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); 362