void fill_fixed_hdr(uint8_t pdu_type, struct stream *stream);
int send_hello(struct isis_circuit *circuit, int level);
int isis_handle_pdu(struct isis_circuit *circuit, uint8_t *ssnpa);
void fill_fixed_hdr(uint8_t pdu_type, struct stream *stream);
int send_hello(struct isis_circuit *circuit, int level);
int isis_handle_pdu(struct isis_circuit *circuit, uint8_t *ssnpa);