more nf_conntrack/ip_conntrack questions

[Amin Azez <azez@ufomechanic.net>]

2 questions, part style, relating to nf_conntrack and ip_conntrack

In nf_conntrack_tuple.h in

#define NF_CT_TUPLE_U_BLANK(tuple) \
do { \
(tuple)->src.u.all = 0; \
(tuple)->dst.u.all = 0; \
memset((tuple)->src.u3.all, 0, \
sizeof(u_int32_t)*NF_CT_TUPLE_L3SIZE); \
memset((tuple)->dst.u3.all, 0, \
sizeof(u_int32_t)*NF_CT_TUPLE_L3SIZE); \
} while (0)

why do we have:
sizeof(u_int32_t)*NF_CT_TUPLE_L3SIZE

as the size, instead of just:
sizeof((tuple)->dst.u3)

it seems to presume that:
1) .all will always be the biggest member
2) .all is always an array of NF_CT_TUPLE_L3SIZE of u_int32_t

I wonder why we need to duplicate this knowledge when a small definition
appears to suffice.

Also; and I asked about somehting similar before, why is
ip_conntrack_tuple.src almost exactly the same as
ip_conntrack_tuple.dst, but .src is defined in terms of pre-declared
structs and unions but dst is declared in terms of (nearly) identical
structs and unions. With nf_conntrack as far as I can tell they are the
same. The inline explanation of "manipulatable" doesn't seem to cover it.

Azez