From 5c137b7d6af54fb54dfe13b65c933b5b6a4c764c Mon Sep 17 00:00:00 2001
From: Jonathan McDowell <noodles@earth.li>
Date: Tue, 23 Sep 2014 22:41:38 +0100
Subject: [PATCH] Add keyd support for systemd socket activation

If we have libsystemd-daemon available then enable support for
systemd socket activation of keyd. Even if this support is compiled
in we will fall back to the old behaviour of setting up our own
listening Unix domain socket if systemd is not in use.
---
 Makefile.in    |  3 ++-
 configure.ac   |  6 +++++
 debian/control |  2 +-
 keyd.c         | 71 ++++++++++++++++++++++++++++++++++++++------------
 4 files changed, 63 insertions(+), 19 deletions(-)

diff --git a/Makefile.in b/Makefile.in
index c35db1a..c572593 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -78,7 +78,8 @@ endif
 
 keyd: keyd.o $(CORE_OBJS) keydb_$(DBTYPE).o
 	$(CC) $(LDFLAGS) $(PROGS_LDFLAGS_EXTRA) \
-		-o keyd keyd.o $(CORE_OBJS) keydb_$(DBTYPE).o $(LIBS)
+		-o keyd keyd.o $(CORE_OBJS) keydb_$(DBTYPE).o $(LIBS) \
+		@SYSTEMD_LIBS@
 
 keydctl: keydctl.o onak-conf.o ll.o log.o
 	$(CC) $(LDFLAGS) $(PROGS_LDFLAGS_EXTRA) \
diff --git a/configure.ac b/configure.ac
index 09c5ac3..740f79c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -11,6 +11,12 @@ AC_C_BIGENDIAN
 m4_include([m4/ax_lib_nettle.m4])
 
 AX_LIB_NETTLE(auto)
+AC_CHECK_HEADER([systemd/sd-daemon.h], [
+	AC_CHECK_LIB([systemd-daemon], [sd_listen_fds],
+		[AC_DEFINE([HAVE_SYSTEMD], [1], [systemd-daemon is available])
+		AC_SUBST([SYSTEMD_LIBS], [-lsystemd-daemon])
+	])
+])
 
 dnl We should always have these backends available.
 backends="file fs keyd"
diff --git a/debian/control b/debian/control
index 4e21b7a..c9dbfc0 100644
--- a/debian/control
+++ b/debian/control
@@ -3,7 +3,7 @@ Section: net
 Priority: optional
 Maintainer: Jonathan McDowell <noodles@earth.li>
 Uploaders: Ross Burton <ross@debian.org>
-Build-Depends: debhelper (>= 9), dh-autoreconf, libdb-dev, nettle-dev, libcurl4-gnutls-dev | libcurl-dev
+Build-Depends: debhelper (>= 9), dh-autoreconf, libdb-dev, nettle-dev, libcurl4-gnutls-dev | libcurl-dev, libsystemd-daemon-dev
 Standards-Version: 3.9.4.0
 Homepage: http://www.earth.li/projectpurple/progs/onak.html
 Vcs-Browser: http://the.earth.li/gitweb/?p=onak.git;a=summary
diff --git a/keyd.c b/keyd.c
index 18e9ddc..6a171d4 100644
--- a/keyd.c
+++ b/keyd.c
@@ -31,6 +31,12 @@
 #include <time.h>
 #include <unistd.h>
 
+#include "config.h"
+
+#ifdef HAVE_SYSTEMD
+#include <systemd/sd-daemon.h>
+#endif
+
 #include "charfuncs.h"
 #include "cleanup.h"
 #include "keyd.h"
@@ -46,6 +52,10 @@
 /* Maximum number of clients we're prepared to accept at once */
 #define MAX_CLIENTS 16
 
+#ifdef HAVE_SYSTEMD
+static bool using_socket_activation = false;
+#endif
+
 static struct keyd_stats *stats;
 
 static void daemonize(void)
@@ -189,26 +199,47 @@ static int sock_init(const char *sockname)
 	struct sockaddr_un sock;
 	int                fd = -1;
 	int                ret = -1;
+#ifdef HAVE_SYSTEMD
+	int                n;
 
-	fd = socket(PF_UNIX, SOCK_STREAM, 0);
-	if (fd != -1) {
-		ret = fcntl(fd, F_SETFD, FD_CLOEXEC);
-	}
+	n = sd_listen_fds(0);
+	if (n > 1) {
+		logthing(LOGTHING_ERROR,
+			"Too many file descriptors received from systemd.");
+	} else if (n == 1) {
+		fd = SD_LISTEN_FDS_START + 0;
+		if (sd_is_socket_unix(fd, SOCK_STREAM, 1, NULL, 0) <= 0) {
+			logthing(LOGTHING_ERROR,
+				"systemd passed an invalid socket.");
+			fd = -1;
+		}
+		using_socket_activation = true;
+	} else {
+#endif
+		fd = socket(PF_UNIX, SOCK_STREAM, 0);
+		if (fd != -1) {
+			ret = fcntl(fd, F_SETFD, FD_CLOEXEC);
+		}
 
-	if (ret != -1) {
-		sock.sun_family = AF_UNIX;
-		strncpy(sock.sun_path, sockname, sizeof(sock.sun_path) - 1);
-		unlink(sockname);
-		ret = bind(fd, (struct sockaddr *) &sock, sizeof(sock));
-	}
+		if (ret != -1) {
+			sock.sun_family = AF_UNIX;
+			strncpy(sock.sun_path, sockname,
+					sizeof(sock.sun_path) - 1);
+			unlink(sockname);
+			ret = bind(fd, (struct sockaddr *) &sock,
+					sizeof(sock));
+		}
 
-	if (ret != -1) {
-		ret = listen(fd, 5);
-		if (ret == -1) {
-			close(fd);
-			fd = -1;
+		if (ret != -1) {
+			ret = listen(fd, 5);
+			if (ret == -1) {
+				close(fd);
+				fd = -1;
+			}
 		}
+#ifdef HAVE_SYSTEMD
 	}
+#endif
 
 	return fd;
 }
@@ -680,8 +711,14 @@ int main(int argc, char *argv[])
 			}
 		}
 		dbctx->cleanupdb(dbctx);
-		sock_close(fd);
-		unlink(sockname);
+#ifdef HAVE_SYSTEMD
+		if (!using_socket_activation) {
+#endif
+			sock_close(fd);
+			unlink(sockname);
+#ifdef HAVE_SYSTEMD
+		}
+#endif
 	}
 
 	free(stats);
-- 
2.39.5