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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 bool srh1_mt6(const struct sk_buff *skb, struct xt_action_param *par)
{
int hdrlen, psidoff, nsidoff, lsidoff, srhoff = 0;
const struct ip6t_srh1 *srhinfo = par->matchinfo;
struct in6_addr *psid, *nsid, *lsid;
struct in6_addr _psid, _nsid, _lsid;
struct ipv6_sr_hdr *srh;
struct ipv6_sr_hdr _srh;
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;
/* Previous SID matching */
if (srhinfo->mt_flags & IP6T_SRH_PSID) {
if (srh->segments_left == srh->first_segment)
return false;
psidoff = srhoff + sizeof(struct ipv6_sr_hdr) +
((srh->segments_left + 1) * sizeof(struct in6_addr));
psid = skb_header_pointer(skb, psidoff, sizeof(_psid), &_psid);
if (!psid)
return false;
if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_PSID,
ipv6_masked_addr_cmp(psid, &srhinfo->psid_msk,
&srhinfo->psid_addr)))
return false;
}
/* Next SID matching */
if (srhinfo->mt_flags & IP6T_SRH_NSID) {
if (srh->segments_left == 0)
return false;
nsidoff = srhoff + sizeof(struct ipv6_sr_hdr) +
((srh->segments_left - 1) * sizeof(struct in6_addr));
nsid = skb_header_pointer(skb, nsidoff, sizeof(_nsid), &_nsid);
if (!nsid)
return false;
if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_NSID,
ipv6_masked_addr_cmp(nsid, &srhinfo->nsid_msk,
&srhinfo->nsid_addr)))
return false;
}
/* Last SID matching */
if (srhinfo->mt_flags & IP6T_SRH_LSID) {
lsidoff = srhoff + sizeof(struct ipv6_sr_hdr);
lsid = skb_header_pointer(skb, lsidoff, sizeof(_lsid), &_lsid);
if (!lsid)
return false;
if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LSID,
ipv6_masked_addr_cmp(lsid, &srhinfo->lsid_msk,
&srhinfo->lsid_addr)))
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_info_ratelimited("unknown srh match flags %X\n",
srhinfo->mt_flags);
return -EINVAL;
}
if (srhinfo->mt_invflags & ~IP6T_SRH_INV_MASK) {
pr_info_ratelimited("unknown srh invflags %X\n",
srhinfo->mt_invflags);
return -EINVAL;
}
return 0;
}
static int srh1_mt6_check(const struct xt_mtchk_param *par)
{
const struct ip6t_srh1 *srhinfo = par->matchinfo;
if (srhinfo->mt_flags & ~IP6T_SRH_MASK) {
pr_info_ratelimited("unknown srh match flags %X\n",
srhinfo->mt_flags);
return -EINVAL;
}
if (srhinfo->mt_invflags & ~IP6T_SRH_INV_MASK) {
pr_info_ratelimited("unknown srh invflags %X\n",
srhinfo->mt_invflags);
return -EINVAL;
}
return 0;
}
static struct xt_match srh_mt6_reg[] __read_mostly = {
{
.name = "srh",
.revision = 0,
.family = NFPROTO_IPV6,
.match = srh_mt6,
.matchsize = sizeof(struct ip6t_srh),
.checkentry = srh_mt6_check,
.me = THIS_MODULE,
},
{
.name = "srh",
.revision = 1,
.family = NFPROTO_IPV6,
.match = srh1_mt6,
.matchsize = sizeof(struct ip6t_srh1),
.checkentry = srh1_mt6_check,
.me = THIS_MODULE,
}
};
static int __init srh_mt6_init(void)
{
return xt_register_matches(srh_mt6_reg, ARRAY_SIZE(srh_mt6_reg));
}
static void __exit srh_mt6_exit(void)
{
xt_unregister_matches(srh_mt6_reg, ARRAY_SIZE(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>");