NBMA GRE over IPsec behind NAT

Hi,

I sent a mail earlier about this subject, see:
http://marc.info/?l=linux-netdev&m=122232910618099&w=4

I've been thinking more about this and reading the code
trying to figure out how to fix this.

One idea for the fix would be:
1. Include the NAT Original Address in NDA_LLADDR (this way
   we don't have to modify struct neighbour)
2. Add new Neighbor Cache Entry Flag (NTF_NATOA?) to specify
   if the NAT-OA is present
3. Modify neighbor cache to cope with the new flag and address
4. Add NAT-OA field for ipv4 in struct flowi
5. ipv4/xfrm4_policy.c: __xfrm4_find_bundle() to compare NAT-OA
   if it is specified in struct flowi.
6. Possibly ipv4/xfrm4_policy.c: _decode_session4() would
   extract the NAT-OA to struct flowi from skb->dst->neighbour.

Does this sound something that might work? Would it be an
acceptable approach?

- Timo