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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * INET An implementation of the TCP/IP protocol suite for the LINUX
4 * operating system. INET is implemented using the BSD Socket
5 * interface as the means of communication with the user level.
6 *
7 * The Internet Protocol (IP) module.
8 *
9 * Authors: Ross Biro
10 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
11 * Donald Becker, <becker@super.org>
12 * Alan Cox, <alan@lxorguk.ukuu.org.uk>
13 * Richard Underwood
14 * Stefan Becker, <stefanb@yello.ping.de>
15 * Jorge Cwik, <jorge@laser.satlink.net>
16 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
17 *
18 * Fixes:
19 * Alan Cox : Commented a couple of minor bits of surplus code
20 * Alan Cox : Undefining IP_FORWARD doesn't include the code
21 * (just stops a compiler warning).
22 * Alan Cox : Frames with >=MAX_ROUTE record routes, strict routes or loose routes
23 * are junked rather than corrupting things.
24 * Alan Cox : Frames to bad broadcast subnets are dumped
25 * We used to process them non broadcast and
26 * boy could that cause havoc.
27 * Alan Cox : ip_forward sets the free flag on the
28 * new frame it queues. Still crap because
29 * it copies the frame but at least it
30 * doesn't eat memory too.
31 * Alan Cox : Generic queue code and memory fixes.
32 * Fred Van Kempen : IP fragment support (borrowed from NET2E)
33 * Gerhard Koerting: Forward fragmented frames correctly.
34 * Gerhard Koerting: Fixes to my fix of the above 8-).
35 * Gerhard Koerting: IP interface addressing fix.
36 * Linus Torvalds : More robustness checks
37 * Alan Cox : Even more checks: Still not as robust as it ought to be
38 * Alan Cox : Save IP header pointer for later
39 * Alan Cox : ip option setting
40 * Alan Cox : Use ip_tos/ip_ttl settings
41 * Alan Cox : Fragmentation bogosity removed
42 * (Thanks to Mark.Bush@prg.ox.ac.uk)
43 * Dmitry Gorodchanin : Send of a raw packet crash fix.
44 * Alan Cox : Silly ip bug when an overlength
45 * fragment turns up. Now frees the
46 * queue.
47 * Linus Torvalds/ : Memory leakage on fragmentation
48 * Alan Cox : handling.
49 * Gerhard Koerting: Forwarding uses IP priority hints
50 * Teemu Rantanen : Fragment problems.
51 * Alan Cox : General cleanup, comments and reformat
52 * Alan Cox : SNMP statistics
53 * Alan Cox : BSD address rule semantics. Also see
54 * UDP as there is a nasty checksum issue
55 * if you do things the wrong way.
56 * Alan Cox : Always defrag, moved IP_FORWARD to the config.in file
57 * Alan Cox : IP options adjust sk->priority.
58 * Pedro Roque : Fix mtu/length error in ip_forward.
59 * Alan Cox : Avoid ip_chk_addr when possible.
60 * Richard Underwood : IP multicasting.
61 * Alan Cox : Cleaned up multicast handlers.
62 * Alan Cox : RAW sockets demultiplex in the BSD style.
63 * Gunther Mayer : Fix the SNMP reporting typo
64 * Alan Cox : Always in group 224.0.0.1
65 * Pauline Middelink : Fast ip_checksum update when forwarding
66 * Masquerading support.
67 * Alan Cox : Multicast loopback error for 224.0.0.1
68 * Alan Cox : IP_MULTICAST_LOOP option.
69 * Alan Cox : Use notifiers.
70 * Bjorn Ekwall : Removed ip_csum (from slhc.c too)
71 * Bjorn Ekwall : Moved ip_fast_csum to ip.h (inline!)
72 * Stefan Becker : Send out ICMP HOST REDIRECT
73 * Arnt Gulbrandsen : ip_build_xmit
74 * Alan Cox : Per socket routing cache
75 * Alan Cox : Fixed routing cache, added header cache.
76 * Alan Cox : Loopback didn't work right in original ip_build_xmit - fixed it.
77 * Alan Cox : Only send ICMP_REDIRECT if src/dest are the same net.
78 * Alan Cox : Incoming IP option handling.
79 * Alan Cox : Set saddr on raw output frames as per BSD.
80 * Alan Cox : Stopped broadcast source route explosions.
81 * Alan Cox : Can disable source routing
82 * Takeshi Sone : Masquerading didn't work.
83 * Dave Bonn,Alan Cox : Faster IP forwarding whenever possible.
84 * Alan Cox : Memory leaks, tramples, misc debugging.
85 * Alan Cox : Fixed multicast (by popular demand 8))
86 * Alan Cox : Fixed forwarding (by even more popular demand 8))
87 * Alan Cox : Fixed SNMP statistics [I think]
88 * Gerhard Koerting : IP fragmentation forwarding fix
89 * Alan Cox : Device lock against page fault.
90 * Alan Cox : IP_HDRINCL facility.
91 * Werner Almesberger : Zero fragment bug
92 * Alan Cox : RAW IP frame length bug
93 * Alan Cox : Outgoing firewall on build_xmit
94 * A.N.Kuznetsov : IP_OPTIONS support throughout the kernel
95 * Alan Cox : Multicast routing hooks
96 * Jos Vos : Do accounting *before* call_in_firewall
97 * Willy Konynenberg : Transparent proxying support
98 *
99 * To Fix:
100 * IP fragmentation wants rewriting cleanly. The RFC815 algorithm is much more efficient
101 * and could be made very efficient with the addition of some virtual memory hacks to permit
102 * the allocation of a buffer that can then be 'grown' by twiddling page tables.
103 * Output fragmentation wants updating along with the buffer management to use a single
104 * interleaved copy algorithm so that fragmenting has a one copy overhead. Actual packet
105 * output should probably do its own fragmentation at the UDP/RAW layer. TCP shouldn't cause
106 * fragmentation anyway.
107 */
108
109#define pr_fmt(fmt) "IPv4: " fmt
110
111#include <linux/module.h>
112#include <linux/types.h>
113#include <linux/kernel.h>
114#include <linux/string.h>
115#include <linux/errno.h>
116#include <linux/slab.h>
117
118#include <linux/net.h>
119#include <linux/socket.h>
120#include <linux/sockios.h>
121#include <linux/in.h>
122#include <linux/inet.h>
123#include <linux/inetdevice.h>
124#include <linux/netdevice.h>
125#include <linux/etherdevice.h>
126#include <linux/indirect_call_wrapper.h>
127
128#include <net/snmp.h>
129#include <net/ip.h>
130#include <net/protocol.h>
131#include <net/route.h>
132#include <linux/skbuff.h>
133#include <net/sock.h>
134#include <net/arp.h>
135#include <net/icmp.h>
136#include <net/raw.h>
137#include <net/checksum.h>
138#include <net/inet_ecn.h>
139#include <linux/netfilter_ipv4.h>
140#include <net/xfrm.h>
141#include <linux/mroute.h>
142#include <linux/netlink.h>
143#include <net/dst_metadata.h>
144
145/*
146 * Process Router Attention IP option (RFC 2113)
147 */
148bool ip_call_ra_chain(struct sk_buff *skb)
149{
150 struct ip_ra_chain *ra;
151 u8 protocol = ip_hdr(skb)->protocol;
152 struct sock *last = NULL;
153 struct net_device *dev = skb->dev;
154 struct net *net = dev_net(dev);
155
156 for (ra = rcu_dereference(net->ipv4.ra_chain); ra; ra = rcu_dereference(ra->next)) {
157 struct sock *sk = ra->sk;
158
159 /* If socket is bound to an interface, only report
160 * the packet if it came from that interface.
161 */
162 if (sk && inet_sk(sk)->inet_num == protocol &&
163 (!sk->sk_bound_dev_if ||
164 sk->sk_bound_dev_if == dev->ifindex)) {
165 if (ip_is_fragment(ip_hdr(skb))) {
166 if (ip_defrag(net, skb, IP_DEFRAG_CALL_RA_CHAIN))
167 return true;
168 }
169 if (last) {
170 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
171 if (skb2)
172 raw_rcv(last, skb2);
173 }
174 last = sk;
175 }
176 }
177
178 if (last) {
179 raw_rcv(last, skb);
180 return true;
181 }
182 return false;
183}
184
185INDIRECT_CALLABLE_DECLARE(int udp_rcv(struct sk_buff *));
186INDIRECT_CALLABLE_DECLARE(int tcp_v4_rcv(struct sk_buff *));
187void ip_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int protocol)
188{
189 const struct net_protocol *ipprot;
190 int raw, ret;
191
192resubmit:
193 raw = raw_local_deliver(skb, protocol);
194
195 ipprot = rcu_dereference(inet_protos[protocol]);
196 if (ipprot) {
197 if (!ipprot->no_policy) {
198 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
199 kfree_skb_reason(skb,
200 SKB_DROP_REASON_XFRM_POLICY);
201 return;
202 }
203 nf_reset_ct(skb);
204 }
205 ret = INDIRECT_CALL_2(ipprot->handler, tcp_v4_rcv, udp_rcv,
206 skb);
207 if (ret < 0) {
208 protocol = -ret;
209 goto resubmit;
210 }
211 __IP_INC_STATS(net, IPSTATS_MIB_INDELIVERS);
212 } else {
213 if (!raw) {
214 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
215 __IP_INC_STATS(net, IPSTATS_MIB_INUNKNOWNPROTOS);
216 icmp_send(skb, ICMP_DEST_UNREACH,
217 ICMP_PROT_UNREACH, 0);
218 }
219 kfree_skb_reason(skb, SKB_DROP_REASON_IP_NOPROTO);
220 } else {
221 __IP_INC_STATS(net, IPSTATS_MIB_INDELIVERS);
222 consume_skb(skb);
223 }
224 }
225}
226
227static int ip_local_deliver_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
228{
229 skb_clear_delivery_time(skb);
230 __skb_pull(skb, skb_network_header_len(skb));
231
232 rcu_read_lock();
233 ip_protocol_deliver_rcu(net, skb, ip_hdr(skb)->protocol);
234 rcu_read_unlock();
235
236 return 0;
237}
238
239/*
240 * Deliver IP Packets to the higher protocol layers.
241 */
242int ip_local_deliver(struct sk_buff *skb)
243{
244 /*
245 * Reassemble IP fragments.
246 */
247 struct net *net = dev_net(skb->dev);
248
249 if (ip_is_fragment(ip_hdr(skb))) {
250 if (ip_defrag(net, skb, IP_DEFRAG_LOCAL_DELIVER))
251 return 0;
252 }
253
254 return NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_IN,
255 net, NULL, skb, skb->dev, NULL,
256 ip_local_deliver_finish);
257}
258EXPORT_SYMBOL(ip_local_deliver);
259
260static inline bool ip_rcv_options(struct sk_buff *skb, struct net_device *dev)
261{
262 struct ip_options *opt;
263 const struct iphdr *iph;
264
265 /* It looks as overkill, because not all
266 IP options require packet mangling.
267 But it is the easiest for now, especially taking
268 into account that combination of IP options
269 and running sniffer is extremely rare condition.
270 --ANK (980813)
271 */
272 if (skb_cow(skb, skb_headroom(skb))) {
273 __IP_INC_STATS(dev_net(dev), IPSTATS_MIB_INDISCARDS);
274 goto drop;
275 }
276
277 iph = ip_hdr(skb);
278 opt = &(IPCB(skb)->opt);
279 opt->optlen = iph->ihl*4 - sizeof(struct iphdr);
280
281 if (ip_options_compile(dev_net(dev), opt, skb)) {
282 __IP_INC_STATS(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
283 goto drop;
284 }
285
286 if (unlikely(opt->srr)) {
287 struct in_device *in_dev = __in_dev_get_rcu(dev);
288
289 if (in_dev) {
290 if (!IN_DEV_SOURCE_ROUTE(in_dev)) {
291 if (IN_DEV_LOG_MARTIANS(in_dev))
292 net_info_ratelimited("source route option %pI4 -> %pI4\n",
293 &iph->saddr,
294 &iph->daddr);
295 goto drop;
296 }
297 }
298
299 if (ip_options_rcv_srr(skb, dev))
300 goto drop;
301 }
302
303 return false;
304drop:
305 return true;
306}
307
308static bool ip_can_use_hint(const struct sk_buff *skb, const struct iphdr *iph,
309 const struct sk_buff *hint)
310{
311 return hint && !skb_dst(skb) && ip_hdr(hint)->daddr == iph->daddr &&
312 ip_hdr(hint)->tos == iph->tos;
313}
314
315int tcp_v4_early_demux(struct sk_buff *skb);
316int udp_v4_early_demux(struct sk_buff *skb);
317static int ip_rcv_finish_core(struct net *net, struct sock *sk,
318 struct sk_buff *skb, struct net_device *dev,
319 const struct sk_buff *hint)
320{
321 const struct iphdr *iph = ip_hdr(skb);
322 int err, drop_reason;
323 struct rtable *rt;
324
325 if (ip_can_use_hint(skb, iph, hint)) {
326 drop_reason = ip_route_use_hint(skb, iph->daddr, iph->saddr,
327 ip4h_dscp(iph), dev, hint);
328 if (unlikely(drop_reason))
329 goto drop_error;
330 }
331
332 drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
333 if (READ_ONCE(net->ipv4.sysctl_ip_early_demux) &&
334 !skb_dst(skb) &&
335 !skb->sk &&
336 !ip_is_fragment(iph)) {
337 switch (iph->protocol) {
338 case IPPROTO_TCP:
339 if (READ_ONCE(net->ipv4.sysctl_tcp_early_demux)) {
340 tcp_v4_early_demux(skb);
341
342 /* must reload iph, skb->head might have changed */
343 iph = ip_hdr(skb);
344 }
345 break;
346 case IPPROTO_UDP:
347 if (READ_ONCE(net->ipv4.sysctl_udp_early_demux)) {
348 err = udp_v4_early_demux(skb);
349 if (unlikely(err))
350 goto drop_error;
351
352 /* must reload iph, skb->head might have changed */
353 iph = ip_hdr(skb);
354 }
355 break;
356 }
357 }
358
359 /*
360 * Initialise the virtual path cache for the packet. It describes
361 * how the packet travels inside Linux networking.
362 */
363 if (!skb_valid_dst(skb)) {
364 drop_reason = ip_route_input_noref(skb, iph->daddr, iph->saddr,
365 ip4h_dscp(iph), dev);
366 if (unlikely(drop_reason))
367 goto drop_error;
368 drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
369 } else {
370 struct in_device *in_dev = __in_dev_get_rcu(dev);
371
372 if (in_dev && IN_DEV_ORCONF(in_dev, NOPOLICY))
373 IPCB(skb)->flags |= IPSKB_NOPOLICY;
374 }
375
376#ifdef CONFIG_IP_ROUTE_CLASSID
377 if (unlikely(skb_dst(skb)->tclassid)) {
378 struct ip_rt_acct *st = this_cpu_ptr(ip_rt_acct);
379 u32 idx = skb_dst(skb)->tclassid;
380 st[idx&0xFF].o_packets++;
381 st[idx&0xFF].o_bytes += skb->len;
382 st[(idx>>16)&0xFF].i_packets++;
383 st[(idx>>16)&0xFF].i_bytes += skb->len;
384 }
385#endif
386
387 if (iph->ihl > 5 && ip_rcv_options(skb, dev))
388 goto drop;
389
390 rt = skb_rtable(skb);
391 if (rt->rt_type == RTN_MULTICAST) {
392 __IP_UPD_PO_STATS(net, IPSTATS_MIB_INMCAST, skb->len);
393 } else if (rt->rt_type == RTN_BROADCAST) {
394 __IP_UPD_PO_STATS(net, IPSTATS_MIB_INBCAST, skb->len);
395 } else if (skb->pkt_type == PACKET_BROADCAST ||
396 skb->pkt_type == PACKET_MULTICAST) {
397 struct in_device *in_dev = __in_dev_get_rcu(dev);
398
399 /* RFC 1122 3.3.6:
400 *
401 * When a host sends a datagram to a link-layer broadcast
402 * address, the IP destination address MUST be a legal IP
403 * broadcast or IP multicast address.
404 *
405 * A host SHOULD silently discard a datagram that is received
406 * via a link-layer broadcast (see Section 2.4) but does not
407 * specify an IP multicast or broadcast destination address.
408 *
409 * This doesn't explicitly say L2 *broadcast*, but broadcast is
410 * in a way a form of multicast and the most common use case for
411 * this is 802.11 protecting against cross-station spoofing (the
412 * so-called "hole-196" attack) so do it for both.
413 */
414 if (in_dev &&
415 IN_DEV_ORCONF(in_dev, DROP_UNICAST_IN_L2_MULTICAST)) {
416 drop_reason = SKB_DROP_REASON_UNICAST_IN_L2_MULTICAST;
417 goto drop;
418 }
419 }
420
421 return NET_RX_SUCCESS;
422
423drop:
424 kfree_skb_reason(skb, drop_reason);
425 return NET_RX_DROP;
426
427drop_error:
428 if (drop_reason == SKB_DROP_REASON_IP_RPFILTER)
429 __NET_INC_STATS(net, LINUX_MIB_IPRPFILTER);
430 goto drop;
431}
432
433static int ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
434{
435 struct net_device *dev = skb->dev;
436 int ret;
437
438 /* if ingress device is enslaved to an L3 master device pass the
439 * skb to its handler for processing
440 */
441 skb = l3mdev_ip_rcv(skb);
442 if (!skb)
443 return NET_RX_SUCCESS;
444
445 ret = ip_rcv_finish_core(net, sk, skb, dev, NULL);
446 if (ret != NET_RX_DROP)
447 ret = dst_input(skb);
448 return ret;
449}
450
451/*
452 * Main IP Receive routine.
453 */
454static struct sk_buff *ip_rcv_core(struct sk_buff *skb, struct net *net)
455{
456 const struct iphdr *iph;
457 int drop_reason;
458 u32 len;
459
460 /* When the interface is in promisc. mode, drop all the crap
461 * that it receives, do not try to analyse it.
462 */
463 if (skb->pkt_type == PACKET_OTHERHOST) {
464 dev_core_stats_rx_otherhost_dropped_inc(skb->dev);
465 drop_reason = SKB_DROP_REASON_OTHERHOST;
466 goto drop;
467 }
468
469 __IP_UPD_PO_STATS(net, IPSTATS_MIB_IN, skb->len);
470
471 skb = skb_share_check(skb, GFP_ATOMIC);
472 if (!skb) {
473 __IP_INC_STATS(net, IPSTATS_MIB_INDISCARDS);
474 goto out;
475 }
476
477 drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
478 if (!pskb_may_pull(skb, sizeof(struct iphdr)))
479 goto inhdr_error;
480
481 iph = ip_hdr(skb);
482
483 /*
484 * RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum.
485 *
486 * Is the datagram acceptable?
487 *
488 * 1. Length at least the size of an ip header
489 * 2. Version of 4
490 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums]
491 * 4. Doesn't have a bogus length
492 */
493
494 if (iph->ihl < 5 || iph->version != 4)
495 goto inhdr_error;
496
497 BUILD_BUG_ON(IPSTATS_MIB_ECT1PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_1);
498 BUILD_BUG_ON(IPSTATS_MIB_ECT0PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_0);
499 BUILD_BUG_ON(IPSTATS_MIB_CEPKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_CE);
500 __IP_ADD_STATS(net,
501 IPSTATS_MIB_NOECTPKTS + (iph->tos & INET_ECN_MASK),
502 max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));
503
504 if (!pskb_may_pull(skb, iph->ihl*4))
505 goto inhdr_error;
506
507 iph = ip_hdr(skb);
508
509 if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
510 goto csum_error;
511
512 len = iph_totlen(skb, iph);
513 if (skb->len < len) {
514 drop_reason = SKB_DROP_REASON_PKT_TOO_SMALL;
515 __IP_INC_STATS(net, IPSTATS_MIB_INTRUNCATEDPKTS);
516 goto drop;
517 } else if (len < (iph->ihl*4))
518 goto inhdr_error;
519
520 /* Our transport medium may have padded the buffer out. Now we know it
521 * is IP we can trim to the true length of the frame.
522 * Note this now means skb->len holds ntohs(iph->tot_len).
523 */
524 if (pskb_trim_rcsum(skb, len)) {
525 __IP_INC_STATS(net, IPSTATS_MIB_INDISCARDS);
526 goto drop;
527 }
528
529 iph = ip_hdr(skb);
530 skb->transport_header = skb->network_header + iph->ihl*4;
531
532 /* Remove any debris in the socket control block */
533 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
534 IPCB(skb)->iif = skb->skb_iif;
535
536 /* Must drop socket now because of tproxy. */
537 if (!skb_sk_is_prefetched(skb))
538 skb_orphan(skb);
539
540 return skb;
541
542csum_error:
543 drop_reason = SKB_DROP_REASON_IP_CSUM;
544 __IP_INC_STATS(net, IPSTATS_MIB_CSUMERRORS);
545inhdr_error:
546 if (drop_reason == SKB_DROP_REASON_NOT_SPECIFIED)
547 drop_reason = SKB_DROP_REASON_IP_INHDR;
548 __IP_INC_STATS(net, IPSTATS_MIB_INHDRERRORS);
549drop:
550 kfree_skb_reason(skb, drop_reason);
551out:
552 return NULL;
553}
554
555/*
556 * IP receive entry point
557 */
558int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
559 struct net_device *orig_dev)
560{
561 struct net *net = dev_net(dev);
562
563 skb = ip_rcv_core(skb, net);
564 if (skb == NULL)
565 return NET_RX_DROP;
566
567 return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,
568 net, NULL, skb, dev, NULL,
569 ip_rcv_finish);
570}
571
572static void ip_sublist_rcv_finish(struct list_head *head)
573{
574 struct sk_buff *skb, *next;
575
576 list_for_each_entry_safe(skb, next, head, list) {
577 skb_list_del_init(skb);
578 dst_input(skb);
579 }
580}
581
582static struct sk_buff *ip_extract_route_hint(const struct net *net,
583 struct sk_buff *skb, int rt_type)
584{
585 if (fib4_has_custom_rules(net) || rt_type == RTN_BROADCAST ||
586 IPCB(skb)->flags & IPSKB_MULTIPATH)
587 return NULL;
588
589 return skb;
590}
591
592static void ip_list_rcv_finish(struct net *net, struct sock *sk,
593 struct list_head *head)
594{
595 struct sk_buff *skb, *next, *hint = NULL;
596 struct dst_entry *curr_dst = NULL;
597 LIST_HEAD(sublist);
598
599 list_for_each_entry_safe(skb, next, head, list) {
600 struct net_device *dev = skb->dev;
601 struct dst_entry *dst;
602
603 skb_list_del_init(skb);
604 /* if ingress device is enslaved to an L3 master device pass the
605 * skb to its handler for processing
606 */
607 skb = l3mdev_ip_rcv(skb);
608 if (!skb)
609 continue;
610 if (ip_rcv_finish_core(net, sk, skb, dev, hint) == NET_RX_DROP)
611 continue;
612
613 dst = skb_dst(skb);
614 if (curr_dst != dst) {
615 hint = ip_extract_route_hint(net, skb,
616 dst_rtable(dst)->rt_type);
617
618 /* dispatch old sublist */
619 if (!list_empty(&sublist))
620 ip_sublist_rcv_finish(&sublist);
621 /* start new sublist */
622 INIT_LIST_HEAD(&sublist);
623 curr_dst = dst;
624 }
625 list_add_tail(&skb->list, &sublist);
626 }
627 /* dispatch final sublist */
628 ip_sublist_rcv_finish(&sublist);
629}
630
631static void ip_sublist_rcv(struct list_head *head, struct net_device *dev,
632 struct net *net)
633{
634 NF_HOOK_LIST(NFPROTO_IPV4, NF_INET_PRE_ROUTING, net, NULL,
635 head, dev, NULL, ip_rcv_finish);
636 ip_list_rcv_finish(net, NULL, head);
637}
638
639/* Receive a list of IP packets */
640void ip_list_rcv(struct list_head *head, struct packet_type *pt,
641 struct net_device *orig_dev)
642{
643 struct net_device *curr_dev = NULL;
644 struct net *curr_net = NULL;
645 struct sk_buff *skb, *next;
646 LIST_HEAD(sublist);
647
648 list_for_each_entry_safe(skb, next, head, list) {
649 struct net_device *dev = skb->dev;
650 struct net *net = dev_net(dev);
651
652 skb_list_del_init(skb);
653 skb = ip_rcv_core(skb, net);
654 if (skb == NULL)
655 continue;
656
657 if (curr_dev != dev || curr_net != net) {
658 /* dispatch old sublist */
659 if (!list_empty(&sublist))
660 ip_sublist_rcv(&sublist, curr_dev, curr_net);
661 /* start new sublist */
662 INIT_LIST_HEAD(&sublist);
663 curr_dev = dev;
664 curr_net = net;
665 }
666 list_add_tail(&skb->list, &sublist);
667 }
668 /* dispatch final sublist */
669 if (!list_empty(&sublist))
670 ip_sublist_rcv(&sublist, curr_dev, curr_net);
671}
1/*
2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
5 *
6 * The Internet Protocol (IP) module.
7 *
8 * Authors: Ross Biro
9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10 * Donald Becker, <becker@super.org>
11 * Alan Cox, <alan@lxorguk.ukuu.org.uk>
12 * Richard Underwood
13 * Stefan Becker, <stefanb@yello.ping.de>
14 * Jorge Cwik, <jorge@laser.satlink.net>
15 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
16 *
17 *
18 * Fixes:
19 * Alan Cox : Commented a couple of minor bits of surplus code
20 * Alan Cox : Undefining IP_FORWARD doesn't include the code
21 * (just stops a compiler warning).
22 * Alan Cox : Frames with >=MAX_ROUTE record routes, strict routes or loose routes
23 * are junked rather than corrupting things.
24 * Alan Cox : Frames to bad broadcast subnets are dumped
25 * We used to process them non broadcast and
26 * boy could that cause havoc.
27 * Alan Cox : ip_forward sets the free flag on the
28 * new frame it queues. Still crap because
29 * it copies the frame but at least it
30 * doesn't eat memory too.
31 * Alan Cox : Generic queue code and memory fixes.
32 * Fred Van Kempen : IP fragment support (borrowed from NET2E)
33 * Gerhard Koerting: Forward fragmented frames correctly.
34 * Gerhard Koerting: Fixes to my fix of the above 8-).
35 * Gerhard Koerting: IP interface addressing fix.
36 * Linus Torvalds : More robustness checks
37 * Alan Cox : Even more checks: Still not as robust as it ought to be
38 * Alan Cox : Save IP header pointer for later
39 * Alan Cox : ip option setting
40 * Alan Cox : Use ip_tos/ip_ttl settings
41 * Alan Cox : Fragmentation bogosity removed
42 * (Thanks to Mark.Bush@prg.ox.ac.uk)
43 * Dmitry Gorodchanin : Send of a raw packet crash fix.
44 * Alan Cox : Silly ip bug when an overlength
45 * fragment turns up. Now frees the
46 * queue.
47 * Linus Torvalds/ : Memory leakage on fragmentation
48 * Alan Cox : handling.
49 * Gerhard Koerting: Forwarding uses IP priority hints
50 * Teemu Rantanen : Fragment problems.
51 * Alan Cox : General cleanup, comments and reformat
52 * Alan Cox : SNMP statistics
53 * Alan Cox : BSD address rule semantics. Also see
54 * UDP as there is a nasty checksum issue
55 * if you do things the wrong way.
56 * Alan Cox : Always defrag, moved IP_FORWARD to the config.in file
57 * Alan Cox : IP options adjust sk->priority.
58 * Pedro Roque : Fix mtu/length error in ip_forward.
59 * Alan Cox : Avoid ip_chk_addr when possible.
60 * Richard Underwood : IP multicasting.
61 * Alan Cox : Cleaned up multicast handlers.
62 * Alan Cox : RAW sockets demultiplex in the BSD style.
63 * Gunther Mayer : Fix the SNMP reporting typo
64 * Alan Cox : Always in group 224.0.0.1
65 * Pauline Middelink : Fast ip_checksum update when forwarding
66 * Masquerading support.
67 * Alan Cox : Multicast loopback error for 224.0.0.1
68 * Alan Cox : IP_MULTICAST_LOOP option.
69 * Alan Cox : Use notifiers.
70 * Bjorn Ekwall : Removed ip_csum (from slhc.c too)
71 * Bjorn Ekwall : Moved ip_fast_csum to ip.h (inline!)
72 * Stefan Becker : Send out ICMP HOST REDIRECT
73 * Arnt Gulbrandsen : ip_build_xmit
74 * Alan Cox : Per socket routing cache
75 * Alan Cox : Fixed routing cache, added header cache.
76 * Alan Cox : Loopback didn't work right in original ip_build_xmit - fixed it.
77 * Alan Cox : Only send ICMP_REDIRECT if src/dest are the same net.
78 * Alan Cox : Incoming IP option handling.
79 * Alan Cox : Set saddr on raw output frames as per BSD.
80 * Alan Cox : Stopped broadcast source route explosions.
81 * Alan Cox : Can disable source routing
82 * Takeshi Sone : Masquerading didn't work.
83 * Dave Bonn,Alan Cox : Faster IP forwarding whenever possible.
84 * Alan Cox : Memory leaks, tramples, misc debugging.
85 * Alan Cox : Fixed multicast (by popular demand 8))
86 * Alan Cox : Fixed forwarding (by even more popular demand 8))
87 * Alan Cox : Fixed SNMP statistics [I think]
88 * Gerhard Koerting : IP fragmentation forwarding fix
89 * Alan Cox : Device lock against page fault.
90 * Alan Cox : IP_HDRINCL facility.
91 * Werner Almesberger : Zero fragment bug
92 * Alan Cox : RAW IP frame length bug
93 * Alan Cox : Outgoing firewall on build_xmit
94 * A.N.Kuznetsov : IP_OPTIONS support throughout the kernel
95 * Alan Cox : Multicast routing hooks
96 * Jos Vos : Do accounting *before* call_in_firewall
97 * Willy Konynenberg : Transparent proxying support
98 *
99 *
100 *
101 * To Fix:
102 * IP fragmentation wants rewriting cleanly. The RFC815 algorithm is much more efficient
103 * and could be made very efficient with the addition of some virtual memory hacks to permit
104 * the allocation of a buffer that can then be 'grown' by twiddling page tables.
105 * Output fragmentation wants updating along with the buffer management to use a single
106 * interleaved copy algorithm so that fragmenting has a one copy overhead. Actual packet
107 * output should probably do its own fragmentation at the UDP/RAW layer. TCP shouldn't cause
108 * fragmentation anyway.
109 *
110 * This program is free software; you can redistribute it and/or
111 * modify it under the terms of the GNU General Public License
112 * as published by the Free Software Foundation; either version
113 * 2 of the License, or (at your option) any later version.
114 */
115
116#define pr_fmt(fmt) "IPv4: " fmt
117
118#include <linux/module.h>
119#include <linux/types.h>
120#include <linux/kernel.h>
121#include <linux/string.h>
122#include <linux/errno.h>
123#include <linux/slab.h>
124
125#include <linux/net.h>
126#include <linux/socket.h>
127#include <linux/sockios.h>
128#include <linux/in.h>
129#include <linux/inet.h>
130#include <linux/inetdevice.h>
131#include <linux/netdevice.h>
132#include <linux/etherdevice.h>
133
134#include <net/snmp.h>
135#include <net/ip.h>
136#include <net/protocol.h>
137#include <net/route.h>
138#include <linux/skbuff.h>
139#include <net/sock.h>
140#include <net/arp.h>
141#include <net/icmp.h>
142#include <net/raw.h>
143#include <net/checksum.h>
144#include <net/inet_ecn.h>
145#include <linux/netfilter_ipv4.h>
146#include <net/xfrm.h>
147#include <linux/mroute.h>
148#include <linux/netlink.h>
149#include <net/dst_metadata.h>
150
151/*
152 * Process Router Attention IP option (RFC 2113)
153 */
154bool ip_call_ra_chain(struct sk_buff *skb)
155{
156 struct ip_ra_chain *ra;
157 u8 protocol = ip_hdr(skb)->protocol;
158 struct sock *last = NULL;
159 struct net_device *dev = skb->dev;
160 struct net *net = dev_net(dev);
161
162 for (ra = rcu_dereference(ip_ra_chain); ra; ra = rcu_dereference(ra->next)) {
163 struct sock *sk = ra->sk;
164
165 /* If socket is bound to an interface, only report
166 * the packet if it came from that interface.
167 */
168 if (sk && inet_sk(sk)->inet_num == protocol &&
169 (!sk->sk_bound_dev_if ||
170 sk->sk_bound_dev_if == dev->ifindex) &&
171 net_eq(sock_net(sk), net)) {
172 if (ip_is_fragment(ip_hdr(skb))) {
173 if (ip_defrag(net, skb, IP_DEFRAG_CALL_RA_CHAIN))
174 return true;
175 }
176 if (last) {
177 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
178 if (skb2)
179 raw_rcv(last, skb2);
180 }
181 last = sk;
182 }
183 }
184
185 if (last) {
186 raw_rcv(last, skb);
187 return true;
188 }
189 return false;
190}
191
192static int ip_local_deliver_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
193{
194 __skb_pull(skb, skb_network_header_len(skb));
195
196 rcu_read_lock();
197 {
198 int protocol = ip_hdr(skb)->protocol;
199 const struct net_protocol *ipprot;
200 int raw;
201
202 resubmit:
203 raw = raw_local_deliver(skb, protocol);
204
205 ipprot = rcu_dereference(inet_protos[protocol]);
206 if (ipprot) {
207 int ret;
208
209 if (!ipprot->no_policy) {
210 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
211 kfree_skb(skb);
212 goto out;
213 }
214 nf_reset(skb);
215 }
216 ret = ipprot->handler(skb);
217 if (ret < 0) {
218 protocol = -ret;
219 goto resubmit;
220 }
221 __IP_INC_STATS(net, IPSTATS_MIB_INDELIVERS);
222 } else {
223 if (!raw) {
224 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
225 __IP_INC_STATS(net, IPSTATS_MIB_INUNKNOWNPROTOS);
226 icmp_send(skb, ICMP_DEST_UNREACH,
227 ICMP_PROT_UNREACH, 0);
228 }
229 kfree_skb(skb);
230 } else {
231 __IP_INC_STATS(net, IPSTATS_MIB_INDELIVERS);
232 consume_skb(skb);
233 }
234 }
235 }
236 out:
237 rcu_read_unlock();
238
239 return 0;
240}
241
242/*
243 * Deliver IP Packets to the higher protocol layers.
244 */
245int ip_local_deliver(struct sk_buff *skb)
246{
247 /*
248 * Reassemble IP fragments.
249 */
250 struct net *net = dev_net(skb->dev);
251
252 if (ip_is_fragment(ip_hdr(skb))) {
253 if (ip_defrag(net, skb, IP_DEFRAG_LOCAL_DELIVER))
254 return 0;
255 }
256
257 return NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_IN,
258 net, NULL, skb, skb->dev, NULL,
259 ip_local_deliver_finish);
260}
261
262static inline bool ip_rcv_options(struct sk_buff *skb)
263{
264 struct ip_options *opt;
265 const struct iphdr *iph;
266 struct net_device *dev = skb->dev;
267
268 /* It looks as overkill, because not all
269 IP options require packet mangling.
270 But it is the easiest for now, especially taking
271 into account that combination of IP options
272 and running sniffer is extremely rare condition.
273 --ANK (980813)
274 */
275 if (skb_cow(skb, skb_headroom(skb))) {
276 __IP_INC_STATS(dev_net(dev), IPSTATS_MIB_INDISCARDS);
277 goto drop;
278 }
279
280 iph = ip_hdr(skb);
281 opt = &(IPCB(skb)->opt);
282 opt->optlen = iph->ihl*4 - sizeof(struct iphdr);
283
284 if (ip_options_compile(dev_net(dev), opt, skb)) {
285 __IP_INC_STATS(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
286 goto drop;
287 }
288
289 if (unlikely(opt->srr)) {
290 struct in_device *in_dev = __in_dev_get_rcu(dev);
291
292 if (in_dev) {
293 if (!IN_DEV_SOURCE_ROUTE(in_dev)) {
294 if (IN_DEV_LOG_MARTIANS(in_dev))
295 net_info_ratelimited("source route option %pI4 -> %pI4\n",
296 &iph->saddr,
297 &iph->daddr);
298 goto drop;
299 }
300 }
301
302 if (ip_options_rcv_srr(skb))
303 goto drop;
304 }
305
306 return false;
307drop:
308 return true;
309}
310
311static int ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
312{
313 const struct iphdr *iph = ip_hdr(skb);
314 struct rtable *rt;
315 struct net_device *dev = skb->dev;
316
317 /* if ingress device is enslaved to an L3 master device pass the
318 * skb to its handler for processing
319 */
320 skb = l3mdev_ip_rcv(skb);
321 if (!skb)
322 return NET_RX_SUCCESS;
323
324 if (net->ipv4.sysctl_ip_early_demux &&
325 !skb_dst(skb) &&
326 !skb->sk &&
327 !ip_is_fragment(iph)) {
328 const struct net_protocol *ipprot;
329 int protocol = iph->protocol;
330
331 ipprot = rcu_dereference(inet_protos[protocol]);
332 if (ipprot && ipprot->early_demux) {
333 ipprot->early_demux(skb);
334 /* must reload iph, skb->head might have changed */
335 iph = ip_hdr(skb);
336 }
337 }
338
339 /*
340 * Initialise the virtual path cache for the packet. It describes
341 * how the packet travels inside Linux networking.
342 */
343 if (!skb_valid_dst(skb)) {
344 int err = ip_route_input_noref(skb, iph->daddr, iph->saddr,
345 iph->tos, dev);
346 if (unlikely(err)) {
347 if (err == -EXDEV)
348 __NET_INC_STATS(net, LINUX_MIB_IPRPFILTER);
349 goto drop;
350 }
351 }
352
353#ifdef CONFIG_IP_ROUTE_CLASSID
354 if (unlikely(skb_dst(skb)->tclassid)) {
355 struct ip_rt_acct *st = this_cpu_ptr(ip_rt_acct);
356 u32 idx = skb_dst(skb)->tclassid;
357 st[idx&0xFF].o_packets++;
358 st[idx&0xFF].o_bytes += skb->len;
359 st[(idx>>16)&0xFF].i_packets++;
360 st[(idx>>16)&0xFF].i_bytes += skb->len;
361 }
362#endif
363
364 if (iph->ihl > 5 && ip_rcv_options(skb))
365 goto drop;
366
367 rt = skb_rtable(skb);
368 if (rt->rt_type == RTN_MULTICAST) {
369 __IP_UPD_PO_STATS(net, IPSTATS_MIB_INMCAST, skb->len);
370 } else if (rt->rt_type == RTN_BROADCAST) {
371 __IP_UPD_PO_STATS(net, IPSTATS_MIB_INBCAST, skb->len);
372 } else if (skb->pkt_type == PACKET_BROADCAST ||
373 skb->pkt_type == PACKET_MULTICAST) {
374 struct in_device *in_dev = __in_dev_get_rcu(dev);
375
376 /* RFC 1122 3.3.6:
377 *
378 * When a host sends a datagram to a link-layer broadcast
379 * address, the IP destination address MUST be a legal IP
380 * broadcast or IP multicast address.
381 *
382 * A host SHOULD silently discard a datagram that is received
383 * via a link-layer broadcast (see Section 2.4) but does not
384 * specify an IP multicast or broadcast destination address.
385 *
386 * This doesn't explicitly say L2 *broadcast*, but broadcast is
387 * in a way a form of multicast and the most common use case for
388 * this is 802.11 protecting against cross-station spoofing (the
389 * so-called "hole-196" attack) so do it for both.
390 */
391 if (in_dev &&
392 IN_DEV_ORCONF(in_dev, DROP_UNICAST_IN_L2_MULTICAST))
393 goto drop;
394 }
395
396 return dst_input(skb);
397
398drop:
399 kfree_skb(skb);
400 return NET_RX_DROP;
401}
402
403/*
404 * Main IP Receive routine.
405 */
406int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
407{
408 const struct iphdr *iph;
409 struct net *net;
410 u32 len;
411
412 /* When the interface is in promisc. mode, drop all the crap
413 * that it receives, do not try to analyse it.
414 */
415 if (skb->pkt_type == PACKET_OTHERHOST)
416 goto drop;
417
418
419 net = dev_net(dev);
420 __IP_UPD_PO_STATS(net, IPSTATS_MIB_IN, skb->len);
421
422 skb = skb_share_check(skb, GFP_ATOMIC);
423 if (!skb) {
424 __IP_INC_STATS(net, IPSTATS_MIB_INDISCARDS);
425 goto out;
426 }
427
428 if (!pskb_may_pull(skb, sizeof(struct iphdr)))
429 goto inhdr_error;
430
431 iph = ip_hdr(skb);
432
433 /*
434 * RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum.
435 *
436 * Is the datagram acceptable?
437 *
438 * 1. Length at least the size of an ip header
439 * 2. Version of 4
440 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums]
441 * 4. Doesn't have a bogus length
442 */
443
444 if (iph->ihl < 5 || iph->version != 4)
445 goto inhdr_error;
446
447 BUILD_BUG_ON(IPSTATS_MIB_ECT1PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_1);
448 BUILD_BUG_ON(IPSTATS_MIB_ECT0PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_0);
449 BUILD_BUG_ON(IPSTATS_MIB_CEPKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_CE);
450 __IP_ADD_STATS(net,
451 IPSTATS_MIB_NOECTPKTS + (iph->tos & INET_ECN_MASK),
452 max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));
453
454 if (!pskb_may_pull(skb, iph->ihl*4))
455 goto inhdr_error;
456
457 iph = ip_hdr(skb);
458
459 if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
460 goto csum_error;
461
462 len = ntohs(iph->tot_len);
463 if (skb->len < len) {
464 __IP_INC_STATS(net, IPSTATS_MIB_INTRUNCATEDPKTS);
465 goto drop;
466 } else if (len < (iph->ihl*4))
467 goto inhdr_error;
468
469 /* Our transport medium may have padded the buffer out. Now we know it
470 * is IP we can trim to the true length of the frame.
471 * Note this now means skb->len holds ntohs(iph->tot_len).
472 */
473 if (pskb_trim_rcsum(skb, len)) {
474 __IP_INC_STATS(net, IPSTATS_MIB_INDISCARDS);
475 goto drop;
476 }
477
478 skb->transport_header = skb->network_header + iph->ihl*4;
479
480 /* Remove any debris in the socket control block */
481 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
482 IPCB(skb)->iif = skb->skb_iif;
483
484 /* Must drop socket now because of tproxy. */
485 skb_orphan(skb);
486
487 return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,
488 net, NULL, skb, dev, NULL,
489 ip_rcv_finish);
490
491csum_error:
492 __IP_INC_STATS(net, IPSTATS_MIB_CSUMERRORS);
493inhdr_error:
494 __IP_INC_STATS(net, IPSTATS_MIB_INHDRERRORS);
495drop:
496 kfree_skb(skb);
497out:
498 return NET_RX_DROP;
499}