Packet Peeper

note that libhashish is licensed under the GPL...

libhashish looks quite good, and supports use of red-black trees for
handling collisions, so would not deteriorate to O(n)

http://libhashish.sourceforge.net/

Benchmark libhashish vs google's hash table

also choose a data structure that will exploit cache

ANY SOLUTION SHOULD BE RESILIENT TO ALGORITHMIC COMPLEXITY ATTACKS

for example a naive hash table could deteriorate to a linked-list given
certain inputs, resulting in dos