unit-file: support UpheldBy= in [Install] settings (adding Upholds= deps

from .upholds/)

Closes #26896

6 files changed, 29 insertions, 11 deletions

diff --git a/src/basic/unit-file.c b/src/basic/unit-file.c
index 41422579d6..54f2137a36 100644
--- a/src/basic/unit-file.c
+++ b/src/basic/unit-file.c
@@ -250,9 +250,10 @@ bool lookup_paths_timestamp_hash_same(const LookupPaths *lp, uint64_t timestamp_
 
 static int directory_name_is_valid(const char *name) {
 
-        /* Accept a directory whose name is a valid unit file name ending in .wants/, .requires/ or .d/ */
+        /* Accept a directory whose name is a valid unit file name ending in .wants/, .requires/,
+         * .upholds/ or .d/ */
 
-        FOREACH_STRING(suffix, ".wants", ".requires", ".d") {
+        FOREACH_STRING(suffix, ".wants", ".requires", ".upholds", ".d") {
                 _cleanup_free_ char *chopped = NULL;
                 const char *e;
 
diff --git a/src/core/load-dropin.c b/src/core/load-dropin.c
index 53d2a3daa1..fd45744261 100644
--- a/src/core/load-dropin.c
+++ b/src/core/load-dropin.c
@@ -88,7 +88,7 @@ int unit_load_dropin(Unit *u) {
 
         assert(u);
 
-        /* Load dependencies from .wants and .requires directories */
+        /* Load dependencies from .wants, .requires and .upholds directories */
         r = process_deps(u, UNIT_WANTS, ".wants");
         if (r < 0)
                 return r;
@@ -97,6 +97,10 @@ int unit_load_dropin(Unit *u) {
         if (r < 0)
                 return r;
 
+        r = process_deps(u, UNIT_UPHOLDS, ".upholds");
+        if (r < 0)
+                return r;
+
         /* Load .conf dropins */
         r = unit_find_dropin_paths(u, &l);
         if (r <= 0)
diff --git a/src/core/load-fragment-gperf.gperf.in b/src/core/load-fragment-gperf.gperf.in
index 110bccb7ad..2a3c2c2cb8 100644
--- a/src/core/load-fragment-gperf.gperf.in
+++ b/src/core/load-fragment-gperf.gperf.in
@@ -580,5 +580,6 @@ Scope.OOMPolicy,                         config_parse_oom_policy,
 Install.Alias,                           NULL,                                        0,                                  0
 Install.WantedBy,                        NULL,                                        0,                                  0
 Install.RequiredBy,                      NULL,                                        0,                                  0
+Install.UpheldBy,                        NULL,                                        0,                                  0
 Install.Also,                            NULL,                                        0,                                  0
 Install.DefaultInstance,                 NULL,                                        0,                                  0
diff --git a/src/shared/install.c b/src/shared/install.c
index 152e517ebc..7903de17b1 100644
--- a/src/shared/install.c
+++ b/src/shared/install.c
@@ -73,7 +73,8 @@ static bool install_info_has_rules(const InstallInfo *i) {
 
         return !strv_isempty(i->aliases) ||
                !strv_isempty(i->wanted_by) ||
-               !strv_isempty(i->required_by);
+               !strv_isempty(i->required_by) ||
+               !strv_isempty(i->upheld_by);
 }
 
 static bool install_info_has_also(const InstallInfo *i) {
@@ -942,7 +943,7 @@ static int find_symlinks(
                         continue;
 
                 suffix = strrchr(de->d_name, '.');
-                if (!STRPTR_IN_SET(suffix, ".wants", ".requires"))
+                if (!STRPTR_IN_SET(suffix, ".wants", ".requires", ".upholds"))
                         continue;
 
                 path = path_join(config_path, de->d_name);
@@ -967,7 +968,8 @@ static int find_symlinks(
                         log_debug_errno(r, "Failed to look up symlinks in \"%s\": %m", path);
         }
 
-        /* We didn't find any suitable symlinks in .wants or .requires directories, let's look for linked unit files in this directory. */
+        /* We didn't find any suitable symlinks in .wants, .requires or .upholds directories,
+         * let's look for linked unit files in this directory. */
         rewinddir(config_dir);
         return find_symlinks_in_directory(config_dir, config_path, root_dir, i,
                                           /* ignore_destination= */ false,
@@ -1081,6 +1083,7 @@ static void install_info_clear(InstallInfo *i) {
         i->aliases = strv_free(i->aliases);
         i->wanted_by = strv_free(i->wanted_by);
         i->required_by = strv_free(i->required_by);
+        i->upheld_by = strv_free(i->upheld_by);
         i->also = strv_free(i->also);
         i->default_instance = mfree(i->default_instance);
         i->symlink_target = mfree(i->symlink_target);
@@ -1337,6 +1340,7 @@ static int unit_file_load(
                 { "Install", "Alias",           config_parse_alias,            0, &info->aliases           },
                 { "Install", "WantedBy",        config_parse_strv,             0, &info->wanted_by         },
                 { "Install", "RequiredBy",      config_parse_strv,             0, &info->required_by       },
+                { "Install", "UpheldBy",        config_parse_strv,             0, &info->upheld_by         },
                 { "Install", "DefaultInstance", config_parse_default_instance, 0, info                     },
                 { "Install", "Also",            config_parse_also,             0, ctx                      },
                 {}
@@ -1440,7 +1444,8 @@ static int unit_file_load(
         return
                 (int) strv_length(info->aliases) +
                 (int) strv_length(info->wanted_by) +
-                (int) strv_length(info->required_by);
+                (int) strv_length(info->required_by) +
+                (int) strv_length(info->upheld_by);
 }
 
 static int unit_file_load_or_readlink(
@@ -2113,6 +2118,10 @@ static int install_info_apply(
         if (r == 0)
                 r = q;
 
+        q = install_info_symlink_wants(scope, file_flags, info, lp, config_path, info->upheld_by, ".upholds/", changes, n_changes);
+        if (r == 0)
+                r = q;
+
         return r;
 }
 
@@ -2733,8 +2742,10 @@ int unit_file_add_dependency(
 
                 if (dep == UNIT_WANTS)
                         l = &info->wanted_by;
-                else
+                else if (dep == UNIT_REQUIRES)
                         l = &info->required_by;
+                else
+                        l = &info->upheld_by;
 
                 strv_free(*l);
                 *l = strv_new(target_info->name);
diff --git a/src/shared/install.h b/src/shared/install.h
index 30b07a725f..bc0c6db828 100644
--- a/src/shared/install.h
+++ b/src/shared/install.h
@@ -92,6 +92,7 @@ struct InstallInfo {
         char **aliases;
         char **wanted_by;
         char **required_by;
+        char **upheld_by;
         char **also;
 
         char *default_instance;
diff --git a/src/systemctl/systemctl-enable.c b/src/systemctl/systemctl-enable.c
index 6d3709705e..940f54607f 100644
--- a/src/systemctl/systemctl-enable.c
+++ b/src/systemctl/systemctl-enable.c
@@ -248,9 +248,9 @@ int verb_enable(int argc, char *argv[], void *userdata) {
         }
 
         if (carries_install_info == 0 && !ignore_carries_install_info)
-                log_notice("The unit files have no installation config (WantedBy=, RequiredBy=, Also=,\n"
-                           "Alias= settings in the [Install] section, and DefaultInstance= for template\n"
-                           "units). This means they are not meant to be enabled or disabled using systemctl.\n"
+                log_notice("The unit files have no installation config (WantedBy=, RequiredBy=, UpheldBy=,\n"
+                           "Also=, or Alias= settings in the [Install] section, and DefaultInstance= for\n"
+                           "template units). This means they are not meant to be enabled or disabled using systemctl.\n"
                            " \n" /* trick: the space is needed so that the line does not get stripped from output */
                            "Possible reasons for having this kind of units are:\n"
                            "%1$s A unit may be statically enabled by being symlinked from another unit's\n"