core: add new "scope" unit type for making a unit of pre-existing processes

"Scope" units are very much like service units, however with the
difference that they are created from pre-existing processes, rather
than processes that systemd itself forks off. This means they are
generated programmatically via the bus API as transient units rather
than from static configuration read from disk. Also, they do not provide
execution-time parameters, as at the time systemd adds the processes to
the scope unit they already exist and the parameters cannot be applied
anymore.

The primary benefit of this new unit type is to create arbitrary cgroups
for worker-processes forked off an existing service.

This commit also adds a a new mode to "systemd-run" to run the specified
processes in a scope rather then a transient service.

1 files changed, 170 insertions, 24 deletions

diff --git a/src/run/run.c b/src/run/run.c
index 9f8bda48af..b45116870c 100644
--- a/src/run/run.c
+++ b/src/run/run.c
@@ -20,22 +20,104 @@
 ***/
 
 #include <stdio.h>
+#include <getopt.h>
 
 #include "sd-bus.h"
 #include "bus-internal.h"
 #include "bus-message.h"
 #include "strv.h"
+#include "build.h"
+#include "unit-name.h"
 
-static int start_transient_service(
-                sd_bus *bus,
-                const char *name,
-                char **argv,
-                sd_bus_error *error) {
+static bool arg_scope = false;
+static bool arg_user = false;
+static const char *arg_unit = NULL;
 
-        _cleanup_bus_message_unref_ sd_bus_message *m = NULL, *reply = NULL;
-        char **i;
+static int help(void) {
+
+        printf("%s [OPTIONS...] [COMMAND LINE...]\n\n"
+               "Notify the init system about service status updates.\n\n"
+               "  -h --help             Show this help\n"
+               "     --version          Show package version\n"
+               "     --user             Run as user unit\n"
+               "     --scope            Run this as scope rather than service\n"
+               "     --unit=UNIT        Run under the specified unit name\n",
+               program_invocation_short_name);
+
+        return 0;
+}
+
+static int parse_argv(int argc, char *argv[]) {
+
+        enum {
+                ARG_VERSION = 0x100,
+                ARG_USER,
+                ARG_SCOPE,
+                ARG_UNIT
+        };
+
+        static const struct option options[] = {
+                { "help",      no_argument,       NULL, 'h'           },
+                { "version",   no_argument,       NULL, ARG_VERSION   },
+                { "user",      no_argument,       NULL, ARG_USER      },
+                { "scope",     no_argument,       NULL, ARG_SCOPE     },
+                { "unit",      required_argument, NULL, ARG_UNIT      },
+                { NULL,        0,                 NULL, 0             }
+        };
+
+        int c;
+
+        assert(argc >= 0);
+        assert(argv);
+
+        while ((c = getopt_long(argc, argv, "+h", options, NULL)) >= 0) {
+
+                switch (c) {
+
+                case 'h':
+                        help();
+                        return 0;
+
+                case ARG_VERSION:
+                        puts(PACKAGE_STRING);
+                        puts(SYSTEMD_FEATURES);
+                        return 0;
+
+                case ARG_USER:
+                        arg_user = true;
+                        break;
+
+                case ARG_SCOPE:
+                        arg_scope = true;
+                        break;
+
+                case ARG_UNIT:
+                        arg_unit = optarg;
+                        break;
+
+                case '?':
+                        return -EINVAL;
+
+                default:
+                        log_error("Unknown option code %c", c);
+                        return -EINVAL;
+                }
+        }
+
+        if (optind >= argc) {
+                log_error("Command line to execute required.");
+                return -EINVAL;
+        }
+
+        return 1;
+}
+
+static int message_start_transient_unit_new(sd_bus *bus, const char *name, sd_bus_message **ret) {
+        _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
         int r;
 
+        log_info("Running as unit %s.", name);
+
         r = sd_bus_message_new_method_call(
                         bus,
                         "org.freedesktop.systemd1",
@@ -57,6 +139,47 @@ static int start_transient_service(
         if (r < 0)
                 return r;
 
+        *ret = m;
+        m = NULL;
+
+        return 0;
+}
+
+static int message_start_transient_unit_send(sd_bus *bus, sd_bus_message *m, sd_bus_error *error, sd_bus_message **reply) {
+        int r;
+
+        r = sd_bus_message_close_container(m);
+        if (r < 0)
+                return r;
+
+        r = sd_bus_message_close_container(m);
+        if (r < 0)
+                return r;
+
+        return sd_bus_send_with_reply_and_block(bus, m, 0, error, reply);
+}
+
+static int start_transient_service(
+                sd_bus *bus,
+                char **argv,
+                sd_bus_error *error) {
+
+        _cleanup_bus_message_unref_ sd_bus_message *m = NULL, *reply = NULL;
+        _cleanup_free_ char *name = NULL;
+        char **i;
+        int r;
+
+        if (arg_unit)
+                name = unit_name_mangle_with_suffix(arg_unit, ".service");
+        else
+                asprintf(&name, "run-%lu.service", (unsigned long) getpid());
+        if (!name)
+                return -ENOMEM;
+
+        r = message_start_transient_unit_new(bus, name, &m);
+        if (r < 0)
+                return r;
+
         r = sd_bus_message_append(m, "s", "ExecStart");
         if (r < 0)
                 return r;
@@ -107,46 +230,69 @@ static int start_transient_service(
         if (r < 0)
                 return r;
 
-        r = sd_bus_message_close_container(m);
+        return  message_start_transient_unit_send(bus, m, error, &reply);
+}
+
+static int start_transient_scope(
+                sd_bus *bus,
+                char **argv,
+                sd_bus_error *error) {
+
+        _cleanup_bus_message_unref_ sd_bus_message *m = NULL, *reply = NULL;
+        _cleanup_free_ char *name = NULL;
+        int r;
+
+        if (arg_unit)
+                name = unit_name_mangle_with_suffix(arg_unit, ".scope");
+        else
+                asprintf(&name, "run-%lu.scope", (unsigned long) getpid());
+        if (!name)
+                return -ENOMEM;
+
+        r = message_start_transient_unit_new(bus, name, &m);
         if (r < 0)
                 return r;
 
-        r = sd_bus_message_close_container(m);
+        r = sd_bus_message_append(m, "sv", "PIDs", "au", 1, (uint32_t) getpid());
+        if (r < 0)
+                return r;
+
+        r = message_start_transient_unit_send(bus, m, error, &reply);
         if (r < 0)
                 return r;
 
-        return sd_bus_send_with_reply_and_block(bus, m, 0, error, &reply);
+        execvp(argv[0], argv);
+        log_error("Failed to execute: %m");
+        return -errno;
 }
 
 int main(int argc, char* argv[]) {
         sd_bus_error error = SD_BUS_ERROR_NULL;
         _cleanup_bus_unref_ sd_bus *bus = NULL;
-        _cleanup_free_ char *name = NULL;
         int r;
 
         log_parse_environment();
         log_open();
 
-        if (argc < 2) {
-                log_error("Missing command line.");
-                r = -EINVAL;
+        r = parse_argv(argc, argv);
+        if (r <= 0)
                 goto fail;
-        }
 
-        r = sd_bus_open_user(&bus);
+        if (arg_user)
+                r = sd_bus_open_user(&bus);
+        else
+                r = sd_bus_open_system(&bus);
         if (r < 0) {
-                log_error("Failed to create new bus: %s", strerror(-r));
-                goto fail;
-        }
-
-        if (asprintf(&name, "run-%lu.service", (unsigned long) getpid()) < 0) {
-                r = log_oom();
+                log_error("Failed to create new bus connection: %s", strerror(-r));
                 goto fail;
         }
 
-        r = start_transient_service(bus, name, argv + 1, &error);
+        if (arg_scope)
+                r = start_transient_scope(bus, argv + optind, &error);
+        else
+                r = start_transient_service(bus, argv + optind, &error);
         if (r < 0) {
-                log_error("Failed start transient service: %s", error.message);
+                log_error("Failed start transient unit: %s", error.message);
                 sd_bus_error_free(&error);
                 goto fail;
         }