From 0f9c2666aca95eb98eb0ef4f4d8d1473c8ce3fa0 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Thu, 9 Jul 2015 18:36:02 +0000 Subject: handle loss of syslog socket connection 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 when this happens, the default destination address associated with the client socket via connect is no longer valid, and attempts to send produce errors.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. --- src/misc/syslog.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/src/misc/syslog.c b/src/misc/syslog.c index e026f9b4..9dd1ddb5 100644 --- a/src/misc/syslog.c +++ b/src/misc/syslog.c @@ -48,12 +48,8 @@ void closelog(void) static void __openlog() { - int fd = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0); - if (fd < 0) return; - if (connect(fd, (void *)&log_addr, sizeof log_addr) < 0) - close(fd); - else - log_fd = fd; + log_fd = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0); + if (log_fd >= 0) connect(log_fd, (void *)&log_addr, sizeof log_addr); } void openlog(const char *ident, int opt, int facility) @@ -78,6 +74,11 @@ void openlog(const char *ident, int opt, int facility) pthread_setcancelstate(cs, 0); } +static int is_lost_conn(int e) +{ + return e==ECONNREFUSED || e==ECONNRESET || e==ENOTCONN || e==EPIPE; +} + static void _vsyslog(int priority, const char *message, va_list ap) { char timebuf[16]; @@ -107,7 +108,10 @@ static void _vsyslog(int priority, const char *message, va_list ap) if (l2 >= sizeof buf - l) l = sizeof buf - 1; else l += l2; if (buf[l-1] != '\n') buf[l++] = '\n'; - if (send(log_fd, buf, l, 0) < 0 && (log_opt & LOG_CONS)) { + if (send(log_fd, buf, l, 0) < 0 && (!is_lost_conn(errno) + || connect(log_fd, (void *)&log_addr, sizeof log_addr) < 0 + || send(log_fd, buf, l, 0) < 0) + && (log_opt & LOG_CONS)) { fd = open("/dev/console", O_WRONLY|O_NOCTTY|O_CLOEXEC); if (fd >= 0) { dprintf(fd, "%.*s", l-hlen, buf+hlen); -- cgit v1.2.1