We will need to do that when we will send IPv6 routes (RFC4760 says we SHOULD
NOT carry this attribute when we will send UPDATE without NLRI). So, we save
the length of all the attributes except NEXT_HOP for later memcpy().
Signed-off-by: Benjamin Cama <benoar@dolka.fr>
Optional Parameters is defined in RFC4271 and Capability advertisement in
RFC3392. For now, we only hande them upon receiving an OPEN message.
Signed-off-by: Benjamin Cama <benoar@dolka.fr>
