Add syslog and fatal signal handler feature

I see random ENOTCONN failures in xfstest generic/013 and generic/014
in my branch, but earliest on the 2nd run - takes ~12hours to get
the issue, but then there are no further information logged.
ENOTCONN points to a daemon crash - I need backtraces and a core dump.

This adds optional handling of fatal signals to print a core dump
and optional syslog logging with these new public functions:

fuse_set_fail_signal_handlers()
    In addition to the existing fuse_set_signal_handlers(). This is not
    enabled together with fuse_set_signal_handlers(), as it is change
    in behavior and file systems might already have their own fatal
    handlers.

fuse_log_enable_syslog
    Print logs to syslog instead of stderr

fuse_log_close_syslog
    Close syslog (for now just does closelog())

Code in fuse_signals.c is also updated, to be an array of signals,
and setting signal handlers is now down with a for-loop instead
of one hand coded set_one_signal_handler() per signal.

1 files changed, 10 insertions, 1 deletions

diff --git a/example/passthrough_hp.cc b/example/passthrough_hp.cc
index e3c8225..708a38e 100644
--- a/example/passthrough_hp.cc
+++ b/example/passthrough_hp.cc
@@ -75,6 +75,7 @@
 #include <fstream>
 #include <thread>
 #include <iomanip>
+#include <syslog.h>
 
 using namespace std;
 
@@ -1436,6 +1437,9 @@ int main(int argc, char *argv[]) {
     if (fuse_set_signal_handlers(se) != 0)
         goto err_out2;
 
+    if (fuse_set_fail_signal_handlers(se) != 0)
+        goto err_out2;
+
     // Don't apply umask, use modes exactly as specified
     umask(0);
 
@@ -1452,12 +1456,14 @@ int main(int argc, char *argv[]) {
 
     fuse_daemonize(fs.foreground);
 
+    if (!fs.foreground)
+        fuse_log_enable_syslog("passthrough-hp", LOG_PID | LOG_CONS, LOG_DAEMON);
+
     if (options.count("single"))
         ret = fuse_session_loop(se);
     else
         ret = fuse_session_loop_mt(se, loop_config);
 
-
     fuse_session_unmount(se);
 
 err_out3:
@@ -1469,6 +1475,9 @@ err_out1:
     fuse_loop_cfg_destroy(loop_config);
     fuse_opt_free_args(&args);
 
+    if (!fs.foreground)
+        fuse_log_close_syslog();
+
     return ret ? 1 : 0;
 }