hostnamectl: rework pretty hostname validation (#3985)

Rework 17eb9a9ddba3f03fcba33445c1c1eedeb948da04 a bit.

Let's make sure we don't clobber the input parameter args[1], following our
coding style to not clobber parameters unless explicitly indicated. (in
particular, as we don't want to have our changes appear in the command line
shown in "ps"...)

No functional change.

1 files changed, 19 insertions, 17 deletions

diff --git a/src/hostname/hostnamectl.c b/src/hostname/hostnamectl.c
index c16a324232..4795324667 100644
--- a/src/hostname/hostnamectl.c
+++ b/src/hostname/hostnamectl.c
@@ -251,7 +251,7 @@ static int set_simple_string(sd_bus *bus, const char *method, const char *value)
 
 static int set_hostname(sd_bus *bus, char **args, unsigned n) {
         _cleanup_free_ char *h = NULL;
-        char *hostname = args[1];
+        const char *hostname = args[1];
         int r;
 
         assert(args);
@@ -263,27 +263,29 @@ static int set_hostname(sd_bus *bus, char **args, unsigned n) {
         if (arg_pretty) {
                 const char *p;
 
-                /* If the passed hostname is already valid, then
-                 * assume the user doesn't know anything about pretty
-                 * hostnames, so let's unset the pretty hostname, and
-                 * just set the passed hostname as static/dynamic
+                /* If the passed hostname is already valid, then assume the user doesn't know anything about pretty
+                 * hostnames, so let's unset the pretty hostname, and just set the passed hostname as static/dynamic
                  * hostname. */
-
-                if (arg_static && hostname_is_valid(hostname, true)) {
-                        p = "";
-                        /* maybe get rid of trailing dot */
-                        hostname = hostname_cleanup(hostname);
-                } else {
-                        p = h = strdup(hostname);
-                        if (!p)
-                                return log_oom();
-
-                        hostname_cleanup(hostname);
-                }
+                if (arg_static && hostname_is_valid(hostname, true))
+                        p = ""; /* No pretty hostname (as it is redundant), just a static one */
+                else
+                        p = hostname; /* Use the passed name as pretty hostname */
 
                 r = set_simple_string(bus, "SetPrettyHostname", p);
                 if (r < 0)
                         return r;
+
+                /* Now that we set the pretty hostname, let's clean up the parameter and use that as static
+                 * hostname. If the hostname was already valid as static hostname, this will only chop off the trailing
+                 * dot if there is one. If it was not valid, then it will be made fully valid by truncating, dropping
+                 * multiple dots, and and dropping weird chars. Note that we clean the name up only if we also are
+                 * supposed to set the pretty name. If the pretty name is not being set we assume the user knows what
+                 * he does and pass the name as-is. */
+                h = strdup(hostname);
+                if (!h)
+                        return log_oom();
+
+                hostname = hostname_cleanup(h); /* Use the cleaned up name as static hostname */
         }
 
         if (arg_static) {