Allow multiple hyphens in domain names

plugins/common/functions

@@ -1065,7 +1065,7 @@ strip_inline_comments() {
 
 is_valid_hostname() {
   declare desc="return 0 if argument is a valid hostname; else return 1"
-  local hostname_string="${1,,}"; local hostname_regex='^(([a-z0-9\*](-?[a-z0-9])*)\.)+([a-z0-9\*](-?[a-z0-9])*)$'
+  local hostname_string="${1,,}"; local hostname_regex='^([a-z0-9\-\*]+\.)*[a-z0-9\-\*]+$'
   if [[ $hostname_string =~ $hostname_regex ]]; then
     return 0
   else