From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Thu, 30 Dec 2021 18:48:17 +0000 (+0900)
Subject: hostname-setup: gracefully handle kernel with empty CONFIG_DEFAULT_HOSTNAME
X-Git-Tag: v251-rc1~609^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d8d6b2275f7b7a5b58c6b0d89b78c927333c6af9;p=thirdparty%2Fsystemd.git

hostname-setup: gracefully handle kernel with empty CONFIG_DEFAULT_HOSTNAME

Previously, sethostname_idempotent_full() calls gethostname_full() with
GET_HOSTNAME_ALLOW_NONE and GET_HOSTNAME_ALLOW_LOCALHOST flags. That
intended to get any values set by kernel. But, that does not work, as
the hostname may be empty.

Let's simplify the logic. The function sethostname_idempotent_full()
intends to set the requested hostname only when the current hostname
is different from the requested one. So, no check in getostname_full()
is required. Hence, simply use the result of uname() here.

Fixes #21896.
---

diff --git a/src/shared/hostname-setup.c b/src/shared/hostname-setup.c
index 1329b0d1894..0fac0ecab71 100644
--- a/src/shared/hostname-setup.c
+++ b/src/shared/hostname-setup.c
@@ -20,16 +20,13 @@
 #include "util.h"
 
 static int sethostname_idempotent_full(const char *s, bool really) {
-        _cleanup_free_ char *buf = NULL;
-        int r;
+        struct utsname u;
 
         assert(s);
 
-        r = gethostname_full(GET_HOSTNAME_ALLOW_NONE | GET_HOSTNAME_ALLOW_LOCALHOST, &buf);
-        if (r < 0)
-                return r;
+        assert_se(uname(&u) >= 0);
 
-        if (streq(buf, s))
+        if (streq_ptr(s, u.nodename))
                 return 0;
 
         if (really &&