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); 363