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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 static struct tcf_common *tcf_nat_ht[NAT_TAB_MASK + 1];
 34 static u32 nat_idx_gen;
 35 static DEFINE_RWLOCK(nat_lock);
 36 
 37 static struct tcf_hashinfo nat_hash_info = {
 38         .htab   =       tcf_nat_ht,
 39         .hmask  =       NAT_TAB_MASK,
 40         .lock   =       &nat_lock,
 41 };
 42 
 43 static const struct nla_policy nat_policy[TCA_NAT_MAX + 1] = {
 44         [TCA_NAT_PARMS] = { .len = sizeof(struct tc_nat) },
 45 };
 46 
 47 static int tcf_nat_init(struct net *net, struct nlattr *nla, struct nlattr *est,
 48                         struct tc_action *a, int ovr, int bind)
 49 {
 50         struct nlattr *tb[TCA_NAT_MAX + 1];
 51         struct tc_nat *parm;
 52         int ret = 0, err;
 53         struct tcf_nat *p;
 54         struct tcf_common *pc;
 55 
 56         if (nla == NULL)
 57                 return -EINVAL;
 58 
 59         err = nla_parse_nested(tb, TCA_NAT_MAX, nla, nat_policy);
 60         if (err < 0)
 61                 return err;
 62 
 63         if (tb[TCA_NAT_PARMS] == NULL)
 64                 return -EINVAL;
 65         parm = nla_data(tb[TCA_NAT_PARMS]);
 66 
 67         pc = tcf_hash_check(parm->index, a, bind, &nat_hash_info);
 68         if (!pc) {
 69                 pc = tcf_hash_create(parm->index, est, a, sizeof(*p), bind,
 70                                      &nat_idx_gen, &nat_hash_info);
 71                 if (IS_ERR(pc))
 72                         return PTR_ERR(pc);
 73                 p = to_tcf_nat(pc);
 74                 ret = ACT_P_CREATED;
 75         } else {
 76                 p = to_tcf_nat(pc);
 77                 if (!ovr) {
 78                         tcf_hash_release(pc, bind, &nat_hash_info);
 79                         return -EEXIST;
 80                 }
 81         }
 82 
 83         spin_lock_bh(&p->tcf_lock);
 84         p->old_addr = parm->old_addr;
 85         p->new_addr = parm->new_addr;
 86         p->mask = parm->mask;
 87         p->flags = parm->flags;
 88 
 89         p->tcf_action = parm->action;
 90         spin_unlock_bh(&p->tcf_lock);
 91 
 92         if (ret == ACT_P_CREATED)
 93                 tcf_hash_insert(pc, &nat_hash_info);
 94 
 95         return ret;
 96 }
 97 
 98 static int tcf_nat_cleanup(struct tc_action *a, int bind)
 99 {
100         struct tcf_nat *p = a->priv;
101 
102         return tcf_hash_release(&p->common, bind, &nat_hash_info);
103 }
104 
105 static int tcf_nat(struct sk_buff *skb, const struct tc_action *a,
106                    struct tcf_result *res)
107 {
108         struct tcf_nat *p = a->priv;
109         struct iphdr *iph;
110         __be32 old_addr;
111         __be32 new_addr;
112         __be32 mask;
113         __be32 addr;
114         int egress;
115         int action;
116         int ihl;
117         int noff;
118 
119         spin_lock(&p->tcf_lock);
120 
121         p->tcf_tm.lastuse = jiffies;
122         old_addr = p->old_addr;
123         new_addr = p->new_addr;
124         mask = p->mask;
125         egress = p->flags & TCA_NAT_FLAG_EGRESS;
126         action = p->tcf_action;
127 
128         bstats_update(&p->tcf_bstats, skb);
129 
130         spin_unlock(&p->tcf_lock);
131 
132         if (unlikely(action == TC_ACT_SHOT))
133                 goto drop;
134 
135         noff = skb_network_offset(skb);
136         if (!pskb_may_pull(skb, sizeof(*iph) + noff))
137                 goto drop;
138 
139         iph = ip_hdr(skb);
140 
141         if (egress)
142                 addr = iph->saddr;
143         else
144                 addr = iph->daddr;
145 
146         if (!((old_addr ^ addr) & mask)) {
147                 if (skb_cloned(skb) &&
148                     !skb_clone_writable(skb, sizeof(*iph) + noff) &&
149                     pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
150                         goto drop;
151 
152                 new_addr &= mask;
153                 new_addr |= addr & ~mask;
154 
155                 /* Rewrite IP header */
156                 iph = ip_hdr(skb);
157                 if (egress)
158                         iph->saddr = new_addr;
159                 else
160                         iph->daddr = new_addr;
161 
162                 csum_replace4(&iph->check, addr, new_addr);
163         } else if ((iph->frag_off & htons(IP_OFFSET)) ||
164                    iph->protocol != IPPROTO_ICMP) {
165                 goto out;
166         }
167 
168         ihl = iph->ihl * 4;
169 
170         /* It would be nice to share code with stateful NAT. */
171         switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) {
172         case IPPROTO_TCP:
173         {
174                 struct tcphdr *tcph;
175 
176                 if (!pskb_may_pull(skb, ihl + sizeof(*tcph) + noff) ||
177                     (skb_cloned(skb) &&
178                      !skb_clone_writable(skb, ihl + sizeof(*tcph) + noff) &&
179                      pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
180                         goto drop;
181 
182                 tcph = (void *)(skb_network_header(skb) + ihl);
183                 inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr, 1);
184                 break;
185         }
186         case IPPROTO_UDP:
187         {
188                 struct udphdr *udph;
189 
190                 if (!pskb_may_pull(skb, ihl + sizeof(*udph) + noff) ||
191                     (skb_cloned(skb) &&
192                      !skb_clone_writable(skb, ihl + sizeof(*udph) + noff) &&
193                      pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
194                         goto drop;
195 
196                 udph = (void *)(skb_network_header(skb) + ihl);
197                 if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
198                         inet_proto_csum_replace4(&udph->check, skb, addr,
199                                                  new_addr, 1);
200                         if (!udph->check)
201                                 udph->check = CSUM_MANGLED_0;
202                 }
203                 break;
204         }
205         case IPPROTO_ICMP:
206         {
207                 struct icmphdr *icmph;
208 
209                 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + noff))
210                         goto drop;
211 
212                 icmph = (void *)(skb_network_header(skb) + ihl);
213 
214                 if ((icmph->type != ICMP_DEST_UNREACH) &&
215                     (icmph->type != ICMP_TIME_EXCEEDED) &&
216                     (icmph->type != ICMP_PARAMETERPROB))
217                         break;
218 
219                 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph) +
220                                         noff))
221                         goto drop;
222 
223                 icmph = (void *)(skb_network_header(skb) + ihl);
224                 iph = (void *)(icmph + 1);
225                 if (egress)
226                         addr = iph->daddr;
227                 else
228                         addr = iph->saddr;
229 
230                 if ((old_addr ^ addr) & mask)
231                         break;
232 
233                 if (skb_cloned(skb) &&
234                     !skb_clone_writable(skb, ihl + sizeof(*icmph) +
235                                              sizeof(*iph) + noff) &&
236                     pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
237                         goto drop;
238 
239                 icmph = (void *)(skb_network_header(skb) + ihl);
240                 iph = (void *)(icmph + 1);
241 
242                 new_addr &= mask;
243                 new_addr |= addr & ~mask;
244 
245                 /* XXX Fix up the inner checksums. */
246                 if (egress)
247                         iph->daddr = new_addr;
248                 else
249                         iph->saddr = new_addr;
250 
251                 inet_proto_csum_replace4(&icmph->checksum, skb, addr, new_addr,
252                                          0);
253                 break;
254         }
255         default:
256                 break;
257         }
258 
259 out:
260         return action;
261 
262 drop:
263         spin_lock(&p->tcf_lock);
264         p->tcf_qstats.drops++;
265         spin_unlock(&p->tcf_lock);
266         return TC_ACT_SHOT;
267 }
268 
269 static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
270                         int bind, int ref)
271 {
272         unsigned char *b = skb_tail_pointer(skb);
273         struct tcf_nat *p = a->priv;
274         struct tc_nat opt = {
275                 .old_addr = p->old_addr,
276                 .new_addr = p->new_addr,
277                 .mask     = p->mask,
278                 .flags    = p->flags,
279 
280                 .index    = p->tcf_index,
281                 .action   = p->tcf_action,
282                 .refcnt   = p->tcf_refcnt - ref,
283                 .bindcnt  = p->tcf_bindcnt - bind,
284         };
285         struct tcf_t t;
286 
287         if (nla_put(skb, TCA_NAT_PARMS, sizeof(opt), &opt))
288                 goto nla_put_failure;
289         t.install = jiffies_to_clock_t(jiffies - p->tcf_tm.install);
290         t.lastuse = jiffies_to_clock_t(jiffies - p->tcf_tm.lastuse);
291         t.expires = jiffies_to_clock_t(p->tcf_tm.expires);
292         if (nla_put(skb, TCA_NAT_TM, sizeof(t), &t))
293                 goto nla_put_failure;
294 
295         return skb->len;
296 
297 nla_put_failure:
298         nlmsg_trim(skb, b);
299         return -1;
300 }
301 
302 static struct tc_action_ops act_nat_ops = {
303         .kind           =       "nat",
304         .hinfo          =       &nat_hash_info,
305         .type           =       TCA_ACT_NAT,
306         .capab          =       TCA_CAP_NONE,
307         .owner          =       THIS_MODULE,
308         .act            =       tcf_nat,
309         .dump           =       tcf_nat_dump,
310         .cleanup        =       tcf_nat_cleanup,
311         .lookup         =       tcf_hash_search,
312         .init           =       tcf_nat_init,
313         .walk           =       tcf_generic_walker
314 };
315 
316 MODULE_DESCRIPTION("Stateless NAT actions");
317 MODULE_LICENSE("GPL");
318 
319 static int __init nat_init_module(void)
320 {
321         return tcf_register_action(&act_nat_ops);
322 }
323 
324 static void __exit nat_cleanup_module(void)
325 {
326         tcf_unregister_action(&act_nat_ops);
327 }
328 
329 module_init(nat_init_module);
330 module_exit(nat_cleanup_module);
331 

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