20-dhcp.conf

filter {             
  grok {
    match => [ "message", "rule (?<rule>.*)\(.*\): (?<action>pass|block) (?<direction>in|out).* on (?<iface>.*): .* proto (?<proto>TCP|UDP|IGMP|ICMP) .*\n\s*(?<src_ip>(\d+\.\d+\.\d+\.\d+))\.?(?<src_port>(\d*)) [<|>] (?<dest_ip>(\d+\.\d+\.\d+\.\d+))\.?(?<dest_port>(\d*)):" ]
        }
          if [prog] =~ /^dhcpd$/ {
          if [message] =~ /^DHCPACK|^DHCPREQUEST|^DHCPOFFER/ {
   grok {
      match => [ "message", "(?<action>.*) (on|for|to) (?<src_ip>[0-2]?[0-9]?[0-9]\.[0-2]?[0-9]?[0-9]\.[0-2]?[0-9]?[0-9]\.[0-2]?[0-9]?[0-9]) .*(?<mac_address>[0-9a-fA-F][0-9a-fA-F]:[0-9a-fA-F][0-9a-fA-F]:[0-9a-fA-F][0-9a-fA-F]:[0-9a-fA-F][0-9a-fA-F]:[0-9a-fA-F][0-9a-fA-F]:[0-9a-fA-F][0-9a-fA-F]).* via (?<iface>.*)" ]
        }
      }
  if [message] =~ /^DHCPDISCOVER/ {
    grok {
      match => [ "message", "(?<action>.*) from (?<mac_address>[0-9a-fA-F][0-9a-fA-F]:[0-9a-fA-F][0-9a-fA-F]:[0-9a-fA-F][0-9a-fA-F]:[0-9a-fA-F][0-9a-fA-F]:[0-9a-fA-F][0-9a-fA-F]:[0-9a-fA-F][0-9a-fA-F]).* via (?<iface>.*)" ]
          }
        }
  if [message] =~ /^DHCPINFORM/ {
    grok {
       match => [ "message", "(?<action>.*) from (?<src_ip>.*).* via (?<iface>.*)" ]
         }
      }
   }
}