Common /usr/share/suricata/rules or /usr/local/share/suricata/rules.
The rules provided by the distribution are installed here as part
of the Suricata install process so will always be installed, even
without the use of install-rules.
Decode Modbus request and response messages, and extracts
MODBUS Application Protocol header and the code function.
In case of read/write function, extracts message contents
(read/write address, quantity, count, data to write).
Links request and response messages in a transaction according to
Transaction Identifier (transaction management based on DNS source code).
MODBUS Messaging on TCP/IP Implementation Guide V1.0b
(http://www.modbus.org/docs/Modbus_Messaging_Implementation_Guide_V1_0b.pdf)
MODBUS Application Protocol Specification V1.1b3
(http://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b3.pdf)
Based on DNS source code.
Signed-off-by: David DIALLO <diallo@et.esia.fr>