This match is a bit strange, being packet content agnostic...
Still, 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 is 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 <eric.dumazet@xxxxxxxxx>
---
include/linux/netfilter/Kbuild | 1
include/linux/netfilter/xt_cpu.h | 8 +++
net/netfilter/Kconfig | 9 ++++
net/netfilter/Makefile | 1
net/netfilter/xt_cpu.c | 65 +++++++++++++++++++++++++++++
5 files changed, 84 insertions(+)
diff --git a/include/linux/netfilter/Kbuild b/include/linux/netfilter/Kbuild
index bb103f4..5c39a56 100644
--- a/include/linux/netfilter/Kbuild
+++ b/include/linux/netfilter/Kbuild
@@ -34,6 +34,7 @@ header-y += xt_helper.h
header-y += xt_length.h
header-y += xt_limit.h
header-y += xt_mac.h
+header-y += xt_cpu.h
header-y += xt_mark.h
header-y += xt_multiport.h
header-y += xt_osf.h
diff --git a/include/linux/netfilter/xt_cpu.h b/include/linux/netfilter/xt_cpu.h
index e69de29..fdf4202 100644
--- a/include/linux/netfilter/xt_cpu.h
+++ b/include/linux/netfilter/xt_cpu.h
@@ -0,0 +1,8 @@
+#ifndef _XT_CPU_H
+#define _XT_CPU_H
+
+struct xt_cpu_info {
+ unsigned int cpu;
+ int invert;
+};
+#endif /*_XT_MAC_H*/
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index aa2f106..85b07bd 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -754,6 +754,15 @@ config NETFILTER_XT_MATCH_MAC
To compile it as a module, choose M here. If unsure, say N.
+config NETFILTER_XT_MATCH_CPU
+ tristate '"cpu" match support'
+ depends on NETFILTER_ADVANCED
+ help
+ CPU matching allows you to match packets based on the CPU
+ currently handling the packet.
+
+ To compile it as a module, choose M here. If unsure, say N.
+
config NETFILTER_XT_MATCH_MARK
tristate '"mark" match support'
depends on NETFILTER_ADVANCED
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index e28420a..0fe7efd 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -79,6 +79,7 @@ obj-$(CONFIG_NETFILTER_XT_MATCH_IPRANGE) += xt_iprange.o
obj-$(CONFIG_NETFILTER_XT_MATCH_LENGTH) += xt_length.o
obj-$(CONFIG_NETFILTER_XT_MATCH_LIMIT) += xt_limit.o
obj-$(CONFIG_NETFILTER_XT_MATCH_MAC) += xt_mac.o
+obj-$(CONFIG_NETFILTER_XT_MATCH_CPU) += xt_cpu.o
obj-$(CONFIG_NETFILTER_XT_MATCH_MULTIPORT) += xt_multiport.o
obj-$(CONFIG_NETFILTER_XT_MATCH_OSF) += xt_osf.o
obj-$(CONFIG_NETFILTER_XT_MATCH_OWNER) += xt_owner.o
diff --git a/net/netfilter/xt_cpu.c b/net/netfilter/xt_cpu.c
index e69de29..23d5a76 100644
--- a/net/netfilter/xt_cpu.c
+++ b/net/netfilter/xt_cpu.c
@@ -0,0 +1,65 @@
+/* Kernel module to match running CPU */
+
+/*
+ * Might be used to distribute connections on several daemons, if
+ * RPS (Remote Packet Steering) is enabled or NIC is multiqueue capable,
+ * each RX queue IRQ affined to one CPU (1:1 mapping)
+ *
+ * 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
+ *
+ */
+
+/* (C) 2010 Eric Dumazet
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/netfilter/xt_cpu.h>
+#include <linux/netfilter/x_tables.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Eric Dumazet <eric.dumazet@xxxxxxxxx>");
+MODULE_DESCRIPTION("Xtables: CPU match");
+
+/*
+ * Yes, packet content is not interesting for us, we only take care
+ * of cpu handling this packet
+ */
+static bool cpu_mt(const struct sk_buff *skb, struct xt_action_param *par)
+{
+ const struct xt_cpu_info *info = par->matchinfo;
+ bool ret;
+
+ ret = info->cpu == smp_processor_id();
+ ret ^= info->invert;
+ return ret;
+}
+
+static struct xt_match cpu_mt_reg __read_mostly = {
+ .name = "cpu",
+ .revision = 0,
+ .family = NFPROTO_UNSPEC,
+ .match = cpu_mt,
+ .matchsize = sizeof(struct xt_cpu_info),
+ .me = THIS_MODULE,
+};
+
+static int __init cpu_mt_init(void)
+{
+ return xt_register_match(&cpu_mt_reg);
+}
+
+static void __exit cpu_mt_exit(void)
+{
+ xt_unregister_match(&cpu_mt_reg);
+}
+
+module_init(cpu_mt_init);
+module_exit(cpu_mt_exit);
--
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