ipv6 connection hash function wanted ...

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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Relevant Pages

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  • Re: ipv6 connection hash function wanted ...
    ... Max Laier wrote: ... this one is something for people who know their math. ... 2x128bit of address and 2x16bit of ports. ... 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. ...
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