nspawn: introduce the new /machine/ tree in the cgroup tree and move containers there

Containers will now carry a label (normally derived from the root
directory name, but configurable by the user), and the container's root
cgroup is /machine/<label>. This label is called "machine name", and can
cover both containers and VMs (as soon as libvirt also makes use of
/machine/).

libsystemd-login can be used to query the machine name from a process.

This patch also includes numerous clean-ups for the cgroup code.

1 files changed, 79 insertions, 52 deletions

diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index b90ccc53e..c25768245 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -75,6 +75,7 @@ static char *arg_directory = NULL;
 static char *arg_user = NULL;
 static char **arg_controllers = NULL;
 static char *arg_uuid = NULL;
+static char *arg_machine = NULL;
 static bool arg_private_network = false;
 static bool arg_read_only = false;
 static bool arg_boot = false;
@@ -113,13 +114,14 @@ static int help(void) {
         printf("%s [OPTIONS...] [PATH] [ARGUMENTS...]\n\n"
                "Spawn a minimal namespace container for debugging, testing and building.\n\n"
                "  -h --help                Show this help\n"
-               "  --version                Print version string\n"
+               "     --version             Print version string\n"
                "  -D --directory=NAME      Root directory for the container\n"
                "  -b --boot                Boot up full system (i.e. invoke init)\n"
                "  -u --user=USER           Run the command under specified user or uid\n"
                "  -C --controllers=LIST    Put the container in specified comma-separated\n"
                "                           cgroup hierarchies\n"
                "     --uuid=UUID           Set a specific machine UUID for the container\n"
+               "  -M --machine=NAME        Set the machine name for the container\n"
                "     --private-network     Disable network in container\n"
                "     --read-only           Mount the root directory read-only\n"
                "     --capability=CAP      In addition to the default, retain specified\n"
@@ -161,6 +163,7 @@ static int parse_argv(int argc, char *argv[]) {
                 { "link-journal",    required_argument, NULL, ARG_LINK_JOURNAL    },
                 { "bind",            required_argument, NULL, ARG_BIND            },
                 { "bind-ro",         required_argument, NULL, ARG_BIND_RO         },
+                { "machine",         required_argument, NULL, 'M'                 },
                 { NULL,              0,                 NULL, 0                   }
         };
 
@@ -194,22 +197,19 @@ static int parse_argv(int argc, char *argv[]) {
 
                 case 'u':
                         free(arg_user);
-                        if (!(arg_user = strdup(optarg))) {
-                                log_error("Failed to duplicate user name.");
-                                return -ENOMEM;
-                        }
+                        arg_user = strdup(optarg);
+                        if (!arg_user)
+                                return log_oom();
 
                         break;
 
                 case 'C':
                         strv_free(arg_controllers);
                         arg_controllers = strv_split(optarg, ",");
-                        if (!arg_controllers) {
-                                log_error("Failed to split controllers list.");
-                                return -ENOMEM;
-                        }
-                        strv_uniq(arg_controllers);
+                        if (!arg_controllers)
+                                return log_oom();
 
+                        cg_shorten_controllers(arg_controllers);
                         break;
 
                 case ARG_PRIVATE_NETWORK:
@@ -224,6 +224,19 @@ static int parse_argv(int argc, char *argv[]) {
                         arg_uuid = optarg;
                         break;
 
+                case 'M':
+                        if (!hostname_is_valid(optarg)) {
+                                log_error("Invalid machine name: %s", optarg);
+                                return -EINVAL;
+                        }
+
+                        free(arg_machine);
+                        arg_machine = strdup(optarg);
+                        if (!arg_machine)
+                                return log_oom();
+
+                        break;
+
                 case ARG_READ_ONLY:
                         arg_read_only = true;
                         break;
@@ -743,25 +756,11 @@ static int setup_kmsg(const char *dest, int kmsg_socket) {
 }
 
 static int setup_hostname(void) {
-        char *hn;
-        int r = 0;
-
-        hn = path_get_file_name(arg_directory);
-        if (hn) {
-                hn = strdup(hn);
-                if (!hn)
-                        return -ENOMEM;
-
-                hostname_cleanup(hn);
 
-                if (!isempty(hn))
-                        if (sethostname(hn, strlen(hn)) < 0)
-                                r = -errno;
-
-                free(hn);
-        }
+        if (sethostname(arg_machine, strlen(arg_machine)) < 0)
+                return -errno;
 
-        return r;
+        return 0;
 }
 
 static int setup_journal(const char *directory) {
@@ -896,6 +895,25 @@ static int setup_journal(const char *directory) {
         return 0;
 }
 
+static int setup_cgroup(const char *path) {
+        char **c;
+        int r;
+
+        r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, path, 1);
+        if (r < 0) {
+                log_error("Failed to create cgroup: %s", strerror(-r));
+                return r;
+        }
+
+        STRV_FOREACH(c, arg_controllers) {
+                r = cg_create_and_attach(*c, path, 1);
+                if (r < 0)
+                        log_warning("Failed to create cgroup in controller %s: %s", *c, strerror(-r));
+        }
+
+        return 0;
+}
+
 static int drop_capabilities(void) {
         return capability_bounding_set_drop(~arg_retain, false);
 }
@@ -1159,9 +1177,9 @@ finish:
 int main(int argc, char *argv[]) {
         pid_t pid = 0;
         int r = EXIT_FAILURE, k;
-        char *oldcg = NULL, *newcg = NULL;
-        char **controller = NULL;
-        int master = -1, n_fd_passed;
+        _cleanup_free_ char *machine_root = NULL, *newcg = NULL;
+        _cleanup_close_ int master = -1;
+        int n_fd_passed;
         const char *console = NULL;
         struct termios saved_attr, raw_attr;
         sigset_t mask;
@@ -1193,6 +1211,20 @@ int main(int argc, char *argv[]) {
 
         path_kill_slashes(arg_directory);
 
+        if (!arg_machine) {
+                arg_machine = strdup(path_get_file_name(arg_directory));
+                if (!arg_machine) {
+                        log_oom();
+                        goto finish;
+                }
+
+                hostname_cleanup(arg_machine);
+                if (isempty(arg_machine)) {
+                        log_error("Failed to determine machine name automatically, please use -M.");
+                        goto finish;
+                }
+        }
+
         if (geteuid() != 0) {
                 log_error("Need to be root.");
                 goto finish;
@@ -1225,27 +1257,26 @@ int main(int argc, char *argv[]) {
         fdset_close_others(fds);
         log_open();
 
-        k = cg_get_by_pid(SYSTEMD_CGROUP_CONTROLLER, 0, &oldcg);
+        k = cg_get_machine_path(&machine_root);
         if (k < 0) {
-                log_error("Failed to determine current cgroup: %s", strerror(-k));
+                log_error("Failed to determine machine cgroup path: %s", strerror(-k));
                 goto finish;
         }
 
-        if (asprintf(&newcg, "%s/nspawn-%lu", oldcg, (unsigned long) getpid()) < 0) {
+        newcg = strjoin(machine_root, "/", arg_machine, NULL);
+        if (!newcg) {
                 log_error("Failed to allocate cgroup path.");
                 goto finish;
         }
 
-        k = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, newcg, 0);
-        if (k < 0)  {
-                log_error("Failed to create cgroup: %s", strerror(-k));
-                goto finish;
-        }
+        r = cg_is_empty_recursive(SYSTEMD_CGROUP_CONTROLLER, newcg, false);
+        if (r <= 0 && r != -ENOENT) {
+                log_error("Container already running.");
 
-        STRV_FOREACH(controller, arg_controllers) {
-                k = cg_create_and_attach(*controller, newcg, 0);
-                if (k < 0)
-                        log_warning("Failed to create cgroup in controller %s: %s", *controller, strerror(-k));
+                free(newcg);
+                newcg = NULL;
+
+                goto finish;
         }
 
         master = posix_openpt(O_RDWR|O_NOCTTY|O_CLOEXEC|O_NDELAY);
@@ -1279,7 +1310,7 @@ int main(int argc, char *argv[]) {
         }
 
         if (socketpair(AF_UNIX, SOCK_DGRAM|SOCK_NONBLOCK|SOCK_CLOEXEC, 0, kmsg_socket_pair) < 0) {
-                log_error("Failed to create kmsg socket pair");
+                log_error("Failed to create kmsg socket pair.");
                 goto finish;
         }
 
@@ -1382,6 +1413,9 @@ int main(int argc, char *argv[]) {
                                 goto child_fail;
                         }
 
+                        if (setup_cgroup(newcg) < 0)
+                                goto child_fail;
+
                         /* Mark everything as slave, so that we still
                          * receive mounts from the real root, but don't
                          * propagate mounts to the real root. */
@@ -1547,7 +1581,7 @@ int main(int argc, char *argv[]) {
                                 }
 
                                 if ((asprintf((char **)(envp + n_env++), "LISTEN_FDS=%u", n_fd_passed) < 0) ||
-                                    (asprintf((char **)(envp + n_env++), "LISTEN_PID=%lu", (unsigned long) getpid()) < 0)) {
+                                    (asprintf((char **)(envp + n_env++), "LISTEN_PID=%lu", (unsigned long) 1) < 0)) {
                                         log_oom();
                                         goto child_fail;
                                 }
@@ -1640,21 +1674,14 @@ finish:
         if (saved_attr_valid)
                 tcsetattr(STDIN_FILENO, TCSANOW, &saved_attr);
 
-        if (master >= 0)
-                close_nointr_nofail(master);
-
         close_pipe(kmsg_socket_pair);
 
-        if (oldcg)
-                cg_attach(SYSTEMD_CGROUP_CONTROLLER, oldcg, 0);
-
         if (newcg)
                 cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, newcg, true);
 
         free(arg_directory);
+        free(arg_machine);
         strv_free(arg_controllers);
-        free(oldcg);
-        free(newcg);
 
         fdset_free(fds);