sysext: rework command line interface to be verb-based

As suggested by @yuwata:

https://github.com/systemd/systemd/pull/18181#pullrequestreview-570826113

2 files changed, 163 insertions, 166 deletions

diff --git a/src/sysext/sysext.c b/src/sysext/sysext.c
index e54f1845f8..98f0e53a60 100644
--- a/src/sysext/sysext.c
+++ b/src/sysext/sysext.c
@@ -29,14 +29,8 @@
 #include "stat-util.h"
 #include "terminal-util.h"
 #include "user-util.h"
+#include "verbs.h"
 
-static enum {
-        ACTION_STATUS,
-        ACTION_MERGE,
-        ACTION_UNMERGE,
-        ACTION_REFRESH,
-        ACTION_LIST,
-} arg_action = ACTION_STATUS;
 static char **arg_hierarchies = NULL; /* "/usr" + "/opt" by default */
 static char *arg_root = NULL;
 static JsonFormatFlags arg_json_format_flags = JSON_FORMAT_OFF;
@@ -149,7 +143,15 @@ static int unmerge(void) {
         return ret;
 }
 
-static int status(void) {
+static int verb_unmerge(int argc, char **argv, void *userdata) {
+
+        if (!have_effective_cap(CAP_SYS_ADMIN))
+                return log_error_errno(SYNTHETIC_ERRNO(EPERM), "Need to be privileged.");
+
+        return unmerge();
+}
+
+static int verb_status(int argc, char **argv, void *userdata) {
         _cleanup_(table_unrefp) Table *t = NULL;
         int r, ret = 0;
         char **p;
@@ -735,7 +737,134 @@ static int merge(Hashmap *images) {
         return r != 123; /* exit code 123 means: didn't do anything */
 }
 
-static int help(void) {
+static int verb_merge(int argc, char **argv, void *userdata) {
+        _cleanup_(hashmap_freep) Hashmap *images = NULL;
+        char **p;
+        int r;
+
+        if (!have_effective_cap(CAP_SYS_ADMIN))
+                return log_error_errno(SYNTHETIC_ERRNO(EPERM), "Need to be privileged.");
+
+        images = hashmap_new(&image_hash_ops);
+        if (!images)
+                return log_oom();
+
+        r = image_discover(IMAGE_EXTENSION, arg_root, images);
+        if (r < 0)
+                return log_error_errno(r, "Failed to discover extension images: %m");
+
+        /* In merge mode fail if things are already merged. (In --refresh mode below we'll unmerge if we find
+         * things are already merged...) */
+        STRV_FOREACH(p, arg_hierarchies) {
+                _cleanup_free_ char *resolved = NULL;
+
+                r = chase_symlinks(*p, arg_root, CHASE_PREFIX_ROOT, &resolved, NULL);
+                if (r == -ENOENT) {
+                        log_debug_errno(r, "Hierarchy '%s%s' does not exist, ignoring.", strempty(arg_root), *p);
+                        continue;
+                }
+                if (r < 0)
+                        return log_error_errno(r, "Failed to resolve path to hierarchy '%s%s': %m", strempty(arg_root), *p);
+
+                r = is_our_mount_point(resolved);
+                if (r < 0)
+                        return r;
+                if (r > 0)
+                        return log_error_errno(SYNTHETIC_ERRNO(EBUSY),
+                                               "Hierarchy '%s' is already merged.", *p);
+        }
+
+        return merge(images);
+}
+
+static int verb_refresh(int argc, char **argv, void *userdata) {
+        _cleanup_(hashmap_freep) Hashmap *images = NULL;
+        int r;
+
+        if (!have_effective_cap(CAP_SYS_ADMIN))
+                return log_error_errno(SYNTHETIC_ERRNO(EPERM), "Need to be privileged.");
+
+        images = hashmap_new(&image_hash_ops);
+        if (!images)
+                return log_oom();
+
+        r = image_discover(IMAGE_EXTENSION, arg_root, images);
+        if (r < 0)
+                return log_error_errno(r, "Failed to discover extension images: %m");
+
+        r = merge(images); /* Returns > 0 if it did something, i.e. a new overlayfs is mounted now. When it
+                            * does so it implicitly unmounts any overlayfs placed there before. Returns == 0
+                            * if it did nothing, i.e. no extension images found. In this case the old
+                            * overlayfs remains in place if there was one. */
+        if (r < 0)
+                return r;
+        if (r == 0) /* No images found? Then unmerge. The goal of --refresh is after all that after having
+                     * called there's a guarantee that the merge status matches the installed extensions. */
+                r = unmerge();
+
+        /* Net result here is that:
+         *
+         * 1. If an overlayfs was mounted before and no extensions exist anymore, we'll have unmerged things.
+         *
+         * 2. If an overlayfs was mounted before, and there are still extensions installed' we'll have
+         *    unmerged and then merged things again.
+         *
+         * 3. If an overlayfs so far wasn't mounted, and there are extensions installed, we'll have it
+         *    mounted now.
+         *
+         * 4. If there was no overlayfs mount so far, and no extensions installed, we implement a NOP.
+         */
+
+        return 0;
+}
+
+static int verb_list(int argc, char **argv, void *userdata) {
+        _cleanup_(hashmap_freep) Hashmap *images = NULL;
+        _cleanup_(table_unrefp) Table *t = NULL;
+        Image *img;
+        int r;
+
+        images = hashmap_new(&image_hash_ops);
+        if (!images)
+                return log_oom();
+
+        r = image_discover(IMAGE_EXTENSION, arg_root, images);
+        if (r < 0)
+                return log_error_errno(r, "Failed to discover extension images: %m");
+
+        if ((arg_json_format_flags & JSON_FORMAT_OFF) && hashmap_isempty(images)) {
+                log_info("No OS extensions found.");
+                return 0;
+        }
+
+        t = table_new("name", "type", "path", "time");
+        if (!t)
+                return log_oom();
+
+        HASHMAP_FOREACH(img, images) {
+                r = table_add_many(
+                                t,
+                                TABLE_STRING, img->name,
+                                TABLE_STRING, image_type_to_string(img->type),
+                                TABLE_PATH, img->path,
+                                TABLE_TIMESTAMP, img->mtime != 0 ? img->mtime : img->crtime);
+                if (r < 0)
+                        return table_log_add_error(r);
+        }
+
+        (void) table_set_sort(t, (size_t) 0, (size_t) -1);
+
+        if (arg_json_format_flags & (JSON_FORMAT_OFF|JSON_FORMAT_PRETTY|JSON_FORMAT_PRETTY_AUTO))
+                (void) pager_open(arg_pager_flags);
+
+        r = table_print_json(t, stdout, arg_json_format_flags);
+        if (r < 0)
+                return table_log_print_error(r);
+
+        return 0;
+}
+
+static int verb_help(int argc, char **argv, void *userdata) {
         _cleanup_free_ char *link = NULL;
         int r;
 
@@ -746,12 +875,13 @@ static int help(void) {
         printf("%1$s [OPTIONS...] [DEVICE]\n"
                "\n%5$sMerge extension images into /usr/ and /opt/ hierarchies.%6$s\n"
                "\n%3$sCommands:%4$s\n"
+               "  status                  Show current merge status (default)\n"
+               "  merge                   Merge extensions into /usr/ and /opt/\n"
+               "  unmerge                 Unmerge extensions from /usr/ and /opt/\n"
+               "  refresh                 Unmerge/merge extensions again\n"
+               "  list                    List installed extensions\n"
                "  -h --help               Show this help\n"
                "     --version            Show package version\n"
-               "  -m --merge              Merge extensions into /usr/ and /opt/\n"
-               "  -u --unmerge            Unmerge extensions from /usr/ and /opt/\n"
-               "  -R --refresh            Unmerge/merge extensions again\n"
-               "  -l --list               List all OS images\n"
                "\n%3$sOptions:%4$s\n"
                "     --no-pager           Do not pipe output into a pager\n"
                "     --root=PATH          Operate relative to root path\n"
@@ -772,10 +902,6 @@ static int parse_argv(int argc, char *argv[]) {
         enum {
                 ARG_VERSION = 0x100,
                 ARG_NO_PAGER,
-                ARG_MERGE,
-                ARG_UNMERGE,
-                ARG_REFRESH,
-                ARG_LIST,
                 ARG_ROOT,
                 ARG_JSON,
         };
@@ -785,10 +911,6 @@ static int parse_argv(int argc, char *argv[]) {
                 { "version",  no_argument,       NULL, ARG_VERSION  },
                 { "no-pager", no_argument,       NULL, ARG_NO_PAGER },
                 { "root",     required_argument, NULL, ARG_ROOT     },
-                { "merge",    no_argument,       NULL, 'm'          },
-                { "unmerge",  no_argument,       NULL, 'u'          },
-                { "refresh",  no_argument,       NULL, 'R'          },
-                { "list",     no_argument,       NULL, 'l'          },
                 { "json",     required_argument, NULL, ARG_JSON     },
                 {}
         };
@@ -798,12 +920,12 @@ static int parse_argv(int argc, char *argv[]) {
         assert(argc >= 0);
         assert(argv);
 
-        while ((c = getopt_long(argc, argv, "hmuRl", options, NULL)) >= 0)
+        while ((c = getopt_long(argc, argv, "h", options, NULL)) >= 0)
 
                 switch (c) {
 
                 case 'h':
-                        return help();
+                        return verb_help(argc, argv, NULL);
 
                 case ARG_VERSION:
                         return version();
@@ -812,22 +934,6 @@ static int parse_argv(int argc, char *argv[]) {
                         arg_pager_flags |= PAGER_DISABLE;
                         break;
 
-                case 'm':
-                        arg_action = ACTION_MERGE;
-                        break;
-
-                case 'u':
-                        arg_action = ACTION_UNMERGE;
-                        break;
-
-                case 'R':
-                        arg_action = ACTION_REFRESH;
-                        break;
-
-                case 'l':
-                        arg_action = ACTION_LIST;
-                        break;
-
                 case ARG_ROOT:
                         r = parse_path_argument_and_warn(optarg, false, &arg_root);
                         if (r < 0)
@@ -848,10 +954,6 @@ static int parse_argv(int argc, char *argv[]) {
                         assert_not_reached("Unhandled option");
                 }
 
-        if (argc - optind > 0)
-                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
-                                       "Unexpected argument.");
-
         return 1;
 }
 
@@ -895,8 +997,22 @@ static int parse_env(void) {
         return 0;
 }
 
+static int sysext_main(int argc, char *argv[]) {
+
+        static const Verb verbs[] = {
+                { "status",   VERB_ANY, 1, VERB_DEFAULT, verb_status  },
+                { "merge",    VERB_ANY, 1, 0,            verb_merge   },
+                { "unmerge",  VERB_ANY, 1, 0,            verb_unmerge },
+                { "refresh",  VERB_ANY, 1, 0,            verb_refresh },
+                { "list",     VERB_ANY, 1, 0,            verb_list    },
+                { "help",     VERB_ANY, 1, 0,            verb_help    },
+                {}
+        };
+
+        return dispatch_verb(argc, argv, verbs, NULL);
+}
+
 static int run(int argc, char *argv[]) {
-        _cleanup_(hashmap_freep) Hashmap *images = NULL;
         int r;
 
         log_setup_cli();
@@ -915,126 +1031,7 @@ static int run(int argc, char *argv[]) {
                         return log_oom();
         }
 
-        /* Given that things deep down in the child process will fail, let's catch the no-privilege issue
-         * early on */
-        if (!IN_SET(arg_action, ACTION_STATUS, ACTION_LIST) && !have_effective_cap(CAP_SYS_ADMIN))
-                return log_error_errno(SYNTHETIC_ERRNO(EPERM), "Need to be privileged.");
-
-        if (arg_action == ACTION_STATUS)
-                return status();
-
-        if (arg_action == ACTION_UNMERGE)
-                return unmerge();
-
-        images = hashmap_new(&image_hash_ops);
-        if (!images)
-                return log_oom();
-
-        r = image_discover(IMAGE_EXTENSION, arg_root, images);
-        if (r < 0)
-                return log_error_errno(r, "Failed to discover extension images: %m");
-
-        switch (arg_action) {
-
-        case ACTION_LIST: {
-                _cleanup_(table_unrefp) Table *t = NULL;
-                Image *img;
-
-                if ((arg_json_format_flags & JSON_FORMAT_OFF) && hashmap_isempty(images)) {
-                        log_info("No OS extensions found.");
-                        return 0;
-                }
-
-                t = table_new("name", "type", "path", "time");
-                if (!t)
-                        return log_oom();
-
-                HASHMAP_FOREACH(img, images) {
-                        r = table_add_many(
-                                        t,
-                                        TABLE_STRING, img->name,
-                                        TABLE_STRING, image_type_to_string(img->type),
-                                        TABLE_PATH, img->path,
-                                        TABLE_TIMESTAMP, img->mtime != 0 ? img->mtime : img->crtime);
-                        if (r < 0)
-                                return table_log_add_error(r);
-                }
-
-                (void) table_set_sort(t, (size_t) 0, (size_t) -1);
-
-                if (arg_json_format_flags & (JSON_FORMAT_OFF|JSON_FORMAT_PRETTY|JSON_FORMAT_PRETTY_AUTO))
-                        (void) pager_open(arg_pager_flags);
-
-                r = table_print_json(t, stdout, arg_json_format_flags);
-                if (r < 0)
-                        return table_log_print_error(r);
-
-                r = 0;
-                break;
-        }
-
-        case ACTION_MERGE: {
-                char **p;
-
-                /* In merge mode fail if things are already merged. (In --refresh mode below we'll unmerge if
-                 * we find things are already merged...) */
-                STRV_FOREACH(p, arg_hierarchies) {
-                        _cleanup_free_ char *resolved = NULL;
-
-                        r = chase_symlinks(*p, arg_root, CHASE_PREFIX_ROOT, &resolved, NULL);
-                        if (r == -ENOENT) {
-                                log_debug_errno(r, "Hierarchy '%s%s' does not exist, ignoring.", strempty(arg_root), *p);
-                                continue;
-                        }
-                        if (r < 0)
-                                return log_error_errno(r, "Failed to resolve path to hierarchy '%s%s': %m", strempty(arg_root), *p);
-
-                        r = is_our_mount_point(resolved);
-                        if (r < 0)
-                                return r;
-                        if (r > 0)
-                                return log_error_errno(SYNTHETIC_ERRNO(EBUSY),
-                                                       "Hierarchy '%s' is already merged.", *p);
-                }
-
-                r = merge(images);
-                break;
-        }
-
-        case ACTION_REFRESH:
-                r = merge(images); /* Returns > 0 if it did something, i.e. a new overlayfs is mounted
-                                    * now. When it does so it implicitly unmounts any overlayfs placed there
-                                    * before. Returns == 0 if it did nothing, i.e. no extension images
-                                    * found. In this case the old overlayfs remains in place if there was
-                                    * one. */
-                if (r < 0)
-                        return r;
-                if (r == 0) /* No images found? Then unmerge. The goal of --refresh is after all that after
-                             * having called there's a guarantee that the merge status matches the installed
-                             * extensions. */
-                        r = unmerge();
-
-                /* Net result here is that:
-                 *
-                 * 1. If an overlayfs was mounted before and no extensions exist anymore, we'll have unmerged
-                 *    things.
-                 *
-                 * 2. If an overlayfs was mounted before, and there are still extensions installed' we'll
-                 *    have unmerged and then merged things again.
-                 *
-                 * 3. If an overlayfs so far wasn't mounted, and there are extensions installed, we'll have
-                 *    it mounted now.
-                 *
-                 * 4. If there was no overlayfs mount so far, and no extensions installed, we implement a
-                 *    NOP.
-                 */
-                break;
-
-        default:
-                assert_not_reached("Uneexpected action");
-        }
-
-        return r;
+        return sysext_main(argc, argv);
 }
 
 DEFINE_MAIN_FUNCTION(run);
diff --git a/units/systemd-sysext.service b/units/systemd-sysext.service
index cc31f9ca9b..35b5edca1d 100644
--- a/units/systemd-sysext.service
+++ b/units/systemd-sysext.service
@@ -24,8 +24,8 @@ ConditionDirectoryNotEmpty=|/usr/lib/extensions
 [Service]
 Type=oneshot
 RemainAfterExit=yes
-ExecStart=systemd-sysext --merge
-ExecStop=systemd-sysext --unmerge
+ExecStart=systemd-sysext merge
+ExecStop=systemd-sysext unmerge
 
 [Install]
 WantedBy=sysinit.target