# MIT Kerberos Documentation

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# krb5_pre_send_fn

`krb5_pre_send_fn`

Hook function for inspecting or modifying messages sent to KDCs.

If the hook function sets reply_out , message will not be sent to the KDC, and the given reply will used instead. If the hook function sets new_message_out , the given message will be sent to the KDC in place of message . If the hook function returns successfully without setting either output, message will be sent to the KDC normally. The hook function should use `krb5_copy_data()` to construct the value for new_message_out or reply_out , to ensure that it can be freed correctly by the library.

## Declaration

typedef krb5_error_code( * krb5_pre_send_fn) (krb5_context context, void *data, const krb5_data *realm, const krb5_data *message, krb5_data **new_message_out, krb5_data **new_reply_out)