Replace two fat signal handlers with function calls in
the main I/O multiplex loop. select() now watches a pipe which is written by the new skinny signal handlers and the received signals are handled inside the loop sequencially. This eliminates a complex signal mask to guarantee async-signal safety.
This commit is contained in:
Hiroki Sato
parent
a2795311af
commit
34694ebe05
@ -321,8 +321,9 @@ static int LogFacPri; /* Put facility and priority in log message: */
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static int KeepKernFac; /* Keep remotely logged kernel facility */
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static int needdofsync = 0; /* Are any file(s) waiting to be fsynced? */
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static struct pidfh *pfh;
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static int sigp[2]; /* Pipe to catch a signal during select(). */
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static volatile sig_atomic_t MarkSet, WantDie;
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static volatile sig_atomic_t MarkSet, WantDie, WantInitialize, WantReapchild;
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static int allowaddr(char *);
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static int addfile(struct filed *);
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@ -340,6 +341,7 @@ static void dofsync(void);
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static void domark(int);
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static void fprintlog(struct filed *, int, const char *);
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static void init(int);
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static void init_sh(int);
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static void logerror(const char *);
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static void logmsg(int, const char *, const char *, int);
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static void log_deadchild(pid_t, int, const char *);
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@ -347,11 +349,13 @@ static void markit(void);
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static int socksetup(struct peer *);
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static int socklist_recv_file(struct socklist *);
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static int socklist_recv_sock(struct socklist *);
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static int socklist_recv_signal(struct socklist *);
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static int skip_message(const char *, const char *, int);
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static void printline(const char *, char *, int);
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static void printsys(char *);
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static int p_open(const char *, pid_t *);
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static void reapchild(int);
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static void reapchild_sh(int);
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static const char *ttymsg_check(struct iovec *, int, char *, int);
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static void usage(void);
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static int validate(struct sockaddr *, const char *);
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@ -435,7 +439,6 @@ main(int argc, char *argv[])
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struct timeval tv, *tvp;
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struct peer *pe;
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struct socklist *sl;
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sigset_t mask;
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pid_t ppid = 1, spid;
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char *p;
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@ -578,6 +581,17 @@ main(int argc, char *argv[])
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if ((argc -= optind) != 0)
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usage();
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/* Pipe to catch a signal during select(). */
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s = pipe2(sigp, O_NONBLOCK);
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if (s < 0) {
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err(1, "cannot open a pipe for signals");
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} else {
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addsock(NULL, 0, &(struct socklist){
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.sl_socket = sigp[1],
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.sl_recv = socklist_recv_signal
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});
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}
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/* Listen by default: /dev/klog. */
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s = open(_PATH_KLOG, O_RDONLY|O_NONBLOCK, 0);
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if (s < 0) {
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@ -632,19 +646,8 @@ main(int argc, char *argv[])
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(void)signal(SIGTERM, dodie);
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(void)signal(SIGINT, Debug ? dodie : SIG_IGN);
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(void)signal(SIGQUIT, Debug ? dodie : SIG_IGN);
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/*
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* We don't want the SIGCHLD and SIGHUP handlers to interfere
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* with each other; they are likely candidates for being called
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* simultaneously (SIGHUP closes pipe descriptor, process dies,
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* SIGCHLD happens).
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*/
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sigemptyset(&mask);
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sigaddset(&mask, SIGHUP);
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(void)sigaction(SIGCHLD, &(struct sigaction){
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.sa_handler = reapchild,
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.sa_mask = mask,
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.sa_flags = SA_RESTART
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}, NULL);
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(void)signal(SIGHUP, init_sh);
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(void)signal(SIGCHLD, reapchild_sh);
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(void)signal(SIGALRM, domark);
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(void)signal(SIGPIPE, SIG_IGN); /* We'll catch EPIPE instead. */
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(void)alarm(TIMERINTVL);
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@ -654,16 +657,6 @@ main(int argc, char *argv[])
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dprintf("off & running....\n");
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init(0);
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/* prevent SIGHUP and SIGCHLD handlers from running in parallel */
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sigemptyset(&mask);
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sigaddset(&mask, SIGCHLD);
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(void)sigaction(SIGHUP, &(struct sigaction){
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.sa_handler = init,
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.sa_mask = mask,
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.sa_flags = SA_RESTART
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}, NULL);
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tvp = &tv;
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tv.tv_sec = tv.tv_usec = 0;
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@ -677,6 +670,12 @@ main(int argc, char *argv[])
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errx(1, "calloc fd_set");
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for (;;) {
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if (Initialized == 0)
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init(0);
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else if (WantInitialize)
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init(WantInitialize);
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if (WantReapchild)
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reapchild(WantReapchild);
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if (MarkSet)
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markit();
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if (WantDie)
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@ -715,6 +714,19 @@ main(int argc, char *argv[])
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free(fdsr);
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}
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static int
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socklist_recv_signal(struct socklist *sl __unused)
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{
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ssize_t len;
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static char buf[BUFSIZ];
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/* Clear an wake-up signal by reading dummy data. */
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while ((len = read(sigp[0], buf, sizeof(buf))) > 0)
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;
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return (0);
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}
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static int
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socklist_recv_sock(struct socklist *sl)
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{
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@ -987,7 +999,7 @@ static void
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logmsg(int pri, const char *msg, const char *from, int flags)
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{
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struct filed *f;
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int i, fac, msglen, omask, prilev;
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int i, fac, msglen, prilev;
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const char *timestamp;
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char prog[NAME_MAX+1];
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char buf[MAXLINE+1];
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@ -995,8 +1007,6 @@ logmsg(int pri, const char *msg, const char *from, int flags)
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dprintf("logmsg: pri %o, flags %x, from %s, msg %s\n",
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pri, flags, from, msg);
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omask = sigblock(sigmask(SIGHUP)|sigmask(SIGALRM));
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/*
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* Check to see if msg looks non-standard.
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*/
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@ -1027,10 +1037,8 @@ logmsg(int pri, const char *msg, const char *from, int flags)
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fac = LOG_FAC(pri);
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/* Check maximum facility number. */
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if (fac > LOG_NFACILITIES) {
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(void)sigsetmask(omask);
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if (fac > LOG_NFACILITIES)
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return;
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}
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prilev = LOG_PRI(pri);
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@ -1067,7 +1075,6 @@ logmsg(int pri, const char *msg, const char *from, int flags)
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close(f->f_file);
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f->f_file = -1;
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}
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(void)sigsetmask(omask);
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return;
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}
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STAILQ_FOREACH(f, &fhead, next) {
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@ -1139,7 +1146,6 @@ logmsg(int pri, const char *msg, const char *from, int flags)
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}
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}
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}
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(void)sigsetmask(omask);
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}
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static void
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@ -1506,6 +1512,17 @@ ttymsg_check(struct iovec *iov, int iovcnt, char *line, int tmout)
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return ttymsg(iov, iovcnt, line, tmout);
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}
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static void
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reapchild_sh(int signo)
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{
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static char buf[BUFSIZ];
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WantReapchild = signo;
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/* Send an wake-up signal to the select() loop. */
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read(sigp[0], buf, sizeof(buf));
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write(sigp[1], &signo, sizeof(signo));
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}
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static void
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reapchild(int signo __unused)
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{
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@ -1514,10 +1531,6 @@ reapchild(int signo __unused)
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struct filed *f;
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while ((pid = wait3(&status, WNOHANG, (struct rusage *)NULL)) > 0) {
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if (!Initialized)
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/* Don't tell while we are initting. */
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continue;
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/* First, look if it's a process from the dead queue. */
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if (deadq_removebypid(pid))
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continue;
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@ -1532,6 +1545,7 @@ reapchild(int signo __unused)
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}
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}
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}
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WantReapchild = 0;
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}
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/*
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@ -1541,7 +1555,6 @@ static const char *
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cvthname(struct sockaddr *f)
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{
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int error, hl;
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sigset_t omask, nmask;
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static char hname[NI_MAXHOST], ip[NI_MAXHOST];
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dprintf("cvthname(%d) len = %d\n", f->sa_family, f->sa_len);
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@ -1556,12 +1569,8 @@ cvthname(struct sockaddr *f)
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if (!resolve)
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return (ip);
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sigemptyset(&nmask);
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sigaddset(&nmask, SIGHUP);
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sigprocmask(SIG_BLOCK, &nmask, &omask);
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error = getnameinfo(f, f->sa_len, hname, sizeof(hname),
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NULL, 0, NI_NAMEREQD);
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sigprocmask(SIG_SETMASK, &omask, NULL);
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if (error) {
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dprintf("Host name for your address (%s) unknown\n", ip);
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return (ip);
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@ -1616,11 +1625,8 @@ die(int signo)
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{
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struct filed *f;
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struct socklist *sl;
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int was_initialized;
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char buf[100];
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was_initialized = Initialized;
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Initialized = 0; /* Don't log SIGCHLDs. */
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STAILQ_FOREACH(f, &fhead, next) {
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/* flush any pending output */
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if (f->f_prevcount)
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@ -1628,7 +1634,6 @@ die(int signo)
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if (f->f_type == F_PIPE && f->fu_pipe_pid > 0)
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close_filed(f);
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}
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Initialized = was_initialized;
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if (signo) {
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dprintf("syslogd: exiting on signal %d\n", signo);
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(void)snprintf(buf, sizeof(buf), "exiting on signal %d", signo);
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@ -1792,6 +1797,17 @@ readconfigfile(FILE *cf, int allow_includes)
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/*
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* INIT -- Initialize syslogd from configuration table
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*/
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static void
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init_sh(int signo)
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{
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static char buf[BUFSIZ];
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WantInitialize = signo;
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/* Send an wake-up signal to the select() loop. */
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read(sigp[0], buf, sizeof(buf));
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write(sigp[1], &signo, sizeof(signo));
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}
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static void
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init(int signo)
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{
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@ -1804,6 +1820,7 @@ init(int signo)
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char bootfileMsg[LINE_MAX];
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dprintf("init\n");
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WantInitialize = 0;
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/*
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* Load hostname (may have changed).
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@ -2669,7 +2686,6 @@ p_open(const char *prog, pid_t *rpid)
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{
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int pfd[2], nulldesc;
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pid_t pid;
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sigset_t omask, mask;
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char *argv[4]; /* sh -c cmd NULL */
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char errmsg[200];
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@ -2679,17 +2695,13 @@ p_open(const char *prog, pid_t *rpid)
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/* we are royally screwed anyway */
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return (-1);
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sigemptyset(&mask);
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sigaddset(&mask, SIGALRM);
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sigaddset(&mask, SIGHUP);
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sigprocmask(SIG_BLOCK, &mask, &omask);
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switch ((pid = fork())) {
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case -1:
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sigprocmask(SIG_SETMASK, &omask, 0);
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close(nulldesc);
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return (-1);
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case 0:
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(void)setsid(); /* Avoid catching SIGHUPs. */
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argv[0] = strdup("sh");
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argv[1] = strdup("-c");
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argv[2] = strdup(prog);
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@ -2700,19 +2712,11 @@ p_open(const char *prog, pid_t *rpid)
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}
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alarm(0);
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(void)setsid(); /* Avoid catching SIGHUPs. */
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/*
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* Throw away pending signals, and reset signal
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* behaviour to standard values.
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*/
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signal(SIGALRM, SIG_IGN);
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signal(SIGHUP, SIG_IGN);
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sigprocmask(SIG_SETMASK, &omask, 0);
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signal(SIGPIPE, SIG_DFL);
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signal(SIGQUIT, SIG_DFL);
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signal(SIGALRM, SIG_DFL);
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signal(SIGHUP, SIG_DFL);
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/* Restore signals marked as SIG_IGN. */
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(void)signal(SIGINT, SIG_DFL);
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(void)signal(SIGQUIT, SIG_DFL);
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(void)signal(SIGPIPE, SIG_DFL);
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dup2(pfd[0], STDIN_FILENO);
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dup2(nulldesc, STDOUT_FILENO);
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@ -2722,8 +2726,6 @@ p_open(const char *prog, pid_t *rpid)
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(void)execvp(_PATH_BSHELL, argv);
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_exit(255);
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}
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sigprocmask(SIG_SETMASK, &omask, 0);
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close(nulldesc);
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close(pfd[0]);
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/*
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