From da80bd7ebd0e9ba1b948be7ba0a0f9cafe6dd4c3 Mon Sep 17 00:00:00 2001
From: Matthew Leach <matthew@mattleach.net>
Date: Sat, 26 Mar 2016 18:50:14 +0000
Subject: [PATCH 3/4] Read the number of sockets passed by systemd.

* src/emacs.c (main): Call sd_listen_fds to read the number of sockets
  passed and call `set_external_socket_descriptor' to set the external
  socket.
---
 src/emacs.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/src/emacs.c b/src/emacs.c
index 95d1905..6a77293 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -56,6 +56,11 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <binary-io.h>
 #endif
 
+#ifdef HAVE_LIBSYSTEMD
+#include <systemd/sd-daemon.h>
+#include <sys/socket.h>
+#endif /* HAVE_LIBSYSTEMD */
+
 #ifdef HAVE_WINDOW_SYSTEM
 #include TERM_HEADER
 #endif /* HAVE_WINDOW_SYSTEM */
@@ -676,6 +681,9 @@ main (int argc, char **argv)
   char dname_arg2[80];
 #endif
   char *ch_to_dir = 0;
+#ifdef HAVE_LIBSYSTEMD
+  int systemd_socket;
+#endif
 
   /* If we use --chdir, this records the original directory.  */
   char *original_pwd = 0;
@@ -997,6 +1005,20 @@ main (int argc, char **argv)
 	  exit (1);
 	}
 
+#ifdef HAVE_LIBSYSTEMD
+      /* Read the number of sockets passed through by systemd. */
+      systemd_socket = sd_listen_fds(1);
+
+      if (systemd_socket > 1)
+        fprintf (stderr, "\nWarning: systemd has passed more than one socket to the Emacs process.\n\
+Try adding 'Accept=false' in the Emacs socket unit file.\n");
+
+      else if (systemd_socket == 1 &&
+               sd_is_socket (SD_LISTEN_FDS_START,
+                             AF_UNSPEC, SOCK_STREAM, 1) >= 0)
+        set_external_socket_descriptor (SD_LISTEN_FDS_START);
+#endif /* HAVE_LIBSYSTEMD */
+
 #ifndef DAEMON_MUST_EXEC
 #ifdef USE_GTK
       fprintf (stderr, "\nWarning: due to a long standing Gtk+ bug\nhttp://bugzilla.gnome.org/show_bug.cgi?id=85715\n\
-- 
2.8.0