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 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);