ipv6 connection hash function wanted ...

[Max Laier]

Hello,

this one is something for people who know their math.

Input: 2x128bit of address (lower ~80bit selectable by user) and 2x16bit 
of ports (more or less selectable by user).  Note that the "flow_id" is 
not useable as several broken stack implementations do not set it 
consistently - and it is user settable as well.
Output: "int" hash value - by default we use the lower 8bit of it.

Problems: Most of the input can be selected by a user meaning it is easy 
to produce collisions.  For legal connections, the lower 64bit are the 
one with the highest entropy - in fact the upper 64bit might be the same 
for many connections coming from/going to the same subnet.  This function 
will be used for every packet that is passed to a dynamic IPFW rule, so 
efficiency is a concern.

Any ideas?  Any papers that deal with this problem?

ref: sys/netinet/ip_fw2.c::hash_packet6

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