IPv6 route cache entry

[Sai Naidu]

Hi All,

I am going through the linux IPV6 routing code and have a query on the
route cache being maintained for IPV6 packets.

Why is there no route-cahe hash list for IPv6 similar to IPv4? For
ipv4 routing, we
have ip_mkroute_input which creates the route-cache entry and adds it
to the "rt_hash_table" Hash Table. For all the subsequent packets, the
route look
up from the routing database being maintained in  trie is avoided. The
route cache from the hast list is used.

But in IPv6, it appears that the route-cache entry, is being
maintained in the routing
tree data structure itself. This would require a route-look to happen
over the routing database for every packet .

What is the basic idea behind this change. What would be the
disadvantages if a hash list similar to ipv4 is maintained for IPv6
route cache.

Thanks.

Regards,
Sai Naidu