Make new sd-path configuration search functionality generic (#39684)

Reverts systemd/systemd#38680

After taking a closer look I'm not convinced by the approach, see below.

First of all, all other SD_PATH_SEARCH_* are either somewhat generic,
i.e. encode the common prefix for configurations, binaries, etc., or are
subdirectories under systemd/ hence in our own "domain". The
tmpfiles/sysctl/binfmt we don't prefix with "systemd" precisely because
the concept is generic and there're actually other impls of them. A
specific SD_PATH_SEARCH_SYSCTL doesn't fit into our existing scheme.
Instead something along the lines of "SEARCH_SYSTEM_CONFIGURATION" shall
be introduced, and consumers will just suffix
sysctl.d/tmpfiles.d/binfmt.d for the final result.

And secondly, I don't grok why systemd-sysctl now unnecessarily calls
into sd-path to obtain the fixed search path. None of our other tools do
that.

-----------

An alternate approach, SD_PATH_SYSTEM_SEARCH_CONFIGURATION, which does
exactly above, will be introduced instead. It provides a universal
interface for querying any system config with our idiomatic
/etc/:/run/:/usr/local/lib/:/usr/lib/ hierarchy.

man/sd_path_lookup.xml

@@ -41,6 +41,7 @@
         <constant>SD_PATH_SYSTEM_STATE_FACTORY</constant>,
 
         <constant>SD_PATH_SYSTEM_CONFIGURATION</constant>,
+        <constant>SD_PATH_SYSTEM_SEARCH_CONFIGURATION</constant>,
         <constant>SD_PATH_SYSTEM_RUNTIME</constant>,
         <constant>SD_PATH_SYSTEM_RUNTIME_LOGS</constant>,
         <constant>SD_PATH_SYSTEM_STATE_PRIVATE</constant>,
@@ -76,7 +77,6 @@
         <constant>SD_PATH_SEARCH_CONFIGURATION_FACTORY</constant>,
         <constant>SD_PATH_SEARCH_STATE_FACTORY</constant>,
         <constant>SD_PATH_SEARCH_CONFIGURATION</constant>,
-        <constant>SD_PATH_SEARCH_SYSCTL</constant>,
 
         <constant>SD_PATH_SYSTEMD_UTIL</constant>,
         <constant>SD_PATH_SYSTEMD_SYSTEM_UNIT</constant>,

src/libsystemd/sd-path/sd-path.c

@@ -524,6 +524,9 @@ static int get_search(uint64_t type, char ***ret) {
 
         switch (type) {
 
+        case SD_PATH_SYSTEM_SEARCH_CONFIGURATION:
+                return strv_from_nulstr(ret, CONF_PATHS_NULSTR(""));
+
         case SD_PATH_SEARCH_BINARIES:
                 return search_from_environment(ret,
                                                NULL,
@@ -683,11 +686,7 @@ static int get_search(uint64_t type, char ***ret) {
 
                 *ret = TAKE_PTR(l);
                 return 0;
-        }
-
-        case SD_PATH_SEARCH_SYSCTL:
-                return strv_from_nulstr(ret, CONF_PATHS_NULSTR("sysctl.d"));
-        }
+        }}
 
         return -EOPNOTSUPP;
 }

src/path/path-tool.c

@@ -22,6 +22,8 @@ static const char* const path_table[_SD_PATH_MAX] = {
         [SD_PATH_TEMPORARY]                                   = "temporary",
         [SD_PATH_TEMPORARY_LARGE]                             = "temporary-large",
 
+        [SD_PATH_SYSTEM_SEARCH_CONFIGURATION]                 = "system-search-configuration",
+
         [SD_PATH_SYSTEM_BINARIES]                             = "system-binaries",
         [SD_PATH_SYSTEM_INCLUDE]                              = "system-include",
         [SD_PATH_SYSTEM_LIBRARY_PRIVATE]                      = "system-library-private",
@@ -66,7 +68,6 @@ static const char* const path_table[_SD_PATH_MAX] = {
         [SD_PATH_SEARCH_CONFIGURATION_FACTORY]                = "search-configuration-factory",
         [SD_PATH_SEARCH_STATE_FACTORY]                        = "search-state-factory",
         [SD_PATH_SEARCH_CONFIGURATION]                        = "search-configuration",
-        [SD_PATH_SEARCH_SYSCTL]                               = "search-sysctl",
 
         [SD_PATH_SYSTEMD_UTIL]                                = "systemd-util",
 

src/sysctl/sysctl.c

@@ -4,8 +4,6 @@
 #include <stdio.h>
 #include <sys/stat.h>
 
-#include "sd-path.h"
-
 #include "alloc-util.h"
 #include "build.h"
 #include "conf-files.h"
@@ -281,10 +279,10 @@ static int parse_line(const char *fname, unsigned line, const char *buffer, bool
         return 0;
 }
 
-static int parse_file(OrderedHashmap **sysctl_options, const char *path, bool ignore_enoent, const char **search_paths) {
+static int parse_file(OrderedHashmap **sysctl_options, const char *path, bool ignore_enoent) {
         return conf_file_read(
                         /* root = */ NULL,
-                        search_paths,
+                        (const char**) CONF_PATHS_STRV("sysctl.d"),
                         path,
                         parse_line,
                         sysctl_options,
@@ -307,7 +305,7 @@ static int read_credential_lines(OrderedHashmap **sysctl_options) {
         if (!j)
                 return log_oom();
 
-        return parse_file(sysctl_options, j, /* ignore_enoent= */ true, /* search_paths= */ NULL);
+        return parse_file(sysctl_options, j, /* ignore_enoent= */ true);
 }
 
 static int cat_config(char **files) {
@@ -442,13 +440,8 @@ static int parse_argv(int argc, char *argv[]) {
 
 static int run(int argc, char *argv[]) {
         _cleanup_ordered_hashmap_free_ OrderedHashmap *sysctl_options = NULL;
-        _cleanup_strv_free_ char **search_paths = NULL;
         int r;
 
-        r = sd_path_lookup_strv(SD_PATH_SEARCH_SYSCTL, /* suffix= */ NULL, &search_paths);
-        if (r < 0)
-               return log_error_errno(r, "Failed to get sysctl.d/ search paths: %m");
-
         r = parse_argv(argc, argv);
         if (r <= 0)
                 return r;
@@ -465,12 +458,12 @@ static int run(int argc, char *argv[]) {
                                 /* Use (argument):n, where n==1 for the first positional arg */
                                 RET_GATHER(r, parse_line("(argument)", ++pos, *arg, /* invalid_config = */ NULL, &sysctl_options));
                         else
-                                RET_GATHER(r, parse_file(&sysctl_options, *arg, /* ignore_enoent= */ false, (const char**) search_paths));
+                                RET_GATHER(r, parse_file(&sysctl_options, *arg, false));
                 }
         } else {
                 _cleanup_strv_free_ char **files = NULL;
 
-                r = conf_files_list_strv(&files, ".conf", NULL, 0, (const char**) search_paths);
+                r = conf_files_list_strv(&files, ".conf", NULL, 0, (const char**) CONF_PATHS_STRV("sysctl.d"));
                 if (r < 0)
                         return log_error_errno(r, "Failed to enumerate sysctl.d files: %m");
 
@@ -478,7 +471,7 @@ static int run(int argc, char *argv[]) {
                         return cat_config(files);
 
                 STRV_FOREACH(f, files)
-                        RET_GATHER(r, parse_file(&sysctl_options, *f, /* ignore_enoent= */ true, /* search_paths= */ NULL));
+                        RET_GATHER(r, parse_file(&sysctl_options, *f, true));
 
                 RET_GATHER(r, read_credential_lines(&sysctl_options));
         }

src/systemd/sd-path.h

@@ -44,6 +44,9 @@ __extension__ enum {
         SD_PATH_SYSTEM_STATE_CACHE,
         SD_PATH_SYSTEM_STATE_SPOOL,
 
+        /* generic system configuration */
+        SD_PATH_SYSTEM_SEARCH_CONFIGURATION,
+
         /* Vendor supplied data */
         SD_PATH_USER_BINARIES,
         SD_PATH_USER_LIBRARY_PRIVATE,
@@ -129,8 +132,6 @@ __extension__ enum {
         SD_PATH_USER_CREDENTIAL_STORE_ENCRYPTED,
         SD_PATH_USER_SEARCH_CREDENTIAL_STORE_ENCRYPTED,
 
-        SD_PATH_SEARCH_SYSCTL,
-
         _SD_PATH_MAX,
         _SD_PATH_INVALID = UINT64_MAX
 };

test/units/TEST-74-AUX-UTILS.path.sh

@@ -51,6 +51,8 @@ assert_eq "$(systemd-path --suffix='' system-runtime)" "/run"
 assert_eq "$(systemd-path --suffix='🤔' system-runtime)" "/run/🤔"
 assert_eq "$(systemd-path --suffix=hello system-runtime)" "/run/hello"
 
+assert_eq "$(systemd-path system-search-configuration --suffix=sysctl.d)" "/etc/sysctl.d:/run/sysctl.d:/usr/local/lib/sysctl.d:/usr/lib/sysctl.d"
+
 # Note for the stuff below: everything defaults to $HOME, only the desktop
 # directory defaults to $HOME/Desktop.
 #