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