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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 | /* (C) 1999-2001 Paul `Rusty' Russell
* (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/types.h>
#include <linux/icmp.h>
#include <linux/ip.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/proc_fs.h>
#include <net/ip.h>
#include <net/checksum.h>
#include <linux/spinlock.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_rule.h>
#include <net/netfilter/nf_nat_protocol.h>
#include <net/netfilter/nf_nat_core.h>
#include <net/netfilter/nf_nat_helper.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#if 0
#define DEBUGP printk
#else
#define DEBUGP(format, args...)
#endif
#ifdef CONFIG_XFRM
static void nat_decode_session(struct sk_buff *skb, struct flowi *fl)
{
struct nf_conn *ct;
struct nf_conntrack_tuple *t;
enum ip_conntrack_info ctinfo;
enum ip_conntrack_dir dir;
unsigned long statusbit;
ct = nf_ct_get(skb, &ctinfo);
if (ct == NULL)
return;
dir = CTINFO2DIR(ctinfo);
t = &ct->tuplehash[dir].tuple;
if (dir == IP_CT_DIR_ORIGINAL)
statusbit = IPS_DST_NAT;
else
statusbit = IPS_SRC_NAT;
if (ct->status & statusbit) {
fl->fl4_dst = t->dst.u3.ip;
if (t->dst.protonum == IPPROTO_TCP ||
t->dst.protonum == IPPROTO_UDP)
fl->fl_ip_dport = t->dst.u.tcp.port;
}
statusbit ^= IPS_NAT_MASK;
if (ct->status & statusbit) {
fl->fl4_src = t->src.u3.ip;
if (t->dst.protonum == IPPROTO_TCP ||
t->dst.protonum == IPPROTO_UDP)
fl->fl_ip_sport = t->src.u.tcp.port;
}
}
#endif
static unsigned int
nf_nat_fn(unsigned int hooknum,
struct sk_buff **pskb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
{
struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
struct nf_conn_nat *nat;
/* maniptype == SRC for postrouting. */
enum nf_nat_manip_type maniptype = HOOK2MANIP(hooknum);
/* We never see fragments: conntrack defrags on pre-routing
and local-out, and nf_nat_out protects post-routing. */
NF_CT_ASSERT(!(ip_hdr(*pskb)->frag_off & htons(IP_MF | IP_OFFSET)));
ct = nf_ct_get(*pskb, &ctinfo);
/* Can't track? It's not due to stress, or conntrack would
have dropped it. Hence it's the user's responsibilty to
packet filter it out, or implement conntrack/NAT for that
protocol. 8) --RR */
if (!ct) {
/* Exception: ICMP redirect to new connection (not in
hash table yet). We must not let this through, in
case we're doing NAT to the same network. */
if (ip_hdr(*pskb)->protocol == IPPROTO_ICMP) {
struct icmphdr _hdr, *hp;
hp = skb_header_pointer(*pskb, ip_hdrlen(*pskb),
sizeof(_hdr), &_hdr);
if (hp != NULL &&
hp->type == ICMP_REDIRECT)
return NF_DROP;
}
return NF_ACCEPT;
}
/* Don't try to NAT if this packet is not conntracked */
if (ct == &nf_conntrack_untracked)
return NF_ACCEPT;
nat = nfct_nat(ct);
if (!nat)
return NF_ACCEPT;
switch (ctinfo) {
case IP_CT_RELATED:
case IP_CT_RELATED+IP_CT_IS_REPLY:
if (ip_hdr(*pskb)->protocol == IPPROTO_ICMP) {
if (!nf_nat_icmp_reply_translation(ct, ctinfo,
hooknum, pskb))
return NF_DROP;
else
return NF_ACCEPT;
}
/* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
case IP_CT_NEW:
/* Seen it before? This can happen for loopback, retrans,
or local packets.. */
if (!nf_nat_initialized(ct, maniptype)) {
unsigned int ret;
if (unlikely(nf_ct_is_confirmed(ct)))
/* NAT module was loaded late */
ret = alloc_null_binding_confirmed(ct, hooknum);
else if (hooknum == NF_IP_LOCAL_IN)
/* LOCAL_IN hook doesn't have a chain! */
ret = alloc_null_binding(ct, hooknum);
else
ret = nf_nat_rule_find(pskb, hooknum, in, out,
ct);
if (ret != NF_ACCEPT) {
return ret;
}
} else
DEBUGP("Already setup manip %s for ct %p\n",
maniptype == IP_NAT_MANIP_SRC ? "SRC" : "DST",
ct);
break;
default:
/* ESTABLISHED */
NF_CT_ASSERT(ctinfo == IP_CT_ESTABLISHED ||
ctinfo == (IP_CT_ESTABLISHED+IP_CT_IS_REPLY));
}
return nf_nat_packet(ct, ctinfo, hooknum, pskb);
}
static unsigned int
nf_nat_in(unsigned int hooknum,
struct sk_buff **pskb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
{
unsigned int ret;
__be32 daddr = ip_hdr(*pskb)->daddr;
ret = nf_nat_fn(hooknum, pskb, in, out, okfn);
if (ret != NF_DROP && ret != NF_STOLEN &&
daddr != ip_hdr(*pskb)->daddr) {
dst_release((*pskb)->dst);
(*pskb)->dst = NULL;
}
return ret;
}
static unsigned int
nf_nat_out(unsigned int hooknum,
struct sk_buff **pskb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
{
#ifdef CONFIG_XFRM
struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
#endif
unsigned int ret;
/* root is playing with raw sockets. */
if ((*pskb)->len < sizeof(struct iphdr) ||
ip_hdrlen(*pskb) < sizeof(struct iphdr))
return NF_ACCEPT;
ret = nf_nat_fn(hooknum, pskb, in, out, okfn);
#ifdef CONFIG_XFRM
if (ret != NF_DROP && ret != NF_STOLEN &&
(ct = nf_ct_get(*pskb, &ctinfo)) != NULL) {
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
if (ct->tuplehash[dir].tuple.src.u3.ip !=
ct->tuplehash[!dir].tuple.dst.u3.ip
|| ct->tuplehash[dir].tuple.src.u.all !=
ct->tuplehash[!dir].tuple.dst.u.all
)
return ip_xfrm_me_harder(pskb) == 0 ? ret : NF_DROP;
}
#endif
return ret;
}
static unsigned int
nf_nat_local_fn(unsigned int hooknum,
struct sk_buff **pskb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
{
struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
unsigned int ret;
/* root is playing with raw sockets. */
if ((*pskb)->len < sizeof(struct iphdr) ||
ip_hdrlen(*pskb) < sizeof(struct iphdr))
return NF_ACCEPT;
ret = nf_nat_fn(hooknum, pskb, in, out, okfn);
if (ret != NF_DROP && ret != NF_STOLEN &&
(ct = nf_ct_get(*pskb, &ctinfo)) != NULL) {
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
if (ct->tuplehash[dir].tuple.dst.u3.ip !=
ct->tuplehash[!dir].tuple.src.u3.ip) {
if (ip_route_me_harder(pskb, RTN_UNSPEC))
ret = NF_DROP;
}
#ifdef CONFIG_XFRM
else if (ct->tuplehash[dir].tuple.dst.u.all !=
ct->tuplehash[!dir].tuple.src.u.all)
if (ip_xfrm_me_harder(pskb))
ret = NF_DROP;
#endif
}
return ret;
}
static unsigned int
nf_nat_adjust(unsigned int hooknum,
struct sk_buff **pskb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
{
struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
ct = nf_ct_get(*pskb, &ctinfo);
if (ct && test_bit(IPS_SEQ_ADJUST_BIT, &ct->status)) {
DEBUGP("nf_nat_standalone: adjusting sequence number\n");
if (!nf_nat_seq_adjust(pskb, ct, ctinfo))
return NF_DROP;
}
return NF_ACCEPT;
}
/* We must be after connection tracking and before packet filtering. */
static struct nf_hook_ops nf_nat_ops[] = {
/* Before packet filtering, change destination */
{
.hook = nf_nat_in,
.owner = THIS_MODULE,
.pf = PF_INET,
.hooknum = NF_IP_PRE_ROUTING,
.priority = NF_IP_PRI_NAT_DST,
},
/* After packet filtering, change source */
{
.hook = nf_nat_out,
.owner = THIS_MODULE,
.pf = PF_INET,
.hooknum = NF_IP_POST_ROUTING,
.priority = NF_IP_PRI_NAT_SRC,
},
/* After conntrack, adjust sequence number */
{
.hook = nf_nat_adjust,
.owner = THIS_MODULE,
.pf = PF_INET,
.hooknum = NF_IP_POST_ROUTING,
.priority = NF_IP_PRI_NAT_SEQ_ADJUST,
},
/* Before packet filtering, change destination */
{
.hook = nf_nat_local_fn,
.owner = THIS_MODULE,
.pf = PF_INET,
.hooknum = NF_IP_LOCAL_OUT,
.priority = NF_IP_PRI_NAT_DST,
},
/* After packet filtering, change source */
{
.hook = nf_nat_fn,
.owner = THIS_MODULE,
.pf = PF_INET,
.hooknum = NF_IP_LOCAL_IN,
.priority = NF_IP_PRI_NAT_SRC,
},
/* After conntrack, adjust sequence number */
{
.hook = nf_nat_adjust,
.owner = THIS_MODULE,
.pf = PF_INET,
.hooknum = NF_IP_LOCAL_IN,
.priority = NF_IP_PRI_NAT_SEQ_ADJUST,
},
};
static int __init nf_nat_standalone_init(void)
{
int size, ret = 0;
need_conntrack();
size = ALIGN(sizeof(struct nf_conn), __alignof__(struct nf_conn_nat)) +
sizeof(struct nf_conn_nat);
ret = nf_conntrack_register_cache(NF_CT_F_NAT, "nf_nat:base", size);
if (ret < 0) {
printk(KERN_ERR "nf_nat_init: Unable to create slab cache\n");
return ret;
}
size = ALIGN(size, __alignof__(struct nf_conn_help)) +
sizeof(struct nf_conn_help);
ret = nf_conntrack_register_cache(NF_CT_F_NAT|NF_CT_F_HELP,
"nf_nat:help", size);
if (ret < 0) {
printk(KERN_ERR "nf_nat_init: Unable to create slab cache\n");
goto cleanup_register_cache;
}
#ifdef CONFIG_XFRM
BUG_ON(ip_nat_decode_session != NULL);
ip_nat_decode_session = nat_decode_session;
#endif
ret = nf_nat_rule_init();
if (ret < 0) {
printk("nf_nat_init: can't setup rules.\n");
goto cleanup_decode_session;
}
ret = nf_register_hooks(nf_nat_ops, ARRAY_SIZE(nf_nat_ops));
if (ret < 0) {
printk("nf_nat_init: can't register hooks.\n");
goto cleanup_rule_init;
}
nf_nat_module_is_loaded = 1;
return ret;
cleanup_rule_init:
nf_nat_rule_cleanup();
cleanup_decode_session:
#ifdef CONFIG_XFRM
ip_nat_decode_session = NULL;
synchronize_net();
#endif
nf_conntrack_unregister_cache(NF_CT_F_NAT|NF_CT_F_HELP);
cleanup_register_cache:
nf_conntrack_unregister_cache(NF_CT_F_NAT);
return ret;
}
static void __exit nf_nat_standalone_fini(void)
{
nf_unregister_hooks(nf_nat_ops, ARRAY_SIZE(nf_nat_ops));
nf_nat_rule_cleanup();
nf_nat_module_is_loaded = 0;
#ifdef CONFIG_XFRM
ip_nat_decode_session = NULL;
synchronize_net();
#endif
/* Conntrack caches are unregistered in nf_conntrack_cleanup */
}
module_init(nf_nat_standalone_init);
module_exit(nf_nat_standalone_fini);
MODULE_LICENSE("GPL");
MODULE_ALIAS("ip_nat");
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