// SPDX-License-Identifier: GPL-2.0-or-later
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/* Kernel module to match Segment Routing Header (SRH) parameters. */
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/* Author:
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* Ahmed Abdelsalam <amsalam20@gmail.com>
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/ipv6.h>
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#include <linux/types.h>
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#include <net/ipv6.h>
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#include <net/seg6.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter_ipv6/ip6t_srh.h>
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#include <linux/netfilter_ipv6/ip6_tables.h>
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/* Test a struct->mt_invflags and a boolean for inequality */
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#define NF_SRH_INVF(ptr, flag, boolean) \
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((boolean) ^ !!((ptr)->mt_invflags & (flag)))
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static bool srh_mt6(const struct sk_buff *skb, struct xt_action_param *par)
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{
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const struct ip6t_srh *srhinfo = par->matchinfo;
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struct ipv6_sr_hdr *srh;
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struct ipv6_sr_hdr _srh;
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int hdrlen, srhoff = 0;
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if (ipv6_find_hdr(skb, &srhoff, IPPROTO_ROUTING, NULL, NULL) < 0)
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return false;
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srh = skb_header_pointer(skb, srhoff, sizeof(_srh), &_srh);
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if (!srh)
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return false;
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hdrlen = ipv6_optlen(srh);
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if (skb->len - srhoff < hdrlen)
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return false;
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if (srh->type != IPV6_SRCRT_TYPE_4)
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return false;
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if (srh->segments_left > srh->first_segment)
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return false;
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/* Next Header matching */
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if (srhinfo->mt_flags & IP6T_SRH_NEXTHDR)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_NEXTHDR,
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!(srh->nexthdr == srhinfo->next_hdr)))
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return false;
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/* Header Extension Length matching */
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if (srhinfo->mt_flags & IP6T_SRH_LEN_EQ)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LEN_EQ,
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!(srh->hdrlen == srhinfo->hdr_len)))
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return false;
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if (srhinfo->mt_flags & IP6T_SRH_LEN_GT)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LEN_GT,
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!(srh->hdrlen > srhinfo->hdr_len)))
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return false;
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if (srhinfo->mt_flags & IP6T_SRH_LEN_LT)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LEN_LT,
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!(srh->hdrlen < srhinfo->hdr_len)))
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return false;
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/* Segments Left matching */
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if (srhinfo->mt_flags & IP6T_SRH_SEGS_EQ)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_SEGS_EQ,
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!(srh->segments_left == srhinfo->segs_left)))
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return false;
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if (srhinfo->mt_flags & IP6T_SRH_SEGS_GT)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_SEGS_GT,
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!(srh->segments_left > srhinfo->segs_left)))
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return false;
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if (srhinfo->mt_flags & IP6T_SRH_SEGS_LT)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_SEGS_LT,
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!(srh->segments_left < srhinfo->segs_left)))
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return false;
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/**
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* Last Entry matching
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* Last_Entry field was introduced in revision 6 of the SRH draft.
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* It was called First_Segment in the previous revision
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*/
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if (srhinfo->mt_flags & IP6T_SRH_LAST_EQ)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LAST_EQ,
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!(srh->first_segment == srhinfo->last_entry)))
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return false;
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if (srhinfo->mt_flags & IP6T_SRH_LAST_GT)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LAST_GT,
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!(srh->first_segment > srhinfo->last_entry)))
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return false;
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if (srhinfo->mt_flags & IP6T_SRH_LAST_LT)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LAST_LT,
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!(srh->first_segment < srhinfo->last_entry)))
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return false;
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/**
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* Tag matchig
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* Tag field was introduced in revision 6 of the SRH draft.
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*/
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if (srhinfo->mt_flags & IP6T_SRH_TAG)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_TAG,
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!(srh->tag == srhinfo->tag)))
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return false;
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return true;
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}
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static bool srh1_mt6(const struct sk_buff *skb, struct xt_action_param *par)
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{
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int hdrlen, psidoff, nsidoff, lsidoff, srhoff = 0;
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const struct ip6t_srh1 *srhinfo = par->matchinfo;
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struct in6_addr *psid, *nsid, *lsid;
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struct in6_addr _psid, _nsid, _lsid;
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struct ipv6_sr_hdr *srh;
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struct ipv6_sr_hdr _srh;
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if (ipv6_find_hdr(skb, &srhoff, IPPROTO_ROUTING, NULL, NULL) < 0)
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return false;
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srh = skb_header_pointer(skb, srhoff, sizeof(_srh), &_srh);
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if (!srh)
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return false;
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hdrlen = ipv6_optlen(srh);
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if (skb->len - srhoff < hdrlen)
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return false;
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if (srh->type != IPV6_SRCRT_TYPE_4)
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return false;
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if (srh->segments_left > srh->first_segment)
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return false;
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/* Next Header matching */
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if (srhinfo->mt_flags & IP6T_SRH_NEXTHDR)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_NEXTHDR,
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!(srh->nexthdr == srhinfo->next_hdr)))
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return false;
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/* Header Extension Length matching */
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if (srhinfo->mt_flags & IP6T_SRH_LEN_EQ)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LEN_EQ,
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!(srh->hdrlen == srhinfo->hdr_len)))
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return false;
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if (srhinfo->mt_flags & IP6T_SRH_LEN_GT)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LEN_GT,
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!(srh->hdrlen > srhinfo->hdr_len)))
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return false;
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if (srhinfo->mt_flags & IP6T_SRH_LEN_LT)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LEN_LT,
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!(srh->hdrlen < srhinfo->hdr_len)))
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return false;
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/* Segments Left matching */
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if (srhinfo->mt_flags & IP6T_SRH_SEGS_EQ)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_SEGS_EQ,
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!(srh->segments_left == srhinfo->segs_left)))
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return false;
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if (srhinfo->mt_flags & IP6T_SRH_SEGS_GT)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_SEGS_GT,
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!(srh->segments_left > srhinfo->segs_left)))
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return false;
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if (srhinfo->mt_flags & IP6T_SRH_SEGS_LT)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_SEGS_LT,
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!(srh->segments_left < srhinfo->segs_left)))
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return false;
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/**
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* Last Entry matching
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* Last_Entry field was introduced in revision 6 of the SRH draft.
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* It was called First_Segment in the previous revision
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*/
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if (srhinfo->mt_flags & IP6T_SRH_LAST_EQ)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LAST_EQ,
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!(srh->first_segment == srhinfo->last_entry)))
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return false;
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if (srhinfo->mt_flags & IP6T_SRH_LAST_GT)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LAST_GT,
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!(srh->first_segment > srhinfo->last_entry)))
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return false;
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if (srhinfo->mt_flags & IP6T_SRH_LAST_LT)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LAST_LT,
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!(srh->first_segment < srhinfo->last_entry)))
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return false;
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/**
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* Tag matchig
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* Tag field was introduced in revision 6 of the SRH draft
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*/
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if (srhinfo->mt_flags & IP6T_SRH_TAG)
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_TAG,
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!(srh->tag == srhinfo->tag)))
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return false;
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/* Previous SID matching */
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if (srhinfo->mt_flags & IP6T_SRH_PSID) {
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if (srh->segments_left == srh->first_segment)
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return false;
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psidoff = srhoff + sizeof(struct ipv6_sr_hdr) +
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((srh->segments_left + 1) * sizeof(struct in6_addr));
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psid = skb_header_pointer(skb, psidoff, sizeof(_psid), &_psid);
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if (!psid)
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return false;
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_PSID,
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ipv6_masked_addr_cmp(psid, &srhinfo->psid_msk,
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&srhinfo->psid_addr)))
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return false;
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}
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/* Next SID matching */
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if (srhinfo->mt_flags & IP6T_SRH_NSID) {
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if (srh->segments_left == 0)
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return false;
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nsidoff = srhoff + sizeof(struct ipv6_sr_hdr) +
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((srh->segments_left - 1) * sizeof(struct in6_addr));
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nsid = skb_header_pointer(skb, nsidoff, sizeof(_nsid), &_nsid);
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if (!nsid)
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return false;
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_NSID,
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ipv6_masked_addr_cmp(nsid, &srhinfo->nsid_msk,
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&srhinfo->nsid_addr)))
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return false;
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}
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/* Last SID matching */
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if (srhinfo->mt_flags & IP6T_SRH_LSID) {
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lsidoff = srhoff + sizeof(struct ipv6_sr_hdr);
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lsid = skb_header_pointer(skb, lsidoff, sizeof(_lsid), &_lsid);
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if (!lsid)
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return false;
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if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LSID,
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ipv6_masked_addr_cmp(lsid, &srhinfo->lsid_msk,
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&srhinfo->lsid_addr)))
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return false;
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}
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return true;
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}
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static int srh_mt6_check(const struct xt_mtchk_param *par)
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{
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const struct ip6t_srh *srhinfo = par->matchinfo;
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if (srhinfo->mt_flags & ~IP6T_SRH_MASK) {
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pr_info_ratelimited("unknown srh match flags %X\n",
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srhinfo->mt_flags);
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return -EINVAL;
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}
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if (srhinfo->mt_invflags & ~IP6T_SRH_INV_MASK) {
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pr_info_ratelimited("unknown srh invflags %X\n",
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srhinfo->mt_invflags);
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return -EINVAL;
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}
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return 0;
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}
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static int srh1_mt6_check(const struct xt_mtchk_param *par)
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{
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const struct ip6t_srh1 *srhinfo = par->matchinfo;
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if (srhinfo->mt_flags & ~IP6T_SRH_MASK) {
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pr_info_ratelimited("unknown srh match flags %X\n",
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srhinfo->mt_flags);
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return -EINVAL;
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}
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if (srhinfo->mt_invflags & ~IP6T_SRH_INV_MASK) {
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pr_info_ratelimited("unknown srh invflags %X\n",
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srhinfo->mt_invflags);
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return -EINVAL;
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}
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return 0;
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}
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static struct xt_match srh_mt6_reg[] __read_mostly = {
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{
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.name = "srh",
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.revision = 0,
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.family = NFPROTO_IPV6,
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.match = srh_mt6,
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.matchsize = sizeof(struct ip6t_srh),
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.checkentry = srh_mt6_check,
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.me = THIS_MODULE,
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},
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{
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.name = "srh",
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.revision = 1,
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.family = NFPROTO_IPV6,
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.match = srh1_mt6,
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.matchsize = sizeof(struct ip6t_srh1),
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.checkentry = srh1_mt6_check,
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.me = THIS_MODULE,
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}
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};
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static int __init srh_mt6_init(void)
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{
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return xt_register_matches(srh_mt6_reg, ARRAY_SIZE(srh_mt6_reg));
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}
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static void __exit srh_mt6_exit(void)
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{
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xt_unregister_matches(srh_mt6_reg, ARRAY_SIZE(srh_mt6_reg));
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}
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module_init(srh_mt6_init);
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module_exit(srh_mt6_exit);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("Xtables: IPv6 Segment Routing Header match");
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MODULE_AUTHOR("Ahmed Abdelsalam <amsalam20@gmail.com>");
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