From: Ahmed Abdelsalam <amsalam20@xxxxxxxxx> It allows matching packets based on Segment Routing Header (SRH) information. The implementation considers revision 7 of the SRH draft. https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-07 Currently supported match options include: (1) Next Header (2) Hdr Ext Len (3) Segments Left (4) Last Entry (5) Tag value of SRH Signed-off-by: Ahmed Abdelsalam <amsalam20@xxxxxxxxx> Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> --- include/uapi/linux/netfilter_ipv6/ip6t_srh.h | 57 ++++++++++ net/ipv6/netfilter/Kconfig | 9 ++ net/ipv6/netfilter/Makefile | 1 + net/ipv6/netfilter/ip6t_srh.c | 161 +++++++++++++++++++++++++++ 4 files changed, 228 insertions(+) create mode 100644 include/uapi/linux/netfilter_ipv6/ip6t_srh.h create mode 100644 net/ipv6/netfilter/ip6t_srh.c diff --git a/include/uapi/linux/netfilter_ipv6/ip6t_srh.h b/include/uapi/linux/netfilter_ipv6/ip6t_srh.h new file mode 100644 index 000000000000..f3cc0ef514a7 --- /dev/null +++ b/include/uapi/linux/netfilter_ipv6/ip6t_srh.h @@ -0,0 +1,57 @@ +/* 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*/ diff --git a/net/ipv6/netfilter/Kconfig b/net/ipv6/netfilter/Kconfig index 806e95375ec8..b6f5edf926d2 100644 --- a/net/ipv6/netfilter/Kconfig +++ b/net/ipv6/netfilter/Kconfig @@ -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' diff --git a/net/ipv6/netfilter/Makefile b/net/ipv6/netfilter/Makefile index 95611c4b39b0..d984057b8395 100644 --- a/net/ipv6/netfilter/Makefile +++ b/net/ipv6/netfilter/Makefile @@ -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 diff --git a/net/ipv6/netfilter/ip6t_srh.c b/net/ipv6/netfilter/ip6t_srh.c new file mode 100644 index 000000000000..9642164107ce --- /dev/null +++ b/net/ipv6/netfilter/ip6t_srh.c @@ -0,0 +1,161 @@ +/* Kernel module to match Segment Routing Header (SRH) parameters. */ + +/* Author: + * Ahmed Abdelsalam <amsalam20@xxxxxxxxx> + * + * 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@xxxxxxxxx>"); 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