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764d8a9f PM |
1 | /* |
2 | * IP6 tables REJECT target module | |
3 | * Linux INET6 implementation | |
4 | * | |
5 | * Copyright (C)2003 USAGI/WIDE Project | |
6 | * | |
7 | * Authors: | |
8 | * Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp> | |
9 | * | |
10 | * Based on net/ipv4/netfilter/ipt_REJECT.c | |
11 | * | |
12 | * This program is free software; you can redistribute it and/or | |
13 | * modify it under the terms of the GNU General Public License | |
14 | * as published by the Free Software Foundation; either version | |
15 | * 2 of the License, or (at your option) any later version. | |
16 | */ | |
ff67e4e4 | 17 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
764d8a9f | 18 | |
5a0e3ad6 | 19 | #include <linux/gfp.h> |
764d8a9f PM |
20 | #include <linux/module.h> |
21 | #include <linux/skbuff.h> | |
22 | #include <linux/icmpv6.h> | |
23 | #include <linux/netdevice.h> | |
24 | #include <net/ipv6.h> | |
25 | #include <net/tcp.h> | |
26 | #include <net/icmp.h> | |
27 | #include <net/ip6_checksum.h> | |
28 | #include <net/ip6_fib.h> | |
29 | #include <net/ip6_route.h> | |
30 | #include <net/flow.h> | |
6709dbbb | 31 | #include <linux/netfilter/x_tables.h> |
764d8a9f PM |
32 | #include <linux/netfilter_ipv6/ip6_tables.h> |
33 | #include <linux/netfilter_ipv6/ip6t_REJECT.h> | |
34 | ||
35 | MODULE_AUTHOR("Yasuyuki KOZAKAI <yasuyuki.kozakai@toshiba.co.jp>"); | |
2ae15b64 | 36 | MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv6"); |
764d8a9f PM |
37 | MODULE_LICENSE("GPL"); |
38 | ||
764d8a9f | 39 | /* Send RST reply */ |
e10aad99 | 40 | static void send_reset(struct net *net, struct sk_buff *oldskb) |
764d8a9f PM |
41 | { |
42 | struct sk_buff *nskb; | |
43 | struct tcphdr otcph, *tcph; | |
44 | unsigned int otcplen, hh_len; | |
45 | int tcphoff, needs_ack; | |
3cf93c96 JE |
46 | const struct ipv6hdr *oip6h = ipv6_hdr(oldskb); |
47 | struct ipv6hdr *ip6h; | |
4319cc0c FLVC |
48 | #define DEFAULT_TOS_VALUE 0x0U |
49 | const __u8 tclass = DEFAULT_TOS_VALUE; | |
764d8a9f PM |
50 | struct dst_entry *dst = NULL; |
51 | u8 proto; | |
75f2811c | 52 | __be16 frag_off; |
4c9483b2 | 53 | struct flowi6 fl6; |
764d8a9f PM |
54 | |
55 | if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) || | |
56 | (!(ipv6_addr_type(&oip6h->daddr) & IPV6_ADDR_UNICAST))) { | |
ff67e4e4 | 57 | pr_debug("addr is not unicast.\n"); |
764d8a9f PM |
58 | return; |
59 | } | |
60 | ||
61 | proto = oip6h->nexthdr; | |
75f2811c | 62 | tcphoff = ipv6_skip_exthdr(oldskb, ((u8*)(oip6h+1) - oldskb->data), &proto, &frag_off); |
764d8a9f PM |
63 | |
64 | if ((tcphoff < 0) || (tcphoff > oldskb->len)) { | |
ff67e4e4 | 65 | pr_debug("Cannot get TCP header.\n"); |
764d8a9f PM |
66 | return; |
67 | } | |
68 | ||
69 | otcplen = oldskb->len - tcphoff; | |
70 | ||
71 | /* IP header checks: fragment, too short. */ | |
7c4e36bc | 72 | if (proto != IPPROTO_TCP || otcplen < sizeof(struct tcphdr)) { |
ff67e4e4 | 73 | pr_debug("proto(%d) != IPPROTO_TCP, " |
0d53778e PM |
74 | "or too short. otcplen = %d\n", |
75 | proto, otcplen); | |
764d8a9f PM |
76 | return; |
77 | } | |
78 | ||
79 | if (skb_copy_bits(oldskb, tcphoff, &otcph, sizeof(struct tcphdr))) | |
80 | BUG(); | |
81 | ||
82 | /* No RST for RST. */ | |
83 | if (otcph.rst) { | |
ff67e4e4 | 84 | pr_debug("RST is set\n"); |
764d8a9f PM |
85 | return; |
86 | } | |
87 | ||
88 | /* Check checksum. */ | |
89 | if (csum_ipv6_magic(&oip6h->saddr, &oip6h->daddr, otcplen, IPPROTO_TCP, | |
90 | skb_checksum(oldskb, tcphoff, otcplen, 0))) { | |
ff67e4e4 | 91 | pr_debug("TCP checksum is invalid\n"); |
764d8a9f PM |
92 | return; |
93 | } | |
94 | ||
4c9483b2 DM |
95 | memset(&fl6, 0, sizeof(fl6)); |
96 | fl6.flowi6_proto = IPPROTO_TCP; | |
4e3fd7a0 AD |
97 | fl6.saddr = oip6h->daddr; |
98 | fl6.daddr = oip6h->saddr; | |
1958b856 DM |
99 | fl6.fl6_sport = otcph.dest; |
100 | fl6.fl6_dport = otcph.source; | |
4c9483b2 DM |
101 | security_skb_classify_flow(oldskb, flowi6_to_flowi(&fl6)); |
102 | dst = ip6_route_output(net, NULL, &fl6); | |
499031ac ED |
103 | if (dst == NULL || dst->error) { |
104 | dst_release(dst); | |
764d8a9f | 105 | return; |
499031ac | 106 | } |
4c9483b2 | 107 | dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0); |
452edd59 | 108 | if (IS_ERR(dst)) |
764d8a9f | 109 | return; |
764d8a9f PM |
110 | |
111 | hh_len = (dst->dev->hard_header_len + 15)&~15; | |
112 | nskb = alloc_skb(hh_len + 15 + dst->header_len + sizeof(struct ipv6hdr) | |
113 | + sizeof(struct tcphdr) + dst->trailer_len, | |
114 | GFP_ATOMIC); | |
115 | ||
116 | if (!nskb) { | |
e87cc472 | 117 | net_dbg_ratelimited("cannot alloc skb\n"); |
764d8a9f PM |
118 | dst_release(dst); |
119 | return; | |
120 | } | |
121 | ||
adf30907 | 122 | skb_dst_set(nskb, dst); |
764d8a9f PM |
123 | |
124 | skb_reserve(nskb, hh_len + dst->header_len); | |
125 | ||
1ced98e8 ACM |
126 | skb_put(nskb, sizeof(struct ipv6hdr)); |
127 | skb_reset_network_header(nskb); | |
0660e03f | 128 | ip6h = ipv6_hdr(nskb); |
3e4e4c1f | 129 | ip6_flow_hdr(ip6h, tclass, 0); |
abbf46ae | 130 | ip6h->hop_limit = ip6_dst_hoplimit(dst); |
764d8a9f | 131 | ip6h->nexthdr = IPPROTO_TCP; |
4e3fd7a0 AD |
132 | ip6h->saddr = oip6h->daddr; |
133 | ip6h->daddr = oip6h->saddr; | |
764d8a9f | 134 | |
c6f40899 | 135 | skb_reset_transport_header(nskb); |
764d8a9f PM |
136 | tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr)); |
137 | /* Truncate to length (no data) */ | |
138 | tcph->doff = sizeof(struct tcphdr)/4; | |
139 | tcph->source = otcph.dest; | |
140 | tcph->dest = otcph.source; | |
141 | ||
142 | if (otcph.ack) { | |
143 | needs_ack = 0; | |
144 | tcph->seq = otcph.ack_seq; | |
145 | tcph->ack_seq = 0; | |
146 | } else { | |
147 | needs_ack = 1; | |
148 | tcph->ack_seq = htonl(ntohl(otcph.seq) + otcph.syn + otcph.fin | |
149 | + otcplen - (otcph.doff<<2)); | |
150 | tcph->seq = 0; | |
151 | } | |
152 | ||
153 | /* Reset flags */ | |
154 | ((u_int8_t *)tcph)[13] = 0; | |
155 | tcph->rst = 1; | |
156 | tcph->ack = needs_ack; | |
157 | tcph->window = 0; | |
158 | tcph->urg_ptr = 0; | |
159 | tcph->check = 0; | |
160 | ||
161 | /* Adjust TCP checksum */ | |
0660e03f ACM |
162 | tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr, |
163 | &ipv6_hdr(nskb)->daddr, | |
764d8a9f | 164 | sizeof(struct tcphdr), IPPROTO_TCP, |
a47362a2 | 165 | csum_partial(tcph, |
764d8a9f PM |
166 | sizeof(struct tcphdr), 0)); |
167 | ||
08857fa7 YK |
168 | nf_ct_attach(nskb, oldskb); |
169 | ||
ef76bc23 | 170 | ip6_local_out(nskb); |
764d8a9f PM |
171 | } |
172 | ||
173 | static inline void | |
e10aad99 AD |
174 | send_unreach(struct net *net, struct sk_buff *skb_in, unsigned char code, |
175 | unsigned int hooknum) | |
764d8a9f | 176 | { |
6e23ae2a | 177 | if (hooknum == NF_INET_LOCAL_OUT && skb_in->dev == NULL) |
e10aad99 | 178 | skb_in->dev = net->loopback_dev; |
764d8a9f | 179 | |
3ffe533c | 180 | icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0); |
764d8a9f PM |
181 | } |
182 | ||
d3c5ee6d | 183 | static unsigned int |
4b560b44 | 184 | reject_tg6(struct sk_buff *skb, const struct xt_action_param *par) |
764d8a9f | 185 | { |
7eb35586 JE |
186 | const struct ip6t_reject_info *reject = par->targinfo; |
187 | struct net *net = dev_net((par->in != NULL) ? par->in : par->out); | |
764d8a9f | 188 | |
0dc47877 | 189 | pr_debug("%s: medium point\n", __func__); |
1ab1457c YH |
190 | switch (reject->with) { |
191 | case IP6T_ICMP6_NO_ROUTE: | |
7eb35586 | 192 | send_unreach(net, skb, ICMPV6_NOROUTE, par->hooknum); |
1ab1457c YH |
193 | break; |
194 | case IP6T_ICMP6_ADM_PROHIBITED: | |
7eb35586 | 195 | send_unreach(net, skb, ICMPV6_ADM_PROHIBITED, par->hooknum); |
1ab1457c YH |
196 | break; |
197 | case IP6T_ICMP6_NOT_NEIGHBOUR: | |
7eb35586 | 198 | send_unreach(net, skb, ICMPV6_NOT_NEIGHBOUR, par->hooknum); |
1ab1457c YH |
199 | break; |
200 | case IP6T_ICMP6_ADDR_UNREACH: | |
7eb35586 | 201 | send_unreach(net, skb, ICMPV6_ADDR_UNREACH, par->hooknum); |
1ab1457c YH |
202 | break; |
203 | case IP6T_ICMP6_PORT_UNREACH: | |
7eb35586 | 204 | send_unreach(net, skb, ICMPV6_PORT_UNREACH, par->hooknum); |
1ab1457c YH |
205 | break; |
206 | case IP6T_ICMP6_ECHOREPLY: | |
764d8a9f PM |
207 | /* Do nothing */ |
208 | break; | |
209 | case IP6T_TCP_RESET: | |
e10aad99 | 210 | send_reset(net, skb); |
764d8a9f PM |
211 | break; |
212 | default: | |
e87cc472 | 213 | net_info_ratelimited("case %u not handled yet\n", reject->with); |
764d8a9f PM |
214 | break; |
215 | } | |
216 | ||
217 | return NF_DROP; | |
218 | } | |
219 | ||
135367b8 | 220 | static int reject_tg6_check(const struct xt_tgchk_param *par) |
764d8a9f | 221 | { |
af5d6dc2 JE |
222 | const struct ip6t_reject_info *rejinfo = par->targinfo; |
223 | const struct ip6t_entry *e = par->entryinfo; | |
764d8a9f | 224 | |
764d8a9f | 225 | if (rejinfo->with == IP6T_ICMP6_ECHOREPLY) { |
ff67e4e4 | 226 | pr_info("ECHOREPLY is not supported.\n"); |
d6b00a53 | 227 | return -EINVAL; |
764d8a9f PM |
228 | } else if (rejinfo->with == IP6T_TCP_RESET) { |
229 | /* Must specify that it's a TCP packet */ | |
3666ed1c JP |
230 | if (e->ipv6.proto != IPPROTO_TCP || |
231 | (e->ipv6.invflags & XT_INV_PROTO)) { | |
ff67e4e4 | 232 | pr_info("TCP_RESET illegal for non-tcp\n"); |
d6b00a53 | 233 | return -EINVAL; |
764d8a9f PM |
234 | } |
235 | } | |
d6b00a53 | 236 | return 0; |
764d8a9f PM |
237 | } |
238 | ||
d3c5ee6d | 239 | static struct xt_target reject_tg6_reg __read_mostly = { |
764d8a9f | 240 | .name = "REJECT", |
ee999d8b | 241 | .family = NFPROTO_IPV6, |
d3c5ee6d | 242 | .target = reject_tg6, |
7f939713 PM |
243 | .targetsize = sizeof(struct ip6t_reject_info), |
244 | .table = "filter", | |
6e23ae2a PM |
245 | .hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) | |
246 | (1 << NF_INET_LOCAL_OUT), | |
d3c5ee6d | 247 | .checkentry = reject_tg6_check, |
764d8a9f PM |
248 | .me = THIS_MODULE |
249 | }; | |
250 | ||
d3c5ee6d | 251 | static int __init reject_tg6_init(void) |
764d8a9f | 252 | { |
d3c5ee6d | 253 | return xt_register_target(&reject_tg6_reg); |
764d8a9f PM |
254 | } |
255 | ||
d3c5ee6d | 256 | static void __exit reject_tg6_exit(void) |
764d8a9f | 257 | { |
d3c5ee6d | 258 | xt_unregister_target(&reject_tg6_reg); |
764d8a9f PM |
259 | } |
260 | ||
d3c5ee6d JE |
261 | module_init(reject_tg6_init); |
262 | module_exit(reject_tg6_exit); |