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Linux/net/sched/act_nat.c

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  1 /*
  2  * Stateless NAT actions
  3  *
  4  * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
  5  *
  6  * This program is free software; you can redistribute it and/or modify it
  7  * under the terms of the GNU General Public License as published by the Free
  8  * Software Foundation; either version 2 of the License, or (at your option)
  9  * any later version.
 10  */
 11 
 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 
 34 static const struct nla_policy nat_policy[TCA_NAT_MAX + 1] = {
 35         [TCA_NAT_PARMS] = { .len = sizeof(struct tc_nat) },
 36 };
 37 
 38 static 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),
 59                                       bind, false);
 60                 if (ret)
 61                         return ret;
 62                 ret = ACT_P_CREATED;
 63         } else {
 64                 if (bind)
 65                         return 0;
 66                 tcf_hash_release(a, bind);
 67                 if (!ovr)
 68                         return -EEXIST;
 69         }
 70         p = to_tcf_nat(a);
 71 
 72         spin_lock_bh(&p->tcf_lock);
 73         p->old_addr = parm->old_addr;
 74         p->new_addr = parm->new_addr;
 75         p->mask = parm->mask;
 76         p->flags = parm->flags;
 77 
 78         p->tcf_action = parm->action;
 79         spin_unlock_bh(&p->tcf_lock);
 80 
 81         if (ret == ACT_P_CREATED)
 82                 tcf_hash_insert(a);
 83 
 84         return ret;
 85 }
 86 
 87 static int tcf_nat(struct sk_buff *skb, const struct tc_action *a,
 88                    struct tcf_result *res)
 89 {
 90         struct tcf_nat *p = a->priv;
 91         struct iphdr *iph;
 92         __be32 old_addr;
 93         __be32 new_addr;
 94         __be32 mask;
 95         __be32 addr;
 96         int egress;
 97         int action;
 98         int ihl;
 99         int noff;
100 
101         spin_lock(&p->tcf_lock);
102 
103         p->tcf_tm.lastuse = jiffies;
104         old_addr = p->old_addr;
105         new_addr = p->new_addr;
106         mask = p->mask;
107         egress = p->flags & TCA_NAT_FLAG_EGRESS;
108         action = p->tcf_action;
109 
110         bstats_update(&p->tcf_bstats, skb);
111 
112         spin_unlock(&p->tcf_lock);
113 
114         if (unlikely(action == TC_ACT_SHOT))
115                 goto drop;
116 
117         noff = skb_network_offset(skb);
118         if (!pskb_may_pull(skb, sizeof(*iph) + noff))
119                 goto drop;
120 
121         iph = ip_hdr(skb);
122 
123         if (egress)
124                 addr = iph->saddr;
125         else
126                 addr = iph->daddr;
127 
128         if (!((old_addr ^ addr) & mask)) {
129                 if (skb_cloned(skb) &&
130                     !skb_clone_writable(skb, sizeof(*iph) + noff) &&
131                     pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
132                         goto drop;
133 
134                 new_addr &= mask;
135                 new_addr |= addr & ~mask;
136 
137                 /* Rewrite IP header */
138                 iph = ip_hdr(skb);
139                 if (egress)
140                         iph->saddr = new_addr;
141                 else
142                         iph->daddr = new_addr;
143 
144                 csum_replace4(&iph->check, addr, new_addr);
145         } else if ((iph->frag_off & htons(IP_OFFSET)) ||
146                    iph->protocol != IPPROTO_ICMP) {
147                 goto out;
148         }
149 
150         ihl = iph->ihl * 4;
151 
152         /* It would be nice to share code with stateful NAT. */
153         switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) {
154         case IPPROTO_TCP:
155         {
156                 struct tcphdr *tcph;
157 
158                 if (!pskb_may_pull(skb, ihl + sizeof(*tcph) + noff) ||
159                     (skb_cloned(skb) &&
160                      !skb_clone_writable(skb, ihl + sizeof(*tcph) + noff) &&
161                      pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
162                         goto drop;
163 
164                 tcph = (void *)(skb_network_header(skb) + ihl);
165                 inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr,
166                                          true);
167                 break;
168         }
169         case IPPROTO_UDP:
170         {
171                 struct udphdr *udph;
172 
173                 if (!pskb_may_pull(skb, ihl + sizeof(*udph) + noff) ||
174                     (skb_cloned(skb) &&
175                      !skb_clone_writable(skb, ihl + sizeof(*udph) + noff) &&
176                      pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
177                         goto drop;
178 
179                 udph = (void *)(skb_network_header(skb) + ihl);
180                 if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
181                         inet_proto_csum_replace4(&udph->check, skb, addr,
182                                                  new_addr, true);
183                         if (!udph->check)
184                                 udph->check = CSUM_MANGLED_0;
185                 }
186                 break;
187         }
188         case IPPROTO_ICMP:
189         {
190                 struct icmphdr *icmph;
191 
192                 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + noff))
193                         goto drop;
194 
195                 icmph = (void *)(skb_network_header(skb) + ihl);
196 
197                 if ((icmph->type != ICMP_DEST_UNREACH) &&
198                     (icmph->type != ICMP_TIME_EXCEEDED) &&
199                     (icmph->type != ICMP_PARAMETERPROB))
200                         break;
201 
202                 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph) +
203                                         noff))
204                         goto drop;
205 
206                 icmph = (void *)(skb_network_header(skb) + ihl);
207                 iph = (void *)(icmph + 1);
208                 if (egress)
209                         addr = iph->daddr;
210                 else
211                         addr = iph->saddr;
212 
213                 if ((old_addr ^ addr) & mask)
214                         break;
215 
216                 if (skb_cloned(skb) &&
217                     !skb_clone_writable(skb, ihl + sizeof(*icmph) +
218                                              sizeof(*iph) + noff) &&
219                     pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
220                         goto drop;
221 
222                 icmph = (void *)(skb_network_header(skb) + ihl);
223                 iph = (void *)(icmph + 1);
224 
225                 new_addr &= mask;
226                 new_addr |= addr & ~mask;
227 
228                 /* XXX Fix up the inner checksums. */
229                 if (egress)
230                         iph->daddr = new_addr;
231                 else
232                         iph->saddr = new_addr;
233 
234                 inet_proto_csum_replace4(&icmph->checksum, skb, addr, new_addr,
235                                          false);
236                 break;
237         }
238         default:
239                 break;
240         }
241 
242 out:
243         return action;
244 
245 drop:
246         spin_lock(&p->tcf_lock);
247         p->tcf_qstats.drops++;
248         spin_unlock(&p->tcf_lock);
249         return TC_ACT_SHOT;
250 }
251 
252 static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
253                         int bind, int ref)
254 {
255         unsigned char *b = skb_tail_pointer(skb);
256         struct tcf_nat *p = a->priv;
257         struct tc_nat opt = {
258                 .old_addr = p->old_addr,
259                 .new_addr = p->new_addr,
260                 .mask     = p->mask,
261                 .flags    = p->flags,
262 
263                 .index    = p->tcf_index,
264                 .action   = p->tcf_action,
265                 .refcnt   = p->tcf_refcnt - ref,
266                 .bindcnt  = p->tcf_bindcnt - bind,
267         };
268         struct tcf_t t;
269 
270         if (nla_put(skb, TCA_NAT_PARMS, sizeof(opt), &opt))
271                 goto nla_put_failure;
272         t.install = jiffies_to_clock_t(jiffies - p->tcf_tm.install);
273         t.lastuse = jiffies_to_clock_t(jiffies - p->tcf_tm.lastuse);
274         t.expires = jiffies_to_clock_t(p->tcf_tm.expires);
275         if (nla_put(skb, TCA_NAT_TM, sizeof(t), &t))
276                 goto nla_put_failure;
277 
278         return skb->len;
279 
280 nla_put_failure:
281         nlmsg_trim(skb, b);
282         return -1;
283 }
284 
285 static struct tc_action_ops act_nat_ops = {
286         .kind           =       "nat",
287         .type           =       TCA_ACT_NAT,
288         .owner          =       THIS_MODULE,
289         .act            =       tcf_nat,
290         .dump           =       tcf_nat_dump,
291         .init           =       tcf_nat_init,
292 };
293 
294 MODULE_DESCRIPTION("Stateless NAT actions");
295 MODULE_LICENSE("GPL");
296 
297 static int __init nat_init_module(void)
298 {
299         return tcf_register_action(&act_nat_ops, NAT_TAB_MASK);
300 }
301 
302 static void __exit nat_cleanup_module(void)
303 {
304         tcf_unregister_action(&act_nat_ops);
305 }
306 
307 module_init(nat_init_module);
308 module_exit(nat_cleanup_module);
309 

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