path: root/src/master/dgram_server.c

/*++
/* NAME
/*	dgram_server 3
/* SUMMARY
/*	skeleton datagram server subsystem
/* SYNOPSIS
/*	#include <mail_server.h>
/*
/*	NORETURN dgram_server_main(argc, argv, service, key, value, ...)
/*	int	argc;
/*	char	**argv;
/*	void	(*service)(char *buf, int len, char *service_name, char **argv);
/*	int	key;
/* DESCRIPTION
/*	This module implements a skeleton for mail subsystem programs
/*	that wake up on client request and perform some activity
/*	without further client interaction.  This module supports
/*	local IPC via a UNIX-domain datagram socket. The resulting
/*	program expects to be run from the \fBmaster\fR process.
/*
/*	dgram_server_main() is the skeleton entry point. It should
/*	be called from the application main program. The skeleton
/*	does the generic command-line options processing, initialization
/*	of configurable parameters, and receiving datagrams. The
/*	skeleton never returns.
/*
/*	Arguments:
/* .IP "void (*service)(char *buf, int len, char *service_name, char **argv)"
/*	A pointer to a function that is called by the skeleton each
/*	time a client sends a datagram to the program's service
/*	port. The function is run after the program has irrevocably
/*	dropped its privileges.  The buffer argument specifies the
/*	data read from the datagram port; this data corresponds to
/*	request.  The len argument specifies how much client data
/*	is available.  The maximal size of the buffer is specified
/*	via the DGRAM_BUF_SIZE manifest constant.  The service name
/*	argument corresponds to the service name in the master.cf
/*	file.  The argv argument specifies command-line arguments
/*	left over after options processing.
/* .PP
/*	Optional arguments are specified as a null-terminated list
/*	with macros that have zero or more arguments:
/* .IP "CA_MAIL_SERVER_INT_TABLE(CONFIG_INT_TABLE *)"
/*	A table with configurable parameters, to be loaded from the
/*	global Postfix configuration file. Tables are loaded in the
/*	order as specified, and multiple instances of the same type
/*	are allowed.
/* .IP "CA_MAIL_SERVER_LONG_TABLE(CONFIG_LONG_TABLE *)"
/*	A table with configurable parameters, to be loaded from the
/*	global Postfix configuration file. Tables are loaded in the
/*	order as specified, and multiple instances of the same type
/*	are allowed.
/* .IP "CA_MAIL_SERVER_STR_TABLE(CONFIG_STR_TABLE *)"
/*	A table with configurable parameters, to be loaded from the
/*	global Postfix configuration file. Tables are loaded in the
/*	order as specified, and multiple instances of the same type
/*	are allowed.
/* .IP "CA_MAIL_SERVER_BOOL_TABLE(CONFIG_BOOL_TABLE *)"
/*	A table with configurable parameters, to be loaded from the
/*	global Postfix configuration file. Tables are loaded in the
/*	order as specified, and multiple instances of the same type
/*	are allowed.
/* .IP "CA_MAIL_SERVER_TIME_TABLE(CONFIG_TIME_TABLE *)"
/*	A table with configurable parameters, to be loaded from the
/*	global Postfix configuration file. Tables are loaded in the
/*	order as specified, and multiple instances of the same type
/*	are allowed.
/* .IP "CA_MAIL_SERVER_RAW_TABLE(CONFIG_RAW_TABLE *)"
/*	A table with configurable parameters, to be loaded from the
/*	global Postfix configuration file. Tables are loaded in the
/*	order as specified, and multiple instances of the same type
/*	are allowed. Raw parameters are not subjected to $name
/*	evaluation.
/* .IP "CA_MAIL_SERVER_NINT_TABLE(CONFIG_NINT_TABLE *)"
/*	A table with configurable parameters, to be loaded from the
/*	global Postfix configuration file. Tables are loaded in the
/*	order as specified, and multiple instances of the same type
/*	are allowed.
/* .IP "CA_MAIL_SERVER_NBOOL_TABLE(CONFIG_NBOOL_TABLE *)"
/*	A table with configurable parameters, to be loaded from the
/*	global Postfix configuration file. Tables are loaded in the
/*	order as specified, and multiple instances of the same type
/*	are allowed.
/* .IP "CA_MAIL_SERVER_PRE_INIT(void *(char *service_name, char **argv))"
/*	A pointer to a function that is called once
/*	by the skeleton after it has read the global configuration file
/*	and after it has processed command-line arguments, but before
/*	the skeleton has optionally relinquished the process privileges.
/* .sp
/*	Only the last instance of this parameter type is remembered.
/* .IP "CA_MAIL_SERVER_POST_INIT(void *(char *service_name, char **argv))"
/*	A pointer to a function that is called once
/*	by the skeleton after it has optionally relinquished the process
/*	privileges, but before servicing client connection requests.
/* .sp
/*	Only the last instance of this parameter type is remembered.
/* .IP "CA_MAIL_SERVER_LOOP(int *(char *service_name, char **argv))"
/*	A pointer to function that is executed from
/*	within the event loop, whenever an I/O or timer event has happened,
/*	or whenever nothing has happened for a specified amount of time.
/*	The result value of the function specifies how long to wait until
/*	the next event. Specify -1 to wait for "as long as it takes".
/* .sp
/*	Only the last instance of this parameter type is remembered.
/* .IP "CA_MAIL_SERVER_EXIT(void *(char *service_name, char **argv))"
/*	A pointer to function that is executed immediately before normal
/*	process termination.
/* .sp
/*	Only the last instance of this parameter type is remembered.
/* .IP "CA_MAIL_SERVER_PRE_ACCEPT(void *(char *service_name, char **argv))"
/*	Function to be executed prior to accepting a new request.
/* .sp
/*	Only the last instance of this parameter type is remembered.
/* .IP "CA_MAIL_SERVER_IN_FLOW_DELAY(none)"
/*	Pause $in_flow_delay seconds when no "mail flow control token"
/*	is available. A token is consumed for each connection request.
/* .IP CA_MAIL_SERVER_SOLITARY
/*	This service must be configured with process limit of 1.
/* .IP CA_MAIL_SERVER_UNLIMITED
/*	This service must be configured with process limit of 0.
/* .IP CA_MAIL_SERVER_PRIVILEGED
/*	This service must be configured as privileged.
/* .IP "CA_MAIL_SERVER_WATCHDOG(int *)"
/*	Override the default 1000s watchdog timeout. The value is
/*	used after command-line and main.cf file processing.
/* .IP "CA_MAIL_SERVER_BOUNCE_INIT(const char *, const char **)"
/*	Initialize the DSN filter for the bounce/defer service
/*	clients with the specified map source and map names.
/* .PP
/*	The var_use_limit variable limits the number of clients that
/*	a server can service before it commits suicide.
/*	This value is taken from the global \fBmain.cf\fR configuration
/*	file. Setting \fBvar_use_limit\fR to zero disables the client limit.
/*
/*	The var_idle_limit variable limits the time that a service
/*	receives no client connection requests before it commits suicide.
/*	This value is taken from the global \fBmain.cf\fR configuration
/*	file. Setting \fBvar_use_limit\fR to zero disables the idle limit.
/* DIAGNOSTICS
/*	Problems and transactions are logged to \fBsyslogd\fR(8)
/*	or \fBpostlogd\fR(8).
/* SEE ALSO
/*	master(8), master process
/*	postlogd(8), Postfix logging
/*	syslogd(8), system logging
/* LICENSE
/* .ad
/* .fi
/*	The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*	Wietse Venema
/*	Google, Inc.
/*	111 8th Avenue
/*	New York, NY 10011, USA
/*--*/

/* System library. */

#include <sys_defs.h>
#include <sys/socket.h>
#include <unistd.h>
#include <signal.h>
#include <stdlib.h>
#include <limits.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#ifdef STRCASECMP_IN_STRINGS_H
#include <strings.h>
#endif
#include <time.h>

/* Utility library. */

#include <msg.h>
#include <msg_vstream.h>
#include <chroot_uid.h>
#include <vstring.h>
#include <vstream.h>
#include <msg_vstream.h>
#include <mymalloc.h>
#include <events.h>
#include <iostuff.h>
#include <stringops.h>
#include <sane_accept.h>
#include <myflock.h>
#include <safe_open.h>
#include <listen.h>
#include <watchdog.h>
#include <split_at.h>

/* Global library. */

#include <mail_params.h>
#include <mail_task.h>
#include <debug_process.h>
#include <mail_conf.h>
#include <mail_dict.h>
#include <resolve_local.h>
#include <mail_flow.h>
#include <mail_version.h>
#include <bounce.h>
#include <maillog_client.h>

/* Process manager. */

#include "master_proto.h"

/* Application-specific */

#include "mail_server.h"

 /*
  * Global state.
  */
static int use_count;

static DGRAM_SERVER_FN dgram_server_service;
static char *dgram_server_name;
static char **dgram_server_argv;
static void (*dgram_server_accept) (int, void *);
static void (*dgram_server_onexit) (char *, char **);
static void (*dgram_server_pre_accept) (char *, char **);
static VSTREAM *dgram_server_lock;
static int dgram_server_in_flow_delay;
static unsigned dgram_server_generation;
static int dgram_server_watchdog = 1000;

/* dgram_server_exit - normal termination */

static NORETURN dgram_server_exit(void)
{
    if (dgram_server_onexit)
	dgram_server_onexit(dgram_server_name, dgram_server_argv);
    exit(0);
}

/* dgram_server_abort - terminate after abnormal master exit */

static void dgram_server_abort(int unused_event, void *unused_context)
{
    if (msg_verbose)
	msg_info("master disconnect -- exiting");
    dgram_server_exit();
}

/* dgram_server_timeout - idle time exceeded */

static void dgram_server_timeout(int unused_event, void *unused_context)
{
    if (msg_verbose)
	msg_info("idle timeout -- exiting");
    dgram_server_exit();
}

/* dgram_server_wakeup - wake up application */

static void dgram_server_wakeup(int fd)
{
    char    buf[DGRAM_BUF_SIZE];
    ssize_t len;

    /*
     * Commit suicide when the master process disconnected from us, after
     * handling the client request.
     */
    if (master_notify(var_pid, dgram_server_generation, MASTER_STAT_TAKEN) < 0)
	 /* void */ ;
    if (dgram_server_in_flow_delay && mail_flow_get(1) < 0)
	doze(var_in_flow_delay * 1000000);
    if ((len = recv(fd, buf, sizeof(buf), 0)) >= 0)
	dgram_server_service(buf, len, dgram_server_name, dgram_server_argv);
    if (master_notify(var_pid, dgram_server_generation, MASTER_STAT_AVAIL) < 0)
	dgram_server_abort(EVENT_NULL_TYPE, EVENT_NULL_CONTEXT);
    if (var_idle_limit > 0)
	event_request_timer(dgram_server_timeout, (void *) 0, var_idle_limit);
    /* Avoid integer wrap-around in a persistent process.  */
    if (use_count < INT_MAX)
	use_count++;
}

/* dgram_server_accept_unix - handle UNIX-domain socket event */

static void dgram_server_accept_unix(int unused_event, void *context)
{
    const char *myname = "dgram_server_accept";
    int     listen_fd = CAST_ANY_PTR_TO_INT(context);

    if (dgram_server_lock != 0
	&& myflock(vstream_fileno(dgram_server_lock), INTERNAL_LOCK,
		   MYFLOCK_OP_NONE) < 0)
	msg_fatal("select unlock: %m");

    if (msg_verbose)
	msg_info("%s: request arrived", myname);

    /*
     * Read whatever the other side wrote. The socket is non-blocking so we
     * won't get stuck when multiple processes wake up.
     */
    if (dgram_server_pre_accept)
	dgram_server_pre_accept(dgram_server_name, dgram_server_argv);
    dgram_server_wakeup(listen_fd);
}

/* dgram_server_main - the real main program */

NORETURN dgram_server_main(int argc, char **argv, DGRAM_SERVER_FN service,...)
{
    const char *myname = "dgram_server_main";
    char   *root_dir = 0;
    char   *user_name = 0;
    int     debug_me = 0;
    int     daemon_mode = 1;
    char   *service_name = basename(argv[0]);
    int     delay;
    int     c;
    int     socket_count = 1;
    int     fd;
    va_list ap;
    MAIL_SERVER_INIT_FN pre_init = 0;
    MAIL_SERVER_INIT_FN post_init = 0;
    MAIL_SERVER_LOOP_FN loop = 0;
    int     key;
    char   *transport = 0;
    char   *lock_path;
    VSTRING *why;
    int     alone = 0;
    int     zerolimit = 0;
    WATCHDOG *watchdog;
    char   *oname_val;
    char   *oname;
    char   *oval;
    const char *err;
    char   *generation;
    int     msg_vstream_needed = 0;
    const char *dsn_filter_title;
    const char **dsn_filter_maps;

    /*
     * Process environment options as early as we can.
     */
    if (getenv(CONF_ENV_VERB))
	msg_verbose = 1;
    if (getenv(CONF_ENV_DEBUG))
	debug_me = 1;

    /*
     * Don't die when a process goes away unexpectedly.
     */
    signal(SIGPIPE, SIG_IGN);

    /*
     * Don't die for frivolous reasons.
     */
#ifdef SIGXFSZ
    signal(SIGXFSZ, SIG_IGN);
#endif

    /*
     * May need this every now and then.
     */
    var_procname = mystrdup(basename(argv[0]));
    set_mail_conf_str(VAR_PROCNAME, var_procname);

    /*
     * Initialize logging and exit handler. Do the syslog first, so that its
     * initialization completes before we enter the optional chroot jail.
     */
    maillog_client_init(mail_task(var_procname), MAILLOG_CLIENT_FLAG_NONE);
    if (msg_verbose)
	msg_info("daemon started");

    /*
     * Check the Postfix library version as soon as we enable logging.
     */
    MAIL_VERSION_CHECK;

    /*
     * Initialize from the configuration file. Allow command-line options to
     * override compiled-in defaults or configured parameter values.
     */
    mail_conf_suck();

    /*
     * After database open error, continue execution with reduced
     * functionality.
     */
    dict_allow_surrogate = 1;

    /*
     * Pick up policy settings from master process. Shut up error messages to
     * stderr, because no-one is going to see them.
     */
    opterr = 0;
    while ((c = GETOPT(argc, argv, "cdDi:lm:n:o:s:t:uvVz")) > 0) {
	switch (c) {
	case 'c':
	    root_dir = "setme";
	    break;
	case 'd':
	    daemon_mode = 0;
	    break;
	case 'D':
	    debug_me = 1;
	    break;
	case 'i':
	    mail_conf_update(VAR_MAX_IDLE, optarg);
	    break;
	case 'l':
	    alone = 1;
	    break;
	case 'm':
	    mail_conf_update(VAR_MAX_USE, optarg);
	    break;
	case 'n':
	    service_name = optarg;
	    break;
	case 'o':
	    oname_val = mystrdup(optarg);
	    if ((err = split_nameval(oname_val, &oname, &oval)) != 0)
		msg_fatal("invalid \"-o %s\" option value: %s", optarg, err);
	    mail_conf_update(oname, oval);
	    myfree(oname_val);
	    break;
	case 's':
	    if ((socket_count = atoi(optarg)) <= 0)
		msg_fatal("invalid socket_count: %s", optarg);
	    break;
	case 't':
	    transport = optarg;
	    break;
	case 'u':
	    user_name = "setme";
	    break;
	case 'v':
	    msg_verbose++;
	    break;
	case 'V':
	    if (++msg_vstream_needed == 1)
		msg_vstream_init(mail_task(var_procname), VSTREAM_ERR);
	    break;
	case 'z':
	    zerolimit = 1;
	    break;
	default:
	    msg_fatal("invalid option: %c", optopt);
	    break;
	}
    }
    set_mail_conf_str(VAR_SERVNAME, service_name);

    /*
     * Initialize generic parameters and re-initialize logging in case of a
     * non-default program name or logging destination.
     */
    mail_params_init();
    maillog_client_init(mail_task(var_procname), MAILLOG_CLIENT_FLAG_NONE);

    /*
     * Register higher-level dictionaries and initialize the support for
     * dynamically-loaded dictionarles.
     */
    mail_dict_init();

    /*
     * If not connected to stdin, stdin must not be a terminal.
     */
    if (daemon_mode && isatty(STDIN_FILENO)) {
	msg_vstream_init(var_procname, VSTREAM_ERR);
	msg_fatal("do not run this command by hand");
    }

    /*
     * Application-specific initialization.
     */
    va_start(ap, service);
    while ((key = va_arg(ap, int)) != 0) {
	switch (key) {
	case MAIL_SERVER_INT_TABLE:
	    get_mail_conf_int_table(va_arg(ap, CONFIG_INT_TABLE *));
	    break;
	case MAIL_SERVER_LONG_TABLE:
	    get_mail_conf_long_table(va_arg(ap, CONFIG_LONG_TABLE *));
	    break;
	case MAIL_SERVER_STR_TABLE:
	    get_mail_conf_str_table(va_arg(ap, CONFIG_STR_TABLE *));
	    break;
	case MAIL_SERVER_BOOL_TABLE:
	    get_mail_conf_bool_table(va_arg(ap, CONFIG_BOOL_TABLE *));
	    break;
	case MAIL_SERVER_TIME_TABLE:
	    get_mail_conf_time_table(va_arg(ap, CONFIG_TIME_TABLE *));
	    break;
	case MAIL_SERVER_RAW_TABLE:
	    get_mail_conf_raw_table(va_arg(ap, CONFIG_RAW_TABLE *));
	    break;
	case MAIL_SERVER_NINT_TABLE:
	    get_mail_conf_nint_table(va_arg(ap, CONFIG_NINT_TABLE *));
	    break;
	case MAIL_SERVER_NBOOL_TABLE:
	    get_mail_conf_nbool_table(va_arg(ap, CONFIG_NBOOL_TABLE *));
	    break;
	case MAIL_SERVER_PRE_INIT:
	    pre_init = va_arg(ap, MAIL_SERVER_INIT_FN);
	    break;
	case MAIL_SERVER_POST_INIT:
	    post_init = va_arg(ap, MAIL_SERVER_INIT_FN);
	    break;
	case MAIL_SERVER_LOOP:
	    loop = va_arg(ap, MAIL_SERVER_LOOP_FN);
	    break;
	case MAIL_SERVER_EXIT:
	    dgram_server_onexit = va_arg(ap, MAIL_SERVER_EXIT_FN);
	    break;
	case MAIL_SERVER_PRE_ACCEPT:
	    dgram_server_pre_accept = va_arg(ap, MAIL_SERVER_ACCEPT_FN);
	    break;
	case MAIL_SERVER_IN_FLOW_DELAY:
	    dgram_server_in_flow_delay = 1;
	    break;
	case MAIL_SERVER_SOLITARY:
	    if (!alone)
		msg_fatal("service %s requires a process limit of 1",
			  service_name);
	    break;
	case MAIL_SERVER_UNLIMITED:
	    if (!zerolimit)
		msg_fatal("service %s requires a process limit of 0",
			  service_name);
	    break;
	case MAIL_SERVER_PRIVILEGED:
	    if (user_name)
		msg_fatal("service %s requires privileged operation",
			  service_name);
	    break;
	case MAIL_SERVER_WATCHDOG:
	    dgram_server_watchdog = *va_arg(ap, int *);
	    break;
	case MAIL_SERVER_BOUNCE_INIT:
	    dsn_filter_title = va_arg(ap, const char *);
	    dsn_filter_maps = va_arg(ap, const char **);
	    bounce_client_init(dsn_filter_title, *dsn_filter_maps);
	    break;
	default:
	    msg_panic("%s: unknown argument type: %d", myname, key);
	}
    }
    va_end(ap);

    if (root_dir)
	root_dir = var_queue_dir;
    if (user_name)
	user_name = var_mail_owner;

    /*
     * Can options be required?
     */
    if (transport == 0)
	msg_fatal("no transport type specified");
    else if (strcasecmp(transport, MASTER_XPORT_NAME_UXDG) == 0)
	dgram_server_accept = dgram_server_accept_unix;
    else
	msg_fatal("unsupported transport type: %s", transport);

    /*
     * Retrieve process generation from environment.
     */
    if ((generation = getenv(MASTER_GEN_NAME)) != 0) {
	if (!alldig(generation))
	    msg_fatal("bad generation: %s", generation);
	OCTAL_TO_UNSIGNED(dgram_server_generation, generation);
	if (msg_verbose)
	    msg_info("process generation: %s (%o)",
		     generation, dgram_server_generation);
    }

    /*
     * Optionally start the debugger on ourself.
     */
    if (debug_me)
	debug_process();

    /*
     * Traditionally, BSD select() can't handle multiple processes selecting
     * on the same socket, and wakes up every process in select(). See TCP/IP
     * Illustrated volume 2 page 532. We avoid select() collisions with an
     * external lock file.
     */
    if (!alone) {
	lock_path = concatenate(DEF_PID_DIR, "/", transport,
				".", service_name, (char *) 0);
	why = vstring_alloc(1);
	if ((dgram_server_lock = safe_open(lock_path, O_CREAT | O_RDWR, 0600,
				      (struct stat *) 0, -1, -1, why)) == 0)
	    msg_fatal("open lock file %s: %s", lock_path, vstring_str(why));
	close_on_exec(vstream_fileno(dgram_server_lock), CLOSE_ON_EXEC);
	myfree(lock_path);
	vstring_free(why);
    }

    /*
     * Set up call-back info.
     */
    dgram_server_service = service;
    dgram_server_name = service_name;
    dgram_server_argv = argv + optind;

    /*
     * Run pre-jail initialization.
     */
    if (chdir(var_queue_dir) < 0)
	msg_fatal("chdir(\"%s\"): %m", var_queue_dir);
    if (pre_init)
	pre_init(dgram_server_name, dgram_server_argv);

    /*
     * Optionally, restrict the damage that this process can do.
     */
    resolve_local_init();
    tzset();
    chroot_uid(root_dir, user_name);

    /*
     * Run post-jail initialization.
     */
    if (post_init)
	post_init(dgram_server_name, dgram_server_argv);

    /*
     * Running as a semi-resident server. Service requests. Terminate when we
     * have serviced a sufficient number of requests, when no-one has been
     * talking to us for a configurable amount of time, or when the master
     * process terminated abnormally.
     */
    if (var_idle_limit > 0)
	event_request_timer(dgram_server_timeout, (void *) 0, var_idle_limit);
    for (fd = MASTER_LISTEN_FD; fd < MASTER_LISTEN_FD + socket_count; fd++) {
	event_enable_read(fd, dgram_server_accept, CAST_INT_TO_VOID_PTR(fd));
	close_on_exec(fd, CLOSE_ON_EXEC);
    }
    event_enable_read(MASTER_STATUS_FD, dgram_server_abort, (void *) 0);
    close_on_exec(MASTER_STATUS_FD, CLOSE_ON_EXEC);
    close_on_exec(MASTER_FLOW_READ, CLOSE_ON_EXEC);
    close_on_exec(MASTER_FLOW_WRITE, CLOSE_ON_EXEC);
    watchdog = watchdog_create(dgram_server_watchdog,
			       (WATCHDOG_FN) 0, (void *) 0);

    /*
     * The event loop, at last.
     */
    while (var_use_limit == 0 || use_count < var_use_limit) {
	if (dgram_server_lock != 0) {
	    watchdog_stop(watchdog);
	    if (myflock(vstream_fileno(dgram_server_lock), INTERNAL_LOCK,
			MYFLOCK_OP_EXCLUSIVE) < 0)
		msg_fatal("select lock: %m");
	}
	watchdog_start(watchdog);
	delay = loop ? loop(dgram_server_name, dgram_server_argv) : -1;
	event_loop(delay);
    }
    dgram_server_exit();
}