kdc: add sd_notify start/stop signals

This commit adds optional integration with systemd's state
notifification system.

When built with libsystemd, the KDC notifies systemd once it is
ready to serve and when it begins a clean shutdown, as well as
publishing a status line reporting how many worker processes are
running.

configure.ac

@@ -196,6 +196,22 @@ AM_CONDITIONAL([HAVE_CAPNG], [test "$with_capng" != "no"])
 AC_SUBST([CAPNG_CFLAGS])
 AC_SUBST([CAPNG_LIBS])
 
+dnl libsystemd
+AC_ARG_WITH([systemd],
+  AC_HELP_STRING([--with-systemd], [use libsystemd for sd_notify service notifications @<:@default=check@:>@]),
+  [],
+  [with_systemd=check])
+if test "$with_systemd" != "no"; then
+  PKG_CHECK_MODULES([SYSTEMD], [libsystemd],
+		    [with_systemd=yes],[with_systemd=no])
+fi
+if test "$with_systemd" = "yes"; then
+  AC_DEFINE_UNQUOTED([HAVE_SYSTEMD], 1, [whether libsystemd is available for sd_notify])
+fi
+AM_CONDITIONAL([HAVE_SYSTEMD], [test "$with_systemd" != "no"])
+AC_SUBST([SYSTEMD_CFLAGS])
+AC_SUBST([SYSTEMD_LIBS])
+
 dnl mitdb
 AC_ARG_WITH([mitdb],
   AC_HELP_STRING([--with-mitdb], [Path to MIT Kerberos DB include header and shared object]),

kdc/Makefile.am

@@ -198,12 +198,12 @@ LDADD = $(top_builddir)/lib/hdb/libhdb.la \
 	$(LIB_roken) \
 	$(DB3LIB) $(DB1LIB) $(LMDBLIB) $(NDBMLIB)
 
-kdc_LDADD = libkdc.la $(LDADD) $(LIB_pidfile) $(CAPNG_LIBS)
+kdc_LDADD = libkdc.la $(LDADD) $(LIB_pidfile) $(CAPNG_LIBS) $(SYSTEMD_LIBS)
 
 if FRAMEWORK_SECURITY
 kdc_LDFLAGS = -framework SystemConfiguration -framework CoreFoundation
 endif
-kdc_CFLAGS = $(CAPNG_CFLAGS)
+kdc_CFLAGS = $(CAPNG_CFLAGS) $(SYSTEMD_CFLAGS)
 
 kdc_replay_LDADD = libkdc.la $(LDADD) $(LIB_pidfile)
 kdc_tester_LDADD = libkdc.la $(LDADD) $(LIB_pidfile) $(LIB_heimbase)

kdc/connect.c

@@ -33,6 +33,10 @@
 
 #include "kdc_locl.h"
 
+#ifdef HAVE_SYSTEMD
+#include <systemd/sd-daemon.h>
+#endif
+
 /*
  * a tuple describing on what to listen
  */
@@ -1209,6 +1213,11 @@ start_kdc(krb5_context context,
 
     roken_detach_finish(NULL, daemon_child);
 
+#ifdef HAVE_SYSTEMD
+    sd_notify(0, "READY=1");
+    sd_notify(0, "STATUS=Serving requests");
+#endif
+
 #ifdef HAVE_FORK
     if (!testing_flag) {
         /* Note that we might never execute the body of this loop */
@@ -1250,12 +1259,20 @@ start_kdc(krb5_context context,
                 kdc_log(context, config, 3, "KDC worker process started: %d",
                         pid);
                 num_kdcs++;
+#ifdef HAVE_SYSTEMD
+                sd_notifyf(0, "STATUS=Serving requests; %d of %d KDC worker "
+                           "process(es) running", num_kdcs, max_kdcs);
+#endif
                 /* Slow down the creation of KDCs... */
                 select_sleep(12500);
                 break;
             }
         }
 
+#ifdef HAVE_SYSTEMD
+        sd_notify(0, "STOPPING=1");
+#endif
+
         /* Closing these sockets should cause the kids to die... */
 
         close(islive[0]);
@@ -1307,11 +1324,17 @@ start_kdc(krb5_context context,
         kdc_log(context, config, 3, "KDC master process exiting");
     } else {
         loop(context, config, &d, &ndescr, -1);
+#ifdef HAVE_SYSTEMD
+        sd_notify(0, "STOPPING=1");
+#endif
         kdc_log(context, config, 3, "KDC exiting");
     }
     free(pids);
 #else
     loop(context, config, &d, &ndescr, -1);
+#ifdef HAVE_SYSTEMD
+    sd_notify(0, "STOPPING=1");
+#endif
     kdc_log(context, config, 3, "KDC exiting");
 #endif