trafgen: proto: Update field value at runtime
Add basic infrastructure for update proto field value at runtime by
dynamic field function.
Extended 'struct packet_dyn' with proto fields which has dynamically
changing values at runtime.
Added 'field_changed' callback for proto header which may be used for
check if csum updating is needed. This callback is called after field
was changed at runtime.
Added 'packet_update' callback to let proto header know when to apply
final proto header changes at runtime (e.g. - csum update).
Signed-off-by: Vadim Kochan <vadim4j@gmail.com>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>