dnsmasq: allow custom configuration via files in /etc/NetworkManager/dnsmasq.d (bgo #679628)

We don't use the default dnsmasq directory because packages often drop files
there that don't take account of NM's specific use-case and end up conflicting
with the specific local caching nameserver functionality that NM uses dnsmasq
for.  NM's private dnsmasq is orthogonal to whatever global dnsmasq
daemon may be running, and with that daemons configuration.

(dcbw: change directory to private one)

src/dns-manager/Makefile.am

@@ -25,7 +25,8 @@ libdns_manager_la_CPPFLAGS = \
 	$(LIBNL_CFLAGS) \
 	$(DBUS_CFLAGS) \
 	$(GLIB_CFLAGS) \
-	-DLOCALSTATEDIR=\"$(localstatedir)\"
+	-DLOCALSTATEDIR=\"$(localstatedir)\" \
+	-DSYSCONFDIR=\"$(sysconfdir)\"
 
 libdns_manager_la_LIBADD = \
 	$(top_builddir)/src/logging/libnm-logging.la \

src/dns-manager/nm-dns-dnsmasq.c

@@ -41,6 +41,7 @@ G_DEFINE_TYPE (NMDnsDnsmasq, nm_dns_dnsmasq, NM_TYPE_DNS_PLUGIN)
 
 #define PIDFILE LOCALSTATEDIR "/run/nm-dns-dnsmasq.pid"
 #define CONFFILE LOCALSTATEDIR "/run/nm-dns-dnsmasq.conf"
+#define CONFDIR SYSCONFDIR "/NetworkManager/dnsmasq.d"
 
 typedef struct {
 	guint32 foo;
@@ -246,7 +247,7 @@ update (NMDnsPlugin *plugin,
 	NMDnsDnsmasq *self = NM_DNS_DNSMASQ (plugin);
 	GString *conf;
 	GSList *iter;
-	const char *argv[11];
+	const char *argv[12];
 	GError *error = NULL;
 	int ignored;
 	GPid pid = 0;
@@ -309,7 +310,8 @@ update (NMDnsPlugin *plugin,
 	argv[7] = "--conf-file=" CONFFILE;
 	argv[8] = "--cache-size=400";
 	argv[9] = "--proxy-dnssec"; /* Allow DNSSEC to pass through */
-	argv[10] = NULL;
+	argv[10] = "--conf-dir=" CONFDIR;
+	argv[11] = NULL;
 
 	/* And finally spawn dnsmasq */
 	pid = nm_dns_plugin_child_spawn (NM_DNS_PLUGIN (self), argv, PIDFILE, "bin/dnsmasq");