systemd/backport-sysctl-apply-prefix-before-calling-glob.patch

From 9ec8c82b8c836f7632ba0a075c296e6ddc53f643 Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Wed, 17 Aug 2022 04:54:06 +0900
Subject: [PATCH] sysctl: apply prefix before calling glob()

Otherwise, if there exist million of network interfaces,
calling glob() for network properties takes much time.

Fixes #24031.
---
 src/sysctl/sysctl.c | 61 +++++++++++++++++++++++++++++++++++++++------
 1 file changed, 53 insertions(+), 8 deletions(-)

diff --git a/src/sysctl/sysctl.c b/src/sysctl/sysctl.c
index fc13529..499ddde 100644
--- a/src/sysctl/sysctl.c
+++ b/src/sysctl/sysctl.c
@@ -86,7 +86,7 @@ static Option *option_new(
         return TAKE_PTR(o);
 }
 
-static int sysctl_write_or_warn(const char *key, const char *value, bool ignore_failure) {
+static int sysctl_write_or_warn(const char *key, const char *value, bool ignore_failure, bool ignore_enoent) {
         int r;
 
         r = sysctl_write(key, value);
@@ -106,7 +106,7 @@ static int sysctl_write_or_warn(const char *key, const char *value, bool ignore_
         return 0;
 }
 
-static int apply_glob_option(OrderedHashmap *sysctl_options, Option *option) {
+static int apply_glob_option_with_prefix(OrderedHashmap *sysctl_options, Option *option, const char *prefix) {
         _cleanup_strv_free_ char **paths = NULL;
         _cleanup_free_ char *pattern = NULL;
         int r, k;
@@ -115,7 +115,35 @@ static int apply_glob_option(OrderedHashmap *sysctl_options, Option *option) {
         assert(sysctl_options);
         assert(option);
 
-        pattern = path_join("/proc/sys", option->key);
+        if (prefix) {
+                _cleanup_free_ char *key = NULL;
+
+                r = path_glob_can_match(option->key, prefix, &key);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to check if the glob '%s' matches prefix '%s': %m",
+                                               option->key, prefix);
+                if (r == 0) {
+                        log_debug("The glob '%s' does not match prefix '%s'.", option->key, prefix);
+                        return 0;
+                }
+
+                log_debug("The glob '%s' is prefixed with '%s': '%s'", option->key, prefix, key);
+
+                if (!string_is_glob(key)) {
+                        /* The prefixed pattern is not glob anymore. Let's skip to call glob(). */
+                        if (ordered_hashmap_contains(sysctl_options, key)) {
+                                log_debug("Not setting %s (explicit setting exists).", key);
+                                return 0;
+                        }
+
+                        return sysctl_write_or_warn(key, option->value,
+                                                    /* ignore_failure = */ option->ignore_failure,
+                                                    /* ignore_enoent = */ true);
+                }
+
+                pattern = path_join("/proc/sys", key);
+        } else
+                pattern = path_join("/proc/sys", option->key);
         if (!pattern)
                 return log_oom();
 
@@ -137,15 +165,30 @@ static int apply_glob_option(OrderedHashmap *sysctl_options, Option *option) {
 
                 assert_se(key = path_startswith(*s, "/proc/sys"));
 
-                if (!test_prefix(key))
-                        continue;
-
                 if (ordered_hashmap_contains(sysctl_options, key)) {
                         log_debug("Not setting %s (explicit setting exists).", key);
                         continue;
                 }
 
-                k = sysctl_write_or_warn(key, option->value, option->ignore_failure);
+                k = sysctl_write_or_warn(key, option->value,
+                                         /* ignore_failure = */ option->ignore_failure,
+                                         /* ignore_enoent = */ false);
+                if (k < 0 && r >= 0)
+                        r = k;
+        }
+
+        return r;
+}
+
+static int apply_glob_option(OrderedHashmap *sysctl_options, Option *option) {
+        int r = 0, k;
+        char **i;
+
+        if (strv_isempty(arg_prefixes))
+                return apply_glob_option_with_prefix(sysctl_options, option, NULL);
+
+        STRV_FOREACH(i, arg_prefixes) {
+                k = apply_glob_option_with_prefix(sysctl_options, option, *i);
                 if (k < 0 && r >= 0)
                         r = k;
         }
@@ -167,7 +210,9 @@ static int apply_all(OrderedHashmap *sysctl_options) {
                 if (string_is_glob(option->key))
                         k = apply_glob_option(sysctl_options, option);
                 else
-                        k = sysctl_write_or_warn(option->key, option->value, option->ignore_failure);
+                        k = sysctl_write_or_warn(option->key, option->value,
+                                                 /* ignore_failure = */ option->ignore_failure,
+                                                 /* ignore_enoent = */ false);
                 if (k < 0 && r >= 0)
                         r = k;
         }
-- 
2.33.0