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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);
} *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)
{
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;
}
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;
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) {
become_root_uid_only();
}
ret = kill(pid, SIGUSR1);
if (euid != 0) {
unbecome_root_uid_only();
}
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));
} 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;
/* 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 False;
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));
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.
****************************************************************************/
BOOL 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.
Notice that all dispatch handlers for a particular msg_type get called,
so you can register multiple handlers for a message.
*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, *next;
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 = next) {
next = 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);
n_handled++;
}
}
if (!n_handled) {
DEBUG(5,("message_dispatch: warning: no handlers registed for "
"msg_type %d in pid %u\n",
msg_type, (unsigned int)sys_getpid()));
}
}
SAFE_FREE(msgs_buf);
}
/****************************************************************************
Register a dispatch function for a particular message 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))
{
struct dispatch_fns *dfn;
dfn = SMB_MALLOC_P(struct dispatch_fns);
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;
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;
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.*/
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 %s doesn't exist - deleting connections %d [%s]\n",
procid_str_static(&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.
*
* @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);
}
/** @} **/
|