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 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 nlattr *tb[TCA_NAT_MAX + 1]; 42 struct tcf_chain *goto_ch = NULL; 43 struct tc_nat *parm; 44 int ret = 0, err; 45 struct tcf_nat *p; 46 u32 index; 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 index = parm->index; 60 err = tcf_idr_check_alloc(tn, &index, a, bind); 61 if (!err) { 62 ret = tcf_idr_create(tn, index, est, a, 63 &act_nat_ops, bind, false, flags); 64 if (ret) { 65 tcf_idr_cleanup(tn, index); 66 return ret; 67 } 68 ret = ACT_P_CREATED; 69 } else if (err > 0) { 70 if (bind) 71 return 0; 72 if (!(flags & TCA_ACT_FLAGS_REPLACE)) { 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 return ret; 96 release_idr: 97 tcf_idr_release(*a, bind); 98 return err; 99 } 100 101 static int tcf_nat_act(struct sk_buff *skb, const struct tc_action *a, 102 struct tcf_result *res) 103 { 104 struct tcf_nat *p = to_tcf_nat(a); 105 struct iphdr *iph; 106 __be32 old_addr; 107 __be32 new_addr; 108 __be32 mask; 109 __be32 addr; 110 int egress; 111 int action; 112 int ihl; 113 int noff; 114 115 spin_lock(&p->tcf_lock); 116 117 tcf_lastuse_update(&p->tcf_tm); 118 old_addr = p->old_addr; 119 new_addr = p->new_addr; 120 mask = p->mask; 121 egress = p->flags & TCA_NAT_FLAG_EGRESS; 122 action = p->tcf_action; 123 124 bstats_update(&p->tcf_bstats, skb); 125 126 spin_unlock(&p->tcf_lock); 127 128 if (unlikely(action == TC_ACT_SHOT)) 129 goto drop; 130 131 noff = skb_network_offset(skb); 132 if (!pskb_may_pull(skb, sizeof(*iph) + noff)) 133 goto drop; 134 135 iph = ip_hdr(skb); 136 137 if (egress) 138 addr = iph->saddr; 139 else 140 addr = iph->daddr; 141 142 if (!((old_addr ^ addr) & mask)) { 143 if (skb_try_make_writable(skb, sizeof(*iph) + noff)) 144 goto drop; 145 146 new_addr &= mask; 147 new_addr |= addr & ~mask; 148 149 /* Rewrite IP header */ 150 iph = ip_hdr(skb); 151 if (egress) 152 iph->saddr = new_addr; 153 else 154 iph->daddr = new_addr; 155 156 csum_replace4(&iph->check, addr, new_addr); 157 } else if ((iph->frag_off & htons(IP_OFFSET)) || 158 iph->protocol != IPPROTO_ICMP) { 159 goto out; 160 } 161 162 ihl = iph->ihl * 4; 163 164 /* It would be nice to share code with stateful NAT. */ 165 switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) { 166 case IPPROTO_TCP: 167 { 168 struct tcphdr *tcph; 169 170 if (!pskb_may_pull(skb, ihl + sizeof(*tcph) + noff) || 171 skb_try_make_writable(skb, ihl + sizeof(*tcph) + noff)) 172 goto drop; 173 174 tcph = (void *)(skb_network_header(skb) + ihl); 175 inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr, 176 true); 177 break; 178 } 179 case IPPROTO_UDP: 180 { 181 struct udphdr *udph; 182 183 if (!pskb_may_pull(skb, ihl + sizeof(*udph) + noff) || 184 skb_try_make_writable(skb, ihl + sizeof(*udph) + noff)) 185 goto drop; 186 187 udph = (void *)(skb_network_header(skb) + ihl); 188 if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) { 189 inet_proto_csum_replace4(&udph->check, skb, addr, 190 new_addr, true); 191 if (!udph->check) 192 udph->check = CSUM_MANGLED_0; 193 } 194 break; 195 } 196 case IPPROTO_ICMP: 197 { 198 struct icmphdr *icmph; 199 200 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + noff)) 201 goto drop; 202 203 icmph = (void *)(skb_network_header(skb) + ihl); 204 205 if (!icmp_is_err(icmph->type)) 206 break; 207 208 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph) + 209 noff)) 210 goto drop; 211 212 icmph = (void *)(skb_network_header(skb) + ihl); 213 iph = (void *)(icmph + 1); 214 if (egress) 215 addr = iph->daddr; 216 else 217 addr = iph->saddr; 218 219 if ((old_addr ^ addr) & mask) 220 break; 221 222 if (skb_try_make_writable(skb, ihl + sizeof(*icmph) + 223 sizeof(*iph) + noff)) 224 goto drop; 225 226 icmph = (void *)(skb_network_header(skb) + ihl); 227 iph = (void *)(icmph + 1); 228 229 new_addr &= mask; 230 new_addr |= addr & ~mask; 231 232 /* XXX Fix up the inner checksums. */ 233 if (egress) 234 iph->daddr = new_addr; 235 else 236 iph->saddr = new_addr; 237 238 inet_proto_csum_replace4(&icmph->checksum, skb, addr, new_addr, 239 false); 240 break; 241 } 242 default: 243 break; 244 } 245 246 out: 247 return action; 248 249 drop: 250 spin_lock(&p->tcf_lock); 251 p->tcf_qstats.drops++; 252 spin_unlock(&p->tcf_lock); 253 return TC_ACT_SHOT; 254 } 255 256 static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a, 257 int bind, int ref) 258 { 259 unsigned char *b = skb_tail_pointer(skb); 260 struct tcf_nat *p = to_tcf_nat(a); 261 struct tc_nat opt = { 262 .index = p->tcf_index, 263 .refcnt = refcount_read(&p->tcf_refcnt) - ref, 264 .bindcnt = atomic_read(&p->tcf_bindcnt) - bind, 265 }; 266 struct tcf_t t; 267 268 spin_lock_bh(&p->tcf_lock); 269 opt.old_addr = p->old_addr; 270 opt.new_addr = p->new_addr; 271 opt.mask = p->mask; 272 opt.flags = p->flags; 273 opt.action = p->tcf_action; 274 275 if (nla_put(skb, TCA_NAT_PARMS, sizeof(opt), &opt)) 276 goto nla_put_failure; 277 278 tcf_tm_dump(&t, &p->tcf_tm); 279 if (nla_put_64bit(skb, TCA_NAT_TM, sizeof(t), &t, TCA_NAT_PAD)) 280 goto nla_put_failure; 281 spin_unlock_bh(&p->tcf_lock); 282 283 return skb->len; 284 285 nla_put_failure: 286 spin_unlock_bh(&p->tcf_lock); 287 nlmsg_trim(skb, b); 288 return -1; 289 } 290 291 static struct tc_action_ops act_nat_ops = { 292 .kind = "nat", 293 .id = TCA_ID_NAT, 294 .owner = THIS_MODULE, 295 .act = tcf_nat_act, 296 .dump = tcf_nat_dump, 297 .init = tcf_nat_init, 298 .size = sizeof(struct tcf_nat), 299 }; 300 301 static __net_init int nat_init_net(struct net *net) 302 { 303 struct tc_action_net *tn = net_generic(net, act_nat_ops.net_id); 304 305 return tc_action_net_init(net, tn, &act_nat_ops); 306 } 307 308 static void __net_exit nat_exit_net(struct list_head *net_list) 309 { 310 tc_action_net_exit(net_list, act_nat_ops.net_id); 311 } 312 313 static struct pernet_operations nat_net_ops = { 314 .init = nat_init_net, 315 .exit_batch = nat_exit_net, 316 .id = &act_nat_ops.net_id, 317 .size = sizeof(struct tc_action_net), 318 }; 319 320 MODULE_DESCRIPTION("Stateless NAT actions"); 321 MODULE_LICENSE("GPL"); 322 323 static int __init nat_init_module(void) 324 { 325 return tcf_register_action(&act_nat_ops, &nat_net_ops); 326 } 327 328 static void __exit nat_cleanup_module(void) 329 { 330 tcf_unregister_action(&act_nat_ops, &nat_net_ops); 331 } 332 333 module_init(nat_init_module); 334 module_exit(nat_cleanup_module); 335