dn42: add routecount collectd stats

hosts/containers/dn42/default.nix

@@ -25,7 +25,17 @@ in {
       statistics.enable = true;
     };
   };
-  services.resolved.enable = false;
+  services.collectd.plugins.exec =
+    let
+      routecount = pkgs.writeScript "run-routecount" ''
+        #!${pkgs.bash}/bin/bash
+
+        export PATH=${lib.makeBinPath (with pkgs; [ ruby iproute ] )}
+        ruby ${./routecount.rb}
+      '';
+    in ''
+      Exec "collectd" "${routecount}"
+    '';
 
   environment.systemPackages = with pkgs; [ vim ];
 

hosts/containers/dn42/routecount.rb

@@ -0,0 +1,38 @@
+#!/usr/bin/env ruby
+
+INTERVAL = ENV['COLLECTD_INTERVAL'].to_i
+HOSTNAME = ENV['COLLECTD_HOSTNAME']
+
+def gather cmd
+  counts = {}
+  `#{cmd}`.lines.each do |l|
+    dev = nil
+    gw = nil
+    if l =~ / dev (\S+)/
+      dev = $1
+    end
+    if l =~ / via (\S+)/
+      gw = $1
+    end
+    if gw and dev
+      target = [gw, dev].join "%"
+      counts[target] = 0 unless counts.has_key? target
+      counts[target] += 1
+    end
+  end
+  counts
+end
+
+loop do
+  v4 = gather "ip -4 route"
+  v4.each do |target,count|
+    puts "PUTVAL \"#{HOSTNAME}/exec-routes4/routes-#{target}\" interval=#{INTERVAL} N:#{count}"
+  end
+
+  v6 = gather "ip -6 route"
+  v6.each do |target,count|
+    puts "PUTVAL \"#{HOSTNAME}/exec-routes6/routes-#{target}\" interval=#{INTERVAL} N:#{count}"
+  end
+
+  sleep INTERVAL
+end