1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *  net/dccp/ipv4.c
4  *
5  *  An implementation of the DCCP protocol
6  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
7  */
8 
9 #include <linux/dccp.h>
10 #include <linux/icmp.h>
11 #include <linux/slab.h>
12 #include <linux/module.h>
13 #include <linux/skbuff.h>
14 #include <linux/random.h>
15 
16 #include <net/icmp.h>
17 #include <net/inet_common.h>
18 #include <net/inet_dscp.h>
19 #include <net/inet_hashtables.h>
20 #include <net/inet_sock.h>
21 #include <net/protocol.h>
22 #include <net/sock.h>
23 #include <net/timewait_sock.h>
24 #include <net/tcp_states.h>
25 #include <net/xfrm.h>
26 #include <net/secure_seq.h>
27 #include <net/netns/generic.h>
28 #include <net/rstreason.h>
29 
30 #include "ackvec.h"
31 #include "ccid.h"
32 #include "dccp.h"
33 #include "feat.h"
34 
35 struct dccp_v4_pernet {
36 	struct sock *v4_ctl_sk;
37 };
38 
39 static unsigned int dccp_v4_pernet_id __read_mostly;
40 
41 /*
42  * The per-net v4_ctl_sk socket is used for responding to
43  * the Out-of-the-blue (OOTB) packets. A control sock will be created
44  * for this socket at the initialization time.
45  */
46 
dccp_v4_connect(struct sock * sk,struct sockaddr * uaddr,int addr_len)47 int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
48 {
49 	const struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
50 	struct inet_sock *inet = inet_sk(sk);
51 	struct dccp_sock *dp = dccp_sk(sk);
52 	__be16 orig_sport, orig_dport;
53 	__be32 daddr, nexthop;
54 	struct flowi4 *fl4;
55 	struct rtable *rt;
56 	int err;
57 	struct ip_options_rcu *inet_opt;
58 
59 	dp->dccps_role = DCCP_ROLE_CLIENT;
60 
61 	if (addr_len < sizeof(struct sockaddr_in))
62 		return -EINVAL;
63 
64 	if (usin->sin_family != AF_INET)
65 		return -EAFNOSUPPORT;
66 
67 	nexthop = daddr = usin->sin_addr.s_addr;
68 
69 	inet_opt = rcu_dereference_protected(inet->inet_opt,
70 					     lockdep_sock_is_held(sk));
71 	if (inet_opt != NULL && inet_opt->opt.srr) {
72 		if (daddr == 0)
73 			return -EINVAL;
74 		nexthop = inet_opt->opt.faddr;
75 	}
76 
77 	orig_sport = inet->inet_sport;
78 	orig_dport = usin->sin_port;
79 	fl4 = &inet->cork.fl.u.ip4;
80 	rt = ip_route_connect(fl4, nexthop, inet->inet_saddr,
81 			      sk->sk_bound_dev_if, IPPROTO_DCCP, orig_sport,
82 			      orig_dport, sk);
83 	if (IS_ERR(rt))
84 		return PTR_ERR(rt);
85 
86 	if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {
87 		ip_rt_put(rt);
88 		return -ENETUNREACH;
89 	}
90 
91 	if (inet_opt == NULL || !inet_opt->opt.srr)
92 		daddr = fl4->daddr;
93 
94 	if (inet->inet_saddr == 0) {
95 		err = inet_bhash2_update_saddr(sk,  &fl4->saddr, AF_INET);
96 		if (err) {
97 			ip_rt_put(rt);
98 			return err;
99 		}
100 	} else {
101 		sk_rcv_saddr_set(sk, inet->inet_saddr);
102 	}
103 
104 	inet->inet_dport = usin->sin_port;
105 	sk_daddr_set(sk, daddr);
106 
107 	inet_csk(sk)->icsk_ext_hdr_len = 0;
108 	if (inet_opt)
109 		inet_csk(sk)->icsk_ext_hdr_len = inet_opt->opt.optlen;
110 	/*
111 	 * Socket identity is still unknown (sport may be zero).
112 	 * However we set state to DCCP_REQUESTING and not releasing socket
113 	 * lock select source port, enter ourselves into the hash tables and
114 	 * complete initialization after this.
115 	 */
116 	dccp_set_state(sk, DCCP_REQUESTING);
117 	err = inet_hash_connect(&dccp_death_row, sk);
118 	if (err != 0)
119 		goto failure;
120 
121 	rt = ip_route_newports(fl4, rt, orig_sport, orig_dport,
122 			       inet->inet_sport, inet->inet_dport, sk);
123 	if (IS_ERR(rt)) {
124 		err = PTR_ERR(rt);
125 		rt = NULL;
126 		goto failure;
127 	}
128 	/* OK, now commit destination to socket.  */
129 	sk_setup_caps(sk, &rt->dst);
130 
131 	dp->dccps_iss = secure_dccp_sequence_number(inet->inet_saddr,
132 						    inet->inet_daddr,
133 						    inet->inet_sport,
134 						    inet->inet_dport);
135 	atomic_set(&inet->inet_id, get_random_u16());
136 
137 	err = dccp_connect(sk);
138 	rt = NULL;
139 	if (err != 0)
140 		goto failure;
141 out:
142 	return err;
143 failure:
144 	/*
145 	 * This unhashes the socket and releases the local port, if necessary.
146 	 */
147 	dccp_set_state(sk, DCCP_CLOSED);
148 	inet_bhash2_reset_saddr(sk);
149 	ip_rt_put(rt);
150 	sk->sk_route_caps = 0;
151 	inet->inet_dport = 0;
152 	goto out;
153 }
154 EXPORT_SYMBOL_GPL(dccp_v4_connect);
155 
156 /*
157  * This routine does path mtu discovery as defined in RFC1191.
158  */
dccp_do_pmtu_discovery(struct sock * sk,const struct iphdr * iph,u32 mtu)159 static inline void dccp_do_pmtu_discovery(struct sock *sk,
160 					  const struct iphdr *iph,
161 					  u32 mtu)
162 {
163 	struct dst_entry *dst;
164 	const struct inet_sock *inet = inet_sk(sk);
165 	const struct dccp_sock *dp = dccp_sk(sk);
166 
167 	/* We are not interested in DCCP_LISTEN and request_socks (RESPONSEs
168 	 * send out by Linux are always < 576bytes so they should go through
169 	 * unfragmented).
170 	 */
171 	if (sk->sk_state == DCCP_LISTEN)
172 		return;
173 
174 	dst = inet_csk_update_pmtu(sk, mtu);
175 	if (!dst)
176 		return;
177 
178 	/* Something is about to be wrong... Remember soft error
179 	 * for the case, if this connection will not able to recover.
180 	 */
181 	if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
182 		WRITE_ONCE(sk->sk_err_soft, EMSGSIZE);
183 
184 	mtu = dst_mtu(dst);
185 
186 	if (inet->pmtudisc != IP_PMTUDISC_DONT &&
187 	    ip_sk_accept_pmtu(sk) &&
188 	    inet_csk(sk)->icsk_pmtu_cookie > mtu) {
189 		dccp_sync_mss(sk, mtu);
190 
191 		/*
192 		 * From RFC 4340, sec. 14.1:
193 		 *
194 		 *	DCCP-Sync packets are the best choice for upward
195 		 *	probing, since DCCP-Sync probes do not risk application
196 		 *	data loss.
197 		 */
198 		dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
199 	} /* else let the usual retransmit timer handle it */
200 }
201 
dccp_do_redirect(struct sk_buff * skb,struct sock * sk)202 static void dccp_do_redirect(struct sk_buff *skb, struct sock *sk)
203 {
204 	struct dst_entry *dst = __sk_dst_check(sk, 0);
205 
206 	if (dst)
207 		dst->ops->redirect(dst, sk, skb);
208 }
209 
dccp_req_err(struct sock * sk,u64 seq)210 void dccp_req_err(struct sock *sk, u64 seq)
211 	{
212 	struct request_sock *req = inet_reqsk(sk);
213 	struct net *net = sock_net(sk);
214 
215 	/*
216 	 * ICMPs are not backlogged, hence we cannot get an established
217 	 * socket here.
218 	 */
219 	if (!between48(seq, dccp_rsk(req)->dreq_iss, dccp_rsk(req)->dreq_gss)) {
220 		__NET_INC_STATS(net, LINUX_MIB_OUTOFWINDOWICMPS);
221 	} else {
222 		/*
223 		 * Still in RESPOND, just remove it silently.
224 		 * There is no good way to pass the error to the newly
225 		 * created socket, and POSIX does not want network
226 		 * errors returned from accept().
227 		 */
228 		inet_csk_reqsk_queue_drop(req->rsk_listener, req);
229 	}
230 	reqsk_put(req);
231 }
232 EXPORT_SYMBOL(dccp_req_err);
233 
234 /*
235  * This routine is called by the ICMP module when it gets some sort of error
236  * condition. If err < 0 then the socket should be closed and the error
237  * returned to the user. If err > 0 it's just the icmp type << 8 | icmp code.
238  * After adjustment header points to the first 8 bytes of the tcp header. We
239  * need to find the appropriate port.
240  *
241  * The locking strategy used here is very "optimistic". When someone else
242  * accesses the socket the ICMP is just dropped and for some paths there is no
243  * check at all. A more general error queue to queue errors for later handling
244  * is probably better.
245  */
dccp_v4_err(struct sk_buff * skb,u32 info)246 static int dccp_v4_err(struct sk_buff *skb, u32 info)
247 {
248 	const struct iphdr *iph = (struct iphdr *)skb->data;
249 	const u8 offset = iph->ihl << 2;
250 	const struct dccp_hdr *dh;
251 	struct dccp_sock *dp;
252 	const int type = icmp_hdr(skb)->type;
253 	const int code = icmp_hdr(skb)->code;
254 	struct sock *sk;
255 	__u64 seq;
256 	int err;
257 	struct net *net = dev_net(skb->dev);
258 
259 	if (!pskb_may_pull(skb, offset + sizeof(*dh)))
260 		return -EINVAL;
261 	dh = (struct dccp_hdr *)(skb->data + offset);
262 	if (!pskb_may_pull(skb, offset + __dccp_basic_hdr_len(dh)))
263 		return -EINVAL;
264 	iph = (struct iphdr *)skb->data;
265 	dh = (struct dccp_hdr *)(skb->data + offset);
266 
267 	sk = __inet_lookup_established(net, &dccp_hashinfo,
268 				       iph->daddr, dh->dccph_dport,
269 				       iph->saddr, ntohs(dh->dccph_sport),
270 				       inet_iif(skb), 0);
271 	if (!sk) {
272 		__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
273 		return -ENOENT;
274 	}
275 
276 	if (sk->sk_state == DCCP_TIME_WAIT) {
277 		inet_twsk_put(inet_twsk(sk));
278 		return 0;
279 	}
280 	seq = dccp_hdr_seq(dh);
281 	if (sk->sk_state == DCCP_NEW_SYN_RECV) {
282 		dccp_req_err(sk, seq);
283 		return 0;
284 	}
285 
286 	bh_lock_sock(sk);
287 	/* If too many ICMPs get dropped on busy
288 	 * servers this needs to be solved differently.
289 	 */
290 	if (sock_owned_by_user(sk))
291 		__NET_INC_STATS(net, LINUX_MIB_LOCKDROPPEDICMPS);
292 
293 	if (sk->sk_state == DCCP_CLOSED)
294 		goto out;
295 
296 	dp = dccp_sk(sk);
297 	if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_LISTEN) &&
298 	    !between48(seq, dp->dccps_awl, dp->dccps_awh)) {
299 		__NET_INC_STATS(net, LINUX_MIB_OUTOFWINDOWICMPS);
300 		goto out;
301 	}
302 
303 	switch (type) {
304 	case ICMP_REDIRECT:
305 		if (!sock_owned_by_user(sk))
306 			dccp_do_redirect(skb, sk);
307 		goto out;
308 	case ICMP_SOURCE_QUENCH:
309 		/* Just silently ignore these. */
310 		goto out;
311 	case ICMP_PARAMETERPROB:
312 		err = EPROTO;
313 		break;
314 	case ICMP_DEST_UNREACH:
315 		if (code > NR_ICMP_UNREACH)
316 			goto out;
317 
318 		if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
319 			if (!sock_owned_by_user(sk))
320 				dccp_do_pmtu_discovery(sk, iph, info);
321 			goto out;
322 		}
323 
324 		err = icmp_err_convert[code].errno;
325 		break;
326 	case ICMP_TIME_EXCEEDED:
327 		err = EHOSTUNREACH;
328 		break;
329 	default:
330 		goto out;
331 	}
332 
333 	switch (sk->sk_state) {
334 	case DCCP_REQUESTING:
335 	case DCCP_RESPOND:
336 		if (!sock_owned_by_user(sk)) {
337 			__DCCP_INC_STATS(DCCP_MIB_ATTEMPTFAILS);
338 			sk->sk_err = err;
339 
340 			sk_error_report(sk);
341 
342 			dccp_done(sk);
343 		} else {
344 			WRITE_ONCE(sk->sk_err_soft, err);
345 		}
346 		goto out;
347 	}
348 
349 	/* If we've already connected we will keep trying
350 	 * until we time out, or the user gives up.
351 	 *
352 	 * rfc1122 4.2.3.9 allows to consider as hard errors
353 	 * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
354 	 * but it is obsoleted by pmtu discovery).
355 	 *
356 	 * Note, that in modern internet, where routing is unreliable
357 	 * and in each dark corner broken firewalls sit, sending random
358 	 * errors ordered by their masters even this two messages finally lose
359 	 * their original sense (even Linux sends invalid PORT_UNREACHs)
360 	 *
361 	 * Now we are in compliance with RFCs.
362 	 *							--ANK (980905)
363 	 */
364 
365 	if (!sock_owned_by_user(sk) && inet_test_bit(RECVERR, sk)) {
366 		sk->sk_err = err;
367 		sk_error_report(sk);
368 	} else { /* Only an error on timeout */
369 		WRITE_ONCE(sk->sk_err_soft, err);
370 	}
371 out:
372 	bh_unlock_sock(sk);
373 	sock_put(sk);
374 	return 0;
375 }
376 
dccp_v4_csum_finish(struct sk_buff * skb,__be32 src,__be32 dst)377 static inline __sum16 dccp_v4_csum_finish(struct sk_buff *skb,
378 				      __be32 src, __be32 dst)
379 {
380 	return csum_tcpudp_magic(src, dst, skb->len, IPPROTO_DCCP, skb->csum);
381 }
382 
dccp_v4_send_check(struct sock * sk,struct sk_buff * skb)383 void dccp_v4_send_check(struct sock *sk, struct sk_buff *skb)
384 {
385 	const struct inet_sock *inet = inet_sk(sk);
386 	struct dccp_hdr *dh = dccp_hdr(skb);
387 
388 	dccp_csum_outgoing(skb);
389 	dh->dccph_checksum = dccp_v4_csum_finish(skb,
390 						 inet->inet_saddr,
391 						 inet->inet_daddr);
392 }
393 EXPORT_SYMBOL_GPL(dccp_v4_send_check);
394 
dccp_v4_init_sequence(const struct sk_buff * skb)395 static inline u64 dccp_v4_init_sequence(const struct sk_buff *skb)
396 {
397 	return secure_dccp_sequence_number(ip_hdr(skb)->daddr,
398 					   ip_hdr(skb)->saddr,
399 					   dccp_hdr(skb)->dccph_dport,
400 					   dccp_hdr(skb)->dccph_sport);
401 }
402 
403 /*
404  * The three way handshake has completed - we got a valid ACK or DATAACK -
405  * now create the new socket.
406  *
407  * This is the equivalent of TCP's tcp_v4_syn_recv_sock
408  */
dccp_v4_request_recv_sock(const struct sock * sk,struct sk_buff * skb,struct request_sock * req,struct dst_entry * dst,struct request_sock * req_unhash,bool * own_req)409 struct sock *dccp_v4_request_recv_sock(const struct sock *sk,
410 				       struct sk_buff *skb,
411 				       struct request_sock *req,
412 				       struct dst_entry *dst,
413 				       struct request_sock *req_unhash,
414 				       bool *own_req)
415 {
416 	struct inet_request_sock *ireq;
417 	struct inet_sock *newinet;
418 	struct sock *newsk;
419 
420 	if (sk_acceptq_is_full(sk))
421 		goto exit_overflow;
422 
423 	newsk = dccp_create_openreq_child(sk, req, skb);
424 	if (newsk == NULL)
425 		goto exit_nonewsk;
426 
427 	newinet		   = inet_sk(newsk);
428 	ireq		   = inet_rsk(req);
429 	RCU_INIT_POINTER(newinet->inet_opt, rcu_dereference(ireq->ireq_opt));
430 	newinet->mc_index  = inet_iif(skb);
431 	newinet->mc_ttl	   = ip_hdr(skb)->ttl;
432 	atomic_set(&newinet->inet_id, get_random_u16());
433 
434 	if (dst == NULL && (dst = inet_csk_route_child_sock(sk, newsk, req)) == NULL)
435 		goto put_and_exit;
436 
437 	sk_setup_caps(newsk, dst);
438 
439 	dccp_sync_mss(newsk, dst_mtu(dst));
440 
441 	if (__inet_inherit_port(sk, newsk) < 0)
442 		goto put_and_exit;
443 	*own_req = inet_ehash_nolisten(newsk, req_to_sk(req_unhash), NULL);
444 	if (*own_req)
445 		ireq->ireq_opt = NULL;
446 	else
447 		newinet->inet_opt = NULL;
448 	return newsk;
449 
450 exit_overflow:
451 	__NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
452 exit_nonewsk:
453 	dst_release(dst);
454 exit:
455 	__NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
456 	return NULL;
457 put_and_exit:
458 	newinet->inet_opt = NULL;
459 	inet_csk_prepare_forced_close(newsk);
460 	dccp_done(newsk);
461 	goto exit;
462 }
463 EXPORT_SYMBOL_GPL(dccp_v4_request_recv_sock);
464 
dccp_v4_route_skb(struct net * net,struct sock * sk,struct sk_buff * skb)465 static struct dst_entry* dccp_v4_route_skb(struct net *net, struct sock *sk,
466 					   struct sk_buff *skb)
467 {
468 	struct rtable *rt;
469 	const struct iphdr *iph = ip_hdr(skb);
470 	struct flowi4 fl4 = {
471 		.flowi4_oif = inet_iif(skb),
472 		.daddr = iph->saddr,
473 		.saddr = iph->daddr,
474 		.flowi4_tos = inet_dscp_to_dsfield(inet_sk_dscp(inet_sk(sk))),
475 		.flowi4_scope = ip_sock_rt_scope(sk),
476 		.flowi4_proto = sk->sk_protocol,
477 		.fl4_sport = dccp_hdr(skb)->dccph_dport,
478 		.fl4_dport = dccp_hdr(skb)->dccph_sport,
479 	};
480 
481 	security_skb_classify_flow(skb, flowi4_to_flowi_common(&fl4));
482 	rt = ip_route_output_flow(net, &fl4, sk);
483 	if (IS_ERR(rt)) {
484 		IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
485 		return NULL;
486 	}
487 
488 	return &rt->dst;
489 }
490 
dccp_v4_send_response(const struct sock * sk,struct request_sock * req)491 static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req)
492 {
493 	int err = -1;
494 	struct sk_buff *skb;
495 	struct dst_entry *dst;
496 	struct flowi4 fl4;
497 
498 	dst = inet_csk_route_req(sk, &fl4, req);
499 	if (dst == NULL)
500 		goto out;
501 
502 	skb = dccp_make_response(sk, dst, req);
503 	if (skb != NULL) {
504 		const struct inet_request_sock *ireq = inet_rsk(req);
505 		struct dccp_hdr *dh = dccp_hdr(skb);
506 
507 		dh->dccph_checksum = dccp_v4_csum_finish(skb, ireq->ir_loc_addr,
508 							      ireq->ir_rmt_addr);
509 		rcu_read_lock();
510 		err = ip_build_and_send_pkt(skb, sk, ireq->ir_loc_addr,
511 					    ireq->ir_rmt_addr,
512 					    rcu_dereference(ireq->ireq_opt),
513 					    READ_ONCE(inet_sk(sk)->tos));
514 		rcu_read_unlock();
515 		err = net_xmit_eval(err);
516 	}
517 
518 out:
519 	dst_release(dst);
520 	return err;
521 }
522 
dccp_v4_ctl_send_reset(const struct sock * sk,struct sk_buff * rxskb,enum sk_rst_reason reason)523 static void dccp_v4_ctl_send_reset(const struct sock *sk, struct sk_buff *rxskb,
524 				   enum sk_rst_reason reason)
525 {
526 	int err;
527 	const struct iphdr *rxiph;
528 	struct sk_buff *skb;
529 	struct dst_entry *dst;
530 	struct net *net = dev_net(skb_dst(rxskb)->dev);
531 	struct dccp_v4_pernet *pn;
532 	struct sock *ctl_sk;
533 
534 	/* Never send a reset in response to a reset. */
535 	if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
536 		return;
537 
538 	if (skb_rtable(rxskb)->rt_type != RTN_LOCAL)
539 		return;
540 
541 	pn = net_generic(net, dccp_v4_pernet_id);
542 	ctl_sk = pn->v4_ctl_sk;
543 	dst = dccp_v4_route_skb(net, ctl_sk, rxskb);
544 	if (dst == NULL)
545 		return;
546 
547 	skb = dccp_ctl_make_reset(ctl_sk, rxskb);
548 	if (skb == NULL)
549 		goto out;
550 
551 	rxiph = ip_hdr(rxskb);
552 	dccp_hdr(skb)->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
553 								 rxiph->daddr);
554 	skb_dst_set(skb, dst_clone(dst));
555 
556 	local_bh_disable();
557 	bh_lock_sock(ctl_sk);
558 	err = ip_build_and_send_pkt(skb, ctl_sk,
559 				    rxiph->daddr, rxiph->saddr, NULL,
560 				    inet_sk(ctl_sk)->tos);
561 	bh_unlock_sock(ctl_sk);
562 
563 	if (net_xmit_eval(err) == 0) {
564 		__DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
565 		__DCCP_INC_STATS(DCCP_MIB_OUTRSTS);
566 	}
567 	local_bh_enable();
568 out:
569 	dst_release(dst);
570 }
571 
dccp_v4_reqsk_destructor(struct request_sock * req)572 static void dccp_v4_reqsk_destructor(struct request_sock *req)
573 {
574 	dccp_feat_list_purge(&dccp_rsk(req)->dreq_featneg);
575 	kfree(rcu_dereference_protected(inet_rsk(req)->ireq_opt, 1));
576 }
577 
dccp_syn_ack_timeout(const struct request_sock * req)578 void dccp_syn_ack_timeout(const struct request_sock *req)
579 {
580 }
581 EXPORT_SYMBOL(dccp_syn_ack_timeout);
582 
583 static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
584 	.family		= PF_INET,
585 	.obj_size	= sizeof(struct dccp_request_sock),
586 	.rtx_syn_ack	= dccp_v4_send_response,
587 	.send_ack	= dccp_reqsk_send_ack,
588 	.destructor	= dccp_v4_reqsk_destructor,
589 	.send_reset	= dccp_v4_ctl_send_reset,
590 	.syn_ack_timeout = dccp_syn_ack_timeout,
591 };
592 
dccp_v4_conn_request(struct sock * sk,struct sk_buff * skb)593 int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
594 {
595 	struct inet_request_sock *ireq;
596 	struct request_sock *req;
597 	struct dccp_request_sock *dreq;
598 	const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
599 	struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
600 
601 	/* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
602 	if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
603 		return 0;	/* discard, don't send a reset here */
604 
605 	if (dccp_bad_service_code(sk, service)) {
606 		dcb->dccpd_reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
607 		goto drop;
608 	}
609 	/*
610 	 * TW buckets are converted to open requests without
611 	 * limitations, they conserve resources and peer is
612 	 * evidently real one.
613 	 */
614 	dcb->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
615 	if (inet_csk_reqsk_queue_is_full(sk))
616 		goto drop;
617 
618 	if (sk_acceptq_is_full(sk))
619 		goto drop;
620 
621 	req = inet_reqsk_alloc(&dccp_request_sock_ops, sk, true);
622 	if (req == NULL)
623 		goto drop;
624 
625 	if (dccp_reqsk_init(req, dccp_sk(sk), skb))
626 		goto drop_and_free;
627 
628 	dreq = dccp_rsk(req);
629 	if (dccp_parse_options(sk, dreq, skb))
630 		goto drop_and_free;
631 
632 	ireq = inet_rsk(req);
633 	sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr);
634 	sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr);
635 	ireq->ir_mark = inet_request_mark(sk, skb);
636 	ireq->ireq_family = AF_INET;
637 	ireq->ir_iif = READ_ONCE(sk->sk_bound_dev_if);
638 
639 	if (security_inet_conn_request(sk, skb, req))
640 		goto drop_and_free;
641 
642 	/*
643 	 * Step 3: Process LISTEN state
644 	 *
645 	 * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
646 	 *
647 	 * Setting S.SWL/S.SWH to is deferred to dccp_create_openreq_child().
648 	 */
649 	dreq->dreq_isr	   = dcb->dccpd_seq;
650 	dreq->dreq_gsr	   = dreq->dreq_isr;
651 	dreq->dreq_iss	   = dccp_v4_init_sequence(skb);
652 	dreq->dreq_gss     = dreq->dreq_iss;
653 	dreq->dreq_service = service;
654 
655 	if (dccp_v4_send_response(sk, req))
656 		goto drop_and_free;
657 
658 	if (unlikely(!inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT)))
659 		reqsk_free(req);
660 	else
661 		reqsk_put(req);
662 
663 	return 0;
664 
665 drop_and_free:
666 	reqsk_free(req);
667 drop:
668 	__DCCP_INC_STATS(DCCP_MIB_ATTEMPTFAILS);
669 	return -1;
670 }
671 EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
672 
dccp_v4_do_rcv(struct sock * sk,struct sk_buff * skb)673 int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
674 {
675 	struct dccp_hdr *dh = dccp_hdr(skb);
676 
677 	if (sk->sk_state == DCCP_OPEN) { /* Fast path */
678 		if (dccp_rcv_established(sk, skb, dh, skb->len))
679 			goto reset;
680 		return 0;
681 	}
682 
683 	/*
684 	 *  Step 3: Process LISTEN state
685 	 *	 If P.type == Request or P contains a valid Init Cookie option,
686 	 *	      (* Must scan the packet's options to check for Init
687 	 *		 Cookies.  Only Init Cookies are processed here,
688 	 *		 however; other options are processed in Step 8.  This
689 	 *		 scan need only be performed if the endpoint uses Init
690 	 *		 Cookies *)
691 	 *	      (* Generate a new socket and switch to that socket *)
692 	 *	      Set S := new socket for this port pair
693 	 *	      S.state = RESPOND
694 	 *	      Choose S.ISS (initial seqno) or set from Init Cookies
695 	 *	      Initialize S.GAR := S.ISS
696 	 *	      Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
697 	 *	      Continue with S.state == RESPOND
698 	 *	      (* A Response packet will be generated in Step 11 *)
699 	 *	 Otherwise,
700 	 *	      Generate Reset(No Connection) unless P.type == Reset
701 	 *	      Drop packet and return
702 	 *
703 	 * NOTE: the check for the packet types is done in
704 	 *	 dccp_rcv_state_process
705 	 */
706 
707 	if (dccp_rcv_state_process(sk, skb, dh, skb->len))
708 		goto reset;
709 	return 0;
710 
711 reset:
712 	dccp_v4_ctl_send_reset(sk, skb, SK_RST_REASON_NOT_SPECIFIED);
713 	kfree_skb(skb);
714 	return 0;
715 }
716 EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
717 
718 /**
719  *	dccp_invalid_packet  -  check for malformed packets
720  *	@skb: Packet to validate
721  *
722  *	Implements RFC 4340, 8.5:  Step 1: Check header basics
723  *	Packets that fail these checks are ignored and do not receive Resets.
724  */
dccp_invalid_packet(struct sk_buff * skb)725 int dccp_invalid_packet(struct sk_buff *skb)
726 {
727 	const struct dccp_hdr *dh;
728 	unsigned int cscov;
729 	u8 dccph_doff;
730 
731 	if (skb->pkt_type != PACKET_HOST)
732 		return 1;
733 
734 	/* If the packet is shorter than 12 bytes, drop packet and return */
735 	if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
736 		DCCP_WARN("pskb_may_pull failed\n");
737 		return 1;
738 	}
739 
740 	dh = dccp_hdr(skb);
741 
742 	/* If P.type is not understood, drop packet and return */
743 	if (dh->dccph_type >= DCCP_PKT_INVALID) {
744 		DCCP_WARN("invalid packet type\n");
745 		return 1;
746 	}
747 
748 	/*
749 	 * If P.Data Offset is too small for packet type, drop packet and return
750 	 */
751 	dccph_doff = dh->dccph_doff;
752 	if (dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
753 		DCCP_WARN("P.Data Offset(%u) too small\n", dccph_doff);
754 		return 1;
755 	}
756 	/*
757 	 * If P.Data Offset is too large for packet, drop packet and return
758 	 */
759 	if (!pskb_may_pull(skb, dccph_doff * sizeof(u32))) {
760 		DCCP_WARN("P.Data Offset(%u) too large\n", dccph_doff);
761 		return 1;
762 	}
763 	dh = dccp_hdr(skb);
764 	/*
765 	 * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
766 	 * has short sequence numbers), drop packet and return
767 	 */
768 	if ((dh->dccph_type < DCCP_PKT_DATA    ||
769 	    dh->dccph_type > DCCP_PKT_DATAACK) && dh->dccph_x == 0)  {
770 		DCCP_WARN("P.type (%s) not Data || [Data]Ack, while P.X == 0\n",
771 			  dccp_packet_name(dh->dccph_type));
772 		return 1;
773 	}
774 
775 	/*
776 	 * If P.CsCov is too large for the packet size, drop packet and return.
777 	 * This must come _before_ checksumming (not as RFC 4340 suggests).
778 	 */
779 	cscov = dccp_csum_coverage(skb);
780 	if (cscov > skb->len) {
781 		DCCP_WARN("P.CsCov %u exceeds packet length %d\n",
782 			  dh->dccph_cscov, skb->len);
783 		return 1;
784 	}
785 
786 	/* If header checksum is incorrect, drop packet and return.
787 	 * (This step is completed in the AF-dependent functions.) */
788 	skb->csum = skb_checksum(skb, 0, cscov, 0);
789 
790 	return 0;
791 }
792 EXPORT_SYMBOL_GPL(dccp_invalid_packet);
793 
794 /* this is called when real data arrives */
dccp_v4_rcv(struct sk_buff * skb)795 static int dccp_v4_rcv(struct sk_buff *skb)
796 {
797 	const struct dccp_hdr *dh;
798 	const struct iphdr *iph;
799 	bool refcounted;
800 	struct sock *sk;
801 	int min_cov;
802 
803 	/* Step 1: Check header basics */
804 
805 	if (dccp_invalid_packet(skb))
806 		goto discard_it;
807 
808 	iph = ip_hdr(skb);
809 	/* Step 1: If header checksum is incorrect, drop packet and return */
810 	if (dccp_v4_csum_finish(skb, iph->saddr, iph->daddr)) {
811 		DCCP_WARN("dropped packet with invalid checksum\n");
812 		goto discard_it;
813 	}
814 
815 	dh = dccp_hdr(skb);
816 
817 	DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
818 	DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
819 
820 	dccp_pr_debug("%8.8s src=%pI4@%-5d dst=%pI4@%-5d seq=%llu",
821 		      dccp_packet_name(dh->dccph_type),
822 		      &iph->saddr, ntohs(dh->dccph_sport),
823 		      &iph->daddr, ntohs(dh->dccph_dport),
824 		      (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
825 
826 	if (dccp_packet_without_ack(skb)) {
827 		DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
828 		dccp_pr_debug_cat("\n");
829 	} else {
830 		DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
831 		dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
832 				  DCCP_SKB_CB(skb)->dccpd_ack_seq);
833 	}
834 
835 lookup:
836 	sk = __inet_lookup_skb(&dccp_hashinfo, skb, __dccp_hdr_len(dh),
837 			       dh->dccph_sport, dh->dccph_dport, 0, &refcounted);
838 	if (!sk) {
839 		dccp_pr_debug("failed to look up flow ID in table and "
840 			      "get corresponding socket\n");
841 		goto no_dccp_socket;
842 	}
843 
844 	/*
845 	 * Step 2:
846 	 *	... or S.state == TIMEWAIT,
847 	 *		Generate Reset(No Connection) unless P.type == Reset
848 	 *		Drop packet and return
849 	 */
850 	if (sk->sk_state == DCCP_TIME_WAIT) {
851 		dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
852 		inet_twsk_put(inet_twsk(sk));
853 		goto no_dccp_socket;
854 	}
855 
856 	if (sk->sk_state == DCCP_NEW_SYN_RECV) {
857 		struct request_sock *req = inet_reqsk(sk);
858 		struct sock *nsk;
859 
860 		sk = req->rsk_listener;
861 		if (unlikely(sk->sk_state != DCCP_LISTEN)) {
862 			inet_csk_reqsk_queue_drop_and_put(sk, req);
863 			goto lookup;
864 		}
865 		sock_hold(sk);
866 		refcounted = true;
867 		nsk = dccp_check_req(sk, skb, req);
868 		if (!nsk) {
869 			reqsk_put(req);
870 			goto discard_and_relse;
871 		}
872 		if (nsk == sk) {
873 			reqsk_put(req);
874 		} else if (dccp_child_process(sk, nsk, skb)) {
875 			dccp_v4_ctl_send_reset(sk, skb, SK_RST_REASON_NOT_SPECIFIED);
876 			goto discard_and_relse;
877 		} else {
878 			sock_put(sk);
879 			return 0;
880 		}
881 	}
882 	/*
883 	 * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
884 	 *	o if MinCsCov = 0, only packets with CsCov = 0 are accepted
885 	 *	o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
886 	 */
887 	min_cov = dccp_sk(sk)->dccps_pcrlen;
888 	if (dh->dccph_cscov && (min_cov == 0 || dh->dccph_cscov < min_cov))  {
889 		dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
890 			      dh->dccph_cscov, min_cov);
891 		/* FIXME: "Such packets SHOULD be reported using Data Dropped
892 		 *         options (Section 11.7) with Drop Code 0, Protocol
893 		 *         Constraints."                                     */
894 		goto discard_and_relse;
895 	}
896 
897 	if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
898 		goto discard_and_relse;
899 	nf_reset_ct(skb);
900 
901 	return __sk_receive_skb(sk, skb, 1, dh->dccph_doff * 4, refcounted);
902 
903 no_dccp_socket:
904 	if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
905 		goto discard_it;
906 	/*
907 	 * Step 2:
908 	 *	If no socket ...
909 	 *		Generate Reset(No Connection) unless P.type == Reset
910 	 *		Drop packet and return
911 	 */
912 	if (dh->dccph_type != DCCP_PKT_RESET) {
913 		DCCP_SKB_CB(skb)->dccpd_reset_code =
914 					DCCP_RESET_CODE_NO_CONNECTION;
915 		dccp_v4_ctl_send_reset(sk, skb, SK_RST_REASON_NOT_SPECIFIED);
916 	}
917 
918 discard_it:
919 	kfree_skb(skb);
920 	return 0;
921 
922 discard_and_relse:
923 	if (refcounted)
924 		sock_put(sk);
925 	goto discard_it;
926 }
927 
928 static const struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
929 	.queue_xmit	   = ip_queue_xmit,
930 	.send_check	   = dccp_v4_send_check,
931 	.rebuild_header	   = inet_sk_rebuild_header,
932 	.conn_request	   = dccp_v4_conn_request,
933 	.syn_recv_sock	   = dccp_v4_request_recv_sock,
934 	.net_header_len	   = sizeof(struct iphdr),
935 	.setsockopt	   = ip_setsockopt,
936 	.getsockopt	   = ip_getsockopt,
937 };
938 
dccp_v4_init_sock(struct sock * sk)939 static int dccp_v4_init_sock(struct sock *sk)
940 {
941 	static __u8 dccp_v4_ctl_sock_initialized;
942 	int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);
943 
944 	if (err == 0) {
945 		if (unlikely(!dccp_v4_ctl_sock_initialized))
946 			dccp_v4_ctl_sock_initialized = 1;
947 		inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
948 	}
949 
950 	return err;
951 }
952 
953 static struct timewait_sock_ops dccp_timewait_sock_ops = {
954 	.twsk_obj_size	= sizeof(struct inet_timewait_sock),
955 };
956 
957 static struct proto dccp_v4_prot = {
958 	.name			= "DCCP",
959 	.owner			= THIS_MODULE,
960 	.close			= dccp_close,
961 	.connect		= dccp_v4_connect,
962 	.disconnect		= dccp_disconnect,
963 	.ioctl			= dccp_ioctl,
964 	.init			= dccp_v4_init_sock,
965 	.setsockopt		= dccp_setsockopt,
966 	.getsockopt		= dccp_getsockopt,
967 	.sendmsg		= dccp_sendmsg,
968 	.recvmsg		= dccp_recvmsg,
969 	.backlog_rcv		= dccp_v4_do_rcv,
970 	.hash			= inet_hash,
971 	.unhash			= inet_unhash,
972 	.accept			= inet_csk_accept,
973 	.get_port		= inet_csk_get_port,
974 	.shutdown		= dccp_shutdown,
975 	.destroy		= dccp_destroy_sock,
976 	.orphan_count		= &dccp_orphan_count,
977 	.max_header		= MAX_DCCP_HEADER,
978 	.obj_size		= sizeof(struct dccp_sock),
979 	.slab_flags		= SLAB_TYPESAFE_BY_RCU,
980 	.rsk_prot		= &dccp_request_sock_ops,
981 	.twsk_prot		= &dccp_timewait_sock_ops,
982 	.h.hashinfo		= &dccp_hashinfo,
983 };
984 
985 static const struct net_protocol dccp_v4_protocol = {
986 	.handler	= dccp_v4_rcv,
987 	.err_handler	= dccp_v4_err,
988 	.no_policy	= 1,
989 	.icmp_strict_tag_validation = 1,
990 };
991 
992 static const struct proto_ops inet_dccp_ops = {
993 	.family		   = PF_INET,
994 	.owner		   = THIS_MODULE,
995 	.release	   = inet_release,
996 	.bind		   = inet_bind,
997 	.connect	   = inet_stream_connect,
998 	.socketpair	   = sock_no_socketpair,
999 	.accept		   = inet_accept,
1000 	.getname	   = inet_getname,
1001 	/* FIXME: work on tcp_poll to rename it to inet_csk_poll */
1002 	.poll		   = dccp_poll,
1003 	.ioctl		   = inet_ioctl,
1004 	.gettstamp	   = sock_gettstamp,
1005 	/* FIXME: work on inet_listen to rename it to sock_common_listen */
1006 	.listen		   = inet_dccp_listen,
1007 	.shutdown	   = inet_shutdown,
1008 	.setsockopt	   = sock_common_setsockopt,
1009 	.getsockopt	   = sock_common_getsockopt,
1010 	.sendmsg	   = inet_sendmsg,
1011 	.recvmsg	   = sock_common_recvmsg,
1012 	.mmap		   = sock_no_mmap,
1013 };
1014 
1015 static struct inet_protosw dccp_v4_protosw = {
1016 	.type		= SOCK_DCCP,
1017 	.protocol	= IPPROTO_DCCP,
1018 	.prot		= &dccp_v4_prot,
1019 	.ops		= &inet_dccp_ops,
1020 	.flags		= INET_PROTOSW_ICSK,
1021 };
1022 
dccp_v4_init_net(struct net * net)1023 static int __net_init dccp_v4_init_net(struct net *net)
1024 {
1025 	struct dccp_v4_pernet *pn = net_generic(net, dccp_v4_pernet_id);
1026 
1027 	if (dccp_hashinfo.bhash == NULL)
1028 		return -ESOCKTNOSUPPORT;
1029 
1030 	return inet_ctl_sock_create(&pn->v4_ctl_sk, PF_INET,
1031 				    SOCK_DCCP, IPPROTO_DCCP, net);
1032 }
1033 
dccp_v4_exit_net(struct net * net)1034 static void __net_exit dccp_v4_exit_net(struct net *net)
1035 {
1036 	struct dccp_v4_pernet *pn = net_generic(net, dccp_v4_pernet_id);
1037 
1038 	inet_ctl_sock_destroy(pn->v4_ctl_sk);
1039 }
1040 
dccp_v4_exit_batch(struct list_head * net_exit_list)1041 static void __net_exit dccp_v4_exit_batch(struct list_head *net_exit_list)
1042 {
1043 	inet_twsk_purge(&dccp_hashinfo);
1044 }
1045 
1046 static struct pernet_operations dccp_v4_ops = {
1047 	.init	= dccp_v4_init_net,
1048 	.exit	= dccp_v4_exit_net,
1049 	.exit_batch = dccp_v4_exit_batch,
1050 	.id	= &dccp_v4_pernet_id,
1051 	.size   = sizeof(struct dccp_v4_pernet),
1052 };
1053 
dccp_v4_init(void)1054 static int __init dccp_v4_init(void)
1055 {
1056 	int err = proto_register(&dccp_v4_prot, 1);
1057 
1058 	if (err)
1059 		goto out;
1060 
1061 	inet_register_protosw(&dccp_v4_protosw);
1062 
1063 	err = register_pernet_subsys(&dccp_v4_ops);
1064 	if (err)
1065 		goto out_destroy_ctl_sock;
1066 
1067 	err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1068 	if (err)
1069 		goto out_proto_unregister;
1070 
1071 out:
1072 	return err;
1073 out_proto_unregister:
1074 	unregister_pernet_subsys(&dccp_v4_ops);
1075 out_destroy_ctl_sock:
1076 	inet_unregister_protosw(&dccp_v4_protosw);
1077 	proto_unregister(&dccp_v4_prot);
1078 	goto out;
1079 }
1080 
dccp_v4_exit(void)1081 static void __exit dccp_v4_exit(void)
1082 {
1083 	inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1084 	unregister_pernet_subsys(&dccp_v4_ops);
1085 	inet_unregister_protosw(&dccp_v4_protosw);
1086 	proto_unregister(&dccp_v4_prot);
1087 }
1088 
1089 module_init(dccp_v4_init);
1090 module_exit(dccp_v4_exit);
1091 
1092 /*
1093  * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
1094  * values directly, Also cover the case where the protocol is not specified,
1095  * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
1096  */
1097 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 33, 6);
1098 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 0, 6);
1099 MODULE_LICENSE("GPL");
1100 MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
1101 MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");
1102