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/pkt_cls.h>
  25 #include <net/icmp.h>
  26 #include <net/ip.h>
  27 #include <net/netlink.h>
  28 #include <net/tc_act/tc_nat.h>
  29 #include <net/tcp.h>
  30 #include <net/udp.h>
  31
  32
  33 static unsigned int nat_net_id;
  34 static struct tc_action_ops act_nat_ops;
  35
  36 static const struct nla_policy nat_policy[TCA_NAT_MAX + 1] = {
  37         [TCA_NAT_PARMS] = { .len = sizeof(struct tc_nat) },
  38 };
  39
  40 static int tcf_nat_init(struct net *net, struct nlattr *nla, struct nlattr *est,
  41                         struct tc_action **a, int ovr, int bind,
  42                         bool rtnl_held, struct tcf_proto *tp,
  43                         struct netlink_ext_ack *extack)
  44 {
  45         struct tc_action_net *tn = net_generic(net, nat_net_id);
  46         struct nlattr *tb[TCA_NAT_MAX + 1];
  47         struct tcf_chain *goto_ch = NULL;
  48         struct tc_nat *parm;
  49         int ret = 0, err;
  50         struct tcf_nat *p;
  51
  52         if (nla == NULL)
  53                 return -EINVAL;
  54
  55         err = nla_parse_nested(tb, TCA_NAT_MAX, nla, nat_policy, NULL);
  56         if (err < 0)
  57                 return err;
  58
  59         if (tb[TCA_NAT_PARMS] == NULL)
  60                 return -EINVAL;
  61         parm = nla_data(tb[TCA_NAT_PARMS]);
  62
  63         err = tcf_idr_check_alloc(tn, &parm->index, a, bind);
  64         if (!err) {
  65                 ret = tcf_idr_create(tn, parm->index, est, a,
  66                                      &act_nat_ops, bind, false);
  67                 if (ret) {
  68                         tcf_idr_cleanup(tn, parm->index);
  69                         return ret;
  70                 }
  71                 ret = ACT_P_CREATED;
  72         } else if (err > 0) {
  73                 if (bind)
  74                         return 0;
  75                 if (!ovr) {
  76                         tcf_idr_release(*a, bind);
  77                         return -EEXIST;
  78                 }
  79         } else {
  80                 return err;
  81         }
  82         err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
  83         if (err < 0)
  84                 goto release_idr;
  85         p = to_tcf_nat(*a);
  86
  87         spin_lock_bh(&p->tcf_lock);
  88         p->old_addr = parm->old_addr;
  89         p->new_addr = parm->new_addr;
  90         p->mask = parm->mask;
  91         p->flags = parm->flags;
  92
  93         goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
  94         spin_unlock_bh(&p->tcf_lock);
  95         if (goto_ch)
  96                 tcf_chain_put_by_act(goto_ch);
  97
  98         if (ret == ACT_P_CREATED)
  99                 tcf_idr_insert(tn, *a);
 100
 101         return ret;
 102 release_idr:
 103         tcf_idr_release(*a, bind);
 104         return err;
 105 }
 106
 107 static int tcf_nat_act(struct sk_buff *skb, const struct tc_action *a,
 108                        struct tcf_result *res)
 109 {
 110         struct tcf_nat *p = to_tcf_nat(a);
 111         struct iphdr *iph;
 112         __be32 old_addr;
 113         __be32 new_addr;
 114         __be32 mask;
 115         __be32 addr;
 116         int egress;
 117         int action;
 118         int ihl;
 119         int noff;
 120
 121         spin_lock(&p->tcf_lock);
 122
 123         tcf_lastuse_update(&p->tcf_tm);
 124         old_addr = p->old_addr;
 125         new_addr = p->new_addr;
 126         mask = p->mask;
 127         egress = p->flags & TCA_NAT_FLAG_EGRESS;
 128         action = p->tcf_action;
 129
 130         bstats_update(&p->tcf_bstats, skb);
 131
 132         spin_unlock(&p->tcf_lock);
 133
 134         if (unlikely(action == TC_ACT_SHOT))
 135                 goto drop;
 136
 137         noff = skb_network_offset(skb);
 138         if (!pskb_may_pull(skb, sizeof(*iph) + noff))
 139                 goto drop;
 140
 141         iph = ip_hdr(skb);
 142
 143         if (egress)
 144                 addr = iph->saddr;
 145         else
 146                 addr = iph->daddr;
 147
 148         if (!((old_addr ^ addr) & mask)) {
 149                 if (skb_try_make_writable(skb, sizeof(*iph) + noff))
 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_try_make_writable(skb, ihl + sizeof(*tcph) + noff))
 178                         goto drop;
 179
 180                 tcph = (void *)(skb_network_header(skb) + ihl);
 181                 inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr,
 182                                          true);
 183                 break;
 184         }
 185         case IPPROTO_UDP:
 186         {
 187                 struct udphdr *udph;
 188
 189                 if (!pskb_may_pull(skb, ihl + sizeof(*udph) + noff) ||
 190                     skb_try_make_writable(skb, ihl + sizeof(*udph) + noff))
 191                         goto drop;
 192
 193                 udph = (void *)(skb_network_header(skb) + ihl);
 194                 if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
 195                         inet_proto_csum_replace4(&udph->check, skb, addr,
 196                                                  new_addr, true);
 197                         if (!udph->check)
 198                                 udph->check = CSUM_MANGLED_0;
 199                 }
 200                 break;
 201         }
 202         case IPPROTO_ICMP:
 203         {
 204                 struct icmphdr *icmph;
 205
 206                 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + noff))
 207                         goto drop;
 208
 209                 icmph = (void *)(skb_network_header(skb) + ihl);
 210
 211                 if ((icmph->type != ICMP_DEST_UNREACH) &&
 212                     (icmph->type != ICMP_TIME_EXCEEDED) &&
 213                     (icmph->type != ICMP_PARAMETERPROB))
 214                         break;
 215
 216                 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph) +
 217                                         noff))
 218                         goto drop;
 219
 220                 icmph = (void *)(skb_network_header(skb) + ihl);
 221                 iph = (void *)(icmph + 1);
 222                 if (egress)
 223                         addr = iph->daddr;
 224                 else
 225                         addr = iph->saddr;
 226
 227                 if ((old_addr ^ addr) & mask)
 228                         break;
 229
 230                 if (skb_try_make_writable(skb, ihl + sizeof(*icmph) +
 231                                           sizeof(*iph) + noff))
 232                         goto drop;
 233
 234                 icmph = (void *)(skb_network_header(skb) + ihl);
 235                 iph = (void *)(icmph + 1);
 236
 237                 new_addr &= mask;
 238                 new_addr |= addr & ~mask;
 239
 240                 /* XXX Fix up the inner checksums. */
 241                 if (egress)
 242                         iph->daddr = new_addr;
 243                 else
 244                         iph->saddr = new_addr;
 245
 246                 inet_proto_csum_replace4(&icmph->checksum, skb, addr, new_addr,
 247                                          false);
 248                 break;
 249         }
 250         default:
 251                 break;
 252         }
 253
 254 out:
 255         return action;
 256
 257 drop:
 258         spin_lock(&p->tcf_lock);
 259         p->tcf_qstats.drops++;
 260         spin_unlock(&p->tcf_lock);
 261         return TC_ACT_SHOT;
 262 }
 263
 264 static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
 265                         int bind, int ref)
 266 {
 267         unsigned char *b = skb_tail_pointer(skb);
 268         struct tcf_nat *p = to_tcf_nat(a);
 269         struct tc_nat opt = {
 270                 .index    = p->tcf_index,
 271                 .refcnt   = refcount_read(&p->tcf_refcnt) - ref,
 272                 .bindcnt  = atomic_read(&p->tcf_bindcnt) - bind,
 273         };
 274         struct tcf_t t;
 275
 276         spin_lock_bh(&p->tcf_lock);
 277         opt.old_addr = p->old_addr;
 278         opt.new_addr = p->new_addr;
 279         opt.mask = p->mask;
 280         opt.flags = p->flags;
 281         opt.action = p->tcf_action;
 282
 283         if (nla_put(skb, TCA_NAT_PARMS, sizeof(opt), &opt))
 284                 goto nla_put_failure;
 285
 286         tcf_tm_dump(&t, &p->tcf_tm);
 287         if (nla_put_64bit(skb, TCA_NAT_TM, sizeof(t), &t, TCA_NAT_PAD))
 288                 goto nla_put_failure;
 289         spin_unlock_bh(&p->tcf_lock);
 290
 291         return skb->len;
 292
 293 nla_put_failure:
 294         spin_unlock_bh(&p->tcf_lock);
 295         nlmsg_trim(skb, b);
 296         return -1;
 297 }
 298
 299 static int tcf_nat_walker(struct net *net, struct sk_buff *skb,
 300                           struct netlink_callback *cb, int type,
 301                           const struct tc_action_ops *ops,
 302                           struct netlink_ext_ack *extack)
 303 {
 304         struct tc_action_net *tn = net_generic(net, nat_net_id);
 305
 306         return tcf_generic_walker(tn, skb, cb, type, ops, extack);
 307 }
 308
 309 static int tcf_nat_search(struct net *net, struct tc_action **a, u32 index)
 310 {
 311         struct tc_action_net *tn = net_generic(net, nat_net_id);
 312
 313         return tcf_idr_search(tn, a, index);
 314 }
 315
 316 static struct tc_action_ops act_nat_ops = {
 317         .kind           =       "nat",
 318         .id             =       TCA_ID_NAT,
 319         .owner          =       THIS_MODULE,
 320         .act            =       tcf_nat_act,
 321         .dump           =       tcf_nat_dump,
 322         .init           =       tcf_nat_init,
 323         .walk           =       tcf_nat_walker,
 324         .lookup         =       tcf_nat_search,
 325         .size           =       sizeof(struct tcf_nat),
 326 };
 327
 328 static __net_init int nat_init_net(struct net *net)
 329 {
 330         struct tc_action_net *tn = net_generic(net, nat_net_id);
 331
 332         return tc_action_net_init(tn, &act_nat_ops);
 333 }
 334
 335 static void __net_exit nat_exit_net(struct list_head *net_list)
 336 {
 337         tc_action_net_exit(net_list, nat_net_id);
 338 }
 339
 340 static struct pernet_operations nat_net_ops = {
 341         .init = nat_init_net,
 342         .exit_batch = nat_exit_net,
 343         .id   = &nat_net_id,
 344         .size = sizeof(struct tc_action_net),
 345 };
 346
 347 MODULE_DESCRIPTION("Stateless NAT actions");
 348 MODULE_LICENSE("GPL");
 349
 350 static int __init nat_init_module(void)
 351 {
 352         return tcf_register_action(&act_nat_ops, &nat_net_ops);
 353 }
 354
 355 static void __exit nat_cleanup_module(void)
 356 {
 357         tcf_unregister_action(&act_nat_ops, &nat_net_ops);
 358 }
 359
 360 module_init(nat_init_module);
 361 module_exit(nat_cleanup_module);