net/sched/act_nat.c

   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);