Check if an iptables chain exists

lib/Rex/Commands/Iptables.pm

@@ -104,7 +104,7 @@ use Rex::Logger;
 
 @EXPORT = qw(iptables is_nat_gateway iptables_list iptables_clear
   open_port close_port redirect_port
-  default_state_rule);
+  default_state_rule chain_exists);
 
 sub iptables;
 
@@ -485,6 +485,44 @@ sub _iptables_list {
   return $ret;
 }
 
+=head2 chain_exists
+
+Returns true if a chain exists in a table, false otherwise.
+
+
+ chain_exists 'foo'; # $table defaulting to 'filter'
+ chain_exists 'foo', table => 'filter';
+ chain_exists -6, 'foo'; # IPv6
+
+
+In this example we create a chain unless it already exists.
+
+ task "create_chain", sub {
+   iptables(t => 'filter', N => 'foo')
+     unless chain_exists('foo');
+ };
+
+
+=cut
+
+sub chain_exists {
+  my @params = @_;
+  my $ipt_version = _get_ip_version( \@params );
+  my ( $chain, %args ) = @params;
+
+  my $table = (delete $args{table} or 'filter');
+
+  eval {
+    iptables($ipt_version, list => $chain);
+  };
+
+  return 0  if $@ && $@ =~ /No chain/;
+  die $@    if $@;
+
+  return 1;
+
+}
+
 =head2 iptables_clear
 
 Remove all iptables rules.

t/commands/iptables.t

@@ -1,7 +1,7 @@
 use strict;
 use warnings;
 
-use Test::More tests => 32;
+use Test::More tests => 36;
 
 use Rex::Commands::Iptables;
 
@@ -55,3 +55,8 @@ is( $rules->{foo}->[0]->[13], "50",                  "up to 50" );
 is( $rules->{foo}->[0]->[14], "j",                   "jump to" );
 is( $rules->{foo}->[0]->[15], "RETURN",              "RETURN" );
 
+is(Rex::Commands::Iptables::chain_exists('foo'),0);
+is(Rex::Commands::Iptables::chain_exists('INPUT'),1);
+
+is(Rex::Commands::Iptables::chain_exists('foo', table => 'filter'),0);
+is(Rex::Commands::Iptables::chain_exists('INPUT', table => 'filter'),1);