From: "Matwey V. Kornilov" <matwey.kornilov@gmail.com>
Date: Tue, 17 Dec 2013 18:16:56 +0400
Subject: [PATCH] Add -systemd option to empd. Check for include
 systemd/sd-daemon.h and wrap systemd code into ifdef-s.


diff --git a/erts/configure.in b/erts/configure.in
index 9ad3671..125e579 100644
--- a/erts/configure.in
+++ b/erts/configure.in
@@ -1565,6 +1565,8 @@ AC_CHECK_MEMBERS([struct ifreq.ifr_enaddr], [], [],
 	 #endif
 	])
 
+AC_CHECK_HEADERS(systemd/sd-daemon.h)
+
 dnl ----------------------------------------------------------------------
 dnl Check the availability for libdlpi
 dnl ----------------------------------------------------------------------
diff --git a/erts/epmd/src/epmd.c b/erts/epmd/src/epmd.c
index 2d55b37..fc58882 100644
--- a/erts/epmd/src/epmd.c
+++ b/erts/epmd/src/epmd.c
@@ -175,6 +175,9 @@ int main(int argc, char** argv)
     g->nodes.reg = g->nodes.unreg = g->nodes.unreg_tail = NULL;
     g->nodes.unreg_count = 0;
     g->active_conn    = 0;
+#ifdef HAVE_SYSTEMD_SD_DAEMON_H
+    g->is_systemd     = 0;
+#endif
 
     for (i = 0; i < MAX_LISTEN_SOCKETS; i++)
 	g->listenfd[i] = -1;
@@ -248,8 +251,12 @@ int main(int argc, char** argv)
 	    else
 		usage(g);
 	    epmd_cleanup_exit(g,0);
-	}
-	else
+#ifdef HAVE_SYSTEMD_SD_DAEMON_H
+	} else if (strcmp(argv[0], "-systemd") == 0) {
+            g->is_systemd = 1;
+            argv++; argc--;
+#endif
+	} else
 	    usage(g);
     }
     dbg_printf(g,1,"epmd running - daemon = %d",g->is_daemon);
@@ -454,6 +461,11 @@ static void usage(EpmdVars *g)
     fprintf(stderr, "        Forcibly unregisters a name with epmd\n");
     fprintf(stderr, "        (only allowed if -relaxed_command_check was given when \n");
     fprintf(stderr, "        epmd was started).\n");
+#ifdef HAVE_SYSTEMD_SD_DAEMON_H
+    fprintf(stderr, "    -systemd\n");
+    fprintf(stderr, "        Wait for socket from systemd. The option makes sense\n");
+    fprintf(stderr, "        when started from .socket unit.\n");
+#endif
     epmd_cleanup_exit(g,1);
 }
 
diff --git a/erts/epmd/src/epmd_int.h b/erts/epmd/src/epmd_int.h
index 656dbd1..bf1ddd8 100644
--- a/erts/epmd/src/epmd_int.h
+++ b/erts/epmd/src/epmd_int.h
@@ -321,6 +321,9 @@ typedef struct {
   int listenfd[MAX_LISTEN_SOCKETS];
   char *addresses;
   char **argv;
+#ifdef HAVE_SYSTEMD_SD_DAEMON_H
+  int is_systemd;
+#endif
 } EpmdVars;
 
 void dbg_printf(EpmdVars*,int,const char*,...);