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
  33static struct tcf_common *tcf_nat_ht[NAT_TAB_MASK + 1];
  34static u32 nat_idx_gen;
  35static DEFINE_RWLOCK(nat_lock);
  36
  37static struct tcf_hashinfo nat_hash_info = {
  38        .htab   =       tcf_nat_ht,
  39        .hmask  =       NAT_TAB_MASK,
  40        .lock   =       &nat_lock,
  41};
  42
  43static const struct nla_policy nat_policy[TCA_NAT_MAX + 1] = {
  44        [TCA_NAT_PARMS] = { .len = sizeof(struct tc_nat) },
  45};
  46
  47static 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
  98static 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
 105static 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
 259out:
 260        return action;
 261
 262drop:
 263        spin_lock(&p->tcf_lock);
 264        p->tcf_qstats.drops++;
 265        spin_unlock(&p->tcf_lock);
 266        return TC_ACT_SHOT;
 267}
 268
 269static 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
 297nla_put_failure:
 298        nlmsg_trim(skb, b);
 299        return -1;
 300}
 301
 302static 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
 316MODULE_DESCRIPTION("Stateless NAT actions");
 317MODULE_LICENSE("GPL");
 318
 319static int __init nat_init_module(void)
 320{
 321        return tcf_register_action(&act_nat_ops);
 322}
 323
 324static void __exit nat_cleanup_module(void)
 325{
 326        tcf_unregister_action(&act_nat_ops);
 327}
 328
 329module_init(nat_init_module);
 330module_exit(nat_cleanup_module);
 331
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