/net/ipv6/netfilter/ip6t_dst.c
C | 278 lines | 213 code | 34 blank | 31 comment | 53 complexity | 3b8dc9e4e1b7f5a0df1a8a3ad9e37c50 MD5 | raw file
Possible License(s): CC-BY-SA-3.0, GPL-2.0, LGPL-2.0, AGPL-1.0
1/* Kernel module to match Hop-by-Hop and Destination parameters. */
2#include <linux/module.h>
3#include <linux/skbuff.h>
4#include <linux/ipv6.h>
5#include <linux/types.h>
6#include <net/checksum.h>
7#include <net/ipv6.h>
8
9#include <asm/byteorder.h>
10
11#include <linux/netfilter_ipv6/ip6_tables.h>
12#include <linux/netfilter_ipv6/ip6t_opts.h>
13
14#define LOW(n) (n & 0x00FF)
15
16#define HOPBYHOP 0
17
18MODULE_LICENSE("GPL");
19#if HOPBYHOP
20MODULE_DESCRIPTION("IPv6 HbH match");
21#else
22MODULE_DESCRIPTION("IPv6 DST match");
23#endif
24MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
25
26#if 0
27#define DEBUGP printk
28#else
29#define DEBUGP(format, args...)
30#endif
31
32/*
33 * (Type & 0xC0) >> 6
34 * 0 -> ignorable
35 * 1 -> must drop the packet
36 * 2 -> send ICMP PARM PROB regardless and drop packet
37 * 3 -> Send ICMP if not a multicast address and drop packet
38 * (Type & 0x20) >> 5
39 * 0 -> invariant
40 * 1 -> can change the routing
41 * (Type & 0x1F) Type
42 * 0 -> PAD0 (only 1 byte!)
43 * 1 -> PAD1 LENGTH info (total length = length + 2)
44 * C0 | 2 -> JUMBO 4 x x x x ( xxxx > 64k )
45 * 5 -> RTALERT 2 x x
46 */
47
48static int
49match(const struct sk_buff *skb,
50 const struct net_device *in,
51 const struct net_device *out,
52 const void *matchinfo,
53 int offset,
54 const void *protohdr,
55 u_int16_t datalen,
56 int *hotdrop)
57{
58 struct ipv6_opt_hdr *optsh = NULL;
59 const struct ip6t_opts *optinfo = matchinfo;
60 unsigned int temp;
61 unsigned int len;
62 u8 nexthdr;
63 unsigned int ptr;
64 unsigned int hdrlen = 0;
65 unsigned int ret = 0;
66 u_int16_t *optdesc = NULL;
67
68 /* type of the 1st exthdr */
69 nexthdr = skb->nh.ipv6h->nexthdr;
70 /* pointer to the 1st exthdr */
71 ptr = sizeof(struct ipv6hdr);
72 /* available length */
73 len = skb->len - ptr;
74 temp = 0;
75
76 while (ip6t_ext_hdr(nexthdr)) {
77 struct ipv6_opt_hdr *hdr;
78
79 DEBUGP("ipv6_opts header iteration \n");
80
81 /* Is there enough space for the next ext header? */
82 if (len < (int)sizeof(struct ipv6_opt_hdr))
83 return 0;
84 /* No more exthdr -> evaluate */
85 if (nexthdr == NEXTHDR_NONE) {
86 break;
87 }
88 /* ESP -> evaluate */
89 if (nexthdr == NEXTHDR_ESP) {
90 break;
91 }
92
93 hdr=(void *)(skb->data)+ptr;
94
95 /* Calculate the header length */
96 if (nexthdr == NEXTHDR_FRAGMENT) {
97 hdrlen = 8;
98 } else if (nexthdr == NEXTHDR_AUTH)
99 hdrlen = (hdr->hdrlen+2)<<2;
100 else
101 hdrlen = ipv6_optlen(hdr);
102
103 /* OPTS -> evaluate */
104#if HOPBYHOP
105 if (nexthdr == NEXTHDR_HOP) {
106 temp |= MASK_HOPOPTS;
107#else
108 if (nexthdr == NEXTHDR_DEST) {
109 temp |= MASK_DSTOPTS;
110#endif
111 break;
112 }
113
114
115 /* set the flag */
116 switch (nexthdr){
117 case NEXTHDR_HOP:
118 case NEXTHDR_ROUTING:
119 case NEXTHDR_FRAGMENT:
120 case NEXTHDR_AUTH:
121 case NEXTHDR_DEST:
122 break;
123 default:
124 DEBUGP("ipv6_opts match: unknown nextheader %u\n",nexthdr);
125 return 0;
126 break;
127 }
128
129 nexthdr = hdr->nexthdr;
130 len -= hdrlen;
131 ptr += hdrlen;
132 if ( ptr > skb->len ) {
133 DEBUGP("ipv6_opts: new pointer is too large! \n");
134 break;
135 }
136 }
137
138 /* OPTIONS header not found */
139#if HOPBYHOP
140 if ( temp != MASK_HOPOPTS ) return 0;
141#else
142 if ( temp != MASK_DSTOPTS ) return 0;
143#endif
144
145 if (len < (int)sizeof(struct ipv6_opt_hdr)){
146 *hotdrop = 1;
147 return 0;
148 }
149
150 if (len < hdrlen){
151 /* Packet smaller than it's length field */
152 return 0;
153 }
154
155 optsh=(void *)(skb->data)+ptr;
156
157 DEBUGP("IPv6 OPTS LEN %u %u ", hdrlen, optsh->hdrlen);
158
159 DEBUGP("len %02X %04X %02X ",
160 optinfo->hdrlen, hdrlen,
161 (!(optinfo->flags & IP6T_OPTS_LEN) ||
162 ((optinfo->hdrlen == hdrlen) ^
163 !!(optinfo->invflags & IP6T_OPTS_INV_LEN))));
164
165 ret = (optsh != NULL)
166 &&
167 (!(optinfo->flags & IP6T_OPTS_LEN) ||
168 ((optinfo->hdrlen == hdrlen) ^
169 !!(optinfo->invflags & IP6T_OPTS_INV_LEN)));
170
171 temp = len = 0;
172 ptr += 2;
173 hdrlen -= 2;
174 if ( !(optinfo->flags & IP6T_OPTS_OPTS) ){
175 return ret;
176 } else if (optinfo->flags & IP6T_OPTS_NSTRICT) {
177 DEBUGP("Not strict - not implemented");
178 } else {
179 DEBUGP("Strict ");
180 DEBUGP("#%d ",optinfo->optsnr);
181 for(temp=0; temp<optinfo->optsnr; temp++){
182 optdesc = (void *)(skb->data)+ptr;
183 /* Type check */
184 if ( (unsigned char)*optdesc !=
185 (optinfo->opts[temp] & 0xFF00)>>8 ){
186 DEBUGP("Tbad %02X %02X\n",
187 (unsigned char)*optdesc,
188 (optinfo->opts[temp] &
189 0xFF00)>>8);
190 return 0;
191 } else {
192 DEBUGP("Tok ");
193 }
194 /* Length check */
195 if (((optinfo->opts[temp] & 0x00FF) != 0xFF) &&
196 (unsigned char)*optdesc != 0){
197 if ( ntohs((u16)*optdesc) !=
198 optinfo->opts[temp] ){
199 DEBUGP("Lbad %02X %04X %04X\n",
200 (unsigned char)*optdesc,
201 ntohs((u16)*optdesc),
202 optinfo->opts[temp]);
203 return 0;
204 } else {
205 DEBUGP("Lok ");
206 }
207 }
208 /* Step to the next */
209 if ((unsigned char)*optdesc == 0){
210 DEBUGP("PAD0 \n");
211 ptr++;
212 hdrlen--;
213 } else {
214 ptr += LOW(ntohs(*optdesc));
215 hdrlen -= LOW(ntohs(*optdesc));
216 DEBUGP("len%04X \n",
217 LOW(ntohs(*optdesc)));
218 }
219 if (ptr > skb->len || ( !hdrlen &&
220 (temp != optinfo->optsnr - 1))) {
221 DEBUGP("new pointer is too large! \n");
222 break;
223 }
224 }
225 if (temp == optinfo->optsnr)
226 return ret;
227 else return 0;
228 }
229
230 return 0;
231}
232
233/* Called when user tries to insert an entry of this type. */
234static int
235checkentry(const char *tablename,
236 const struct ip6t_ip6 *ip,
237 void *matchinfo,
238 unsigned int matchinfosize,
239 unsigned int hook_mask)
240{
241 const struct ip6t_opts *optsinfo = matchinfo;
242
243 if (matchinfosize != IP6T_ALIGN(sizeof(struct ip6t_opts))) {
244 DEBUGP("ip6t_opts: matchsize %u != %u\n",
245 matchinfosize, IP6T_ALIGN(sizeof(struct ip6t_opts)));
246 return 0;
247 }
248 if (optsinfo->invflags & ~IP6T_OPTS_INV_MASK) {
249 DEBUGP("ip6t_opts: unknown flags %X\n",
250 optsinfo->invflags);
251 return 0;
252 }
253
254 return 1;
255}
256
257static struct ip6t_match opts_match = {
258#if HOPBYHOP
259 .name = "hbh",
260#else
261 .name = "dst",
262#endif
263 .match = &match,
264 .checkentry = &checkentry,
265};
266
267static int __init init(void)
268{
269 return ip6t_register_match(&opts_match);
270}
271
272static void __exit cleanup(void)
273{
274 ip6t_unregister_match(&opts_match);
275}
276
277module_init(init);
278module_exit(cleanup);