1 /* (C) 1999-2001 Paul `Rusty' Russell
2 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 */
8
9 #include <linux/module.h>
10 #include <net/ipv6.h>
11 #include <net/ip6_route.h>
12 #include <net/ip6_fib.h>
13 #include <net/ip6_checksum.h>
14 #include <net/netfilter/ipv6/nf_reject.h>
15 #include <linux/netfilter_ipv6.h>
16 #include <linux/netfilter_bridge.h>
17
18 const struct tcphdr *nf_reject_ip6_tcphdr_get(struct sk_buff *oldskb,
19 struct tcphdr *otcph,
20 unsigned int *otcplen, int hook)
21 {
22 const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
23 u8 proto;
24 __be16 frag_off;
25 int tcphoff;
26
27 proto = oip6h->nexthdr;
28 tcphoff = ipv6_skip_exthdr(oldskb, ((u8 *)(oip6h + 1) - oldskb->data),
29 &proto, &frag_off);
30
31 if ((tcphoff < 0) || (tcphoff > oldskb->len)) {
32 pr_debug("Cannot get TCP header.\n");
33 return NULL;
34 }
35
36 *otcplen = oldskb->len - tcphoff;
37
38 /* IP header checks: fragment, too short. */
39 if (proto != IPPROTO_TCP || *otcplen < sizeof(struct tcphdr)) {
40 pr_debug("proto(%d) != IPPROTO_TCP or too short (len = %d)\n",
41 proto, *otcplen);
42 return NULL;
43 }
44
45 otcph = skb_header_pointer(oldskb, tcphoff, sizeof(struct tcphdr),
46 otcph);
47 if (otcph == NULL)
48 return NULL;
49
50 /* No RST for RST. */
51 if (otcph->rst) {
52 pr_debug("RST is set\n");
53 return NULL;
54 }
55
56 /* Check checksum. */
57 if (nf_ip6_checksum(oldskb, hook, tcphoff, IPPROTO_TCP)) {
58 pr_debug("TCP checksum is invalid\n");
59 return NULL;
60 }
61
62 return otcph;
63 }
64 EXPORT_SYMBOL_GPL(nf_reject_ip6_tcphdr_get);
65
66 struct ipv6hdr *nf_reject_ip6hdr_put(struct sk_buff *nskb,
67 const struct sk_buff *oldskb,
68 __u8 protocol, int hoplimit)
69 {
70 struct ipv6hdr *ip6h;
71 const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
72 #define DEFAULT_TOS_VALUE 0x0U
73 const __u8 tclass = DEFAULT_TOS_VALUE;
74
75 skb_put(nskb, sizeof(struct ipv6hdr));
76 skb_reset_network_header(nskb);
77 ip6h = ipv6_hdr(nskb);
78 ip6_flow_hdr(ip6h, tclass, 0);
79 ip6h->hop_limit = hoplimit;
80 ip6h->nexthdr = protocol;
81 ip6h->saddr = oip6h->daddr;
82 ip6h->daddr = oip6h->saddr;
83
84 nskb->protocol = htons(ETH_P_IPV6);
85
86 return ip6h;
87 }
88 EXPORT_SYMBOL_GPL(nf_reject_ip6hdr_put);
89
90 void nf_reject_ip6_tcphdr_put(struct sk_buff *nskb,
91 const struct sk_buff *oldskb,
92 const struct tcphdr *oth, unsigned int otcplen)
93 {
94 struct tcphdr *tcph;
95 int needs_ack;
96
97 skb_reset_transport_header(nskb);
98 tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr));
99 /* Truncate to length (no data) */
100 tcph->doff = sizeof(struct tcphdr)/4;
101 tcph->source = oth->dest;
102 tcph->dest = oth->source;
103
104 if (oth->ack) {
105 needs_ack = 0;
106 tcph->seq = oth->ack_seq;
107 tcph->ack_seq = 0;
108 } else {
109 needs_ack = 1;
110 tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
111 otcplen - (oth->doff<<2));
112 tcph->seq = 0;
113 }
114
115 /* Reset flags */
116 ((u_int8_t *)tcph)[13] = 0;
117 tcph->rst = 1;
118 tcph->ack = needs_ack;
119 tcph->window = 0;
120 tcph->urg_ptr = 0;
121 tcph->check = 0;
122
123 /* Adjust TCP checksum */
124 tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr,
125 &ipv6_hdr(nskb)->daddr,
126 sizeof(struct tcphdr), IPPROTO_TCP,
127 csum_partial(tcph,
128 sizeof(struct tcphdr), 0));
129 }
130 EXPORT_SYMBOL_GPL(nf_reject_ip6_tcphdr_put);
131
132 void nf_send_reset6(struct net *net, struct sk_buff *oldskb, int hook)
133 {
134 struct sk_buff *nskb;
135 struct tcphdr _otcph;
136 const struct tcphdr *otcph;
137 unsigned int otcplen, hh_len;
138 const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
139 struct ipv6hdr *ip6h;
140 struct dst_entry *dst = NULL;
141 struct flowi6 fl6;
142
143 if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) ||
144 (!(ipv6_addr_type(&oip6h->daddr) & IPV6_ADDR_UNICAST))) {
145 pr_debug("addr is not unicast.\n");
146 return;
147 }
148
149 otcph = nf_reject_ip6_tcphdr_get(oldskb, &_otcph, &otcplen, hook);
150 if (!otcph)
151 return;
152
153 memset(&fl6, 0, sizeof(fl6));
154 fl6.flowi6_proto = IPPROTO_TCP;
155 fl6.saddr = oip6h->daddr;
156 fl6.daddr = oip6h->saddr;
157 fl6.fl6_sport = otcph->dest;
158 fl6.fl6_dport = otcph->source;
159 security_skb_classify_flow(oldskb, flowi6_to_flowi(&fl6));
160 dst = ip6_route_output(net, NULL, &fl6);
161 if (dst->error) {
162 dst_release(dst);
163 return;
164 }
165 dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
166 if (IS_ERR(dst))
167 return;
168
169 hh_len = (dst->dev->hard_header_len + 15)&~15;
170 nskb = alloc_skb(hh_len + 15 + dst->header_len + sizeof(struct ipv6hdr)
171 + sizeof(struct tcphdr) + dst->trailer_len,
172 GFP_ATOMIC);
173
174 if (!nskb) {
175 net_dbg_ratelimited("cannot alloc skb\n");
176 dst_release(dst);
177 return;
178 }
179
180 skb_dst_set(nskb, dst);
181
182 skb_reserve(nskb, hh_len + dst->header_len);
183 ip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_TCP,
184 ip6_dst_hoplimit(dst));
185 nf_reject_ip6_tcphdr_put(nskb, oldskb, otcph, otcplen);
186
187 nf_ct_attach(nskb, oldskb);
188
189 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
190 /* If we use ip6_local_out for bridged traffic, the MAC source on
191 * the RST will be ours, instead of the destination's. This confuses
192 * some routers/firewalls, and they drop the packet. So we need to
193 * build the eth header using the original destination's MAC as the
194 * source, and send the RST packet directly.
195 */
196 if (oldskb->nf_bridge) {
197 struct ethhdr *oeth = eth_hdr(oldskb);
198
199 nskb->dev = nf_bridge_get_physindev(oldskb);
200 nskb->protocol = htons(ETH_P_IPV6);
201 ip6h->payload_len = htons(sizeof(struct tcphdr));
202 if (dev_hard_header(nskb, nskb->dev, ntohs(nskb->protocol),
203 oeth->h_source, oeth->h_dest, nskb->len) < 0)
204 return;
205 dev_queue_xmit(nskb);
206 } else
207 #endif
208 ip6_local_out(net, nskb->sk, nskb);
209 }
210 EXPORT_SYMBOL_GPL(nf_send_reset6);
211
212 static bool reject6_csum_ok(struct sk_buff *skb, int hook)
213 {
214 const struct ipv6hdr *ip6h = ipv6_hdr(skb);
215 int thoff;
216 __be16 fo;
217 u8 proto;
218
219 if (skb->csum_bad)
220 return false;
221
222 if (skb_csum_unnecessary(skb))
223 return true;
224
225 proto = ip6h->nexthdr;
226 thoff = ipv6_skip_exthdr(skb, ((u8 *)(ip6h + 1) - skb->data), &proto, &fo);
227
228 if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0)
229 return false;
230
231 return nf_ip6_checksum(skb, hook, thoff, proto) == 0;
232 }
233
234 void nf_send_unreach6(struct net *net, struct sk_buff *skb_in,
235 unsigned char code, unsigned int hooknum)
236 {
237 if (!reject6_csum_ok(skb_in, hooknum))
238 return;
239
240 if (hooknum == NF_INET_LOCAL_OUT && skb_in->dev == NULL)
241 skb_in->dev = net->loopback_dev;
242
243 icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0);
244 }
245 EXPORT_SYMBOL_GPL(nf_send_unreach6);
246
247 MODULE_LICENSE("GPL");
248
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