Scalability performance work on iptables/libiptc

There are scalability/performance issues with iptables in libiptc.c, when parsing/pulling-out the ruleset blob. As I discussed shortly with Harald and Martin during the workshop.

These patches performance optimize two scalability issues.

1) Sorting chain during pull-out give worst-case runtime O(Chains^2), reduced to O(Chains) only when creating a new chain.

2) Finding jump chains is suboptimal O(Chain*Rules), reduced to O(R) and chain offset lookup to O(1).

The idea behind these fixes are based upon patches posted by Paul C. Diem <[email protected]> back in June+Oct 2006.

These performance issues will only be noticed when the rule set is large enough. For me, in real life, its actually a real performance issue. On one production system (Rules=26209 and Chains=6233) it takes 10 seconds to create a new chain by calling "iptables -N test", with these patches its reduced to 0.145 second.

Med venlig hilsen / Best regards
  Jesper Brouer
  ComX Networks A/S
  Linux Network developer
  Cand. Scient Datalog / MSc.
  Author of http://adsl-optimizer.dk
  LinkedIn: http://www.linkedin.com/in/brouer