systemd: directly notify systemd instead of using sd_notify

The sd_notify method is used to tell systemd when libvirtd
has finished starting up. All it does is send a datagram
containing the string parameter to systemd on a UNIX socket
named in the NOTIFY_SOCKET environment variable. Rather than
pulling in the systemd libraries for this, just code the
notification directly in libvirt as this is a stable ABI
from systemd's POV which explicitly allows independant
implementations:

See "Reimplementable Independently" column in the
"$NOTIFY_SOCKET Daemon Notifications" row:

https://www.freedesktop.org/wiki/Software/systemd/InterfacePortabilityAndStabilityChart/

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1314881

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

configure.ac

@@ -256,7 +256,6 @@ LIBVIRT_CHECK_SANLOCK
 LIBVIRT_CHECK_SASL
 LIBVIRT_CHECK_SELINUX
 LIBVIRT_CHECK_SSH2
-LIBVIRT_CHECK_SYSTEMD_DAEMON
 LIBVIRT_CHECK_UDEV
 LIBVIRT_CHECK_WIRESHARK
 LIBVIRT_CHECK_NSS
@@ -2787,7 +2786,6 @@ LIBVIRT_RESULT_SANLOCK
 LIBVIRT_RESULT_SASL
 LIBVIRT_RESULT_SELINUX
 LIBVIRT_RESULT_SSH2
-LIBVIRT_RESULT_SYSTEMD_DAEMON
 LIBVIRT_RESULT_UDEV
 LIBVIRT_RESULT_WIRESHARK
 LIBVIRT_RESULT_NSS

libvirt.spec.in

@@ -79,7 +79,6 @@
 %define with_firewalld     0%{!?_without_firewalld:0}
 %define with_libssh2       0%{!?_without_libssh2:0}
 %define with_wireshark     0%{!?_without_wireshark:0}
-%define with_systemd_daemon 0%{!?_without_systemd_daemon:0}
 %define with_pm_utils      1
 
 # Finally set the OS / architecture specific special cases
@@ -133,7 +132,6 @@
 # Fedora has systemd, libvirt still used sysvinit there.
 %if 0%{?fedora} || 0%{?rhel} >= 7
     %define with_systemd 1
-    %define with_systemd_daemon 1
     %define with_pm_utils 0
 %endif
 
@@ -268,9 +266,6 @@ BuildRequires: python
 %if %{with_systemd}
 BuildRequires: systemd-units
 %endif
-%if %{with_systemd_daemon}
-BuildRequires: systemd-devel
-%endif
 %if %{with_xen} || %{with_libxl}
 BuildRequires: xen-devel
 %endif
@@ -1061,12 +1056,6 @@ rm -rf .git
     %define arg_wireshark --without-wireshark-dissector
 %endif
 
-%if %{with_systemd_daemon}
-    %define arg_systemd_daemon --with-systemd-daemon
-%else
-    %define arg_systemd_daemon --without-systemd-daemon
-%endif
-
 %if %{with_pm_utils}
     %define arg_pm_utils --with-pm-utils
 %else
@@ -1157,7 +1146,6 @@ rm -f po/stamp-po
            --with-driver-modules \
            %{?arg_firewalld} \
            %{?arg_wireshark} \
-           %{?arg_systemd_daemon} \
            %{?arg_pm_utils} \
            --with-nss-plugin \
            %{arg_packager} \

m4/virt-systemd-daemon.m4

@@ -1,34 +0,0 @@
-dnl The libsystemd-daemon.so library
-dnl
-dnl Copyright (C) 2012-2013 Red Hat, Inc.
-dnl
-dnl This library is free software; you can redistribute it and/or
-dnl modify it under the terms of the GNU Lesser General Public
-dnl License as published by the Free Software Foundation; either
-dnl version 2.1 of the License, or (at your option) any later version.
-dnl
-dnl This library is distributed in the hope that it will be useful,
-dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
-dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-dnl Lesser General Public License for more details.
-dnl
-dnl You should have received a copy of the GNU Lesser General Public
-dnl License along with this library.  If not, see
-dnl <http://www.gnu.org/licenses/>.
-dnl
-
-AC_DEFUN([LIBVIRT_CHECK_SYSTEMD_DAEMON],[
-  LIBVIRT_CHECK_PKG([SYSTEMD_DAEMON], [libsystemd-daemon], [0.27.1])
-
-    old_CFLAGS="$CFLAGS"
-    old_LIBS="$LIBS"
-    CFLAGS="$CFLAGS $SYSTEMD_DAEMON_CFLAGS"
-    LIBS="$LIBS $SYSTEMD_DAEMON_LIBS"
-    AC_CHECK_FUNCS([sd_notify])
-    CFLAGS="$old_CFLAGS"
-    LIBS="$old_LIBS"
-])
-
-AC_DEFUN([LIBVIRT_RESULT_SYSTEMD_DAEMON],[
-  LIBVIRT_RESULT_LIB([SYSTEMD_DAEMON])
-])

src/Makefile.am

@@ -1107,12 +1107,12 @@ libvirt_util_la_SOURCES =					\
 libvirt_util_la_CFLAGS = $(CAPNG_CFLAGS) $(YAJL_CFLAGS) $(LIBNL_CFLAGS) \
 		$(AM_CFLAGS) $(AUDIT_CFLAGS) $(DEVMAPPER_CFLAGS) \
 		$(DBUS_CFLAGS) $(LDEXP_LIBM) $(NUMACTL_CFLAGS)	\
-		$(SYSTEMD_DAEMON_CFLAGS) $(POLKIT_CFLAGS) $(GNUTLS_CFLAGS) \
+		$(POLKIT_CFLAGS) $(GNUTLS_CFLAGS) \
 		-I$(srcdir)/conf
 libvirt_util_la_LIBADD = $(CAPNG_LIBS) $(YAJL_LIBS) $(LIBNL_LIBS) \
 		$(THREAD_LIBS) $(AUDIT_LIBS) $(DEVMAPPER_LIBS) \
 		$(LIB_CLOCK_GETTIME) $(DBUS_LIBS) $(MSCOM_LIBS) $(LIBXML_LIBS) \
-		$(SECDRIVER_LIBS) $(NUMACTL_LIBS) $(SYSTEMD_DAEMON_LIBS) \
+		$(SECDRIVER_LIBS) $(NUMACTL_LIBS) \
 		$(POLKIT_LIBS)
 
 

src/util/virsystemd.c

@@ -21,8 +21,9 @@
 
 #include <config.h>
 
-#ifdef WITH_SYSTEMD_DAEMON
+#include <sys/socket.h>
-# include <systemd/sd-daemon.h>
+#ifdef HAVE_SYS_UN_H
+# include <sys/un.h>
 #endif
 
 #include "virsystemd.h"
@@ -34,6 +35,7 @@
 #include "virutil.h"
 #include "virlog.h"
 #include "virerror.h"
+#include "virfile.h"
 
 #define VIR_FROM_THIS VIR_FROM_SYSTEMD
 
@@ -480,9 +482,50 @@ int virSystemdTerminateMachine(const char *name)
 void
 virSystemdNotifyStartup(void)
 {
-#ifdef WITH_SYSTEMD_DAEMON
+#ifdef HAVE_SYS_UN_H
-    sd_notify(0, "READY=1");
+    const char *path;
-#endif
+    const char *msg = "READY=1";
+    int fd;
+    struct sockaddr_un un = {
+        .sun_family = AF_UNIX,
+    };
+    struct iovec iov = {
+        .iov_base = (char *)msg,
+        .iov_len = strlen(msg),
+    };
+    struct msghdr mh = {
+        .msg_name = &un,
+        .msg_namelen = sizeof(un),
+        .msg_iov = &iov,
+        .msg_iovlen = 1,
+    };
+
+    if (!(path = virGetEnvBlockSUID("NOTIFY_SOCKET"))) {
+        VIR_DEBUG("Skipping systemd notify, not requested");
+        return;
+    }
+
+    /* NB sun_path field is *not* NUL-terminated, hence >, not >= */
+    if (strlen(path) > sizeof(un.sun_path)) {
+        VIR_WARN("Systemd notify socket path '%s' too long", path);
+        return;
+    }
+
+    memcpy(un.sun_path, path, strlen(path));
+    if (un.sun_path[0] == '@')
+        un.sun_path[0] = '\0';
+
+    fd = socket(AF_UNIX, SOCK_DGRAM, 0);
+    if (fd < 0) {
+        VIR_WARN("Unable to create socket FD");
+        return;
+    }
+
+    if (sendmsg(fd, &mh, MSG_NOSIGNAL) < 0)
+        VIR_WARN("Failed to notify systemd");
+
+    VIR_FORCE_CLOSE(fd);
+#endif /* HAVE_SYS_UN_H */
 }
 
 static int