From 851c706e74acf0f76ee39e0c9ffa75f1e2ed1e23 Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Wed, 12 Mar 2025 06:44:21 +0900
Subject: [PATCH 1/2] test: add test cases for hostname_substitute_wildcards()

The function is indirectly tested through read_etc_hostname(), but let's
also test it directly.
---
 src/test/test-hostname-setup.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/src/test/test-hostname-setup.c b/src/test/test-hostname-setup.c
index da6e379699..8243d600e1 100644
--- a/src/test/test-hostname-setup.c
+++ b/src/test/test-hostname-setup.c
@@ -76,6 +76,32 @@ TEST(read_etc_hostname) {
         assert(hostname == (char*) 0x1234);  /* does not touch argument on error */
 }
 
+TEST(hostname_substitute_wildcards) {
+        int r;
+
+        r = sd_id128_get_machine(NULL);
+        if (ERRNO_IS_NEG_MACHINE_ID_UNSET(r))
+                return (void) log_tests_skipped_errno(r, "skipping wildcard hostname tests, no machine ID defined");
+
+        _cleanup_free_ char *buf = NULL;
+        ASSERT_NOT_NULL((buf = strdup("")));
+        ASSERT_OK(hostname_substitute_wildcards(buf));
+        ASSERT_STREQ(buf, "");
+        ASSERT_NULL((buf = mfree(buf)));
+
+        ASSERT_NOT_NULL((buf = strdup("hogehoge")));
+        ASSERT_OK(hostname_substitute_wildcards(buf));
+        ASSERT_STREQ(buf, "hogehoge");
+        ASSERT_NULL((buf = mfree(buf)));
+
+        ASSERT_NOT_NULL((buf = strdup("hoge??hoge??foo?")));
+        ASSERT_OK(hostname_substitute_wildcards(buf));
+        log_debug("hostname_substitute_wildcards(\"hoge??hoge??foo?\"): → \"%s\"", buf);
+        ASSERT_EQ(fnmatch("hoge??hoge??foo?", buf, /* flags= */ 0), 0);
+        ASSERT_TRUE(hostname_is_valid(buf, /* flags= */ 0));
+        ASSERT_NULL((buf = mfree(buf)));
+}
+
 TEST(hostname_setup) {
         hostname_setup(false);
 }

From 35d5defc4e78fa97730370762953a58a27f9f560 Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Wed, 12 Mar 2025 06:46:36 +0900
Subject: [PATCH 2/2] hostname-setup: use strchr() to find wildcard character

Addresses https://github.com/systemd/systemd/pull/36647#discussion_r1990048751.
---
 src/shared/hostname-setup.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/src/shared/hostname-setup.c b/src/shared/hostname-setup.c
index af89f92bdc..33b6a05ad8 100644
--- a/src/shared/hostname-setup.c
+++ b/src/shared/hostname-setup.c
@@ -268,9 +268,10 @@ int hostname_substitute_wildcards(char *name) {
          * Note that this does not directly use the machine ID, because that's not necessarily supposed to be
          * public information to be broadcast on the network, while the hostname certainly is. */
 
-        for (char *n = name; *n; n++) {
-                if (*n != '?')
-                        continue;
+        for (char *n = name; ; n++) {
+                n = strchr(n, '?');
+                if (!n)
+                        return 0;
 
                 if (left_bits <= 0) {
                         if (sd_id128_is_null(mid)) {
@@ -293,8 +294,6 @@ int hostname_substitute_wildcards(char *name) {
                 h >>= 4;
                 left_bits -= 4;
         }
-
-        return 0;
 }
 
 char* get_default_hostname(void) {