TT#11537 Add helper template for gethostbyname

For iptables firewall rules it is necessary to translate hostnames,
which may be used in config.yml into a list of IPs as returned by
"gethostbyname".

Change-Id: I149227d5031534d3826a2c91012a599f7c7c4756

lib/get_host_by_name

@@ -0,0 +1,27 @@
+[%
+  # Return an array of IPs from a given hostname
+  #
+  # @param argv.name    The hostname to lookup
+  # @param argv.type    The address family to lookup ("AF_INET" for IPv4,
+  #                     "AF_INET6" for IPv6, and "" for both)
+  # @return out         The array of ips
+-%]
+[% out = [] -%]
+[% LOAD_PERL => 1 -%]
+[% PERL -%]
+   use Socket qw(:all);
+
+   my $err;
+   my $ipaddr;
+   my @res;
+   my @ips;
+
+   ($err, @res) = getaddrinfo("[% argv.name %]", "", {socktype => SOCK_RAW, family => [% argv.type %]});
+   while( my $ai = shift @res ) {
+      ($err, $ipaddr) = getnameinfo($ai->{addr}, NI_NUMERICHOST, NIx_NOSERV);
+      push(@ips, $ipaddr);
+   }
+
+   $stash->set(out => \@ips);
+[% END -%]
+[% out = out.sort -%]