gnutls_dtls_cookie_send(3) gnutls gnutls_dtls_cookie_send(3)

gnutls_dtls_cookie_send - API function

#include <gnutls/dtls.h>

int gnutls_dtls_cookie_send(gnutls_datum_t * key, void * client_data, size_t client_data_size, gnutls_dtls_prestate_st * prestate, gnutls_transport_ptr_t ptr, gnutls_push_func push_func);

is a random key to be used at cookie generation
contains data identifying the client (i.e. address)
The size of client's data
The previous cookie returned by gnutls_dtls_cookie_verify()
A transport pointer to be used by push_func
A function that will be used to reply

This function can be used to prevent denial of service attacks to a DTLS server by requiring the client to reply using a cookie sent by this function. That way it can be ensured that a client we allocated resources for (i.e. gnutls_session_t) is the one that the original incoming packet was originated from.

This function must be called at the first incoming packet, prior to allocating any resources and must be succeeded by gnutls_dtls_cookie_verify().

the number of bytes sent, or a negative error code.


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3.8.5 gnutls