path: root/extensions/libxt_cpu.c
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* extensions: remove no longer necessary default: casesJan Engelhardt2011-01-081-3/+0
| | | | | | | Match and target parse functions now only get option characters they have defined themselves. Signed-off-by: Jan Engelhardt <>
* all: consistent syntax use in struct optionJan Engelhardt2010-07-231-2/+3
| | | | | | Try to inhibit copypasting old stuff. Signed-off-by: Jan Engelhardt <>
* extension: add xt_cpu matchEric Dumazet2010-07-231-0/+98
Kernel 2.6.36 supports xt_cpu match In some situations a CPU match permits a better spreading of connections, or select targets only for a given cpu. With Remote Packet Steering or multiqueue NIC and appropriate IRQ affinities, we can distribute trafic on available cpus, per session. (all RX packets for a given flow are handled by a given cpu) Some legacy applications being not SMP friendly, one way to scale a server is to run multiple copies of them. Instead of randomly choosing an instance, we can use the cpu number as a key so that softirq handler for a whole instance is running on a single cpu, maximizing cache effects in TCP/UDP stacks. Using NAT for example, a four ways machine might run four copies of server application, using a separate listening port for each instance, but still presenting an unique external port : iptables -t nat -A PREROUTING -p tcp --dport 80 -m cpu --cpu 0 \ -j REDIRECT --to-port 8080 iptables -t nat -A PREROUTING -p tcp --dport 80 -m cpu --cpu 1 \ -j REDIRECT --to-port 8081 iptables -t nat -A PREROUTING -p tcp --dport 80 -m cpu --cpu 2 \ -j REDIRECT --to-port 8082 iptables -t nat -A PREROUTING -p tcp --dport 80 -m cpu --cpu 3 \ -j REDIRECT --to-port 8083 Signed-off-by: Eric Dumazet <> Signed-off-by: Patrick McHardy <>