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From: Max Laier <max@love2party.net>
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Date: Tue, 14 Nov 2006 17:09:20 +0100
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Subject: ipv6 connection hash function wanted ...
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Hello,

this one is something for people who know their math.

Input: 2x128bit of address (lower ~80bit selectable by user) and 2x16bit=20
of ports (more or less selectable by user).  Note that the "flow_id" is=20
not useable as several broken stack implementations do not set it=20
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=20
to produce collisions.  For legal connections, the lower 64bit are the=20
one with the highest entropy - in fact the upper 64bit might be the same=20
for many connections coming from/going to the same subnet.  This function=20
will be used for every packet that is passed to a dynamic IPFW rule, so=20
efficiency is a concern.

Any ideas?  Any papers that deal with this problem?

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

=2D-=20
/"\  Best regards,                      | mlaier@freebsd.org
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