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/*++
/* NAME
/* master_sig 3
/* SUMMARY
/* Postfix master - signal processing
/* SYNOPSIS
/* #include "master.h"
/*
/* int master_gotsighup;
/* int master_gotsigchld;
/*
/* int master_sigsetup()
/* DESCRIPTION
/* This module implements the master process signal handling interface.
/*
/* master_gotsighup (master_gotsigchld) is set to SIGHUP (SIGCHLD)
/* when the process receives a hangup (child death) signal.
/*
/* master_sigsetup() enables processing of hangup and child death signals.
/* Receipt of SIGINT, SIGQUIT, SIGSEGV, SIGILL, or SIGTERM
/* is interpreted as a request for termination. Child processes are
/* notified of the master\'s demise by sending them a SIGTERM signal.
/* DIAGNOSTICS
/* BUGS
/* Need a way to register cleanup actions.
/* SEE ALSO
/* LICENSE
/* .ad
/* .fi
/* The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/* Wietse Venema
/* IBM T.J. Watson Research
/* P.O. Box 704
/* Yorktown Heights, NY 10598, USA
/*
/* Wietse Venema
/* Google, Inc.
/* 111 8th Avenue
/* New York, NY 10011, USA
/*--*/
/* System libraries. */
#include <sys_defs.h>
#include <signal.h>
#include <unistd.h>
/* Utility library. */
#include <msg.h>
#include <posix_signals.h>
#include <killme_after.h>
/* Application-specific. */
#include "master.h"
#ifdef USE_SIG_RETURN
#include <sys/syscall.h>
#undef USE_SIG_PIPE
#else
#define USE_SIG_PIPE
#endif
/* Local stuff. */
#ifdef USE_SIG_PIPE
#include <errno.h>
#include <fcntl.h>
#include <iostuff.h>
#include <events.h>
int master_sig_pipe[2];
#define SIG_PIPE_WRITE_FD master_sig_pipe[1]
#define SIG_PIPE_READ_FD master_sig_pipe[0]
#endif
int master_gotsigchld;
int master_gotsighup;
#ifdef USE_SIG_RETURN
/* master_sighup - register arrival of hangup signal */
static void master_sighup(int sig)
{
/*
* WARNING WARNING WARNING.
*
* This code runs at unpredictable moments, as a signal handler. Don't put
* any code here other than for setting a global flag.
*/
master_gotsighup = sig;
}
/* master_sigchld - register arrival of child death signal */
static void master_sigchld(int sig, int code, struct sigcontext * scp)
{
/*
* WARNING WARNING WARNING.
*
* This code runs at unpredictable moments, as a signal handler. Don't put
* any code here other than for setting a global flag, or code that is
* intended to be run within a signal handler.
*/
master_gotsigchld = sig;
if (scp != NULL && scp->sc_syscall == SYS_select) {
scp->sc_syscall_action = SIG_RETURN;
#ifndef SA_RESTART
} else if (scp != NULL) {
scp->sc_syscall_action = SIG_RESTART;
#endif
}
}
#else
/* master_sighup - register arrival of hangup signal */
static void master_sighup(int sig)
{
int saved_errno = errno;
/*
* WARNING WARNING WARNING.
*
* This code runs at unpredictable moments, as a signal handler. Don't put
* any code here other than for setting a global flag, or code that is
* intended to be run within a signal handler. Restore errno in case we
* are interrupting the epilog of a failed system call.
*/
master_gotsighup = sig;
if (write(SIG_PIPE_WRITE_FD, "", 1) != 1)
msg_warn("write to SIG_PIPE_WRITE_FD failed: %m");
errno = saved_errno;
}
/* master_sigchld - force wakeup from select() */
static void master_sigchld(int unused_sig)
{
int saved_errno = errno;
/*
* WARNING WARNING WARNING.
*
* This code runs at unpredictable moments, as a signal handler. Don't put
* any code here other than for setting a global flag, or code that is
* intended to be run within a signal handler. Restore errno in case we
* are interrupting the epilog of a failed system call.
*/
master_gotsigchld = 1;
if (write(SIG_PIPE_WRITE_FD, "", 1) != 1)
msg_warn("write to SIG_PIPE_WRITE_FD failed: %m");
errno = saved_errno;
}
/* master_sig_event - called upon return from select() */
static void master_sig_event(int unused_event, void *unused_context)
{
char c[1];
while (read(SIG_PIPE_READ_FD, c, 1) > 0)
/* void */ ;
}
#endif
/* master_sigdeath - die, women and children first */
static void master_sigdeath(int sig)
{
const char *myname = "master_sigdeath";
struct sigaction action;
pid_t pid = getpid();
/*
* Set alarm clock here for suicide after 5s.
*/
killme_after(5);
/*
* Terminate all processes in our process group, except ourselves.
*/
sigemptyset(&action.sa_mask);
action.sa_flags = 0;
action.sa_handler = SIG_IGN;
if (sigaction(SIGTERM, &action, (struct sigaction *) 0) < 0)
msg_fatal("%s: sigaction: %m", myname);
if (kill(-pid, SIGTERM) < 0)
msg_fatal("%s: kill process group: %m", myname);
/*
* XXX We're running from a signal handler, and should not call complex
* routines at all, but it would be even worse to silently terminate
* without informing the sysadmin. For this reason, msg(3) was made safe
* for usage by signal handlers that terminate the process.
*/
msg_info("terminating on signal %d", sig);
/*
* Undocumented: when a process runs with PID 1, Linux won't deliver a
* signal unless the process specifies a handler (i.e. SIG_DFL is treated
* as SIG_IGN).
*/
if (init_mode)
/* Don't call exit() from a signal handler. */
_exit(0);
/*
* Deliver the signal to ourselves and clean up. XXX We're running as a
* signal handler and really should not be doing complicated things...
*/
sigemptyset(&action.sa_mask);
action.sa_flags = 0;
action.sa_handler = SIG_DFL;
if (sigaction(sig, &action, (struct sigaction *) 0) < 0)
msg_fatal("%s: sigaction: %m", myname);
if (kill(pid, sig) < 0)
msg_fatal("%s: kill myself: %m", myname);
}
/* master_sigsetup - set up signal handlers */
void master_sigsetup(void)
{
const char *myname = "master_sigsetup";
struct sigaction action;
static int sigs[] = {
SIGINT, SIGQUIT, SIGILL, SIGBUS, SIGSEGV, SIGTERM,
};
unsigned i;
sigemptyset(&action.sa_mask);
action.sa_flags = 0;
/*
* Prepare to kill our children when we receive any of the above signals.
*/
action.sa_handler = master_sigdeath;
for (i = 0; i < sizeof(sigs) / sizeof(sigs[0]); i++)
if (sigaction(sigs[i], &action, (struct sigaction *) 0) < 0)
msg_fatal("%s: sigaction(%d): %m", myname, sigs[i]);
#ifdef USE_SIG_PIPE
if (pipe(master_sig_pipe))
msg_fatal("pipe: %m");
non_blocking(SIG_PIPE_WRITE_FD, NON_BLOCKING);
non_blocking(SIG_PIPE_READ_FD, NON_BLOCKING);
close_on_exec(SIG_PIPE_WRITE_FD, CLOSE_ON_EXEC);
close_on_exec(SIG_PIPE_READ_FD, CLOSE_ON_EXEC);
event_enable_read(SIG_PIPE_READ_FD, master_sig_event, (void *) 0);
#endif
/*
* Intercept SIGHUP (re-read config file) and SIGCHLD (child exit).
*/
#ifdef SA_RESTART
action.sa_flags |= SA_RESTART;
#endif
action.sa_handler = master_sighup;
if (sigaction(SIGHUP, &action, (struct sigaction *) 0) < 0)
msg_fatal("%s: sigaction(%d): %m", myname, SIGHUP);
action.sa_flags |= SA_NOCLDSTOP;
action.sa_handler = master_sigchld;
if (sigaction(SIGCHLD, &action, (struct sigaction *) 0) < 0)
msg_fatal("%s: sigaction(%d): %m", myname, SIGCHLD);
}
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