1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
|
/* 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_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",
.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>");
|
