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/icmp.h> 25 #include <net/ip.h> 26 #include <net/netlink.h> 27 #include <net/tc_act/tc_nat.h> 28 #include <net/tcp.h> 29 #include <net/udp.h> 30 31 32 #define NAT_TAB_MASK 15 33 static struct tcf_common *tcf_nat_ht[NAT_TAB_MASK + 1]; 34 static u32 nat_idx_gen; 35 static DEFINE_RWLOCK(nat_lock); 36 37 static struct tcf_hashinfo nat_hash_info = { 38 .htab = tcf_nat_ht, 39 .hmask = NAT_TAB_MASK, 40 .lock = &nat_lock, 41 }; 42 43 static const struct nla_policy nat_policy[TCA_NAT_MAX + 1] = { 44 [TCA_NAT_PARMS] = { .len = sizeof(struct tc_nat) }, 45 }; 46 47 static int tcf_nat_init(struct nlattr *nla, struct nlattr *est, 48 struct tc_action *a, int ovr, int bind) 49 { 50 struct nlattr *tb[TCA_NAT_MAX + 1]; 51 struct tc_nat *parm; 52 int ret = 0, err; 53 struct tcf_nat *p; 54 struct tcf_common *pc; 55 56 if (nla == NULL) 57 return -EINVAL; 58 59 err = nla_parse_nested(tb, TCA_NAT_MAX, nla, nat_policy); 60 if (err < 0) 61 return err; 62 63 if (tb[TCA_NAT_PARMS] == NULL) 64 return -EINVAL; 65 parm = nla_data(tb[TCA_NAT_PARMS]); 66 67 pc = tcf_hash_check(parm->index, a, bind, &nat_hash_info); 68 if (!pc) { 69 pc = tcf_hash_create(parm->index, est, a, sizeof(*p), bind, 70 &nat_idx_gen, &nat_hash_info); 71 if (unlikely(!pc)) 72 return -ENOMEM; 73 p = to_tcf_nat(pc); 74 ret = ACT_P_CREATED; 75 } else { 76 p = to_tcf_nat(pc); 77 if (!ovr) { 78 tcf_hash_release(pc, bind, &nat_hash_info); 79 return -EEXIST; 80 } 81 } 82 83 spin_lock_bh(&p->tcf_lock); 84 p->old_addr = parm->old_addr; 85 p->new_addr = parm->new_addr; 86 p->mask = parm->mask; 87 p->flags = parm->flags; 88 89 p->tcf_action = parm->action; 90 spin_unlock_bh(&p->tcf_lock); 91 92 if (ret == ACT_P_CREATED) 93 tcf_hash_insert(pc, &nat_hash_info); 94 95 return ret; 96 } 97 98 static int tcf_nat_cleanup(struct tc_action *a, int bind) 99 { 100 struct tcf_nat *p = a->priv; 101 102 return tcf_hash_release(&p->common, bind, &nat_hash_info); 103 } 104 105 static int tcf_nat(struct sk_buff *skb, struct tc_action *a, 106 struct tcf_result *res) 107 { 108 struct tcf_nat *p = a->priv; 109 struct iphdr *iph; 110 __be32 old_addr; 111 __be32 new_addr; 112 __be32 mask; 113 __be32 addr; 114 int egress; 115 int action; 116 int ihl; 117 118 spin_lock(&p->tcf_lock); 119 120 p->tcf_tm.lastuse = jiffies; 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 p->tcf_bstats.bytes += skb->len; 128 p->tcf_bstats.packets++; 129 130 spin_unlock(&p->tcf_lock); 131 132 if (unlikely(action == TC_ACT_SHOT)) 133 goto drop; 134 135 if (!pskb_may_pull(skb, sizeof(*iph))) 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_cloned(skb) && 147 !skb_clone_writable(skb, sizeof(*iph)) && 148 pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) 149 goto drop; 150 151 new_addr &= mask; 152 new_addr |= addr & ~mask; 153 154 /* Rewrite IP header */ 155 iph = ip_hdr(skb); 156 if (egress) 157 iph->saddr = new_addr; 158 else 159 iph->daddr = new_addr; 160 161 csum_replace4(&iph->check, addr, new_addr); 162 } 163 164 ihl = iph->ihl * 4; 165 166 /* It would be nice to share code with stateful NAT. */ 167 switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) { 168 case IPPROTO_TCP: 169 { 170 struct tcphdr *tcph; 171 172 if (!pskb_may_pull(skb, ihl + sizeof(*tcph)) || 173 (skb_cloned(skb) && 174 !skb_clone_writable(skb, ihl + sizeof(*tcph)) && 175 pskb_expand_head(skb, 0, 0, GFP_ATOMIC))) 176 goto drop; 177 178 tcph = (void *)(skb_network_header(skb) + ihl); 179 inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr, 1); 180 break; 181 } 182 case IPPROTO_UDP: 183 { 184 struct udphdr *udph; 185 186 if (!pskb_may_pull(skb, ihl + sizeof(*udph)) || 187 (skb_cloned(skb) && 188 !skb_clone_writable(skb, ihl + sizeof(*udph)) && 189 pskb_expand_head(skb, 0, 0, GFP_ATOMIC))) 190 goto drop; 191 192 udph = (void *)(skb_network_header(skb) + ihl); 193 if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) { 194 inet_proto_csum_replace4(&udph->check, skb, addr, 195 new_addr, 1); 196 if (!udph->check) 197 udph->check = CSUM_MANGLED_0; 198 } 199 break; 200 } 201 case IPPROTO_ICMP: 202 { 203 struct icmphdr *icmph; 204 205 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph))) 206 goto drop; 207 208 icmph = (void *)(skb_network_header(skb) + ihl); 209 210 if ((icmph->type != ICMP_DEST_UNREACH) && 211 (icmph->type != ICMP_TIME_EXCEEDED) && 212 (icmph->type != ICMP_PARAMETERPROB)) 213 break; 214 215 iph = (void *)(icmph + 1); 216 if (egress) 217 addr = iph->daddr; 218 else 219 addr = iph->saddr; 220 221 if ((old_addr ^ addr) & mask) 222 break; 223 224 if (skb_cloned(skb) && 225 !skb_clone_writable(skb, 226 ihl + sizeof(*icmph) + sizeof(*iph)) && 227 pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) 228 goto drop; 229 230 icmph = (void *)(skb_network_header(skb) + ihl); 231 iph = (void *)(icmph + 1); 232 233 new_addr &= mask; 234 new_addr |= addr & ~mask; 235 236 /* XXX Fix up the inner checksums. */ 237 if (egress) 238 iph->daddr = new_addr; 239 else 240 iph->saddr = new_addr; 241 242 inet_proto_csum_replace4(&icmph->checksum, skb, addr, new_addr, 243 1); 244 break; 245 } 246 default: 247 break; 248 } 249 250 return action; 251 252 drop: 253 spin_lock(&p->tcf_lock); 254 p->tcf_qstats.drops++; 255 spin_unlock(&p->tcf_lock); 256 return TC_ACT_SHOT; 257 } 258 259 static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a, 260 int bind, int ref) 261 { 262 unsigned char *b = skb_tail_pointer(skb); 263 struct tcf_nat *p = a->priv; 264 struct tc_nat *opt; 265 struct tcf_t t; 266 int s; 267 268 s = sizeof(*opt); 269 270 /* netlink spinlocks held above us - must use ATOMIC */ 271 opt = kzalloc(s, GFP_ATOMIC); 272 if (unlikely(!opt)) 273 return -ENOBUFS; 274 275 opt->old_addr = p->old_addr; 276 opt->new_addr = p->new_addr; 277 opt->mask = p->mask; 278 opt->flags = p->flags; 279 280 opt->index = p->tcf_index; 281 opt->action = p->tcf_action; 282 opt->refcnt = p->tcf_refcnt - ref; 283 opt->bindcnt = p->tcf_bindcnt - bind; 284 285 NLA_PUT(skb, TCA_NAT_PARMS, s, opt); 286 t.install = jiffies_to_clock_t(jiffies - p->tcf_tm.install); 287 t.lastuse = jiffies_to_clock_t(jiffies - p->tcf_tm.lastuse); 288 t.expires = jiffies_to_clock_t(p->tcf_tm.expires); 289 NLA_PUT(skb, TCA_NAT_TM, sizeof(t), &t); 290 291 kfree(opt); 292 293 return skb->len; 294 295 nla_put_failure: 296 nlmsg_trim(skb, b); 297 kfree(opt); 298 return -1; 299 } 300 301 static struct tc_action_ops act_nat_ops = { 302 .kind = "nat", 303 .hinfo = &nat_hash_info, 304 .type = TCA_ACT_NAT, 305 .capab = TCA_CAP_NONE, 306 .owner = THIS_MODULE, 307 .act = tcf_nat, 308 .dump = tcf_nat_dump, 309 .cleanup = tcf_nat_cleanup, 310 .lookup = tcf_hash_search, 311 .init = tcf_nat_init, 312 .walk = tcf_generic_walker 313 }; 314 315 MODULE_DESCRIPTION("Stateless NAT actions"); 316 MODULE_LICENSE("GPL"); 317 318 static int __init nat_init_module(void) 319 { 320 return tcf_register_action(&act_nat_ops); 321 } 322 323 static void __exit nat_cleanup_module(void) 324 { 325 tcf_unregister_action(&act_nat_ops); 326 } 327 328 module_init(nat_init_module); 329 module_exit(nat_cleanup_module); 330