[Bug 253912] [PATCH] Ineffective lookup of incoming packets in libalias

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=253912

            Bug ID: 253912
           Summary: [PATCH] Ineffective lookup of incoming packets in
                    libalias
           Product: Base System
           Version: CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: bugs at FreeBSD.org
          Reporter: 8an at praha12.net

Created attachment 222878
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=222878&action=edit
Change lookup of incoming packets to use both addresses

While lookup of outgoing packets uses hash based on both source and destination
address, for incoming packets only alias address and port is used. So when
multiple connections from different addresses target the same port of
redirected address (using redirect_addr or redirect_port in IPFW), the link
table must be searched sequentially - tens of thousand of items for every
incoming packet. To make it worse, the search is under a lock, so it is forced
to run on a single core. Consequently just 1000pps from different addresses are
enough to bring down a server with the fastest CPU available in under a minute.

The attached patch fixes the problem by using both addresses and ports for
lookup of incoming packets. We are running it currently on 11.2, but it applies
to CURRENT without changes.

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