msg_version = MESSAGE_VERSION;
rec.msg_type = msg_type;
rec.dest = pid;
rec.src = sys_getpid();
rec.len = len;
kbuf = message_key_pid(pid);
/* lock the record for the destination */
tdb_chainlock(tdb, kbuf);
dbuf = tdb_fetch(tdb, kbuf);
if (!dbuf.dptr) {
/* its a new record */
p = (void *)malloc(len + sizeof(rec));
if (!p) goto failed;
memcpy(p, &rec, sizeof(rec));
if (len > 0) memcpy((void *)((char*)p+sizeof(rec)), buf, len);
dbuf.dptr = p;
dbuf.dsize = len + sizeof(rec);
tdb_store(tdb, kbuf, dbuf, TDB_REPLACE);
SAFE_FREE(p);
goto ok;
}
if (!duplicates_allowed) {
char *ptr;
struct message_rec prec;
for(ptr = (char *)dbuf.dptr; ptr < dbuf.dptr + 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))) {
DEBUG(10,("message_send_pid: discarding duplicate message.\n"));
SAFE_FREE(dbuf.dptr);
tdb_chainunlock(tdb, kbuf);
return True;
}
}
memcpy(&prec, ptr, sizeof(prec));
ptr += sizeof(rec) + prec.len;
}
}
/* we're adding to an existing entry */
p = (void *)malloc(dbuf.dsize + len + sizeof(rec));
if (!p) goto failed;
memcpy(p, dbuf.dptr, dbuf.dsize);
memcpy((void *)((char*)p+dbuf.dsize), &rec, sizeof(rec));
if (len > 0) memcpy((void *)((char*)p+dbuf.dsize+sizeof(rec)), buf, len);
SAFE_FREE(dbuf.dptr);
dbuf.dptr = p;
dbuf.dsize += len + sizeof(rec);
tdb_store(tdb, kbuf, dbuf, TDB_REPLACE);
SAFE_FREE(dbuf.dptr);
ok:
tdb_chainunlock(tdb, kbuf);
errno = 0; /* paranoia */
return message_notify(pid);
failed:
tdb_chainunlock(tdb, kbuf);
errno = 0; /* paranoia */
return False;
}
/****************************************************************************
Retrieve the next message for the current process.
****************************************************************************/
static BOOL message_recv(int *msg_type, pid_t *src, void **buf, size_t *len)
{
TDB_DATA kbuf;
TDB_DATA dbuf;
struct message_rec rec;
kbuf = message_key_pid(sys_getpid());
tdb_chainlock(tdb, kbuf);
dbuf = tdb_fetch(tdb, kbuf);
if (dbuf.dptr == NULL || dbuf.dsize == 0) goto failed;
memcpy(&rec, dbuf.dptr, sizeof(rec));
if (rec.msg_version != MESSAGE_VERSION) {
DEBUG(0,("message version %d received (expected %d)\n", rec.msg_version, MESSAGE_VERSION));
goto failed;
}
if (rec.len > 0) {
(*buf) = (void *)malloc(rec.len);
if (!(*buf)) goto failed;
memcpy(*buf, dbuf.dptr+sizeof(rec), rec.len);
} else {
*buf = NULL;
}
*len = rec.len;
*msg_type = rec.msg_type;
*src = rec.src;
if (dbuf.dsize - (sizeof(rec)+rec.len) > 0)
memmove(dbuf.dptr, dbuf.dptr+sizeof(rec)+rec.len, dbuf.dsize - (sizeof(rec)+rec.len));
dbuf.dsize -= sizeof(rec)+rec.len;
if (dbuf.dsize == 0)
tdb_delete(tdb, kbuf);
else
tdb_store(tdb, kbuf, dbuf, TDB_REPLACE);
SAFE_FREE(dbuf.dptr);
tdb_chainunlock(tdb, kbuf);
return True;
failed:
tdb_chainunlock(tdb, kbuf);
return False;
}
/****************************************************************************
Receive and dispatch any messages pending for this process.
Notice that all dispatch handlers for a particular msg_type get called,
so you can register multiple handlers for a message.
****************************************************************************/
void message_dispatch(void)
{
int msg_type;
pid_t src;
void *buf;
size_t len;
struct dispatch_fns *dfn;
if (!received_signal) return;
DEBUG(10,("message_dispatch: received_signal = %d\n", received_signal));
received_signal = 0;
while (message_recv(&msg_type, &src, &buf, &len)) {
DEBUG(10,("message_dispatch: received msg_type=%d src_pid=%d\n",
msg_type, (int) src));
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, buf, len);
}
}
SAFE_FREE(buf);
}
}
/****************************************************************************
Register a dispatch function for a particular message type.
****************************************************************************/
void message_register(int msg_type,
void (*fn)(int msg_type, pid_t pid, void *buf, size_t len))
{
struct dispatch_fns *dfn;
dfn = (struct dispatch_fns *)malloc(sizeof(*dfn));
if (dfn != NULL) {
ZERO_STRUCTPN(dfn);
dfn->msg_type = msg_type;
dfn->fn = fn;
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);
}
}
}
struct msg_all {
int msg_type;
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;
if (dbuf.dsize != sizeof(crec))
return 0;
memcpy(&crec, dbuf.dptr, sizeof(crec));
if (crec.cnum != -1)
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.*/
if (!message_send_pid(crec.pid, msg_all->msg_type,
msg_all->buf, msg_all->len,
msg_all->duplicates)) {
/* if the pid was not found delete the entry from connections.tdb */
if (errno == ESRCH) {
DEBUG(2,("pid %u doesn't exist - deleting connections %d [%s]\n",
(unsigned int)crec.pid, crec.cnum, crec.name));
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.
*
* @return 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;
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;
}
/** @} **/
|