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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), 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 
 86 static 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                 /* Rewrite IP header */
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         /* It would be nice to share code with stateful NAT. */
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                 /* XXX Fix up the inner checksums. */
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 
240 out:
241         return action;
242 
243 drop:
244         spin_lock(&p->tcf_lock);
245         p->tcf_qstats.drops++;
246         spin_unlock(&p->tcf_lock);
247         return TC_ACT_SHOT;
248 }
249 
250 static 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 
278 nla_put_failure:
279         nlmsg_trim(skb, b);
280         return -1;
281 }
282 
283 static 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 
292 MODULE_DESCRIPTION("Stateless NAT actions");
293 MODULE_LICENSE("GPL");
294 
295 static int __init nat_init_module(void)
296 {
297         return tcf_register_action(&act_nat_ops, NAT_TAB_MASK);
298 }
299 
300 static void __exit nat_cleanup_module(void)
301 {
302         tcf_unregister_action(&act_nat_ops);
303 }
304 
305 module_init(nat_init_module);
306 module_exit(nat_cleanup_module);
307 

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