login: add new call sd_get_machine_names() to get a list of current virtual machines and containers

3 files changed, 52 insertions, 2 deletions

diff --git a/src/login/libsystemd-login.sym b/src/login/libsystemd-login.sym
index f4cd209700..925fb91095 100644
--- a/src/login/libsystemd-login.sym
+++ b/src/login/libsystemd-login.sym
@@ -70,3 +70,8 @@ global:
         sd_pid_get_user_unit;
         sd_pid_get_machine_name;
 } LIBSYSTEMD_LOGIN_201;
+
+LIBSYSTEMD_LOGIN_203 {
+global:
+        sd_get_machine_names;
+} LIBSYSTEMD_LOGIN_202;
diff --git a/src/login/sd-login.c b/src/login/sd-login.c
index 157b7e0fb4..35deb85f2d 100644
--- a/src/login/sd-login.c
+++ b/src/login/sd-login.c
@@ -591,6 +591,43 @@ _public_ int sd_get_uids(uid_t **users) {
         return r;
 }
 
+int sd_get_machine_names(char ***machines) {
+        _cleanup_closedir_ DIR *d = NULL;
+        _cleanup_strv_free_ char **l = NULL;
+        _cleanup_free_ char *md = NULL;
+        char *n;
+        int c = 0, r;
+
+        r = cg_get_machine_path(&md);
+        if (r < 0)
+                return r;
+
+        r = cg_enumerate_subgroups(SYSTEMD_CGROUP_CONTROLLER, md, &d);
+        if (r < 0)
+                return r;
+
+        while ((r = cg_read_subgroup(d, &n)) > 0) {
+
+                r = strv_push(&l, n);
+                if (r < 0) {
+                        free(n);
+                        return -ENOMEM;
+                }
+
+                c++;
+        }
+
+        if (r < 0)
+                return r;
+
+        if (machines) {
+                *machines = l;
+                l = NULL;
+        }
+
+        return c;
+}
+
 static inline int MONITOR_TO_FD(sd_login_monitor *m) {
         return (int) (unsigned long) m - 1;
 }
diff --git a/src/login/test-login.c b/src/login/test-login.c
index e4d0c93378..945cb38be9 100644
--- a/src/login/test-login.c
+++ b/src/login/test-login.c
@@ -35,7 +35,7 @@ int main(int argc, char* argv[]) {
         char *state;
         char *session2;
         char *t;
-        char **seats, **sessions;
+        char **seats, **sessions, **machines;
         uid_t *uids;
         unsigned n;
         struct pollfd pollfd;
@@ -180,9 +180,17 @@ int main(int argc, char* argv[]) {
         printf("n_uids = %i\n", r);
         assert_se(sd_get_uids(NULL) == r);
 
-        r = sd_login_monitor_new("session", &m);
+        r = sd_get_machine_names(&machines);
         assert_se(r >= 0);
+        assert_se(r == (int) strv_length(machines));
+        assert_se(t = strv_join(machines, ", "));
+        strv_free(machines);
+        printf("n_machines = %i\n", r);
+        printf("machines = %s\n", t);
+        free(t);
 
+        r = sd_login_monitor_new("session", &m);
+        assert_se(r >= 0);
 
         for (n = 0; n < 5; n++) {
                 usec_t timeout, nw;