[PATCH v2 2/4] Read the number of sockets passed by systemd.

[Matthew Leach <matthew@mattleach.net>]

* src/emacs.c (systemd_socket): New variable for storing the socket
  descriptor passed in by systemd.
  (main): Call sd_listen_fds to read the number of sockets passed.
---
 src/emacs.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/src/emacs.c b/src/emacs.c
index 95d1905..df5fade 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_SYSTEMD
+#include <systemd/sd-daemon.h>
+#include <sys/socket.h>
+#endif /* HAVE_SYSTEMD */
+
 #ifdef HAVE_WINDOW_SYSTEM
 #include TERM_HEADER
 #endif /* HAVE_WINDOW_SYSTEM */
@@ -195,6 +200,12 @@ int daemon_pipe[2];
 HANDLE w32_daemon_event;
 #endif
 
+#ifdef HAVE_SYSTEMD
+/* The socket descriptor passed by systemd.  If nothing has been
+   passed, this will be 0. */
+int systemd_socket = 0;
+#endif /* HAVE_SYSTEMD */
+
 /* Save argv and argc.  */
 char **initial_argv;
 int initial_argc;
@@ -997,6 +1008,24 @@ main (int argc, char **argv)
 	  exit (1);
 	}
 
+#ifdef HAVE_SYSTEMD
+      /* 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");
+          systemd_socket = 0;
+        }
+      else if (systemd_socket == 1 &&
+               sd_is_socket (SD_LISTEN_FDS_START,
+                             AF_UNSPEC, SOCK_STREAM, 1) >= 0)
+        systemd_socket = SD_LISTEN_FDS_START;
+      else
+        systemd_socket = 0;
+#endif
+
 #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\
-- 
2.7.4