patch for destination field

[ghost]

I do not consider this patch copyrightable.

commit f15289ad055d9d575653651019253e3097641bd6
Author: Cameron Nemo <[email protected]>
Date:   Thu Jul 30 14:14:51 2020 -0700

    feat: assign network to destination field
    
    It can be desirable to know which specific network was matched,
    so I added an option to set a destination field based on that info.

diff --git a/lib/logstash/filters/cidr.rb b/lib/logstash/filters/cidr.rb
index 3bb19b0..7ee2a63 100644
--- a/lib/logstash/filters/cidr.rb
+++ b/lib/logstash/filters/cidr.rb
@@ -56,6 +56,9 @@ class LogStash::Filters::CIDR < LogStash::Filters::Base
   # pointed by network_path.
   config :separator, :validate => :string, :default => "\n"
 
+  # The destination field where the matching IP network is written.
+  config :destination, :validate => :string
+
   public
   def register
     rw_lock = java.util.concurrent.locks.ReentrantReadWriteLock.new
@@ -169,6 +172,9 @@ class LogStash::Filters::CIDR < LogStash::Filters::Base
     address.product(network).each do |a, n|
       @logger.debug("Checking IP inclusion", :address => a, :network => n)
       if n.include?(a)
+        if @destination
+          event.set(@destination, n.to_s + '/' + n.prefix.to_s)
+        end
         filter_matched(event)
         return
       end
diff --git a/spec/filters/cidr_spec.rb b/spec/filters/cidr_spec.rb
index 04511b8..b4b7835 100644
--- a/spec/filters/cidr_spec.rb
+++ b/spec/filters/cidr_spec.rb
@@ -188,4 +188,24 @@ describe LogStash::Filters::CIDR do
       expect { subject.register }.to raise_error(LogStash::ConfigurationError)
     end
   end
+
+  describe "destination" do
+    let(:config) { Hash.new }
+    config <<-CONFIG
+      filter {
+        cidr {
+          address     => "%{clientip}"
+          network     => ["192.168.1.0/24"]
+          destination => "clientnet"
+        }
+      }
+    CONFIG
+
+    sample("clientip" => "192.168.1.1") do
+      expect(subject.get("clientnet")).to eq("192.168.1.0/24")
+    end
+    sample("clientip" => "192.168.2.1") do
+      expect(subject.get("clientnet").nil?).to eq(true)
+    end
+  end
 end

[TheVastyDeep]

It would be helpful if someone opened a actual PR containing these code changes, then it might get considered for merging.