From 93039cb9e88b48d0651c568595db4ccab43b3826 Mon Sep 17 00:00:00 2001
From: Steve Kemp <steve@steve.org.uk>
Date: Tue, 20 Nov 2012 09:59:46 +0000
Subject:   Added utility class.

---
 lib/custodian/dnsutil.rb | 72 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)
 create mode 100644 lib/custodian/dnsutil.rb

diff --git a/lib/custodian/dnsutil.rb b/lib/custodian/dnsutil.rb
new file mode 100644
index 0000000..e42d5e3
--- /dev/null
+++ b/lib/custodian/dnsutil.rb
@@ -0,0 +1,72 @@
+
+
+require 'ipaddr'
+require 'socket'
+require 'timeout'
+
+
+
+#
+#  This class is responsible for doing forward/reverse DNS lookups
+#
+class DNSUtil
+
+
+  #
+  # Return the reverse DNS for the specified IP address, nil on failure.
+  #
+  def DNSUtil.ip_to_hostname( ip )
+    resolved = nil
+    begin
+      timeout( 4 ) do
+        begin
+          Socket.getaddrinfo(ip, 'echo').each do |a|
+            resolved = a[2] if ( a )
+          end
+        rescue SocketError
+          resolved = nil
+        end
+      end
+    rescue Timeout::Error => e
+      resolved = nil
+    end
+    resolved
+  end
+
+
+  #
+  # Convert a hostname to an IP address, return nil on failure.
+  #
+  def DNSUtil.hostname_to_ip( hostname )
+
+    resolved = nil
+
+    begin
+      timeout( 4 ) do
+        begin
+          Socket.getaddrinfo(hostname, 'echo').each do |a|
+            resolved = a[3] if ( a )
+          end
+        rescue SocketError
+          resolved = nil
+        end
+      end
+    rescue Timeout::Error => e
+      resolved = nil
+    end
+    resolved
+  end
+
+end
+
+
+if __FILE__ == $0 then
+
+  %w( ssh.steve.org.uk ipv6.steve.org.uk ).each do |name|
+    puts "Hostname test: #{name} #{DNSUtil.hostname_to_ip(name) }"
+  end
+
+  %w( 80.68.85.46 80.68.85.48 2001:41c8:125:46::22 ).each do |name|
+    puts "Hostname test: #{name} #{DNSUtil.ip_to_hostname(name) }"
+  end
+end
-- 
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