1 /* Kernel module to match FRAG parameters. */
2
3 /* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 */
9
10 #include <linux/module.h>
11 #include <linux/skbuff.h>
12 #include <linux/ipv6.h>
13 #include <linux/types.h>
14 #include <net/checksum.h>
15 #include <net/ipv6.h>
16
17 #include <linux/netfilter/x_tables.h>
18 #include <linux/netfilter_ipv6/ip6_tables.h>
19 #include <linux/netfilter_ipv6/ip6t_frag.h>
20
21 MODULE_LICENSE("GPL");
22 MODULE_DESCRIPTION("Xtables: IPv6 fragment match");
23 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
24
25 /* Returns 1 if the id is matched by the range, 0 otherwise */
26 static inline bool
27 id_match(u_int32_t min, u_int32_t max, u_int32_t id, bool invert)
28 {
29 bool r;
30 pr_debug("frag id_match:%c 0x%x <= 0x%x <= 0x%x", invert ? '!' : ' ',
31 min, id, max);
32 r = (id >= min && id <= max) ^ invert;
33 pr_debug(" result %s\n", r ? "PASS" : "FAILED");
34 return r;
35 }
36
37 static bool
38 frag_mt6(const struct sk_buff *skb, const struct net_device *in,
39 const struct net_device *out, const struct xt_match *match,
40 const void *matchinfo, int offset, unsigned int protoff,
41 bool *hotdrop)
42 {
43 struct frag_hdr _frag;
44 const struct frag_hdr *fh;
45 const struct ip6t_frag *fraginfo = matchinfo;
46 unsigned int ptr;
47 int err;
48
49 err = ipv6_find_hdr(skb, &ptr, NEXTHDR_FRAGMENT, NULL);
50 if (err < 0) {
51 if (err != -ENOENT)
52 *hotdrop = true;
53 return false;
54 }
55
56 fh = skb_header_pointer(skb, ptr, sizeof(_frag), &_frag);
57 if (fh == NULL) {
58 *hotdrop = true;
59 return false;
60 }
61
62 pr_debug("INFO %04X ", fh->frag_off);
63 pr_debug("OFFSET %04X ", ntohs(fh->frag_off) & ~0x7);
64 pr_debug("RES %02X %04X", fh->reserved, ntohs(fh->frag_off) & 0x6);
65 pr_debug("MF %04X ", fh->frag_off & htons(IP6_MF));
66 pr_debug("ID %u %08X\n", ntohl(fh->identification),
67 ntohl(fh->identification));
68
69 pr_debug("IPv6 FRAG id %02X ",
70 id_match(fraginfo->ids[0], fraginfo->ids[1],
71 ntohl(fh->identification),
72 !!(fraginfo->invflags & IP6T_FRAG_INV_IDS)));
73 pr_debug("res %02X %02X%04X %02X ",
74 fraginfo->flags & IP6T_FRAG_RES, fh->reserved,
75 ntohs(fh->frag_off) & 0x6,
76 !((fraginfo->flags & IP6T_FRAG_RES)
77 && (fh->reserved || (ntohs(fh->frag_off) & 0x06))));
78 pr_debug("first %02X %02X %02X ",
79 fraginfo->flags & IP6T_FRAG_FST,
80 ntohs(fh->frag_off) & ~0x7,
81 !((fraginfo->flags & IP6T_FRAG_FST)
82 && (ntohs(fh->frag_off) & ~0x7)));
83 pr_debug("mf %02X %02X %02X ",
84 fraginfo->flags & IP6T_FRAG_MF,
85 ntohs(fh->frag_off) & IP6_MF,
86 !((fraginfo->flags & IP6T_FRAG_MF)
87 && !((ntohs(fh->frag_off) & IP6_MF))));
88 pr_debug("last %02X %02X %02X\n",
89 fraginfo->flags & IP6T_FRAG_NMF,
90 ntohs(fh->frag_off) & IP6_MF,
91 !((fraginfo->flags & IP6T_FRAG_NMF)
92 && (ntohs(fh->frag_off) & IP6_MF)));
93
94 return (fh != NULL)
95 &&
96 id_match(fraginfo->ids[0], fraginfo->ids[1],
97 ntohl(fh->identification),
98 !!(fraginfo->invflags & IP6T_FRAG_INV_IDS))
99 &&
100 !((fraginfo->flags & IP6T_FRAG_RES)
101 && (fh->reserved || (ntohs(fh->frag_off) & 0x6)))
102 &&
103 !((fraginfo->flags & IP6T_FRAG_FST)
104 && (ntohs(fh->frag_off) & ~0x7))
105 &&
106 !((fraginfo->flags & IP6T_FRAG_MF)
107 && !(ntohs(fh->frag_off) & IP6_MF))
108 &&
109 !((fraginfo->flags & IP6T_FRAG_NMF)
110 && (ntohs(fh->frag_off) & IP6_MF));
111 }
112
113 /* Called when user tries to insert an entry of this type. */
114 static bool
115 frag_mt6_check(const char *tablename, const void *ip,
116 const struct xt_match *match, void *matchinfo,
117 unsigned int hook_mask)
118 {
119 const struct ip6t_frag *fraginfo = matchinfo;
120
121 if (fraginfo->invflags & ~IP6T_FRAG_INV_MASK) {
122 pr_debug("ip6t_frag: unknown flags %X\n", fraginfo->invflags);
123 return false;
124 }
125 return true;
126 }
127
128 static struct xt_match frag_mt6_reg __read_mostly = {
129 .name = "frag",
130 .family = AF_INET6,
131 .match = frag_mt6,
132 .matchsize = sizeof(struct ip6t_frag),
133 .checkentry = frag_mt6_check,
134 .me = THIS_MODULE,
135 };
136
137 static int __init frag_mt6_init(void)
138 {
139 return xt_register_match(&frag_mt6_reg);
140 }
141
142 static void __exit frag_mt6_exit(void)
143 {
144 xt_unregister_match(&frag_mt6_reg);
145 }
146
147 module_init(frag_mt6_init);
148 module_exit(frag_mt6_exit);
149
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