net/sched/act_nat.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Stateless NAT actions
   4  *
   5  * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
   6  */
   7
   8 #include <linux/errno.h>
   9 #include <linux/init.h>
  10 #include <linux/kernel.h>
  11 #include <linux/module.h>
  12 #include <linux/netfilter.h>
  13 #include <linux/rtnetlink.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/slab.h>
  16 #include <linux/spinlock.h>
  17 #include <linux/string.h>
  18 #include <linux/tc_act/tc_nat.h>
  19 #include <net/act_api.h>
  20 #include <net/pkt_cls.h>
  21 #include <net/icmp.h>
  22 #include <net/ip.h>
  23 #include <net/netlink.h>
  24 #include <net/tc_act/tc_nat.h>
  25 #include <net/tcp.h>
  26 #include <net/udp.h>
  27 #include <net/tc_wrapper.h>
  28
  29 static struct tc_action_ops act_nat_ops;
  30
  31 static const struct nla_policy nat_policy[TCA_NAT_MAX + 1] = {
  32         [TCA_NAT_PARMS] = { .len = sizeof(struct tc_nat) },
  33 };
  34
  35 static int tcf_nat_init(struct net *net, struct nlattr *nla, struct nlattr *est,
  36                         struct tc_action **a, struct tcf_proto *tp,
  37                         u32 flags, struct netlink_ext_ack *extack)
  38 {
  39         struct tc_action_net *tn = net_generic(net, act_nat_ops.net_id);
  40         bool bind = flags & TCA_ACT_FLAGS_BIND;
  41         struct tcf_nat_parms *nparm, *oparm;
  42         struct nlattr *tb[TCA_NAT_MAX + 1];
  43         struct tcf_chain *goto_ch = NULL;
  44         struct tc_nat *parm;
  45         int ret = 0, err;
  46         struct tcf_nat *p;
  47         u32 index;
  48
  49         if (nla == NULL)
  50                 return -EINVAL;
  51
  52         err = nla_parse_nested_deprecated(tb, TCA_NAT_MAX, nla, nat_policy,
  53                                           NULL);
  54         if (err < 0)
  55                 return err;
  56
  57         if (tb[TCA_NAT_PARMS] == NULL)
  58                 return -EINVAL;
  59         parm = nla_data(tb[TCA_NAT_PARMS]);
  60         index = parm->index;
  61         err = tcf_idr_check_alloc(tn, &index, a, bind);
  62         if (!err) {
  63                 ret = tcf_idr_create_from_flags(tn, index, est, a, &act_nat_ops,
  64                                                 bind, flags);
  65                 if (ret) {
  66                         tcf_idr_cleanup(tn, index);
  67                         return ret;
  68                 }
  69                 ret = ACT_P_CREATED;
  70         } else if (err > 0) {
  71                 if (bind)
  72                         return ACT_P_BOUND;
  73                 if (!(flags & TCA_ACT_FLAGS_REPLACE)) {
  74                         tcf_idr_release(*a, bind);
  75                         return -EEXIST;
  76                 }
  77         } else {
  78                 return err;
  79         }
  80         err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
  81         if (err < 0)
  82                 goto release_idr;
  83
  84         nparm = kzalloc(sizeof(*nparm), GFP_KERNEL);
  85         if (!nparm) {
  86                 err = -ENOMEM;
  87                 goto release_idr;
  88         }
  89
  90         nparm->old_addr = parm->old_addr;
  91         nparm->new_addr = parm->new_addr;
  92         nparm->mask = parm->mask;
  93         nparm->flags = parm->flags;
  94
  95         p = to_tcf_nat(*a);
  96
  97         spin_lock_bh(&p->tcf_lock);
  98         goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
  99         oparm = rcu_replace_pointer(p->parms, nparm, lockdep_is_held(&p->tcf_lock));
 100         spin_unlock_bh(&p->tcf_lock);
 101
 102         if (goto_ch)
 103                 tcf_chain_put_by_act(goto_ch);
 104
 105         if (oparm)
 106                 kfree_rcu(oparm, rcu);
 107
 108         return ret;
 109 release_idr:
 110         tcf_idr_release(*a, bind);
 111         return err;
 112 }
 113
 114 TC_INDIRECT_SCOPE int tcf_nat_act(struct sk_buff *skb,
 115                                   const struct tc_action *a,
 116                                   struct tcf_result *res)
 117 {
 118         struct tcf_nat *p = to_tcf_nat(a);
 119         struct tcf_nat_parms *parms;
 120         struct iphdr *iph;
 121         __be32 old_addr;
 122         __be32 new_addr;
 123         __be32 mask;
 124         __be32 addr;
 125         int egress;
 126         int action;
 127         int ihl;
 128         int noff;
 129
 130         tcf_lastuse_update(&p->tcf_tm);
 131         tcf_action_update_bstats(&p->common, skb);
 132
 133         action = READ_ONCE(p->tcf_action);
 134
 135         parms = rcu_dereference_bh(p->parms);
 136         old_addr = parms->old_addr;
 137         new_addr = parms->new_addr;
 138         mask = parms->mask;
 139         egress = parms->flags & TCA_NAT_FLAG_EGRESS;
 140
 141         if (unlikely(action == TC_ACT_SHOT))
 142                 goto drop;
 143
 144         noff = skb_network_offset(skb);
 145         if (!pskb_may_pull(skb, sizeof(*iph) + noff))
 146                 goto drop;
 147
 148         iph = ip_hdr(skb);
 149
 150         if (egress)
 151                 addr = iph->saddr;
 152         else
 153                 addr = iph->daddr;
 154
 155         if (!((old_addr ^ addr) & mask)) {
 156                 if (skb_try_make_writable(skb, sizeof(*iph) + noff))
 157                         goto drop;
 158
 159                 new_addr &= mask;
 160                 new_addr |= addr & ~mask;
 161
 162                 /* Rewrite IP header */
 163                 iph = ip_hdr(skb);
 164                 if (egress)
 165                         iph->saddr = new_addr;
 166                 else
 167                         iph->daddr = new_addr;
 168
 169                 csum_replace4(&iph->check, addr, new_addr);
 170         } else if ((iph->frag_off & htons(IP_OFFSET)) ||
 171                    iph->protocol != IPPROTO_ICMP) {
 172                 goto out;
 173         }
 174
 175         ihl = iph->ihl * 4;
 176
 177         /* It would be nice to share code with stateful NAT. */
 178         switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) {
 179         case IPPROTO_TCP:
 180         {
 181                 struct tcphdr *tcph;
 182
 183                 if (!pskb_may_pull(skb, ihl + sizeof(*tcph) + noff) ||
 184                     skb_try_make_writable(skb, ihl + sizeof(*tcph) + noff))
 185                         goto drop;
 186
 187                 tcph = (void *)(skb_network_header(skb) + ihl);
 188                 inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr,
 189                                          true);
 190                 break;
 191         }
 192         case IPPROTO_UDP:
 193         {
 194                 struct udphdr *udph;
 195
 196                 if (!pskb_may_pull(skb, ihl + sizeof(*udph) + noff) ||
 197                     skb_try_make_writable(skb, ihl + sizeof(*udph) + noff))
 198                         goto drop;
 199
 200                 udph = (void *)(skb_network_header(skb) + ihl);
 201                 if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
 202                         inet_proto_csum_replace4(&udph->check, skb, addr,
 203                                                  new_addr, true);
 204                         if (!udph->check)
 205                                 udph->check = CSUM_MANGLED_0;
 206                 }
 207                 break;
 208         }
 209         case IPPROTO_ICMP:
 210         {
 211                 struct icmphdr *icmph;
 212
 213                 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + noff))
 214                         goto drop;
 215
 216                 icmph = (void *)(skb_network_header(skb) + ihl);
 217
 218                 if (!icmp_is_err(icmph->type))
 219                         break;
 220
 221                 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph) +
 222                                         noff))
 223                         goto drop;
 224
 225                 icmph = (void *)(skb_network_header(skb) + ihl);
 226                 iph = (void *)(icmph + 1);
 227                 if (egress)
 228                         addr = iph->daddr;
 229                 else
 230                         addr = iph->saddr;
 231
 232                 if ((old_addr ^ addr) & mask)
 233                         break;
 234
 235                 if (skb_try_make_writable(skb, ihl + sizeof(*icmph) +
 236                                           sizeof(*iph) + noff))
 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                                          false);
 253                 break;
 254         }
 255         default:
 256                 break;
 257         }
 258
 259 out:
 260         return action;
 261
 262 drop:
 263         tcf_action_inc_drop_qstats(&p->common);
 264         return TC_ACT_SHOT;
 265 }
 266
 267 static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
 268                         int bind, int ref)
 269 {
 270         unsigned char *b = skb_tail_pointer(skb);
 271         struct tcf_nat *p = to_tcf_nat(a);
 272         struct tc_nat opt = {
 273                 .index    = p->tcf_index,
 274                 .refcnt   = refcount_read(&p->tcf_refcnt) - ref,
 275                 .bindcnt  = atomic_read(&p->tcf_bindcnt) - bind,
 276         };
 277         struct tcf_nat_parms *parms;
 278         struct tcf_t t;
 279
 280         spin_lock_bh(&p->tcf_lock);
 281
 282         opt.action = p->tcf_action;
 283
 284         parms = rcu_dereference_protected(p->parms, lockdep_is_held(&p->tcf_lock));
 285
 286         opt.old_addr = parms->old_addr;
 287         opt.new_addr = parms->new_addr;
 288         opt.mask = parms->mask;
 289         opt.flags = parms->flags;
 290
 291         if (nla_put(skb, TCA_NAT_PARMS, sizeof(opt), &opt))
 292                 goto nla_put_failure;
 293
 294         tcf_tm_dump(&t, &p->tcf_tm);
 295         if (nla_put_64bit(skb, TCA_NAT_TM, sizeof(t), &t, TCA_NAT_PAD))
 296                 goto nla_put_failure;
 297         spin_unlock_bh(&p->tcf_lock);
 298
 299         return skb->len;
 300
 301 nla_put_failure:
 302         spin_unlock_bh(&p->tcf_lock);
 303         nlmsg_trim(skb, b);
 304         return -1;
 305 }
 306
 307 static void tcf_nat_cleanup(struct tc_action *a)
 308 {
 309         struct tcf_nat *p = to_tcf_nat(a);
 310         struct tcf_nat_parms *parms;
 311
 312         parms = rcu_dereference_protected(p->parms, 1);
 313         if (parms)
 314                 kfree_rcu(parms, rcu);
 315 }
 316
 317 static struct tc_action_ops act_nat_ops = {
 318         .kind           =       "nat",
 319         .id             =       TCA_ID_NAT,
 320         .owner          =       THIS_MODULE,
 321         .act            =       tcf_nat_act,
 322         .dump           =       tcf_nat_dump,
 323         .init           =       tcf_nat_init,
 324         .cleanup        =       tcf_nat_cleanup,
 325         .size           =       sizeof(struct tcf_nat),
 326 };
 327 MODULE_ALIAS_NET_ACT("nat");
 328
 329 static __net_init int nat_init_net(struct net *net)
 330 {
 331         struct tc_action_net *tn = net_generic(net, act_nat_ops.net_id);
 332
 333         return tc_action_net_init(net, tn, &act_nat_ops);
 334 }
 335
 336 static void __net_exit nat_exit_net(struct list_head *net_list)
 337 {
 338         tc_action_net_exit(net_list, act_nat_ops.net_id);
 339 }
 340
 341 static struct pernet_operations nat_net_ops = {
 342         .init = nat_init_net,
 343         .exit_batch = nat_exit_net,
 344         .id   = &act_nat_ops.net_id,
 345         .size = sizeof(struct tc_action_net),
 346 };
 347
 348 MODULE_DESCRIPTION("Stateless NAT actions");
 349 MODULE_LICENSE("GPL");
 350
 351 static int __init nat_init_module(void)
 352 {
 353         return tcf_register_action(&act_nat_ops, &nat_net_ops);
 354 }
 355
 356 static void __exit nat_cleanup_module(void)
 357 {
 358         tcf_unregister_action(&act_nat_ops, &nat_net_ops);
 359 }
 360
 361 module_init(nat_init_module);
 362 module_exit(nat_cleanup_module);