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
  28
  29 static unsigned int nat_net_id;
  30 static struct tc_action_ops act_nat_ops;
  31
  32 static const struct nla_policy nat_policy[TCA_NAT_MAX + 1] = {
  33         [TCA_NAT_PARMS] = { .len = sizeof(struct tc_nat) },
  34 };
  35
  36 static int tcf_nat_init(struct net *net, struct nlattr *nla, struct nlattr *est,
  37                         struct tc_action **a, int ovr, int bind,
  38                         bool rtnl_held, struct tcf_proto *tp,
  39                         struct netlink_ext_ack *extack)
  40 {
  41         struct tc_action_net *tn = net_generic(net, nat_net_id);
  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
  48         if (nla == NULL)
  49                 return -EINVAL;
  50
  51         err = nla_parse_nested_deprecated(tb, TCA_NAT_MAX, nla, nat_policy,
  52                                           NULL);
  53         if (err < 0)
  54                 return err;
  55
  56         if (tb[TCA_NAT_PARMS] == NULL)
  57                 return -EINVAL;
  58         parm = nla_data(tb[TCA_NAT_PARMS]);
  59
  60         err = tcf_idr_check_alloc(tn, &parm->index, a, bind);
  61         if (!err) {
  62                 ret = tcf_idr_create(tn, parm->index, est, a,
  63                                      &act_nat_ops, bind, false);
  64                 if (ret) {
  65                         tcf_idr_cleanup(tn, parm->index);
  66                         return ret;
  67                 }
  68                 ret = ACT_P_CREATED;
  69         } else if (err > 0) {
  70                 if (bind)
  71                         return 0;
  72                 if (!ovr) {
  73                         tcf_idr_release(*a, bind);
  74                         return -EEXIST;
  75                 }
  76         } else {
  77                 return err;
  78         }
  79         err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
  80         if (err < 0)
  81                 goto release_idr;
  82         p = to_tcf_nat(*a);
  83
  84         spin_lock_bh(&p->tcf_lock);
  85         p->old_addr = parm->old_addr;
  86         p->new_addr = parm->new_addr;
  87         p->mask = parm->mask;
  88         p->flags = parm->flags;
  89
  90         goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
  91         spin_unlock_bh(&p->tcf_lock);
  92         if (goto_ch)
  93                 tcf_chain_put_by_act(goto_ch);
  94
  95         if (ret == ACT_P_CREATED)
  96                 tcf_idr_insert(tn, *a);
  97
  98         return ret;
  99 release_idr:
 100         tcf_idr_release(*a, bind);
 101         return err;
 102 }
 103
 104 static int tcf_nat_act(struct sk_buff *skb, const struct tc_action *a,
 105                        struct tcf_result *res)
 106 {
 107         struct tcf_nat *p = to_tcf_nat(a);
 108         struct iphdr *iph;
 109         __be32 old_addr;
 110         __be32 new_addr;
 111         __be32 mask;
 112         __be32 addr;
 113         int egress;
 114         int action;
 115         int ihl;
 116         int noff;
 117
 118         spin_lock(&p->tcf_lock);
 119
 120         tcf_lastuse_update(&p->tcf_tm);
 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         bstats_update(&p->tcf_bstats, skb);
 128
 129         spin_unlock(&p->tcf_lock);
 130
 131         if (unlikely(action == TC_ACT_SHOT))
 132                 goto drop;
 133
 134         noff = skb_network_offset(skb);
 135         if (!pskb_may_pull(skb, sizeof(*iph) + noff))
 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_try_make_writable(skb, sizeof(*iph) + noff))
 147                         goto drop;
 148
 149                 new_addr &= mask;
 150                 new_addr |= addr & ~mask;
 151
 152                 /* Rewrite IP header */
 153                 iph = ip_hdr(skb);
 154                 if (egress)
 155                         iph->saddr = new_addr;
 156                 else
 157                         iph->daddr = new_addr;
 158
 159                 csum_replace4(&iph->check, addr, new_addr);
 160         } else if ((iph->frag_off & htons(IP_OFFSET)) ||
 161                    iph->protocol != IPPROTO_ICMP) {
 162                 goto out;
 163         }
 164
 165         ihl = iph->ihl * 4;
 166
 167         /* It would be nice to share code with stateful NAT. */
 168         switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) {
 169         case IPPROTO_TCP:
 170         {
 171                 struct tcphdr *tcph;
 172
 173                 if (!pskb_may_pull(skb, ihl + sizeof(*tcph) + noff) ||
 174                     skb_try_make_writable(skb, ihl + sizeof(*tcph) + noff))
 175                         goto drop;
 176
 177                 tcph = (void *)(skb_network_header(skb) + ihl);
 178                 inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr,
 179                                          true);
 180                 break;
 181         }
 182         case IPPROTO_UDP:
 183         {
 184                 struct udphdr *udph;
 185
 186                 if (!pskb_may_pull(skb, ihl + sizeof(*udph) + noff) ||
 187                     skb_try_make_writable(skb, ihl + sizeof(*udph) + noff))
 188                         goto drop;
 189
 190                 udph = (void *)(skb_network_header(skb) + ihl);
 191                 if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
 192                         inet_proto_csum_replace4(&udph->check, skb, addr,
 193                                                  new_addr, true);
 194                         if (!udph->check)
 195                                 udph->check = CSUM_MANGLED_0;
 196                 }
 197                 break;
 198         }
 199         case IPPROTO_ICMP:
 200         {
 201                 struct icmphdr *icmph;
 202
 203                 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + noff))
 204                         goto drop;
 205
 206                 icmph = (void *)(skb_network_header(skb) + ihl);
 207
 208                 if ((icmph->type != ICMP_DEST_UNREACH) &&
 209                     (icmph->type != ICMP_TIME_EXCEEDED) &&
 210                     (icmph->type != ICMP_PARAMETERPROB))
 211                         break;
 212
 213                 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph) +
 214                                         noff))
 215                         goto drop;
 216
 217                 icmph = (void *)(skb_network_header(skb) + ihl);
 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_try_make_writable(skb, ihl + sizeof(*icmph) +
 228                                           sizeof(*iph) + noff))
 229                         goto drop;
 230
 231                 icmph = (void *)(skb_network_header(skb) + ihl);
 232                 iph = (void *)(icmph + 1);
 233
 234                 new_addr &= mask;
 235                 new_addr |= addr & ~mask;
 236
 237                 /* XXX Fix up the inner checksums. */
 238                 if (egress)
 239                         iph->daddr = new_addr;
 240                 else
 241                         iph->saddr = new_addr;
 242
 243                 inet_proto_csum_replace4(&icmph->checksum, skb, addr, new_addr,
 244                                          false);
 245                 break;
 246         }
 247         default:
 248                 break;
 249         }
 250
 251 out:
 252         return action;
 253
 254 drop:
 255         spin_lock(&p->tcf_lock);
 256         p->tcf_qstats.drops++;
 257         spin_unlock(&p->tcf_lock);
 258         return TC_ACT_SHOT;
 259 }
 260
 261 static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
 262                         int bind, int ref)
 263 {
 264         unsigned char *b = skb_tail_pointer(skb);
 265         struct tcf_nat *p = to_tcf_nat(a);
 266         struct tc_nat opt = {
 267                 .index    = p->tcf_index,
 268                 .refcnt   = refcount_read(&p->tcf_refcnt) - ref,
 269                 .bindcnt  = atomic_read(&p->tcf_bindcnt) - bind,
 270         };
 271         struct tcf_t t;
 272
 273         spin_lock_bh(&p->tcf_lock);
 274         opt.old_addr = p->old_addr;
 275         opt.new_addr = p->new_addr;
 276         opt.mask = p->mask;
 277         opt.flags = p->flags;
 278         opt.action = p->tcf_action;
 279
 280         if (nla_put(skb, TCA_NAT_PARMS, sizeof(opt), &opt))
 281                 goto nla_put_failure;
 282
 283         tcf_tm_dump(&t, &p->tcf_tm);
 284         if (nla_put_64bit(skb, TCA_NAT_TM, sizeof(t), &t, TCA_NAT_PAD))
 285                 goto nla_put_failure;
 286         spin_unlock_bh(&p->tcf_lock);
 287
 288         return skb->len;
 289
 290 nla_put_failure:
 291         spin_unlock_bh(&p->tcf_lock);
 292         nlmsg_trim(skb, b);
 293         return -1;
 294 }
 295
 296 static int tcf_nat_walker(struct net *net, struct sk_buff *skb,
 297                           struct netlink_callback *cb, int type,
 298                           const struct tc_action_ops *ops,
 299                           struct netlink_ext_ack *extack)
 300 {
 301         struct tc_action_net *tn = net_generic(net, nat_net_id);
 302
 303         return tcf_generic_walker(tn, skb, cb, type, ops, extack);
 304 }
 305
 306 static int tcf_nat_search(struct net *net, struct tc_action **a, u32 index)
 307 {
 308         struct tc_action_net *tn = net_generic(net, nat_net_id);
 309
 310         return tcf_idr_search(tn, a, index);
 311 }
 312
 313 static struct tc_action_ops act_nat_ops = {
 314         .kind           =       "nat",
 315         .id             =       TCA_ID_NAT,
 316         .owner          =       THIS_MODULE,
 317         .act            =       tcf_nat_act,
 318         .dump           =       tcf_nat_dump,
 319         .init           =       tcf_nat_init,
 320         .walk           =       tcf_nat_walker,
 321         .lookup         =       tcf_nat_search,
 322         .size           =       sizeof(struct tcf_nat),
 323 };
 324
 325 static __net_init int nat_init_net(struct net *net)
 326 {
 327         struct tc_action_net *tn = net_generic(net, nat_net_id);
 328
 329         return tc_action_net_init(tn, &act_nat_ops);
 330 }
 331
 332 static void __net_exit nat_exit_net(struct list_head *net_list)
 333 {
 334         tc_action_net_exit(net_list, nat_net_id);
 335 }
 336
 337 static struct pernet_operations nat_net_ops = {
 338         .init = nat_init_net,
 339         .exit_batch = nat_exit_net,
 340         .id   = &nat_net_id,
 341         .size = sizeof(struct tc_action_net),
 342 };
 343
 344 MODULE_DESCRIPTION("Stateless NAT actions");
 345 MODULE_LICENSE("GPL");
 346
 347 static int __init nat_init_module(void)
 348 {
 349         return tcf_register_action(&act_nat_ops, &nat_net_ops);
 350 }
 351
 352 static void __exit nat_cleanup_module(void)
 353 {
 354         tcf_unregister_action(&act_nat_ops, &nat_net_ops);
 355 }
 356
 357 module_init(nat_init_module);
 358 module_exit(nat_cleanup_module);