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Linux/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c

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  1 
  2 /* (C) 1999-2001 Paul `Rusty' Russell
  3  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
  4  * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
  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/ip.h>
 13 #include <linux/netfilter.h>
 14 #include <linux/module.h>
 15 #include <linux/skbuff.h>
 16 #include <linux/icmp.h>
 17 #include <linux/sysctl.h>
 18 #include <net/route.h>
 19 #include <net/ip.h>
 20 
 21 #include <linux/netfilter_ipv4.h>
 22 #include <net/netfilter/nf_conntrack.h>
 23 #include <net/netfilter/nf_conntrack_helper.h>
 24 #include <net/netfilter/nf_conntrack_l4proto.h>
 25 #include <net/netfilter/nf_conntrack_l3proto.h>
 26 #include <net/netfilter/nf_conntrack_zones.h>
 27 #include <net/netfilter/nf_conntrack_core.h>
 28 #include <net/netfilter/nf_conntrack_seqadj.h>
 29 #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
 30 #include <net/netfilter/nf_nat_helper.h>
 31 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
 32 #include <net/netfilter/nf_log.h>
 33 
 34 static int conntrack4_net_id __read_mostly;
 35 static DEFINE_MUTEX(register_ipv4_hooks);
 36 
 37 struct conntrack4_net {
 38         unsigned int users;
 39 };
 40 
 41 static bool ipv4_pkt_to_tuple(const struct sk_buff *skb, unsigned int nhoff,
 42                               struct nf_conntrack_tuple *tuple)
 43 {
 44         const __be32 *ap;
 45         __be32 _addrs[2];
 46         ap = skb_header_pointer(skb, nhoff + offsetof(struct iphdr, saddr),
 47                                 sizeof(u_int32_t) * 2, _addrs);
 48         if (ap == NULL)
 49                 return false;
 50 
 51         tuple->src.u3.ip = ap[0];
 52         tuple->dst.u3.ip = ap[1];
 53 
 54         return true;
 55 }
 56 
 57 static bool ipv4_invert_tuple(struct nf_conntrack_tuple *tuple,
 58                               const struct nf_conntrack_tuple *orig)
 59 {
 60         tuple->src.u3.ip = orig->dst.u3.ip;
 61         tuple->dst.u3.ip = orig->src.u3.ip;
 62 
 63         return true;
 64 }
 65 
 66 static void ipv4_print_tuple(struct seq_file *s,
 67                             const struct nf_conntrack_tuple *tuple)
 68 {
 69         seq_printf(s, "src=%pI4 dst=%pI4 ",
 70                    &tuple->src.u3.ip, &tuple->dst.u3.ip);
 71 }
 72 
 73 static int ipv4_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
 74                             unsigned int *dataoff, u_int8_t *protonum)
 75 {
 76         const struct iphdr *iph;
 77         struct iphdr _iph;
 78 
 79         iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
 80         if (iph == NULL)
 81                 return -NF_ACCEPT;
 82 
 83         /* Conntrack defragments packets, we might still see fragments
 84          * inside ICMP packets though. */
 85         if (iph->frag_off & htons(IP_OFFSET))
 86                 return -NF_ACCEPT;
 87 
 88         *dataoff = nhoff + (iph->ihl << 2);
 89         *protonum = iph->protocol;
 90 
 91         /* Check bogus IP headers */
 92         if (*dataoff > skb->len) {
 93                 pr_debug("nf_conntrack_ipv4: bogus IPv4 packet: "
 94                          "nhoff %u, ihl %u, skblen %u\n",
 95                          nhoff, iph->ihl << 2, skb->len);
 96                 return -NF_ACCEPT;
 97         }
 98 
 99         return NF_ACCEPT;
100 }
101 
102 static unsigned int ipv4_helper(void *priv,
103                                 struct sk_buff *skb,
104                                 const struct nf_hook_state *state)
105 {
106         struct nf_conn *ct;
107         enum ip_conntrack_info ctinfo;
108         const struct nf_conn_help *help;
109         const struct nf_conntrack_helper *helper;
110 
111         /* This is where we call the helper: as the packet goes out. */
112         ct = nf_ct_get(skb, &ctinfo);
113         if (!ct || ctinfo == IP_CT_RELATED_REPLY)
114                 return NF_ACCEPT;
115 
116         help = nfct_help(ct);
117         if (!help)
118                 return NF_ACCEPT;
119 
120         /* rcu_read_lock()ed by nf_hook_thresh */
121         helper = rcu_dereference(help->helper);
122         if (!helper)
123                 return NF_ACCEPT;
124 
125         return helper->help(skb, skb_network_offset(skb) + ip_hdrlen(skb),
126                             ct, ctinfo);
127 }
128 
129 static unsigned int ipv4_confirm(void *priv,
130                                  struct sk_buff *skb,
131                                  const struct nf_hook_state *state)
132 {
133         struct nf_conn *ct;
134         enum ip_conntrack_info ctinfo;
135 
136         ct = nf_ct_get(skb, &ctinfo);
137         if (!ct || ctinfo == IP_CT_RELATED_REPLY)
138                 goto out;
139 
140         /* adjust seqs for loopback traffic only in outgoing direction */
141         if (test_bit(IPS_SEQ_ADJUST_BIT, &ct->status) &&
142             !nf_is_loopback_packet(skb)) {
143                 if (!nf_ct_seq_adjust(skb, ct, ctinfo, ip_hdrlen(skb))) {
144                         NF_CT_STAT_INC_ATOMIC(nf_ct_net(ct), drop);
145                         return NF_DROP;
146                 }
147         }
148 out:
149         /* We've seen it coming out the other side: confirm it */
150         return nf_conntrack_confirm(skb);
151 }
152 
153 static unsigned int ipv4_conntrack_in(void *priv,
154                                       struct sk_buff *skb,
155                                       const struct nf_hook_state *state)
156 {
157         return nf_conntrack_in(state->net, PF_INET, state->hook, skb);
158 }
159 
160 static unsigned int ipv4_conntrack_local(void *priv,
161                                          struct sk_buff *skb,
162                                          const struct nf_hook_state *state)
163 {
164         /* root is playing with raw sockets. */
165         if (skb->len < sizeof(struct iphdr) ||
166             ip_hdrlen(skb) < sizeof(struct iphdr))
167                 return NF_ACCEPT;
168 
169         if (ip_is_fragment(ip_hdr(skb))) /* IP_NODEFRAG setsockopt set */
170                 return NF_ACCEPT;
171 
172         return nf_conntrack_in(state->net, PF_INET, state->hook, skb);
173 }
174 
175 /* Connection tracking may drop packets, but never alters them, so
176    make it the first hook. */
177 static struct nf_hook_ops ipv4_conntrack_ops[] __read_mostly = {
178         {
179                 .hook           = ipv4_conntrack_in,
180                 .pf             = NFPROTO_IPV4,
181                 .hooknum        = NF_INET_PRE_ROUTING,
182                 .priority       = NF_IP_PRI_CONNTRACK,
183         },
184         {
185                 .hook           = ipv4_conntrack_local,
186                 .pf             = NFPROTO_IPV4,
187                 .hooknum        = NF_INET_LOCAL_OUT,
188                 .priority       = NF_IP_PRI_CONNTRACK,
189         },
190         {
191                 .hook           = ipv4_helper,
192                 .pf             = NFPROTO_IPV4,
193                 .hooknum        = NF_INET_POST_ROUTING,
194                 .priority       = NF_IP_PRI_CONNTRACK_HELPER,
195         },
196         {
197                 .hook           = ipv4_confirm,
198                 .pf             = NFPROTO_IPV4,
199                 .hooknum        = NF_INET_POST_ROUTING,
200                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
201         },
202         {
203                 .hook           = ipv4_helper,
204                 .pf             = NFPROTO_IPV4,
205                 .hooknum        = NF_INET_LOCAL_IN,
206                 .priority       = NF_IP_PRI_CONNTRACK_HELPER,
207         },
208         {
209                 .hook           = ipv4_confirm,
210                 .pf             = NFPROTO_IPV4,
211                 .hooknum        = NF_INET_LOCAL_IN,
212                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
213         },
214 };
215 
216 /* Fast function for those who don't want to parse /proc (and I don't
217    blame them). */
218 /* Reversing the socket's dst/src point of view gives us the reply
219    mapping. */
220 static int
221 getorigdst(struct sock *sk, int optval, void __user *user, int *len)
222 {
223         const struct inet_sock *inet = inet_sk(sk);
224         const struct nf_conntrack_tuple_hash *h;
225         struct nf_conntrack_tuple tuple;
226 
227         memset(&tuple, 0, sizeof(tuple));
228         tuple.src.u3.ip = inet->inet_rcv_saddr;
229         tuple.src.u.tcp.port = inet->inet_sport;
230         tuple.dst.u3.ip = inet->inet_daddr;
231         tuple.dst.u.tcp.port = inet->inet_dport;
232         tuple.src.l3num = PF_INET;
233         tuple.dst.protonum = sk->sk_protocol;
234 
235         /* We only do TCP and SCTP at the moment: is there a better way? */
236         if (sk->sk_protocol != IPPROTO_TCP && sk->sk_protocol != IPPROTO_SCTP) {
237                 pr_debug("SO_ORIGINAL_DST: Not a TCP/SCTP socket\n");
238                 return -ENOPROTOOPT;
239         }
240 
241         if ((unsigned int) *len < sizeof(struct sockaddr_in)) {
242                 pr_debug("SO_ORIGINAL_DST: len %d not %zu\n",
243                          *len, sizeof(struct sockaddr_in));
244                 return -EINVAL;
245         }
246 
247         h = nf_conntrack_find_get(sock_net(sk), &nf_ct_zone_dflt, &tuple);
248         if (h) {
249                 struct sockaddr_in sin;
250                 struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
251 
252                 sin.sin_family = AF_INET;
253                 sin.sin_port = ct->tuplehash[IP_CT_DIR_ORIGINAL]
254                         .tuple.dst.u.tcp.port;
255                 sin.sin_addr.s_addr = ct->tuplehash[IP_CT_DIR_ORIGINAL]
256                         .tuple.dst.u3.ip;
257                 memset(sin.sin_zero, 0, sizeof(sin.sin_zero));
258 
259                 pr_debug("SO_ORIGINAL_DST: %pI4 %u\n",
260                          &sin.sin_addr.s_addr, ntohs(sin.sin_port));
261                 nf_ct_put(ct);
262                 if (copy_to_user(user, &sin, sizeof(sin)) != 0)
263                         return -EFAULT;
264                 else
265                         return 0;
266         }
267         pr_debug("SO_ORIGINAL_DST: Can't find %pI4/%u-%pI4/%u.\n",
268                  &tuple.src.u3.ip, ntohs(tuple.src.u.tcp.port),
269                  &tuple.dst.u3.ip, ntohs(tuple.dst.u.tcp.port));
270         return -ENOENT;
271 }
272 
273 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
274 
275 #include <linux/netfilter/nfnetlink.h>
276 #include <linux/netfilter/nfnetlink_conntrack.h>
277 
278 static int ipv4_tuple_to_nlattr(struct sk_buff *skb,
279                                 const struct nf_conntrack_tuple *tuple)
280 {
281         if (nla_put_in_addr(skb, CTA_IP_V4_SRC, tuple->src.u3.ip) ||
282             nla_put_in_addr(skb, CTA_IP_V4_DST, tuple->dst.u3.ip))
283                 goto nla_put_failure;
284         return 0;
285 
286 nla_put_failure:
287         return -1;
288 }
289 
290 static const struct nla_policy ipv4_nla_policy[CTA_IP_MAX+1] = {
291         [CTA_IP_V4_SRC] = { .type = NLA_U32 },
292         [CTA_IP_V4_DST] = { .type = NLA_U32 },
293 };
294 
295 static int ipv4_nlattr_to_tuple(struct nlattr *tb[],
296                                 struct nf_conntrack_tuple *t)
297 {
298         if (!tb[CTA_IP_V4_SRC] || !tb[CTA_IP_V4_DST])
299                 return -EINVAL;
300 
301         t->src.u3.ip = nla_get_in_addr(tb[CTA_IP_V4_SRC]);
302         t->dst.u3.ip = nla_get_in_addr(tb[CTA_IP_V4_DST]);
303 
304         return 0;
305 }
306 
307 static int ipv4_nlattr_tuple_size(void)
308 {
309         return nla_policy_len(ipv4_nla_policy, CTA_IP_MAX + 1);
310 }
311 #endif
312 
313 static struct nf_sockopt_ops so_getorigdst = {
314         .pf             = PF_INET,
315         .get_optmin     = SO_ORIGINAL_DST,
316         .get_optmax     = SO_ORIGINAL_DST+1,
317         .get            = getorigdst,
318         .owner          = THIS_MODULE,
319 };
320 
321 static int ipv4_hooks_register(struct net *net)
322 {
323         struct conntrack4_net *cnet = net_generic(net, conntrack4_net_id);
324         int err = 0;
325 
326         mutex_lock(&register_ipv4_hooks);
327 
328         cnet->users++;
329         if (cnet->users > 1)
330                 goto out_unlock;
331 
332         err = nf_defrag_ipv4_enable(net);
333         if (err) {
334                 cnet->users = 0;
335                 goto out_unlock;
336         }
337 
338         err = nf_register_net_hooks(net, ipv4_conntrack_ops,
339                                     ARRAY_SIZE(ipv4_conntrack_ops));
340 
341         if (err)
342                 cnet->users = 0;
343  out_unlock:
344         mutex_unlock(&register_ipv4_hooks);
345         return err;
346 }
347 
348 static void ipv4_hooks_unregister(struct net *net)
349 {
350         struct conntrack4_net *cnet = net_generic(net, conntrack4_net_id);
351 
352         mutex_lock(&register_ipv4_hooks);
353         if (cnet->users && (--cnet->users == 0))
354                 nf_unregister_net_hooks(net, ipv4_conntrack_ops,
355                                         ARRAY_SIZE(ipv4_conntrack_ops));
356         mutex_unlock(&register_ipv4_hooks);
357 }
358 
359 struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4 __read_mostly = {
360         .l3proto         = PF_INET,
361         .name            = "ipv4",
362         .pkt_to_tuple    = ipv4_pkt_to_tuple,
363         .invert_tuple    = ipv4_invert_tuple,
364         .print_tuple     = ipv4_print_tuple,
365         .get_l4proto     = ipv4_get_l4proto,
366 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
367         .tuple_to_nlattr = ipv4_tuple_to_nlattr,
368         .nlattr_tuple_size = ipv4_nlattr_tuple_size,
369         .nlattr_to_tuple = ipv4_nlattr_to_tuple,
370         .nla_policy      = ipv4_nla_policy,
371 #endif
372         .net_ns_get      = ipv4_hooks_register,
373         .net_ns_put      = ipv4_hooks_unregister,
374         .me              = THIS_MODULE,
375 };
376 
377 module_param_call(hashsize, nf_conntrack_set_hashsize, param_get_uint,
378                   &nf_conntrack_htable_size, 0600);
379 
380 MODULE_ALIAS("nf_conntrack-" __stringify(AF_INET));
381 MODULE_ALIAS("ip_conntrack");
382 MODULE_LICENSE("GPL");
383 
384 static struct nf_conntrack_l4proto *builtin_l4proto4[] = {
385         &nf_conntrack_l4proto_tcp4,
386         &nf_conntrack_l4proto_udp4,
387         &nf_conntrack_l4proto_icmp,
388 #ifdef CONFIG_NF_CT_PROTO_DCCP
389         &nf_conntrack_l4proto_dccp4,
390 #endif
391 #ifdef CONFIG_NF_CT_PROTO_SCTP
392         &nf_conntrack_l4proto_sctp4,
393 #endif
394 #ifdef CONFIG_NF_CT_PROTO_UDPLITE
395         &nf_conntrack_l4proto_udplite4,
396 #endif
397 };
398 
399 static int ipv4_net_init(struct net *net)
400 {
401         int ret = 0;
402 
403         ret = nf_ct_l4proto_pernet_register(net, builtin_l4proto4,
404                                             ARRAY_SIZE(builtin_l4proto4));
405         if (ret < 0)
406                 return ret;
407         ret = nf_ct_l3proto_pernet_register(net, &nf_conntrack_l3proto_ipv4);
408         if (ret < 0) {
409                 pr_err("nf_conntrack_ipv4: pernet registration failed\n");
410                 nf_ct_l4proto_pernet_unregister(net, builtin_l4proto4,
411                                                 ARRAY_SIZE(builtin_l4proto4));
412         }
413         return ret;
414 }
415 
416 static void ipv4_net_exit(struct net *net)
417 {
418         nf_ct_l3proto_pernet_unregister(net, &nf_conntrack_l3proto_ipv4);
419         nf_ct_l4proto_pernet_unregister(net, builtin_l4proto4,
420                                         ARRAY_SIZE(builtin_l4proto4));
421 }
422 
423 static struct pernet_operations ipv4_net_ops = {
424         .init = ipv4_net_init,
425         .exit = ipv4_net_exit,
426         .id = &conntrack4_net_id,
427         .size = sizeof(struct conntrack4_net),
428 };
429 
430 static int __init nf_conntrack_l3proto_ipv4_init(void)
431 {
432         int ret = 0;
433 
434         need_conntrack();
435 
436         ret = nf_register_sockopt(&so_getorigdst);
437         if (ret < 0) {
438                 pr_err("Unable to register netfilter socket option\n");
439                 return ret;
440         }
441 
442         ret = register_pernet_subsys(&ipv4_net_ops);
443         if (ret < 0) {
444                 pr_err("nf_conntrack_ipv4: can't register pernet ops\n");
445                 goto cleanup_sockopt;
446         }
447 
448         ret = nf_ct_l4proto_register(builtin_l4proto4,
449                                      ARRAY_SIZE(builtin_l4proto4));
450         if (ret < 0)
451                 goto cleanup_pernet;
452 
453         ret = nf_ct_l3proto_register(&nf_conntrack_l3proto_ipv4);
454         if (ret < 0) {
455                 pr_err("nf_conntrack_ipv4: can't register ipv4 proto.\n");
456                 goto cleanup_l4proto;
457         }
458 
459         return ret;
460 cleanup_l4proto:
461         nf_ct_l4proto_unregister(builtin_l4proto4,
462                                  ARRAY_SIZE(builtin_l4proto4));
463  cleanup_pernet:
464         unregister_pernet_subsys(&ipv4_net_ops);
465  cleanup_sockopt:
466         nf_unregister_sockopt(&so_getorigdst);
467         return ret;
468 }
469 
470 static void __exit nf_conntrack_l3proto_ipv4_fini(void)
471 {
472         synchronize_net();
473         nf_ct_l3proto_unregister(&nf_conntrack_l3proto_ipv4);
474         nf_ct_l4proto_unregister(builtin_l4proto4,
475                                  ARRAY_SIZE(builtin_l4proto4));
476         unregister_pernet_subsys(&ipv4_net_ops);
477         nf_unregister_sockopt(&so_getorigdst);
478 }
479 
480 module_init(nf_conntrack_l3proto_ipv4_init);
481 module_exit(nf_conntrack_l3proto_ipv4_fini);
482 

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