Log to syslog when running in background

Log messages are unconditionally written to stderr, and are therefore
lost after the fork when running in the background (`-g`). If syslog
support is detected at compile time, and provided we're not on a
platform for which an alternative non-stderr logging facility is
provided (i.e. Windows), send log messages to syslog when running in the
background.

Author: chrisnovakovic

CMakeLists.txt

@@ -103,6 +103,10 @@ set(SERVER_DEBUG ${ENABLE_DEBUG_SERVER})
 
 
 check_symbol_exists(getopt "unistd.h" HAVE_GETOPT)
+check_symbol_exists(vsyslog "syslog.h" HAVE_VSYSLOG)
+if (HAVE_VSYSLOG)
+  add_compile_definitions(HAVE_VSYSLOG)
+endif ()
 
 # Does the compiler accept the "format" attribute?
 try_compile(HAVE_ATTR_FORMAT

src/log.c

@@ -35,12 +35,74 @@
 #include <sys/timeb.h>
 #endif
 
+#if defined(HAVE_VSYSLOG)
+#include <syslog.h>
+#endif
+
 #include "log.h"
 
+stubby_log_target_t log_target = STUBBY_LOG_STDERR;
+
+#if defined(HAVE_VSYSLOG)
+static void stubby_syslog_open()
+{
+	static int is_syslog_open = 0;
+
+	if (!is_syslog_open) {
+		openlog("stubby", LOG_PID, LOG_DAEMON);
+		is_syslog_open = 1;
+	}
+}
+
+static int stubby_syslog_priority(getdns_loglevel_type level)
+{
+	int priority = LOG_INFO;
+
+	switch (level) {
+		case GETDNS_LOG_EMERG:
+			priority = LOG_EMERG;
+			break;
+		case GETDNS_LOG_ALERT:
+			priority = LOG_ALERT;
+			break;
+		case GETDNS_LOG_CRIT:
+			priority = LOG_CRIT;
+			break;
+		case GETDNS_LOG_ERR:
+			priority = LOG_ERR;
+			break;
+		case GETDNS_LOG_WARNING:
+			priority = LOG_WARNING;
+			break;
+		case GETDNS_LOG_NOTICE:
+			priority = LOG_NOTICE;
+			break;
+		case GETDNS_LOG_INFO:
+			priority = LOG_INFO;
+			break;
+		case GETDNS_LOG_DEBUG:
+			priority = LOG_DEBUG;
+			break;
+	}
+
+	return priority;
+}
+#endif
+
 static void default_stubby_verror(getdns_loglevel_type level, const char *fmt, va_list ap)
 {
-        (void) level;
-        (void) vfprintf(stderr, fmt, ap);
+	switch (log_target) {
+#if defined(HAVE_VSYSLOG)
+		case STUBBY_LOG_SYSLOG:
+			stubby_syslog_open();
+			vsyslog(stubby_syslog_priority(level), fmt, ap);
+			break;
+#endif
+		case STUBBY_LOG_STDERR:
+			(void) level;
+			(void) vfprintf(stderr, fmt, ap);
+			break;
+	}
 }
 
 long log_level = GETDNS_LOG_DEBUG + 1;
@@ -49,27 +111,40 @@ static void default_stubby_vlog(void *userarg, uint64_t system,
                                 getdns_loglevel_type level,
                                 const char *fmt, va_list ap)
 {
-        struct timeval tv;
-        struct tm tm;
-        char buf[10];
+	(void)userarg; (void)system;
+
+	switch (log_target) {
+#if defined(HAVE_VSYSLOG)
+		case STUBBY_LOG_SYSLOG:
+			stubby_syslog_open();
+			vsyslog(stubby_syslog_priority(level), fmt, ap);
+			break;
+#endif
+		case STUBBY_LOG_STDERR:
+			(void)0;
+			struct timeval tv;
+			struct tm tm;
+			char buf[10];
 #if defined(STUBBY_ON_WINDOWS)
-        struct _timeb timeb;
-        time_t tsec;
-	if (level > log_level) return;
-
-        _ftime_s(&timeb);
-        tsec = (time_t)timeb.time;
-        tv.tv_usec = timeb.millitm * 1000;
-        gmtime_s(&tm, &tsec);
+			struct _timeb timeb;
+			time_t tsec;
+			if (level > log_level) return;
+
+			_ftime_s(&timeb);
+			tsec = (time_t)timeb.time;
+			tv.tv_usec = timeb.millitm * 1000;
+			gmtime_s(&tm, &tsec);
 #else
-	if (level > log_level) return;
-        gettimeofday(&tv, NULL);
-        gmtime_r(&tv.tv_sec, &tm);
+			if (level > log_level) return;
+			gettimeofday(&tv, NULL);
+			gmtime_r(&tv.tv_sec, &tm);
 #endif
-        strftime(buf, 10, "%H:%M:%S", &tm);
-        (void)userarg; (void)system; (void)level;
-        (void) fprintf(stderr, "[%s.%.6d] STUBBY: ", buf, (int)tv.tv_usec);
-        (void) vfprintf(stderr, fmt, ap);
+			strftime(buf, 10, "%H:%M:%S", &tm);
+			(void)level;
+			(void) fprintf(stderr, "[%s.%.6d] STUBBY: ", buf, (int)tv.tv_usec);
+			(void) vfprintf(stderr, fmt, ap);
+			break;
+	}
 }
 
 static stubby_verror_t stubby_verror = default_stubby_verror;
@@ -114,6 +189,11 @@ void stubby_set_log_funcs(stubby_verror_t errfunc, stubby_vlog_t logfunc)
         stubby_vlog = logfunc;
 }
 
+void stubby_set_log_target(stubby_log_target_t target)
+{
+	log_target = target;
+}
+
 void stubby_set_getdns_logging(getdns_context *context, int loglevel)
 {
         (void) getdns_context_set_logfunc(context, NULL, GETDNS_LOG_UPSTREAM_STATS, loglevel, stubby_vlog);

src/log.h

@@ -34,6 +34,13 @@
 #include <getdns/getdns.h>
 #include <getdns/getdns_extra.h>
 
+typedef enum stubby_log_target {
+#if defined(HAVE_VSYSLOG)
+	STUBBY_LOG_SYSLOG,
+#endif
+	STUBBY_LOG_STDERR
+} stubby_log_target_t;
+
 typedef void(*stubby_verror_t)(getdns_loglevel_type level, const char *fmt, va_list ap);
 typedef void(*stubby_vlog_t)(void *userarg, uint64_t system,
                              getdns_loglevel_type level,
@@ -50,6 +57,7 @@ void stubby_warning(const char *fmt, ...);
 void stubby_debug(const char *fmt, ...);
 
 void stubby_set_log_funcs(stubby_verror_t errfunc, stubby_vlog_t logfunc);
+void stubby_set_log_target(stubby_log_target_t target);
 
 void stubby_set_getdns_logging(getdns_context *context, int loglevel);
 

src/stubby.c

@@ -169,6 +169,12 @@ main(int argc, char **argv)
 	}
 #endif
 
+#if defined(HAVE_VSYSLOG) && !defined(STUBBY_ON_WINDOWS)
+	if (!run_in_foreground) {
+		stubby_set_log_target(STUBBY_LOG_SYSLOG);
+	}
+#endif
+
 	if ((r = getdns_context_create(&context, 1))) {
 		stubby_error("Create context failed: %s",
 		        stubby_getdns_strerror(r));