Commit ccc007e4 authored by Eyal Birger's avatar Eyal Birger Committed by David S. Miller
Browse files

net: sched: add em_ipt ematch for calling xtables matches 



The commit a new tc ematch for using netfilter xtable matches.

This allows early classification as well as mirroning/redirecting traffic
based on logic implemented in netfilter extensions.

Current supported use case is classification based on the incoming IPSec
state used during decpsulation using the 'policy' iptables extension
(xt_policy).

The module dynamically fetches the netfilter match module and calls
it using a fake xt_action_param structure based on validated userspace
provided parameters.

As the xt_policy match does not access skb->data, no skb modifications
are needed on match.

Signed-off-by: default avatarEyal Birger <eyal.birger@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 022ddbca

include/uapi/linux/pkt_cls.h

+2 −1
Original line number Diff line number Diff line
@@ -555,7 +555,8 @@ enum { 
#define	TCF_EM_VLAN		6

#define	TCF_EM_CANID		7

#define	TCF_EM_IPSET		8

#define	TCF_EM_MAX		8

#define	TCF_EM_IPT		9

#define	TCF_EM_MAX		9



enum {

	TCF_EM_PROG_TC

include/uapi/linux/tc_ematch/tc_em_ipt.h

0 → 100644
+20 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */

#ifndef __LINUX_TC_EM_IPT_H

#define __LINUX_TC_EM_IPT_H



#include <linux/types.h>

#include <linux/pkt_cls.h>



enum {

	TCA_EM_IPT_UNSPEC,

	TCA_EM_IPT_HOOK,

	TCA_EM_IPT_MATCH_NAME,

	TCA_EM_IPT_MATCH_REVISION,

	TCA_EM_IPT_NFPROTO,

	TCA_EM_IPT_MATCH_DATA,

	__TCA_EM_IPT_MAX

};



#define TCA_EM_IPT_MAX (__TCA_EM_IPT_MAX - 1)



#endif

net/sched/Kconfig

+12 −0
Original line number Diff line number Diff line
@@ -658,6 +658,18 @@ config NET_EMATCH_IPSET 
	  To compile this code as a module, choose M here: the

	  module will be called em_ipset.



config NET_EMATCH_IPT

	tristate "IPtables Matches"

	depends on NET_EMATCH && NETFILTER && NETFILTER_XTABLES

	---help---

	  Say Y here to be able to classify packets based on iptables

	  matches.

	  Current supported match is "policy" which allows packet classification

	  based on IPsec policy that was used during decapsulation



	  To compile this code as a module, choose M here: the

	  module will be called em_ipt.



config NET_CLS_ACT

	bool "Actions"

	select NET_CLS

net/sched/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -75,3 +75,4 @@ obj-$(CONFIG_NET_EMATCH_META) += em_meta.o 
obj-$(CONFIG_NET_EMATCH_TEXT)	+= em_text.o

obj-$(CONFIG_NET_EMATCH_CANID)	+= em_canid.o

obj-$(CONFIG_NET_EMATCH_IPSET)	+= em_ipset.o

obj-$(CONFIG_NET_EMATCH_IPT)	+= em_ipt.o

net/sched/em_ipt.c

0 → 100644
+257 −0
Original line number Diff line number Diff line 
/*

 * net/sched/em_ipt.c IPtables matches Ematch

 *

 * (c) 2018 Eyal Birger <eyal.birger@gmail.com>

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License

 * as published by the Free Software Foundation; either version

 * 2 of the License, or (at your option) any later version.

 */



#include <linux/gfp.h>

#include <linux/module.h>

#include <linux/types.h>

#include <linux/kernel.h>

#include <linux/string.h>

#include <linux/skbuff.h>

#include <linux/tc_ematch/tc_em_ipt.h>

#include <linux/netfilter.h>

#include <linux/netfilter/x_tables.h>

#include <linux/netfilter_ipv4/ip_tables.h>

#include <linux/netfilter_ipv6/ip6_tables.h>

#include <net/pkt_cls.h>



struct em_ipt_match {

	const struct xt_match *match;

	u32 hook;

	u8 match_data[0] __aligned(8);

};



struct em_ipt_xt_match {

	char *match_name;

	int (*validate_match_data)(struct nlattr **tb, u8 mrev);

};



static const struct nla_policy em_ipt_policy[TCA_EM_IPT_MAX + 1] = {

	[TCA_EM_IPT_MATCH_NAME]		= { .type = NLA_STRING,

					    .len = XT_EXTENSION_MAXNAMELEN },

	[TCA_EM_IPT_MATCH_REVISION]	= { .type = NLA_U8 },

	[TCA_EM_IPT_HOOK]		= { .type = NLA_U32 },

	[TCA_EM_IPT_NFPROTO]		= { .type = NLA_U8 },

	[TCA_EM_IPT_MATCH_DATA]		= { .type = NLA_UNSPEC },

};



static int check_match(struct net *net, struct em_ipt_match *im, int mdata_len)

{

	struct xt_mtchk_param mtpar = {};

	union {

		struct ipt_entry e4;

		struct ip6t_entry e6;

	} e = {};



	mtpar.net	= net;

	mtpar.table	= "filter";

	mtpar.hook_mask	= 1 << im->hook;

	mtpar.family	= im->match->family;

	mtpar.match	= im->match;

	mtpar.entryinfo = &e;

	mtpar.matchinfo	= (void *)im->match_data;

	return xt_check_match(&mtpar, mdata_len, 0, 0);

}



static int policy_validate_match_data(struct nlattr **tb, u8 mrev)

{

	if (mrev != 0) {

		pr_err("only policy match revision 0 supported");

		return -EINVAL;

	}



	if (nla_get_u32(tb[TCA_EM_IPT_HOOK]) != NF_INET_PRE_ROUTING) {

		pr_err("policy can only be matched on NF_INET_PRE_ROUTING");

		return -EINVAL;

	}



	return 0;

}



static const struct em_ipt_xt_match em_ipt_xt_matches[] = {

	{

		.match_name = "policy",

		.validate_match_data = policy_validate_match_data

	},

	{}

};



static struct xt_match *get_xt_match(struct nlattr **tb)

{

	const struct em_ipt_xt_match *m;

	struct nlattr *mname_attr;

	u8 nfproto, mrev = 0;

	int ret;



	mname_attr = tb[TCA_EM_IPT_MATCH_NAME];

	for (m = em_ipt_xt_matches; m->match_name; m++) {

		if (!nla_strcmp(mname_attr, m->match_name))

			break;

	}



	if (!m->match_name) {

		pr_err("Unsupported xt match");

		return ERR_PTR(-EINVAL);

	}



	if (tb[TCA_EM_IPT_MATCH_REVISION])

		mrev = nla_get_u8(tb[TCA_EM_IPT_MATCH_REVISION]);



	ret = m->validate_match_data(tb, mrev);

	if (ret < 0)

		return ERR_PTR(ret);



	nfproto = nla_get_u8(tb[TCA_EM_IPT_NFPROTO]);

	return xt_request_find_match(nfproto, m->match_name, mrev);

}



static int em_ipt_change(struct net *net, void *data, int data_len,

			 struct tcf_ematch *em)

{

	struct nlattr *tb[TCA_EM_IPT_MAX + 1];

	struct em_ipt_match *im = NULL;

	struct xt_match *match;

	int mdata_len, ret;



	ret = nla_parse(tb, TCA_EM_IPT_MAX, data, data_len, em_ipt_policy,

			NULL);

	if (ret < 0)

		return ret;



	if (!tb[TCA_EM_IPT_HOOK] || !tb[TCA_EM_IPT_MATCH_NAME] ||

	    !tb[TCA_EM_IPT_MATCH_DATA] || !tb[TCA_EM_IPT_NFPROTO])

		return -EINVAL;



	match = get_xt_match(tb);

	if (IS_ERR(match)) {

		pr_err("unable to load match\n");

		return PTR_ERR(match);

	}



	mdata_len = XT_ALIGN(nla_len(tb[TCA_EM_IPT_MATCH_DATA]));

	im = kzalloc(sizeof(*im) + mdata_len, GFP_KERNEL);

	if (!im) {

		ret = -ENOMEM;

		goto err;

	}



	im->match = match;

	im->hook = nla_get_u32(tb[TCA_EM_IPT_HOOK]);

	nla_memcpy(im->match_data, tb[TCA_EM_IPT_MATCH_DATA], mdata_len);



	ret = check_match(net, im, mdata_len);

	if (ret)

		goto err;



	em->datalen = sizeof(*im) + mdata_len;

	em->data = (unsigned long)im;

	return 0;



err:

	kfree(im);

	module_put(match->me);

	return ret;

}



static void em_ipt_destroy(struct tcf_ematch *em)

{

	struct em_ipt_match *im = (void *)em->data;



	if (!im)

		return;



	if (im->match->destroy) {

		struct xt_mtdtor_param par = {

			.net = em->net,

			.match = im->match,

			.matchinfo = im->match_data,

			.family = im->match->family

		};

		im->match->destroy(&par);

	}

	module_put(im->match->me);

	kfree((void *)im);

}



static int em_ipt_match(struct sk_buff *skb, struct tcf_ematch *em,

			struct tcf_pkt_info *info)

{

	const struct em_ipt_match *im = (const void *)em->data;

	struct xt_action_param acpar = {};

	struct net_device *indev = NULL;

	struct nf_hook_state state;

	int ret;



	rcu_read_lock();



	if (skb->skb_iif)

		indev = dev_get_by_index_rcu(em->net, skb->skb_iif);



	nf_hook_state_init(&state, im->hook, im->match->family,

			   indev ?: skb->dev, skb->dev, NULL, em->net, NULL);



	acpar.match = im->match;

	acpar.matchinfo = im->match_data;

	acpar.state = &state;



	ret = im->match->match(skb, &acpar);



	rcu_read_unlock();

	return ret;

}



static int em_ipt_dump(struct sk_buff *skb, struct tcf_ematch *em)

{

	struct em_ipt_match *im = (void *)em->data;



	if (nla_put_string(skb, TCA_EM_IPT_MATCH_NAME, im->match->name) < 0)

		return -EMSGSIZE;

	if (nla_put_u32(skb, TCA_EM_IPT_HOOK, im->hook) < 0)

		return -EMSGSIZE;

	if (nla_put_u8(skb, TCA_EM_IPT_MATCH_REVISION, im->match->revision) < 0)

		return -EMSGSIZE;

	if (nla_put_u8(skb, TCA_EM_IPT_NFPROTO, im->match->family) < 0)

		return -EMSGSIZE;

	if (nla_put(skb, TCA_EM_IPT_MATCH_DATA,

		    im->match->usersize ?: im->match->matchsize,

		    im->match_data) < 0)

		return -EMSGSIZE;



	return 0;

}



static struct tcf_ematch_ops em_ipt_ops = {

	.kind	  = TCF_EM_IPT,

	.change	  = em_ipt_change,

	.destroy  = em_ipt_destroy,

	.match	  = em_ipt_match,

	.dump	  = em_ipt_dump,

	.owner	  = THIS_MODULE,

	.link	  = LIST_HEAD_INIT(em_ipt_ops.link)

};



static int __init init_em_ipt(void)

{

	return tcf_em_register(&em_ipt_ops);

}



static void __exit exit_em_ipt(void)

{

	tcf_em_unregister(&em_ipt_ops);

}



MODULE_LICENSE("GPL");

MODULE_AUTHOR("Eyal Birger <eyal.birger@gmail.com>");

MODULE_DESCRIPTION("TC extended match for IPtables matches");



module_init(init_em_ipt);

module_exit(exit_em_ipt);



MODULE_ALIAS_TCF_EMATCH(TCF_EM_IPT);

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