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12#include <linux/errno.h>
13#include <linux/init.h>
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/netfilter.h>
17#include <linux/rtnetlink.h>
18#include <linux/skbuff.h>
19#include <linux/slab.h>
20#include <linux/spinlock.h>
21#include <linux/string.h>
22#include <linux/tc_act/tc_nat.h>
23#include <net/act_api.h>
24#include <net/icmp.h>
25#include <net/ip.h>
26#include <net/netlink.h>
27#include <net/tc_act/tc_nat.h>
28#include <net/tcp.h>
29#include <net/udp.h>
30
31
32#define NAT_TAB_MASK 15
33
34static const struct nla_policy nat_policy[TCA_NAT_MAX + 1] = {
35 [TCA_NAT_PARMS] = { .len = sizeof(struct tc_nat) },
36};
37
38static int tcf_nat_init(struct net *net, struct nlattr *nla, struct nlattr *est,
39 struct tc_action *a, int ovr, int bind)
40{
41 struct nlattr *tb[TCA_NAT_MAX + 1];
42 struct tc_nat *parm;
43 int ret = 0, err;
44 struct tcf_nat *p;
45
46 if (nla == NULL)
47 return -EINVAL;
48
49 err = nla_parse_nested(tb, TCA_NAT_MAX, nla, nat_policy);
50 if (err < 0)
51 return err;
52
53 if (tb[TCA_NAT_PARMS] == NULL)
54 return -EINVAL;
55 parm = nla_data(tb[TCA_NAT_PARMS]);
56
57 if (!tcf_hash_check(parm->index, a, bind)) {
58 ret = tcf_hash_create(parm->index, est, a, sizeof(*p), bind);
59 if (ret)
60 return ret;
61 ret = ACT_P_CREATED;
62 } else {
63 if (bind)
64 return 0;
65 tcf_hash_release(a, bind);
66 if (!ovr)
67 return -EEXIST;
68 }
69 p = to_tcf_nat(a);
70
71 spin_lock_bh(&p->tcf_lock);
72 p->old_addr = parm->old_addr;
73 p->new_addr = parm->new_addr;
74 p->mask = parm->mask;
75 p->flags = parm->flags;
76
77 p->tcf_action = parm->action;
78 spin_unlock_bh(&p->tcf_lock);
79
80 if (ret == ACT_P_CREATED)
81 tcf_hash_insert(a);
82
83 return ret;
84}
85
86static int tcf_nat(struct sk_buff *skb, const struct tc_action *a,
87 struct tcf_result *res)
88{
89 struct tcf_nat *p = a->priv;
90 struct iphdr *iph;
91 __be32 old_addr;
92 __be32 new_addr;
93 __be32 mask;
94 __be32 addr;
95 int egress;
96 int action;
97 int ihl;
98 int noff;
99
100 spin_lock(&p->tcf_lock);
101
102 p->tcf_tm.lastuse = jiffies;
103 old_addr = p->old_addr;
104 new_addr = p->new_addr;
105 mask = p->mask;
106 egress = p->flags & TCA_NAT_FLAG_EGRESS;
107 action = p->tcf_action;
108
109 bstats_update(&p->tcf_bstats, skb);
110
111 spin_unlock(&p->tcf_lock);
112
113 if (unlikely(action == TC_ACT_SHOT))
114 goto drop;
115
116 noff = skb_network_offset(skb);
117 if (!pskb_may_pull(skb, sizeof(*iph) + noff))
118 goto drop;
119
120 iph = ip_hdr(skb);
121
122 if (egress)
123 addr = iph->saddr;
124 else
125 addr = iph->daddr;
126
127 if (!((old_addr ^ addr) & mask)) {
128 if (skb_cloned(skb) &&
129 !skb_clone_writable(skb, sizeof(*iph) + noff) &&
130 pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
131 goto drop;
132
133 new_addr &= mask;
134 new_addr |= addr & ~mask;
135
136
137 iph = ip_hdr(skb);
138 if (egress)
139 iph->saddr = new_addr;
140 else
141 iph->daddr = new_addr;
142
143 csum_replace4(&iph->check, addr, new_addr);
144 } else if ((iph->frag_off & htons(IP_OFFSET)) ||
145 iph->protocol != IPPROTO_ICMP) {
146 goto out;
147 }
148
149 ihl = iph->ihl * 4;
150
151
152 switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) {
153 case IPPROTO_TCP:
154 {
155 struct tcphdr *tcph;
156
157 if (!pskb_may_pull(skb, ihl + sizeof(*tcph) + noff) ||
158 (skb_cloned(skb) &&
159 !skb_clone_writable(skb, ihl + sizeof(*tcph) + noff) &&
160 pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
161 goto drop;
162
163 tcph = (void *)(skb_network_header(skb) + ihl);
164 inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr, 1);
165 break;
166 }
167 case IPPROTO_UDP:
168 {
169 struct udphdr *udph;
170
171 if (!pskb_may_pull(skb, ihl + sizeof(*udph) + noff) ||
172 (skb_cloned(skb) &&
173 !skb_clone_writable(skb, ihl + sizeof(*udph) + noff) &&
174 pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
175 goto drop;
176
177 udph = (void *)(skb_network_header(skb) + ihl);
178 if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
179 inet_proto_csum_replace4(&udph->check, skb, addr,
180 new_addr, 1);
181 if (!udph->check)
182 udph->check = CSUM_MANGLED_0;
183 }
184 break;
185 }
186 case IPPROTO_ICMP:
187 {
188 struct icmphdr *icmph;
189
190 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + noff))
191 goto drop;
192
193 icmph = (void *)(skb_network_header(skb) + ihl);
194
195 if ((icmph->type != ICMP_DEST_UNREACH) &&
196 (icmph->type != ICMP_TIME_EXCEEDED) &&
197 (icmph->type != ICMP_PARAMETERPROB))
198 break;
199
200 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph) +
201 noff))
202 goto drop;
203
204 icmph = (void *)(skb_network_header(skb) + ihl);
205 iph = (void *)(icmph + 1);
206 if (egress)
207 addr = iph->daddr;
208 else
209 addr = iph->saddr;
210
211 if ((old_addr ^ addr) & mask)
212 break;
213
214 if (skb_cloned(skb) &&
215 !skb_clone_writable(skb, ihl + sizeof(*icmph) +
216 sizeof(*iph) + noff) &&
217 pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
218 goto drop;
219
220 icmph = (void *)(skb_network_header(skb) + ihl);
221 iph = (void *)(icmph + 1);
222
223 new_addr &= mask;
224 new_addr |= addr & ~mask;
225
226
227 if (egress)
228 iph->daddr = new_addr;
229 else
230 iph->saddr = new_addr;
231
232 inet_proto_csum_replace4(&icmph->checksum, skb, addr, new_addr,
233 0);
234 break;
235 }
236 default:
237 break;
238 }
239
240out:
241 return action;
242
243drop:
244 spin_lock(&p->tcf_lock);
245 p->tcf_qstats.drops++;
246 spin_unlock(&p->tcf_lock);
247 return TC_ACT_SHOT;
248}
249
250static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
251 int bind, int ref)
252{
253 unsigned char *b = skb_tail_pointer(skb);
254 struct tcf_nat *p = a->priv;
255 struct tc_nat opt = {
256 .old_addr = p->old_addr,
257 .new_addr = p->new_addr,
258 .mask = p->mask,
259 .flags = p->flags,
260
261 .index = p->tcf_index,
262 .action = p->tcf_action,
263 .refcnt = p->tcf_refcnt - ref,
264 .bindcnt = p->tcf_bindcnt - bind,
265 };
266 struct tcf_t t;
267
268 if (nla_put(skb, TCA_NAT_PARMS, sizeof(opt), &opt))
269 goto nla_put_failure;
270 t.install = jiffies_to_clock_t(jiffies - p->tcf_tm.install);
271 t.lastuse = jiffies_to_clock_t(jiffies - p->tcf_tm.lastuse);
272 t.expires = jiffies_to_clock_t(p->tcf_tm.expires);
273 if (nla_put(skb, TCA_NAT_TM, sizeof(t), &t))
274 goto nla_put_failure;
275
276 return skb->len;
277
278nla_put_failure:
279 nlmsg_trim(skb, b);
280 return -1;
281}
282
283static struct tc_action_ops act_nat_ops = {
284 .kind = "nat",
285 .type = TCA_ACT_NAT,
286 .owner = THIS_MODULE,
287 .act = tcf_nat,
288 .dump = tcf_nat_dump,
289 .init = tcf_nat_init,
290};
291
292MODULE_DESCRIPTION("Stateless NAT actions");
293MODULE_LICENSE("GPL");
294
295static int __init nat_init_module(void)
296{
297 return tcf_register_action(&act_nat_ops, NAT_TAB_MASK);
298}
299
300static void __exit nat_cleanup_module(void)
301{
302 tcf_unregister_action(&act_nat_ops);
303}
304
305module_init(nat_init_module);
306module_exit(nat_cleanup_module);
307
