s6-rc: switch to bare s6 based model

The current form of s6-rc is unsuitable for dynamic activation on
external events, such as dbus activation events. Therefore we switch to
a different model based on a dedicated s6 scandir (we don't need
dependency handling), separated from the rest of the services.

README.md

@@ -13,30 +13,27 @@ implementation, and are capable of running both system and session buses.
 This is also a starting point to explore the feasibility of a runit/s6
 controller.
 
-## dbus-controller-s6rc
+## dbus-controller-s6
 
-Build with `meson -Ds6-rc=enabled build`.
+Build with `meson -Ds6=enabled build`.
 
-Usage: `dbus-controller-s6rc -h`.
+Usage: `dbus-controller-s6 -h`.
 
-The [s6-rc] controller looks in a s6-rc livedir for services containing the
-file `data/dbus-activatable-name` with a dbus activatable name provided by the
-service. It issues `s6-rc change <service>` when it receives an activation
+The [s6] controller looks in a s6 scandir for services containing the file
+`data/dbus-activatable-name` with a dbus activatable name provided by the
+service. It issues `s6-svc -u <service>` when it receives an activation
 request.
 
-Such dbus activatable services can be autogenerated by `tools/s6rc-generator`,
-which generates a s6-rc source database called `dbus` that can be included in
-the list of your databases to compile with `s6-rc-compile`.
-
+Such dbus activatable services can be autogenerated by `tools/s6-generator`.
 It is typically invoked as:
 ```
-./s6rc-generator /usr/share/dbus-1/system-services/*
-./s6rc-generator /usr/share/dbus-1/services/*
+./s6-generator /usr/share/dbus-1/system-services/*
+./s6-generator /usr/share/dbus-1/services/*
 ```
 for the system and session bus, respectively.
 
-You are free to further tweak this source database as you like, for example
-removing unwanted activatable services.
+You are free to further tweak this scandir as you like, for example removing
+unwanted activatable services.
 
 [dbus-broker]: https://github.com/bus1/dbus-broker
-[s6-rc]: https://skarnet.org/software/s6-rc
+[s6]: https://skarnet.org/software/s6

activation.c

@@ -48,25 +48,19 @@ struct service {
 tll(struct service) service_list = tll_init();
 
 #define NAMEFILE "data/dbus-activatable-name"
-#define SERVICEDIRS "servicedirs"
 #define SIZE(array) (sizeof(array)/sizeof(*array))
 
-void add_s6rc_servicedirs(const char* s6rc_livedir) {
+void add_s6_servicedirs(const char* s6_dbuscandir) {
 	struct dirent **namelist;
 	int n;
 
-	size_t s6rc_livedir_len = strlen(s6rc_livedir);
-	char path[s6rc_livedir_len+1+SIZE(SERVICEDIRS)];
-	memcpy(path, s6rc_livedir, s6rc_livedir_len);
-	path[s6rc_livedir_len] = '/';
-	memcpy(path+s6rc_livedir_len+1, SERVICEDIRS, SIZE(SERVICEDIRS));
-	n = scandir(path, &namelist, NULL, alphasort);
+	n = scandir(s6_dbuscandir, &namelist, NULL, alphasort);
 	if (n == -1) {
 		perror("scandir");
 		exit(EXIT_FAILURE);
 	}
 
-	chdir(path); // TODO: remove this, the directory could be deleted by s6-rc-update
+	chdir(s6_dbuscandir);
 	while (n--) {
 		if (namelist[n]->d_name[0] != '.') {
 			struct service service = {0};
@@ -110,16 +104,33 @@ static struct service *find_service_by_id(int id) {
         return NULL;
 }
 
-const char* s6rc_livedir; // TODO: pass around properly
+const char* s6_dbuscandir; // TODO: pass around properly
 
 int start_service(int id) {
 	int r = -1;
 	struct service* service = find_service_by_id(id);
 	if (service) {
 		char cmd[256];
-		sprintf(cmd, "s6-rc -l %s change %s", s6rc_livedir, service->s6rc.s);
+		sprintf(cmd, "s6-svc -uwu -T 1000 %s/%s", s6_dbuscandir, service->s6rc.s);
 		fprintf(stderr, "%s\n", cmd);
 		r = system(cmd);
 	}
 	return r;
 }
+
+static int stop_service(int id) {
+	int r = -1;
+	struct service* service = find_service_by_id(id);
+	if (service) {
+		char cmd[256];
+		sprintf(cmd, "s6-svc -d %s/%s", s6_dbuscandir, service->s6rc.s);
+		fprintf(stderr, "%s\n", cmd);
+		r = system(cmd);
+	}
+	return r;
+}
+
+void stop_all_services() {
+        tll_foreach(service_list, it)
+		stop_service(it->item.id);
+}

controller.c

@@ -116,3 +116,33 @@ void controller_run() {
                 if (r < 0) handle_error("Failed to wait on bus");
         }
 }
+
+#ifdef HAVE_S6
+
+#include <skalibs/iopause.h>
+#include <skalibs/selfpipe.h>
+
+void controller_run_signals() {
+	iopause_fd x[2] = {
+		{ sd_bus_get_fd(bus_controller), IOPAUSE_READ, 0 },
+		{ selfpipe_init(), IOPAUSE_READ, 0 },
+	};
+	int r = selfpipe_trap(SIGTERM);
+	for (;;) {
+		/* Wait for the next request to process */
+		r = iopause(x, 2, NULL, NULL);
+		if (r < 0) handle_error("Failed to wait on bus");
+		if (x[0].revents & IOPAUSE_READ)
+			/* Process requests */
+			while ((r = sd_bus_process(bus_controller, NULL)))
+				if (r < 0) handle_error("Failed to process bus");
+		if (x[1].revents & IOPAUSE_READ) {
+			int c = selfpipe_read();
+			break;
+		}
+	}
+	selfpipe_finish();
+	stop_all_services();
+}
+
+#endif

main.c

@@ -13,8 +13,8 @@
 
 static const char* default_dbus_socket_path = "/run/dbus/system_bus_socket";
 #ifdef HAVE_S6
-static const char* default_s6rc_livedir = "/run/s6-rc";
-extern const char* s6rc_livedir; // TODO: pass around properly
+static const char* default_s6_dbuscandir = "/run/dbus_activated_services";
+extern const char* s6_dbuscandir; // TODO: pass around properly
 #endif
 static const char* dummy_machine_id = "00000000000000000000000000000001";
 
@@ -35,7 +35,7 @@ optional arguments:\n\
   -3                    notify readiness on fd 3\n"
 #ifdef HAVE_S6
 "\n\
-  -l                    s6-rc livedir (default: %s)\n"
+  -a                    s6 scandir of dbus-activated services (default: %s)\n"
 #endif
 "\n\
   -h                    show this help message and exit\n";
@@ -45,12 +45,12 @@ int main(int argc, char* argv[]) {
 	bool notif = false;
 	bool syslog = false;
 #ifdef HAVE_S6
-	s6rc_livedir = default_s6rc_livedir;
+	s6_dbuscandir = default_s6_dbuscandir;
 #endif
 
 	int opt;
 #ifdef HAVE_S6
-	while ((opt = getopt(argc, argv, "d:hl:s3")) != -1) {
+	while ((opt = getopt(argc, argv, "d:ha:s3")) != -1) {
 #else
 	while ((opt = getopt(argc, argv, "d:hs3")) != -1) {
 #endif
@@ -59,12 +59,12 @@ int main(int argc, char* argv[]) {
 			case 's': syslog = true; break;
 			case '3': check_3_open(); notif = true; break;
 #ifdef HAVE_S6
-			case 'l': s6rc_livedir = optarg; break;
+			case 'a': s6_dbuscandir = optarg; break;
 #endif
 			default:
 				printf(usage, default_dbus_socket_path
 #ifdef HAVE_S6
-				, default_s6rc_livedir
+				, default_s6_dbuscandir
 #endif
 				);
 				return EXIT_FAILURE;
@@ -115,7 +115,7 @@ int main(int argc, char* argv[]) {
 		if (logfd >= 0) close(logfd);
 
 #ifdef HAVE_S6
-		add_s6rc_servicedirs(s6rc_livedir);
+		add_s6_servicedirs(s6_dbuscandir);
 #endif
 
 		controller_setup(controller[0], dbus_socket_path);
@@ -125,8 +125,11 @@ int main(int argc, char* argv[]) {
 			close(3);
 		}
 
+#ifdef HAVE_S6
+		controller_run_signals();
+#else
 		controller_run();
-		int wstatus;
-		waitpid(cpid, &wstatus, 0);
+#endif
+		// do we need to do something here to make the broker exit "cleanly"?
 	}
 }

meson.build

@@ -27,11 +27,11 @@ add_project_arguments('-DHAVE_' + sdbus.name().to_upper() + '=1', language: 'c')
 
 executable('dbus-controller-dummy', ['controller.c', 'dbus.c', 'main.c', 'policy.c', 'syslog.c'], dependencies: [sdbus])
 
-if get_option('s6-rc').enabled()
+if get_option('s6').enabled()
 tllist = dependency('tllist')
 
 cc = meson.get_compiler('c')
 skalibs = cc.find_library('skarnet')
 
-executable('dbus-controller-s6rc', ['activation.c', 'controller.c', 'dbus.c', 'main.c', 'policy.c', 'syslog.c'], dependencies: [sdbus, skalibs, tllist], c_args : '-DHAVE_S6=1')
+executable('dbus-controller-s6', ['activation.c', 'controller.c', 'dbus.c', 'main.c', 'policy.c', 'syslog.c'], dependencies: [sdbus, skalibs, tllist], c_args : '-DHAVE_S6=1')
 endif

meson_options.txt

@@ -1,2 +1,2 @@
 option('sd-bus-provider', type: 'combo', choices: ['auto', 'libsystemd', 'libelogind', 'basu'], value: 'auto', description: 'Provider of the sd-bus library')
-option('s6-rc', type: 'feature', value: 'disabled')
+option('s6', type: 'feature', value: 'disabled')

tools/s6rc-generator → tools/s6-generator

@@ -1,13 +1,9 @@
 #!/bin/sh -e
-# Generate s6-rc service definitions for dbus services
+# Generate s6 service definitions for dbus services
 # usage: pass the absolute paths of dbus service definitions, i.e.
 # /usr/share/dbus-1/system-services/* (for the system bus)
 # or /usr/share/dbus-1/services/* (for the session bus)
 
-# The name of the dbus service which launches controller/broker
-# all dbus activated services depend on it
-DBUS_S6RC_SERVICE=dbus
-
 mkdir -p 'dbus'
 cd 'dbus'
 
@@ -20,8 +16,8 @@ for service in "$@"; do
 	mkdir "$name_/data"
 	echo "$name_" >> "$name_/data/dbus-activatable-name"
 	echo 'longrun' >> "$name_/type"
-	echo "$DBUS_S6RC_SERVICE" >> "$name_/dependencies"
 	echo '#!/bin/execlineb -P' >> "$name_/run"
 	echo "$exec_" >> "$name_/run"
 	chmod +x "$name_/run"
+	touch "$name_/down"
 done