> ## Documentation Index
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> Use this file to discover all available pages before exploring further.

# CAPLfunctionOnSecurityOfNodePDUPreTx

# OnSecurityOfNodePDUPreTx

[Valid for](../../../Shared/FeatureAvailability.md):  CANoe DE • CANoe4SW DE

## Function Syntax

```c theme={null}
void OnSecurityOfNodePDUPreTx(char nodeName[], char networkName[], char pduName[], dword dataId, byte payload[], dword payloadLength, qword& authInfoHigh, qword& authInfo, dword authInfoBitLength, qword& freshness, dword freshnessBitLength, dword freshnessValueId)
```

## Description

This callback handler is called before the specified node on the specified network transmits a secured PDU, after all data updates and the automatic Authenticator (MAC) calculation have been done.

Payload, authInfo (Authentication Information) and Freshness can be modified before the transmission starts. By this a fault injection is easily possible.

You have to call [SecurityLocalStartControlSimulationNode](../Functions/CAPLfunctionSecurityLocalStartControlSimulationNode.md) before this callback is called.

## Parameters

* **char nodeName\[]**: The name of the node.
* **char networkName\[]**: The name of the network the node is on.
* **char pduName\[]**: The name of the PDU.
* **dword dataId**: The data ID of the PDU.
* **byte payload\[]**: The payload of the PDU.
* **dword payloadLength**: The payload length of the PDU in bytes.
* **qword& authInfoHigh \[Out]**: Upper 64 bits of the authenticator (MAC), if authenticator is larger than 64 bits. Otherwise 0;
* **qword& authInfo \[Out]**: The full authenticator value or the lower 64 bits of the authenticator (MAC), if authenticator is larger than 64 bits.
* **dword authInfoBitLength**: Length of complete received authenticator (length of authInfo if the authenticator is \<= 64 bit, otherwise length of authInfo + authInfoHigh)
* **qword& freshness \[Out]**: The freshness value.
* **dword freshnessBitLength**: The freshness value length in bits.
* **dword freshnessValueId**: The freshness value ID of the PDU.

## Return Values

* **byte payload\[]**: The payload of the PDU.
* **qword& authInfoHigh \[Out]**: Upper 64 bits of the authenticator (MAC), if authenticator is larger than 64 bits. Otherwise 0;
* **qword& authInfo \[Out]**: The full authenticator value or the lower 64 bits of the authenticator (MAC), if authenticator is larger than 64 bits.
* **qword& freshness \[Out]**: The freshness value.

## Example

```plaintext theme={null}
void OnSecurityOfNodePDUPreTx(char nodeName[], char networkName[], char pduName[], dword dataId, byte payload[], dword payloadLength, qword& authInfoHigh, qword& authInfo, dword authInfoBitLength, qword& freshness, dword freshnessBitLength, dword freshnessValueId)
{
    char testNodeName[10] = "ECU1";
    char testNetworkName[10] = "CAN1";

    if((!strncmp(nodeName,testNodeName,strlen(nodeName)))&&(!strncmp(networkName,testNetworkName,strlen(networkName))))
    {
        if (dataId == 1)
        {
            authInfo = 0x123456; // change mac
            // freshness = 0x02; // change freshness
            // payload[0] = 0xFF; // change payload;
        }
    }
}
```