hostnamed: stop discriminating against "localhost" in /etc/hostname

We would sometimes ignore localhost-style names in /etc/hostname. That is
brittle. If the user configured some hostname, it's most likely because they
want to use that as the hostname. If they don't want to use such a hostname,
they should just not create the config. Everything becomes simples if we just
use the configured hostname as-is.

This behaviour seems to have been a workaround for Anaconda installer and other
tools writing out /etc/hostname with the default of "localhost.localdomain".
Anaconda PR to stop doing that: https://github.com/rhinstaller/anaconda/pull/3040.
That might have been useful as a work-around for other programs misbehaving if
/etc/hostname was not present, but nowadays it's not useful because systemd
mostly controls the hostname and it is perfectly happy without that file.

Apart from making things simpler, this allows users to set a hostname like
"localhost" and have it honoured, if such a whim strikes them.

2 files changed, 6 insertions, 17 deletions

diff --git a/man/hostnamectl.xml b/man/hostnamectl.xml
index f50cefa217..224dab78a7 100644
--- a/man/hostnamectl.xml
+++ b/man/hostnamectl.xml
@@ -39,8 +39,8 @@
     and this tool distinguish three different hostnames: the high-level "pretty" hostname which might include
     all kinds of special characters (e.g. "Lennart's Laptop"), the "static" hostname which is the
     user-configured hostname (e.g. "lennarts-laptop"), and the transient hostname which is a fallback value
-    received from network configuration (e.g. "node12345678"). If a static hostname is set, and is valid
-    (something other than localhost), then the transient hostname is not used.</para>
+    received from network configuration (e.g. "node12345678"). If a static hostname is set to a valid value,
+    then the transient hostname is not used.</para>
 
     <para>Note that the pretty hostname has little restrictions on the characters and length used, while the static and
     transient hostnames are limited to the usually accepted characters of Internet domain names, and 64 characters at
diff --git a/src/hostname/hostnamed.c b/src/hostname/hostnamed.c
index 43b5c11612..9e8a4dd8a4 100644
--- a/src/hostname/hostnamed.c
+++ b/src/hostname/hostnamed.c
@@ -312,15 +312,11 @@ static char* context_fallback_icon_name(Context *c) {
         return strdup("computer");
 }
 
-static bool hostname_is_useful(const char *hn) {
-        return !isempty(hn) && !is_localhost(hn);
-}
-
 static int context_update_kernel_hostname(
                 Context *c,
                 const char *transient_hn) {
 
-        const char *static_hn, *hn;
+        const char *hn;
         struct utsname u;
         int r;
 
@@ -333,21 +329,14 @@ static int context_update_kernel_hostname(
                         isempty(u.nodename) || streq(u.nodename, "(none)") ? NULL : u.nodename;
         }
 
-        static_hn = c->data[PROP_STATIC_HOSTNAME];
-
-        /* /etc/hostname with something other than "localhost"
-         * has the highest preference ... */
-        if (hostname_is_useful(static_hn))
-                hn = static_hn;
+        /* /etc/hostname has the highest preference ... */
+        if (c->data[PROP_STATIC_HOSTNAME])
+                hn = c->data[PROP_STATIC_HOSTNAME];
 
         /* ... the transient hostname, (ie: DHCP) comes next ... */
         else if (!isempty(transient_hn))
                 hn = transient_hn;
 
-        /* ... fallback to static "localhost.*" ignored above ... */
-        else if (!isempty(static_hn))
-                hn = static_hn;
-
         /* ... and the ultimate fallback */
         else
                 hn = FALLBACK_HOSTNAME;