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 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, 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
 118         spin_lock(&p->tcf_lock);
 119
 120         p->tcf_tm.lastuse = jiffies;
 121         old_addr = p->old_addr;
 122         new_addr = p->new_addr;
 123         mask = p->mask;
 124         egress = p->flags & TCA_NAT_FLAG_EGRESS;
 125         action = p->tcf_action;
 126
 127         p->tcf_bstats.bytes += qdisc_pkt_len(skb);
 128         p->tcf_bstats.packets++;
 129
 130         spin_unlock(&p->tcf_lock);
 131
 132         if (unlikely(action == TC_ACT_SHOT))
 133                 goto drop;
 134
 135         if (!pskb_may_pull(skb, sizeof(*iph)))
 136                 goto drop;
 137
 138         iph = ip_hdr(skb);
 139
 140         if (egress)
 141                 addr = iph->saddr;
 142         else
 143                 addr = iph->daddr;
 144
 145         if (!((old_addr ^ addr) & mask)) {
 146                 if (skb_cloned(skb) &&
 147                     !skb_clone_writable(skb, sizeof(*iph)) &&
 148                     pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 149                         goto drop;
 150
 151                 new_addr &= mask;
 152                 new_addr |= addr & ~mask;
 153
 154                 /* Rewrite IP header */
 155                 iph = ip_hdr(skb);
 156                 if (egress)
 157                         iph->saddr = new_addr;
 158                 else
 159                         iph->daddr = new_addr;
 160
 161                 csum_replace4(&iph->check, addr, new_addr);
 162         } else if ((iph->frag_off & htons(IP_OFFSET)) ||
 163                    iph->protocol != IPPROTO_ICMP) {
 164                 goto out;
 165         }
 166
 167         ihl = iph->ihl * 4;
 168
 169         /* It would be nice to share code with stateful NAT. */
 170         switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) {
 171         case IPPROTO_TCP:
 172         {
 173                 struct tcphdr *tcph;
 174
 175                 if (!pskb_may_pull(skb, ihl + sizeof(*tcph)) ||
 176                     (skb_cloned(skb) &&
 177                      !skb_clone_writable(skb, ihl + sizeof(*tcph)) &&
 178                      pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
 179                         goto drop;
 180
 181                 tcph = (void *)(skb_network_header(skb) + ihl);
 182                 inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr, 1);
 183                 break;
 184         }
 185         case IPPROTO_UDP:
 186         {
 187                 struct udphdr *udph;
 188
 189                 if (!pskb_may_pull(skb, ihl + sizeof(*udph)) ||
 190                     (skb_cloned(skb) &&
 191                      !skb_clone_writable(skb, ihl + sizeof(*udph)) &&
 192                      pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
 193                         goto drop;
 194
 195                 udph = (void *)(skb_network_header(skb) + ihl);
 196                 if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
 197                         inet_proto_csum_replace4(&udph->check, skb, addr,
 198                                                  new_addr, 1);
 199                         if (!udph->check)
 200                                 udph->check = CSUM_MANGLED_0;
 201                 }
 202                 break;
 203         }
 204         case IPPROTO_ICMP:
 205         {
 206                 struct icmphdr *icmph;
 207
 208                 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph)))
 209                         goto drop;
 210
 211                 icmph = (void *)(skb_network_header(skb) + ihl);
 212
 213                 if ((icmph->type != ICMP_DEST_UNREACH) &&
 214                     (icmph->type != ICMP_TIME_EXCEEDED) &&
 215                     (icmph->type != ICMP_PARAMETERPROB))
 216                         break;
 217
 218                 iph = (void *)(icmph + 1);
 219                 if (egress)
 220                         addr = iph->daddr;
 221                 else
 222                         addr = iph->saddr;
 223
 224                 if ((old_addr ^ addr) & mask)
 225                         break;
 226
 227                 if (skb_cloned(skb) &&
 228                     !skb_clone_writable(skb,
 229                                         ihl + sizeof(*icmph) + sizeof(*iph)) &&
 230                     pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 231                         goto drop;
 232
 233                 icmph = (void *)(skb_network_header(skb) + ihl);
 234                 iph = (void *)(icmph + 1);
 235
 236                 new_addr &= mask;
 237                 new_addr |= addr & ~mask;
 238
 239                 /* XXX Fix up the inner checksums. */
 240                 if (egress)
 241                         iph->daddr = new_addr;
 242                 else
 243                         iph->saddr = new_addr;
 244
 245                 inet_proto_csum_replace4(&icmph->checksum, skb, addr, new_addr,
 246                                          1);
 247                 break;
 248         }
 249         default:
 250                 break;
 251         }
 252
 253 out:
 254         return action;
 255
 256 drop:
 257         spin_lock(&p->tcf_lock);
 258         p->tcf_qstats.drops++;
 259         spin_unlock(&p->tcf_lock);
 260         return TC_ACT_SHOT;
 261 }
 262
 263 static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
 264                         int bind, int ref)
 265 {
 266         unsigned char *b = skb_tail_pointer(skb);
 267         struct tcf_nat *p = a->priv;
 268         struct tc_nat *opt;
 269         struct tcf_t t;
 270         int s;
 271
 272         s = sizeof(*opt);
 273
 274         /* netlink spinlocks held above us - must use ATOMIC */
 275         opt = kzalloc(s, GFP_ATOMIC);
 276         if (unlikely(!opt))
 277                 return -ENOBUFS;
 278
 279         opt->old_addr = p->old_addr;
 280         opt->new_addr = p->new_addr;
 281         opt->mask = p->mask;
 282         opt->flags = p->flags;
 283
 284         opt->index = p->tcf_index;
 285         opt->action = p->tcf_action;
 286         opt->refcnt = p->tcf_refcnt - ref;
 287         opt->bindcnt = p->tcf_bindcnt - bind;
 288
 289         NLA_PUT(skb, TCA_NAT_PARMS, s, opt);
 290         t.install = jiffies_to_clock_t(jiffies - p->tcf_tm.install);
 291         t.lastuse = jiffies_to_clock_t(jiffies - p->tcf_tm.lastuse);
 292         t.expires = jiffies_to_clock_t(p->tcf_tm.expires);
 293         NLA_PUT(skb, TCA_NAT_TM, sizeof(t), &t);
 294
 295         kfree(opt);
 296
 297         return skb->len;
 298
 299 nla_put_failure:
 300         nlmsg_trim(skb, b);
 301         kfree(opt);
 302         return -1;
 303 }
 304
 305 static struct tc_action_ops act_nat_ops = {
 306         .kind           =       "nat",
 307         .hinfo          =       &nat_hash_info,
 308         .type           =       TCA_ACT_NAT,
 309         .capab          =       TCA_CAP_NONE,
 310         .owner          =       THIS_MODULE,
 311         .act            =       tcf_nat,
 312         .dump           =       tcf_nat_dump,
 313         .cleanup        =       tcf_nat_cleanup,
 314         .lookup         =       tcf_hash_search,
 315         .init           =       tcf_nat_init,
 316         .walk           =       tcf_generic_walker
 317 };
 318
 319 MODULE_DESCRIPTION("Stateless NAT actions");
 320 MODULE_LICENSE("GPL");
 321
 322 static int __init nat_init_module(void)
 323 {
 324         return tcf_register_action(&act_nat_ops);
 325 }
 326
 327 static void __exit nat_cleanup_module(void)
 328 {
 329         tcf_unregister_action(&act_nat_ops);
 330 }
 331
 332 module_init(nat_init_module);
 333 module_exit(nat_cleanup_module);