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## Implementation that outputs the register identification and the register
## value. The correct register count is not checked and might lead to indexing
## errors.
module Midbro;
## DATA STRUCTURES
export {
redef enum Log::ID += { LOG };
type Transaction: record {
start_address: count;
quantity: count;
};
type TransactionTable: table[count] of Transaction;
type Info: record {
transactions: TransactionTable &default=TransactionTable();
};
type Entry: record {
ip: addr &log;
uid: count &log;
regtype: string &log;
address: count &log;
register: count &log;
};
}
redef record connection += {
midbro: Info &default=Info();
};
## CUSTOM EVENTS
event midbro_entry(entry: Entry)
{
Log::write(Midbro::LOG, entry);
}
event midbro_unmatched(tid: count)
{
print fmt("Unmatched response: tid=%d", tid);
}
## CUSTOM FUNCTIONS
function midbro_generate_events(transaction: Transaction, c: connection, headers: ModbusHeaders, registers: ModbusRegisters, regtype: string)
{
# TODO: check registers size
local i = 0;
while ( i < transaction$quantity )
{
local entry = Entry(
$ip=c$id$orig_h,
$uid=headers$uid,
$regtype=regtype,
$address=transaction$start_address + i,
$register=registers[i]
);
event midbro_entry(entry);
++i;
}
}
## EVENT HANDLERS
event bro_init() &priority=5
{
Log::create_stream(Midbro::LOG, [$columns=Entry, $path="midbro-parsed"]);
}
event modbus_read_holding_registers_request(c: connection, headers: ModbusHeaders, start_address: count, quantity: count)
{
local tid = headers$tid;
local transaction = Transaction(
$start_address=start_address,
$quantity=quantity
);
c$midbro$transactions[tid] = transaction;
}
event modbus_read_holding_registers_response(c: connection, headers: ModbusHeaders, registers: ModbusRegisters)
{
local tid = headers$tid;
if ( tid !in c$midbro$transactions )
{
event midbro_unmatched(tid);
return;
}
local transaction = c$midbro$transactions[tid];
delete c$midbro$transactions[tid];
midbro_generate_events(transaction, c, headers, registers, "h");
}
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