netfilter: add IPv6 segment routing header 'srh' match (202a8ff5) · Commits · 戴 / test

include/uapi/linux/netfilter_ipv6/ip6t_srh.h

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		/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
		#ifndef _IP6T_SRH_H
		#define _IP6T_SRH_H

		#include <linux/types.h>
		#include <linux/netfilter.h>

		/* Values for "mt_flags" field in struct ip6t_srh */
		#define IP6T_SRH_NEXTHDR 0x0001
		#define IP6T_SRH_LEN_EQ 0x0002
		#define IP6T_SRH_LEN_GT 0x0004
		#define IP6T_SRH_LEN_LT 0x0008
		#define IP6T_SRH_SEGS_EQ 0x0010
		#define IP6T_SRH_SEGS_GT 0x0020
		#define IP6T_SRH_SEGS_LT 0x0040
		#define IP6T_SRH_LAST_EQ 0x0080
		#define IP6T_SRH_LAST_GT 0x0100
		#define IP6T_SRH_LAST_LT 0x0200
		#define IP6T_SRH_TAG 0x0400
		#define IP6T_SRH_MASK 0x07FF

		/* Values for "mt_invflags" field in struct ip6t_srh */
		#define IP6T_SRH_INV_NEXTHDR 0x0001
		#define IP6T_SRH_INV_LEN_EQ 0x0002
		#define IP6T_SRH_INV_LEN_GT 0x0004
		#define IP6T_SRH_INV_LEN_LT 0x0008
		#define IP6T_SRH_INV_SEGS_EQ 0x0010
		#define IP6T_SRH_INV_SEGS_GT 0x0020
		#define IP6T_SRH_INV_SEGS_LT 0x0040
		#define IP6T_SRH_INV_LAST_EQ 0x0080
		#define IP6T_SRH_INV_LAST_GT 0x0100
		#define IP6T_SRH_INV_LAST_LT 0x0200
		#define IP6T_SRH_INV_TAG 0x0400
		#define IP6T_SRH_INV_MASK 0x07FF

		/**
		* struct ip6t_srh - SRH match options
		* @ next_hdr: Next header field of SRH
		* @ hdr_len: Extension header length field of SRH
		* @ segs_left: Segments left field of SRH
		* @ last_entry: Last entry field of SRH
		* @ tag: Tag field of SRH
		* @ mt_flags: match options
		* @ mt_invflags: Invert the sense of match options
		*/

		struct ip6t_srh {
		__u8 next_hdr;
		__u8 hdr_len;
		__u8 segs_left;
		__u8 last_entry;
		__u16 tag;
		__u16 mt_flags;
		__u16 mt_invflags;
		};

		#endif /_IP6T_SRH_H/

net/ipv6/netfilter/Kconfig

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		@@ -240,6 +240,15 @@ config IP6_NF_MATCH_RT

		To compile it as a module, choose M here. If unsure, say N.

		config IP6_NF_MATCH_SRH
		tristate '"srh" Segment Routing header match support'
		depends on NETFILTER_ADVANCED
		help
		srh matching allows you to match packets based on the segment
		routing header of the packet.

		To compile it as a module, choose M here. If unsure, say N.

		# The targets
		config IP6_NF_TARGET_HL
		tristate '"HL" hoplimit target support'

net/ipv6/netfilter/Makefile

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		@@ -57,6 +57,7 @@ obj-$(CONFIG_IP6_NF_MATCH_MH) += ip6t_mh.o
		obj-$(CONFIG_IP6_NF_MATCH_OPTS) += ip6t_hbh.o
		obj-$(CONFIG_IP6_NF_MATCH_RPFILTER) += ip6t_rpfilter.o
		obj-$(CONFIG_IP6_NF_MATCH_RT) += ip6t_rt.o
		obj-$(CONFIG_IP6_NF_MATCH_SRH) += ip6t_srh.o

		# targets
		obj-$(CONFIG_IP6_NF_TARGET_MASQUERADE) += ip6t_MASQUERADE.o

net/ipv6/netfilter/ip6t_srh.c

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		/* Kernel module to match Segment Routing Header (SRH) parameters. */

		/* Author:
		* Ahmed Abdelsalam <amsalam20@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.
		*/

		#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
		#include <linux/module.h>
		#include <linux/skbuff.h>
		#include <linux/ipv6.h>
		#include <linux/types.h>
		#include <net/ipv6.h>
		#include <net/seg6.h>

		#include <linux/netfilter/x_tables.h>
		#include <linux/netfilter_ipv6/ip6t_srh.h>
		#include <linux/netfilter_ipv6/ip6_tables.h>

		/* Test a struct->mt_invflags and a boolean for inequality */
		#define NF_SRH_INVF(ptr, flag, boolean) \
		((boolean) ^ !!((ptr)->mt_invflags & (flag)))

		static bool srh_mt6(const struct sk_buff skb, struct xt_action_param par)
		{
		const struct ip6t_srh *srhinfo = par->matchinfo;
		struct ipv6_sr_hdr *srh;
		struct ipv6_sr_hdr _srh;
		int hdrlen, srhoff = 0;

		if (ipv6_find_hdr(skb, &srhoff, IPPROTO_ROUTING, NULL, NULL) < 0)
		return false;
		srh = skb_header_pointer(skb, srhoff, sizeof(_srh), &_srh);
		if (!srh)
		return false;

		hdrlen = ipv6_optlen(srh);
		if (skb->len - srhoff < hdrlen)
		return false;

		if (srh->type != IPV6_SRCRT_TYPE_4)
		return false;

		if (srh->segments_left > srh->first_segment)
		return false;

		/* Next Header matching */
		if (srhinfo->mt_flags & IP6T_SRH_NEXTHDR)
		if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_NEXTHDR,
		!(srh->nexthdr == srhinfo->next_hdr)))
		return false;

		/* Header Extension Length matching */
		if (srhinfo->mt_flags & IP6T_SRH_LEN_EQ)
		if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LEN_EQ,
		!(srh->hdrlen == srhinfo->hdr_len)))
		return false;

		if (srhinfo->mt_flags & IP6T_SRH_LEN_GT)
		if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LEN_GT,
		!(srh->hdrlen > srhinfo->hdr_len)))
		return false;

		if (srhinfo->mt_flags & IP6T_SRH_LEN_LT)
		if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LEN_LT,
		!(srh->hdrlen < srhinfo->hdr_len)))
		return false;

		/* Segments Left matching */
		if (srhinfo->mt_flags & IP6T_SRH_SEGS_EQ)
		if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_SEGS_EQ,
		!(srh->segments_left == srhinfo->segs_left)))
		return false;

		if (srhinfo->mt_flags & IP6T_SRH_SEGS_GT)
		if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_SEGS_GT,
		!(srh->segments_left > srhinfo->segs_left)))
		return false;

		if (srhinfo->mt_flags & IP6T_SRH_SEGS_LT)
		if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_SEGS_LT,
		!(srh->segments_left < srhinfo->segs_left)))
		return false;

		/**
		* Last Entry matching
		* Last_Entry field was introduced in revision 6 of the SRH draft.
		* It was called First_Segment in the previous revision
		*/
		if (srhinfo->mt_flags & IP6T_SRH_LAST_EQ)
		if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LAST_EQ,
		!(srh->first_segment == srhinfo->last_entry)))
		return false;

		if (srhinfo->mt_flags & IP6T_SRH_LAST_GT)
		if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LAST_GT,
		!(srh->first_segment > srhinfo->last_entry)))
		return false;

		if (srhinfo->mt_flags & IP6T_SRH_LAST_LT)
		if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LAST_LT,
		!(srh->first_segment < srhinfo->last_entry)))
		return false;

		/**
		* Tag matchig
		* Tag field was introduced in revision 6 of the SRH draft.
		*/
		if (srhinfo->mt_flags & IP6T_SRH_TAG)
		if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_TAG,
		!(srh->tag == srhinfo->tag)))
		return false;
		return true;
		}

		static int srh_mt6_check(const struct xt_mtchk_param *par)
		{
		const struct ip6t_srh *srhinfo = par->matchinfo;

		if (srhinfo->mt_flags & ~IP6T_SRH_MASK) {
		pr_err("unknown srh match flags %X\n", srhinfo->mt_flags);
		return -EINVAL;
		}

		if (srhinfo->mt_invflags & ~IP6T_SRH_INV_MASK) {
		pr_err("unknown srh invflags %X\n", srhinfo->mt_invflags);
		return -EINVAL;
		}

		return 0;
		}

		static struct xt_match srh_mt6_reg __read_mostly = {
		.name = "srh",
		.family = NFPROTO_IPV6,
		.match = srh_mt6,
		.matchsize = sizeof(struct ip6t_srh),
		.checkentry = srh_mt6_check,
		.me = THIS_MODULE,
		};

		static int __init srh_mt6_init(void)
		{
		return xt_register_match(&srh_mt6_reg);
		}

		static void __exit srh_mt6_exit(void)
		{
		xt_unregister_match(&srh_mt6_reg);
		}

		module_init(srh_mt6_init);
		module_exit(srh_mt6_exit);

		MODULE_LICENSE("GPL");
		MODULE_DESCRIPTION("Xtables: IPv6 Segment Routing Header match");
		MODULE_AUTHOR("Ahmed Abdelsalam <amsalam20@gmail.com>");

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