1// SPDX-License-Identifier: GPL-2.0-only
2/* Kernel module to match FRAG parameters. */
3
4/* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
5 */
6#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
7#include <linux/module.h>
8#include <linux/skbuff.h>
9#include <linux/ipv6.h>
10#include <linux/types.h>
11#include <net/checksum.h>
12#include <net/ipv6.h>
13
14#include <linux/netfilter/x_tables.h>
15#include <linux/netfilter_ipv6/ip6_tables.h>
16#include <linux/netfilter_ipv6/ip6t_frag.h>
17
18MODULE_LICENSE("GPL");
19MODULE_DESCRIPTION("Xtables: IPv6 fragment match");
20MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
21
22/* Returns 1 if the id is matched by the range, 0 otherwise */
23static inline bool
24id_match(u_int32_t min, u_int32_t max, u_int32_t id, bool invert)
25{
26 bool r;
27 pr_debug("id_match:%c 0x%x <= 0x%x <= 0x%x\n", invert ? '!' : ' ',
28 min, id, max);
29 r = (id >= min && id <= max) ^ invert;
30 pr_debug(" result %s\n", r ? "PASS" : "FAILED");
31 return r;
32}
33
34static bool
35frag_mt6(const struct sk_buff *skb, struct xt_action_param *par)
36{
37 struct frag_hdr _frag;
38 const struct frag_hdr *fh;
39 const struct ip6t_frag *fraginfo = par->matchinfo;
40 unsigned int ptr = 0;
41 int err;
42
43 err = ipv6_find_hdr(skb, offset: &ptr, NEXTHDR_FRAGMENT, NULL, NULL);
44 if (err < 0) {
45 if (err != -ENOENT)
46 par->hotdrop = true;
47 return false;
48 }
49
50 fh = skb_header_pointer(skb, offset: ptr, len: sizeof(_frag), buffer: &_frag);
51 if (fh == NULL) {
52 par->hotdrop = true;
53 return false;
54 }
55
56 pr_debug("INFO %04X ", fh->frag_off);
57 pr_debug("OFFSET %04X ", ntohs(fh->frag_off) & ~0x7);
58 pr_debug("RES %02X %04X", fh->reserved, ntohs(fh->frag_off) & 0x6);
59 pr_debug("MF %04X ", fh->frag_off & htons(IP6_MF));
60 pr_debug("ID %u %08X\n", ntohl(fh->identification),
61 ntohl(fh->identification));
62
63 pr_debug("IPv6 FRAG id %02X ",
64 id_match(fraginfo->ids[0], fraginfo->ids[1],
65 ntohl(fh->identification),
66 !!(fraginfo->invflags & IP6T_FRAG_INV_IDS)));
67 pr_debug("res %02X %02X%04X %02X ",
68 fraginfo->flags & IP6T_FRAG_RES, fh->reserved,
69 ntohs(fh->frag_off) & 0x6,
70 !((fraginfo->flags & IP6T_FRAG_RES) &&
71 (fh->reserved || (ntohs(fh->frag_off) & 0x06))));
72 pr_debug("first %02X %02X %02X ",
73 fraginfo->flags & IP6T_FRAG_FST,
74 ntohs(fh->frag_off) & ~0x7,
75 !((fraginfo->flags & IP6T_FRAG_FST) &&
76 (ntohs(fh->frag_off) & ~0x7)));
77 pr_debug("mf %02X %02X %02X ",
78 fraginfo->flags & IP6T_FRAG_MF,
79 ntohs(fh->frag_off) & IP6_MF,
80 !((fraginfo->flags & IP6T_FRAG_MF) &&
81 !((ntohs(fh->frag_off) & IP6_MF))));
82 pr_debug("last %02X %02X %02X\n",
83 fraginfo->flags & IP6T_FRAG_NMF,
84 ntohs(fh->frag_off) & IP6_MF,
85 !((fraginfo->flags & IP6T_FRAG_NMF) &&
86 (ntohs(fh->frag_off) & IP6_MF)));
87
88 return id_match(min: fraginfo->ids[0], max: fraginfo->ids[1],
89 ntohl(fh->identification),
90 invert: !!(fraginfo->invflags & IP6T_FRAG_INV_IDS)) &&
91 !((fraginfo->flags & IP6T_FRAG_RES) &&
92 (fh->reserved || (ntohs(fh->frag_off) & 0x6))) &&
93 !((fraginfo->flags & IP6T_FRAG_FST) &&
94 (ntohs(fh->frag_off) & ~0x7)) &&
95 !((fraginfo->flags & IP6T_FRAG_MF) &&
96 !(ntohs(fh->frag_off) & IP6_MF)) &&
97 !((fraginfo->flags & IP6T_FRAG_NMF) &&
98 (ntohs(fh->frag_off) & IP6_MF));
99}
100
101static int frag_mt6_check(const struct xt_mtchk_param *par)
102{
103 const struct ip6t_frag *fraginfo = par->matchinfo;
104
105 if (fraginfo->invflags & ~IP6T_FRAG_INV_MASK) {
106 pr_debug("unknown flags %X\n", fraginfo->invflags);
107 return -EINVAL;
108 }
109 return 0;
110}
111
112static struct xt_match frag_mt6_reg __read_mostly = {
113 .name = "frag",
114 .family = NFPROTO_IPV6,
115 .match = frag_mt6,
116 .matchsize = sizeof(struct ip6t_frag),
117 .checkentry = frag_mt6_check,
118 .me = THIS_MODULE,
119};
120
121static int __init frag_mt6_init(void)
122{
123 return xt_register_match(target: &frag_mt6_reg);
124}
125
126static void __exit frag_mt6_exit(void)
127{
128 xt_unregister_match(target: &frag_mt6_reg);
129}
130
131module_init(frag_mt6_init);
132module_exit(frag_mt6_exit);
133

source code of linux/net/ipv6/netfilter/ip6t_frag.c