Re: [PATCH nf-next-2.6] netfilter: add xt_cpu match

[Eric Dumazet <eric.dumazet@gmail.com>]

Le jeudi 22 juillet 2010 à 16:19 +0200, Jan Engelhardt a écrit :
> On Thursday 2010-07-22 16:03, Eric Dumazet wrote:
> 
> >This match is a bit strange, being packet content agnostic...
> >+/*
> >+ * Yes, packet content is not interesting for us, we only take care
> >+ * of cpu handling this packet
> >+ */
> 
> That is not so strange after all, we have many packet agnostic matches: 
> xt_time, xt_condition, xt_IDLETIMER, xt_iface.
> So this little comment looks a bit redundant.
> 
> Or it seems that academia can't come up with enough new protocols in time that
> we have to resort to do -m coffeemaker :)
> 
> >@@ -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*/
> 
> Please take a read in "Writing Netfilter Modules" e-book :-)
> It will tell you that types other than fixed ones are a no-no.

Ok, let's do that, but I doubt sizeof(int) can be different than 4 on a
Linux 2.6 host right now.

I prefer not doing the !!info->invert, and do the check only once.

Thanks

[PATCH nf-next-2.6] netfilter: add 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 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@gmail.com>
---
 include/linux/netfilter/Kbuild   |    3 -
 include/linux/netfilter/xt_cpu.h |   11 +++++
 net/netfilter/Kconfig            |    9 ++++
 net/netfilter/Makefile           |    1 
 net/netfilter/xt_cpu.c           |   63 +++++++++++++++++++++++++++++
 5 files changed, 86 insertions(+), 1 deletion(-)

diff --git a/include/linux/netfilter/Kbuild b/include/linux/netfilter/Kbuild
index bb103f4..1041a1d 100644
--- a/include/linux/netfilter/Kbuild
+++ b/include/linux/netfilter/Kbuild
@@ -19,12 +19,13 @@ header-y += xt_TCPMSS.h
 header-y += xt_TCPOPTSTRIP.h
 header-y += xt_TEE.h
 header-y += xt_TPROXY.h
+header-y += xt_cluster.h
 header-y += xt_comment.h
 header-y += xt_connbytes.h
 header-y += xt_connlimit.h
 header-y += xt_connmark.h
 header-y += xt_conntrack.h
-header-y += xt_cluster.h
+header-y += xt_cpu.h
 header-y += xt_dccp.h
 header-y += xt_dscp.h
 header-y += xt_esp.h
diff --git a/include/linux/netfilter/xt_cpu.h b/include/linux/netfilter/xt_cpu.h
index e69de29..93c7f11 100644
--- a/include/linux/netfilter/xt_cpu.h
+++ b/include/linux/netfilter/xt_cpu.h
@@ -0,0 +1,11 @@
+#ifndef _XT_CPU_H
+#define _XT_CPU_H
+
+#include <linux/types.h>
+
+struct xt_cpu_info {
+	__u32	cpu;
+	__u32	invert;
+};
+
+#endif /*_XT_CPU_H*/
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index aa2f106..523e8d0 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -647,6 +647,15 @@ config NETFILTER_XT_MATCH_CONNTRACK
 
 	  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_DCCP
 	tristate '"dccp" protocol match support'
 	depends on NETFILTER_ADVANCED
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index e28420a..6da84c3 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -69,6 +69,7 @@ obj-$(CONFIG_NETFILTER_XT_MATCH_COMMENT) += xt_comment.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_CONNBYTES) += xt_connbytes.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_CONNLIMIT) += xt_connlimit.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_CONNTRACK) += xt_conntrack.o
+obj-$(CONFIG_NETFILTER_XT_MATCH_CPU) += xt_cpu.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_DCCP) += xt_dccp.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_DSCP) += xt_dscp.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_ESP) += xt_esp.o
diff --git a/net/netfilter/xt_cpu.c b/net/netfilter/xt_cpu.c
index e69de29..b39db8a 100644
--- a/net/netfilter/xt_cpu.c
+++ b/net/netfilter/xt_cpu.c
@@ -0,0 +1,63 @@
+/* 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)
+ *
+ */
+
+/* (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@gmail.com>");
+MODULE_DESCRIPTION("Xtables: CPU match");
+
+static int cpu_mt_check(const struct xt_mtchk_param *par)
+{
+	const struct xt_cpu_info *info = par->matchinfo;
+
+	if (info->invert & ~1)
+		return -EINVAL;
+	return 0;
+}
+
+static bool cpu_mt(const struct sk_buff *skb, struct xt_action_param *par)
+{
+	const struct xt_cpu_info *info = par->matchinfo;
+
+	return (info->cpu == smp_processor_id()) ^ info->invert;
+}
+
+static struct xt_match cpu_mt_reg __read_mostly = {
+	.name       = "cpu",
+	.revision   = 0,
+	.family     = NFPROTO_UNSPEC,
+	.checkentry = cpu_mt_check,
+	.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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