Rich Felker
0f9c2666ac
when traditional syslogd implementations are restarted, the old server socket ceases to exist and a new unix socket with the same pathname is created. when this happens, the default destination address associated with the client socket via connect is no longer valid, and attempts to send produce errors. this happens despite the socket being datagram type, and is in contrast to the behavior that would be seen with an IP datagram (UDP) socket. in order to avoid a situation where the application is unable to send further syslog messages without calling closelog, this patch makes syslog attempt to reconnect the socket when send returns an error indicating a lost connection. additionally, initial failure to connect the socket no longer results in the socket being closed. this ensures that an application which calls openlog to reserve the socket file descriptor will not run into a situation where transient connection failure (e.g. due to syslogd restart) prevents fd reservation. however, applications which may be unable to connect the socket later (e.g. due to chroot, restricted permissions, seccomp, etc.) will still fail to log if the syslog socket cannot be connected at openlog time or if it has to be reconnected later.
145 lines
3.1 KiB
C
145 lines
3.1 KiB
C
#include <stdarg.h>
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#include <sys/socket.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <syslog.h>
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#include <time.h>
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#include <signal.h>
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#include <string.h>
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#include <pthread.h>
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#include <errno.h>
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#include <fcntl.h>
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#include "libc.h"
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static volatile int lock[2];
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static char log_ident[32];
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static int log_opt;
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static int log_facility = LOG_USER;
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static int log_mask = 0xff;
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static int log_fd = -1;
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int setlogmask(int maskpri)
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{
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LOCK(lock);
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int ret = log_mask;
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if (maskpri) log_mask = maskpri;
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UNLOCK(lock);
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return ret;
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}
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static const struct {
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short sun_family;
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char sun_path[9];
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} log_addr = {
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AF_UNIX,
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"/dev/log"
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};
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void closelog(void)
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{
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int cs;
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pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
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LOCK(lock);
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close(log_fd);
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log_fd = -1;
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UNLOCK(lock);
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pthread_setcancelstate(cs, 0);
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}
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static void __openlog()
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{
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log_fd = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0);
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if (log_fd >= 0) connect(log_fd, (void *)&log_addr, sizeof log_addr);
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}
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void openlog(const char *ident, int opt, int facility)
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{
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int cs;
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pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
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LOCK(lock);
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if (ident) {
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size_t n = strnlen(ident, sizeof log_ident - 1);
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memcpy(log_ident, ident, n);
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log_ident[n] = 0;
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} else {
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log_ident[0] = 0;
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}
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log_opt = opt;
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log_facility = facility;
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if ((opt & LOG_NDELAY) && log_fd<0) __openlog();
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UNLOCK(lock);
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pthread_setcancelstate(cs, 0);
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}
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static int is_lost_conn(int e)
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{
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return e==ECONNREFUSED || e==ECONNRESET || e==ENOTCONN || e==EPIPE;
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}
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static void _vsyslog(int priority, const char *message, va_list ap)
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{
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char timebuf[16];
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time_t now;
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struct tm tm;
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char buf[1024];
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int errno_save = errno;
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int pid;
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int l, l2;
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int hlen;
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int fd;
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if (log_fd < 0) __openlog();
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if (!(priority & LOG_FACMASK)) priority |= log_facility;
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now = time(NULL);
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gmtime_r(&now, &tm);
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strftime(timebuf, sizeof timebuf, "%b %e %T", &tm);
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pid = (log_opt & LOG_PID) ? getpid() : 0;
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l = snprintf(buf, sizeof buf, "<%d>%s %n%s%s%.0d%s: ",
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priority, timebuf, &hlen, log_ident, "["+!pid, pid, "]"+!pid);
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errno = errno_save;
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l2 = vsnprintf(buf+l, sizeof buf - l, message, ap);
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if (l2 >= 0) {
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if (l2 >= sizeof buf - l) l = sizeof buf - 1;
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else l += l2;
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if (buf[l-1] != '\n') buf[l++] = '\n';
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if (send(log_fd, buf, l, 0) < 0 && (!is_lost_conn(errno)
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|| connect(log_fd, (void *)&log_addr, sizeof log_addr) < 0
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|| send(log_fd, buf, l, 0) < 0)
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&& (log_opt & LOG_CONS)) {
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fd = open("/dev/console", O_WRONLY|O_NOCTTY|O_CLOEXEC);
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if (fd >= 0) {
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dprintf(fd, "%.*s", l-hlen, buf+hlen);
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close(fd);
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}
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}
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if (log_opt & LOG_PERROR) dprintf(2, "%.*s", l-hlen, buf+hlen);
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}
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}
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void __vsyslog(int priority, const char *message, va_list ap)
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{
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int cs;
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if (!(log_mask & LOG_MASK(priority&7)) || (priority&~0x3ff)) return;
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pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
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LOCK(lock);
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_vsyslog(priority, message, ap);
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UNLOCK(lock);
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pthread_setcancelstate(cs, 0);
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}
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void syslog(int priority, const char *message, ...)
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{
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va_list ap;
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va_start(ap, message);
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__vsyslog(priority, message, ap);
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va_end(ap);
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}
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weak_alias(__vsyslog, vsyslog);
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