From 96ae8abf6cfec45d52d3fd8367760087e6aaaf40 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ji=C5=99=C3=AD=20Kub=C3=AD=C4=8Dek?=
 <jiri.kubicek@kraxnet.cz>
Date: Sat, 9 Mar 2024 06:12:12 +0100
Subject: [PATCH] reverse dns

---
 examples/nic.rb          |  1 +
 lib/xmon.rb              |  1 +
 lib/xmon/descriptions.rb |  7 ++++++-
 lib/xmon/reverse_dns.rb  | 25 +++++++++++++++++++++++++
 4 files changed, 33 insertions(+), 1 deletion(-)
 create mode 100644 lib/xmon/reverse_dns.rb

diff --git a/examples/nic.rb b/examples/nic.rb
index 81e572a..57a6105 100644
--- a/examples/nic.rb
+++ b/examples/nic.rb
@@ -15,6 +15,7 @@
 end
 
 ipv4 "217.31.205.50" do
+  ptr "www.nic.cz"
   tcp 80 do
     status :open
   end
diff --git a/lib/xmon.rb b/lib/xmon.rb
index 97aa2ca..2015d8a 100644
--- a/lib/xmon.rb
+++ b/lib/xmon.rb
@@ -11,6 +11,7 @@
 require_relative "xmon/ssl"
 require_relative "xmon/dns"
 require_relative "xmon/rdap"
+require_relative "xmon/reverse_dns"
 
 module Xmon
   class Error < StandardError; end
diff --git a/lib/xmon/descriptions.rb b/lib/xmon/descriptions.rb
index ce44258..7291b40 100644
--- a/lib/xmon/descriptions.rb
+++ b/lib/xmon/descriptions.rb
@@ -37,7 +37,7 @@ def describe(*args, **kwargs, &)
       if block_given?
         @description.instance_eval(&)
       else
-        @description = @description.class.new(*args, **kwargs)
+        #  @description = @description.class.new(*args, **kwargs)
       end
       @descriptions ||= []
       @descriptions << @description
@@ -92,6 +92,11 @@ def friendly_name
       @address
     end
 
+    def ptr(*, **, &)
+      @description = Xmon::ReverseDNS.new(self, *, **)
+      describe(&)
+    end
+
     def udp(*, **, &)
       @description = Xmon::UDP.new(self, *, **)
       describe(&)
diff --git a/lib/xmon/reverse_dns.rb b/lib/xmon/reverse_dns.rb
new file mode 100644
index 0000000..48741de
--- /dev/null
+++ b/lib/xmon/reverse_dns.rb
@@ -0,0 +1,25 @@
+require "dnsruby"
+
+module Xmon
+  class ReverseDNS < Description
+    def initialize(parent, value = nil)
+      if parent
+        puts "NEW REVERSE DNS #{value} #{parent.address}"
+        @parent = parent
+        @address = parent.address
+        @hostname = value
+      else
+        puts "NEW REVERSE DNS #{value}"
+      end
+    end
+
+    def fetch(record, type = "A")
+      puts "fetching #{record} #{type}"
+      Dnsruby::Resolver.new.query(record, type).answer.map { |a| a.rdata.to_s }.join
+    end
+
+    def check
+      [Xmon.compare(@hostname, fetch(@address, "PTR"), self)]
+    end
+  end
+end