fix issue 1553 makedns failed when input invalid hostname into /etc/hosts

xCAT-server/lib/xcat/plugins/ddns.pm

@@ -423,6 +423,8 @@ sub process_request {
         my $names;
         my @hosts;
         my %nodehash;
+        my @eachhost;
+        my $invalid;
 
         foreach (@contents) {
             chomp;            #no newline
@@ -440,6 +442,18 @@ sub process_request {
                 next;
             }
 
+            @eachhost = split(/ /,$names);
+            foreach my $hname (@eachhost) {
+                unless ($hname !~ /^\.[a-z0-9]+/i) {
+                    xCAT::SvrUtils::sendmsg(":Ignoring line $_ in /etc/hosts, names  $names start with . ", $callback);
+                    $invalid = $names;
+                    last;
+                }
+            }
+            if ($invalid) {
+                next;
+            }
+
             my ($host, $ip) = xCAT::NetworkUtils->gethostnameandip($addr);
             push @hosts, $host;
             $nodehash{$addr}{names} = $names;