sysext: support EXTENSION_RELOAD_MANAGER metadata

This metadata (EXTENSION_RELOAD_MANAGER) can be set to "1" to reload the manager
when merging/refreshing/unmerging a system extension image. This can be useful in case the sysext
image provides systemd units that need to be loaded.

With `--no-reload`, one can deactivate the EXTENSION_RELOAD_MANAGER metadata interpretation.

Signed-off-by: Mathieu Tortuyaux <mtortuyaux@microsoft.com>

1 files changed, 121 insertions, 1 deletions

diff --git a/src/sysext/sysext.c b/src/sysext/sysext.c
index b043eac562..98640c026b 100644
--- a/src/sysext/sysext.c
+++ b/src/sysext/sysext.c
@@ -7,9 +7,16 @@
 #include <sys/mount.h>
 #include <unistd.h>
 
+#include "sd-bus.h"
+
 #include "build.h"
+#include "bus-locator.h"
+#include "bus-error.h"
+#include "bus-unit-util.h"
+#include "bus-util.h"
 #include "capability-util.h"
 #include "chase.h"
+#include "constants.h"
 #include "devnum-util.h"
 #include "discover-image.h"
 #include "dissect-image.h"
@@ -45,6 +52,7 @@ static JsonFormatFlags arg_json_format_flags = JSON_FORMAT_OFF;
 static PagerFlags arg_pager_flags = 0;
 static bool arg_legend = true;
 static bool arg_force = false;
+static bool arg_no_reload = false;
 static int arg_noexec = -1;
 static ImagePolicy *arg_image_policy = NULL;
 
@@ -144,6 +152,87 @@ static int is_our_mount_point(const char *p) {
         return true;
 }
 
+static int need_reload(void) {
+        /* Parse the mounted images to find out if we need
+        to reload the daemon. */
+        int r;
+
+        if (arg_no_reload)
+                return false;
+
+        STRV_FOREACH(p, arg_hierarchies) {
+                _cleanup_free_ char *f = NULL, *buf = NULL, *resolved = NULL;
+                _cleanup_strv_free_ char **mounted_extensions = NULL;
+
+                r = chase(*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) {
+                        log_warning_errno(r, "Failed to resolve path to hierarchy '%s%s': %m, ignoring.", strempty(arg_root), *p);
+                        continue;
+                }
+
+                r = is_our_mount_point(resolved);
+                if (r < 0)
+                        return r;
+                if (!r)
+                        continue;
+
+                f = path_join(*p, image_class_info[arg_image_class].dot_directory_name, image_class_info[arg_image_class].short_identifier_plural);
+                if (!f)
+                        return log_oom();
+
+                r = read_full_file(f, &buf, NULL);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to open '%s': %m", f);
+
+                mounted_extensions = strv_split_newlines(buf);
+                if (!mounted_extensions)
+                        return log_oom();
+
+                STRV_FOREACH(extension, mounted_extensions) {
+                        _cleanup_strv_free_ char **extension_release = NULL;
+                        const char *extension_reload_manager = NULL;
+                        int b;
+
+                        r = load_extension_release_pairs(arg_root, arg_image_class, *extension, /* relax_extension_release_check */ true, &extension_release);
+                        if (r < 0) {
+                                log_debug_errno(r, "Failed to parse extension-release metadata of %s, ignoring: %m", *extension);
+                                continue;
+                        }
+
+                        extension_reload_manager = strv_env_pairs_get(extension_release, "EXTENSION_RELOAD_MANAGER");
+                        if (isempty(extension_reload_manager))
+                                continue;
+
+                        b = parse_boolean(extension_reload_manager);
+                        if (b < 0) {
+                                log_warning_errno(b, "Failed to parse the extension metadata to know if the manager needs to be reloaded, ignoring: %m");
+                                continue;
+                        }
+
+                        if (b)
+                                /* If at least one extension wants a reload, we reload. */
+                                return true;
+                }
+        }
+
+        return false;
+}
+
+static int daemon_reload(void) {
+        sd_bus *bus;
+        int r;
+
+        r = bus_connect_system_systemd(&bus);
+        if (r < 0)
+                return log_error_errno(r, "Failed to get D-Bus connection: %m");
+
+        return bus_service_manager_reload(bus);
+}
+
 static int unmerge_hierarchy(const char *p) {
         int r;
 
@@ -169,6 +258,12 @@ static int unmerge_hierarchy(const char *p) {
 
 static int unmerge(void) {
         int r, ret = 0;
+        bool need_to_reload;
+
+        r = need_reload();
+        if (r < 0)
+                return r;
+        need_to_reload = r > 0;
 
         STRV_FOREACH(p, arg_hierarchies) {
                 _cleanup_free_ char *resolved = NULL;
@@ -191,6 +286,12 @@ static int unmerge(void) {
                         ret = r;
         }
 
+        if (need_to_reload) {
+                r = daemon_reload();
+                if (r < 0)
+                        return r;
+        }
+
         return ret;
 }
 
@@ -784,7 +885,19 @@ static int merge(Hashmap *images) {
         if (r < 0)
                 return r;
 
-        return r != 123; /* exit code 123 means: didn't do anything */
+        if (r == 123) /* exit code 123 means: didn't do anything */
+                return 0;
+
+        r = need_reload();
+        if (r < 0)
+                return r;
+        if (r > 0) {
+                r = daemon_reload();
+                if (r < 0)
+                        return r;
+        }
+
+        return 1;
 }
 
 static int image_discover_and_read_metadata(Hashmap **ret_images) {
@@ -955,6 +1068,7 @@ static int verb_help(int argc, char **argv, void *userdata) {
                "     --json=pretty|short|off\n"
                "                          Generate JSON output\n"
                "     --force              Ignore version incompatibilities\n"
+               "     --no-reload          Do not reload the service manager\n"
                "     --image-policy=POLICY\n"
                "                          Specify disk image dissection policy\n"
                "     --noexec=BOOL        Whether to mount extension overlay with noexec\n"
@@ -980,6 +1094,7 @@ static int parse_argv(int argc, char *argv[]) {
                 ARG_FORCE,
                 ARG_IMAGE_POLICY,
                 ARG_NOEXEC,
+                ARG_NO_RELOAD,
         };
 
         static const struct option options[] = {
@@ -992,6 +1107,7 @@ static int parse_argv(int argc, char *argv[]) {
                 { "force",        no_argument,       NULL, ARG_FORCE        },
                 { "image-policy", required_argument, NULL, ARG_IMAGE_POLICY },
                 { "noexec",       required_argument, NULL, ARG_NOEXEC       },
+                { "no-reload",    no_argument,       NULL, ARG_NO_RELOAD    },
                 {}
         };
 
@@ -1049,6 +1165,10 @@ static int parse_argv(int argc, char *argv[]) {
                         arg_noexec = r;
                         break;
 
+                case ARG_NO_RELOAD:
+                        arg_no_reload = true;
+                        break;
+
                 case '?':
                         return -EINVAL;