Linux Kernel  3.7.1
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
nf_nat_l3proto_ipv4.c
Go to the documentation of this file.
1 /*
2  * (C) 1999-2001 Paul `Rusty' Russell
3  * (C) 2002-2006 Netfilter Core Team <[email protected]>
4  * (C) 2011 Patrick McHardy <[email protected]>
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  */
10 
11 #include <linux/types.h>
12 #include <linux/module.h>
13 #include <linux/skbuff.h>
14 #include <linux/ip.h>
15 #include <linux/icmp.h>
16 #include <linux/netfilter.h>
17 #include <linux/netfilter_ipv4.h>
18 #include <net/secure_seq.h>
19 #include <net/checksum.h>
20 #include <net/route.h>
21 #include <net/ip.h>
22 
23 #include <net/netfilter/nf_conntrack_core.h>
24 #include <net/netfilter/nf_conntrack.h>
25 #include <net/netfilter/nf_nat_core.h>
26 #include <net/netfilter/nf_nat_l3proto.h>
27 #include <net/netfilter/nf_nat_l4proto.h>
28 
29 static const struct nf_nat_l3proto nf_nat_l3proto_ipv4;
30 
31 #ifdef CONFIG_XFRM
32 static void nf_nat_ipv4_decode_session(struct sk_buff *skb,
33  const struct nf_conn *ct,
34  enum ip_conntrack_dir dir,
35  unsigned long statusbit,
36  struct flowi *fl)
37 {
38  const struct nf_conntrack_tuple *t = &ct->tuplehash[dir].tuple;
39  struct flowi4 *fl4 = &fl->u.ip4;
40 
41  if (ct->status & statusbit) {
42  fl4->daddr = t->dst.u3.ip;
43  if (t->dst.protonum == IPPROTO_TCP ||
44  t->dst.protonum == IPPROTO_UDP ||
45  t->dst.protonum == IPPROTO_UDPLITE ||
46  t->dst.protonum == IPPROTO_DCCP ||
47  t->dst.protonum == IPPROTO_SCTP)
48  fl4->fl4_dport = t->dst.u.all;
49  }
50 
51  statusbit ^= IPS_NAT_MASK;
52 
53  if (ct->status & statusbit) {
54  fl4->saddr = t->src.u3.ip;
55  if (t->dst.protonum == IPPROTO_TCP ||
56  t->dst.protonum == IPPROTO_UDP ||
57  t->dst.protonum == IPPROTO_UDPLITE ||
58  t->dst.protonum == IPPROTO_DCCP ||
59  t->dst.protonum == IPPROTO_SCTP)
60  fl4->fl4_sport = t->src.u.all;
61  }
62 }
63 #endif /* CONFIG_XFRM */
64 
65 static bool nf_nat_ipv4_in_range(const struct nf_conntrack_tuple *t,
66  const struct nf_nat_range *range)
67 {
68  return ntohl(t->src.u3.ip) >= ntohl(range->min_addr.ip) &&
69  ntohl(t->src.u3.ip) <= ntohl(range->max_addr.ip);
70 }
71 
72 static u32 nf_nat_ipv4_secure_port(const struct nf_conntrack_tuple *t,
73  __be16 dport)
74 {
75  return secure_ipv4_port_ephemeral(t->src.u3.ip, t->dst.u3.ip, dport);
76 }
77 
78 static bool nf_nat_ipv4_manip_pkt(struct sk_buff *skb,
79  unsigned int iphdroff,
80  const struct nf_nat_l4proto *l4proto,
81  const struct nf_conntrack_tuple *target,
82  enum nf_nat_manip_type maniptype)
83 {
84  struct iphdr *iph;
85  unsigned int hdroff;
86 
87  if (!skb_make_writable(skb, iphdroff + sizeof(*iph)))
88  return false;
89 
90  iph = (void *)skb->data + iphdroff;
91  hdroff = iphdroff + iph->ihl * 4;
92 
93  if (!l4proto->manip_pkt(skb, &nf_nat_l3proto_ipv4, iphdroff, hdroff,
94  target, maniptype))
95  return false;
96  iph = (void *)skb->data + iphdroff;
97 
98  if (maniptype == NF_NAT_MANIP_SRC) {
99  csum_replace4(&iph->check, iph->saddr, target->src.u3.ip);
100  iph->saddr = target->src.u3.ip;
101  } else {
102  csum_replace4(&iph->check, iph->daddr, target->dst.u3.ip);
103  iph->daddr = target->dst.u3.ip;
104  }
105  return true;
106 }
107 
108 static void nf_nat_ipv4_csum_update(struct sk_buff *skb,
109  unsigned int iphdroff, __sum16 *check,
110  const struct nf_conntrack_tuple *t,
111  enum nf_nat_manip_type maniptype)
112 {
113  struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
114  __be32 oldip, newip;
115 
116  if (maniptype == NF_NAT_MANIP_SRC) {
117  oldip = iph->saddr;
118  newip = t->src.u3.ip;
119  } else {
120  oldip = iph->daddr;
121  newip = t->dst.u3.ip;
122  }
123  inet_proto_csum_replace4(check, skb, oldip, newip, 1);
124 }
125 
126 static void nf_nat_ipv4_csum_recalc(struct sk_buff *skb,
127  u8 proto, void *data, __sum16 *check,
128  int datalen, int oldlen)
129 {
130  const struct iphdr *iph = ip_hdr(skb);
131  struct rtable *rt = skb_rtable(skb);
132 
133  if (skb->ip_summed != CHECKSUM_PARTIAL) {
134  if (!(rt->rt_flags & RTCF_LOCAL) &&
135  (!skb->dev || skb->dev->features & NETIF_F_V4_CSUM)) {
136  skb->ip_summed = CHECKSUM_PARTIAL;
137  skb->csum_start = skb_headroom(skb) +
138  skb_network_offset(skb) +
139  ip_hdrlen(skb);
140  skb->csum_offset = (void *)check - data;
141  *check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
142  datalen, proto, 0);
143  } else {
144  *check = 0;
145  *check = csum_tcpudp_magic(iph->saddr, iph->daddr,
146  datalen, proto,
147  csum_partial(data, datalen,
148  0));
149  if (proto == IPPROTO_UDP && !*check)
150  *check = CSUM_MANGLED_0;
151  }
152  } else
153  inet_proto_csum_replace2(check, skb,
154  htons(oldlen), htons(datalen), 1);
155 }
156 
157 static int nf_nat_ipv4_nlattr_to_range(struct nlattr *tb[],
158  struct nf_nat_range *range)
159 {
160  if (tb[CTA_NAT_V4_MINIP]) {
161  range->min_addr.ip = nla_get_be32(tb[CTA_NAT_V4_MINIP]);
162  range->flags |= NF_NAT_RANGE_MAP_IPS;
163  }
164 
165  if (tb[CTA_NAT_V4_MAXIP])
166  range->max_addr.ip = nla_get_be32(tb[CTA_NAT_V4_MAXIP]);
167  else
168  range->max_addr.ip = range->min_addr.ip;
169 
170  return 0;
171 }
172 
173 static const struct nf_nat_l3proto nf_nat_l3proto_ipv4 = {
174  .l3proto = NFPROTO_IPV4,
175  .in_range = nf_nat_ipv4_in_range,
176  .secure_port = nf_nat_ipv4_secure_port,
177  .manip_pkt = nf_nat_ipv4_manip_pkt,
178  .csum_update = nf_nat_ipv4_csum_update,
179  .csum_recalc = nf_nat_ipv4_csum_recalc,
180  .nlattr_to_range = nf_nat_ipv4_nlattr_to_range,
181 #ifdef CONFIG_XFRM
182  .decode_session = nf_nat_ipv4_decode_session,
183 #endif
184 };
185 
186 int nf_nat_icmp_reply_translation(struct sk_buff *skb,
187  struct nf_conn *ct,
188  enum ip_conntrack_info ctinfo,
189  unsigned int hooknum)
190 {
191  struct {
192  struct icmphdr icmp;
193  struct iphdr ip;
194  } *inside;
195  enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
196  enum nf_nat_manip_type manip = HOOK2MANIP(hooknum);
197  unsigned int hdrlen = ip_hdrlen(skb);
198  const struct nf_nat_l4proto *l4proto;
199  struct nf_conntrack_tuple target;
200  unsigned long statusbit;
201 
202  NF_CT_ASSERT(ctinfo == IP_CT_RELATED || ctinfo == IP_CT_RELATED_REPLY);
203 
204  if (!skb_make_writable(skb, hdrlen + sizeof(*inside)))
205  return 0;
206  if (nf_ip_checksum(skb, hooknum, hdrlen, 0))
207  return 0;
208 
209  inside = (void *)skb->data + hdrlen;
210  if (inside->icmp.type == ICMP_REDIRECT) {
211  if ((ct->status & IPS_NAT_DONE_MASK) != IPS_NAT_DONE_MASK)
212  return 0;
213  if (ct->status & IPS_NAT_MASK)
214  return 0;
215  }
216 
217  if (manip == NF_NAT_MANIP_SRC)
218  statusbit = IPS_SRC_NAT;
219  else
220  statusbit = IPS_DST_NAT;
221 
222  /* Invert if this is reply direction */
223  if (dir == IP_CT_DIR_REPLY)
224  statusbit ^= IPS_NAT_MASK;
225 
226  if (!(ct->status & statusbit))
227  return 1;
228 
229  l4proto = __nf_nat_l4proto_find(NFPROTO_IPV4, inside->ip.protocol);
230  if (!nf_nat_ipv4_manip_pkt(skb, hdrlen + sizeof(inside->icmp),
231  l4proto, &ct->tuplehash[!dir].tuple, !manip))
232  return 0;
233 
234  if (skb->ip_summed != CHECKSUM_PARTIAL) {
235  /* Reloading "inside" here since manip_pkt may reallocate */
236  inside = (void *)skb->data + hdrlen;
237  inside->icmp.checksum = 0;
238  inside->icmp.checksum =
239  csum_fold(skb_checksum(skb, hdrlen,
240  skb->len - hdrlen, 0));
241  }
242 
243  /* Change outer to look like the reply to an incoming packet */
244  nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
245  l4proto = __nf_nat_l4proto_find(NFPROTO_IPV4, 0);
246  if (!nf_nat_ipv4_manip_pkt(skb, 0, l4proto, &target, manip))
247  return 0;
248 
249  return 1;
250 }
251 EXPORT_SYMBOL_GPL(nf_nat_icmp_reply_translation);
252 
253 static int __init nf_nat_l3proto_ipv4_init(void)
254 {
255  int err;
256 
257  err = nf_nat_l4proto_register(NFPROTO_IPV4, &nf_nat_l4proto_icmp);
258  if (err < 0)
259  goto err1;
260  err = nf_nat_l3proto_register(&nf_nat_l3proto_ipv4);
261  if (err < 0)
262  goto err2;
263  return err;
264 
265 err2:
266  nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_icmp);
267 err1:
268  return err;
269 }
270 
271 static void __exit nf_nat_l3proto_ipv4_exit(void)
272 {
273  nf_nat_l3proto_unregister(&nf_nat_l3proto_ipv4);
274  nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_icmp);
275 }
276 
277 MODULE_LICENSE("GPL");
278 MODULE_ALIAS("nf-nat-" __stringify(AF_INET));
279 
280 module_init(nf_nat_l3proto_ipv4_init);
281 module_exit(nf_nat_l3proto_ipv4_exit);
Generated on Thu Jan 10 2013 14:58:42 for Linux Kernel by   doxygen 1.8.2