xref: /openbmc/linux/net/dccp/output.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
1 /*
2  *  net/dccp/output.c
3  *
4  *  An implementation of the DCCP protocol
5  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
6  *
7  *	This program is free software; you can redistribute it and/or
8  *	modify it under the terms of the GNU General Public License
9  *	as published by the Free Software Foundation; either version
10  *	2 of the License, or (at your option) any later version.
11  */
12 
13 #include <linux/dccp.h>
14 #include <linux/kernel.h>
15 #include <linux/skbuff.h>
16 
17 #include <net/inet_sock.h>
18 #include <net/sock.h>
19 
20 #include "ackvec.h"
21 #include "ccid.h"
22 #include "dccp.h"
23 
24 static inline void dccp_event_ack_sent(struct sock *sk)
25 {
26 	inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
27 }
28 
29 static void dccp_skb_entail(struct sock *sk, struct sk_buff *skb)
30 {
31 	skb_set_owner_w(skb, sk);
32 	WARN_ON(sk->sk_send_head);
33 	sk->sk_send_head = skb;
34 }
35 
36 /*
37  * All SKB's seen here are completely headerless. It is our
38  * job to build the DCCP header, and pass the packet down to
39  * IP so it can do the same plus pass the packet off to the
40  * device.
41  */
42 static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
43 {
44 	if (likely(skb != NULL)) {
45 		const struct inet_sock *inet = inet_sk(sk);
46 		const struct inet_connection_sock *icsk = inet_csk(sk);
47 		struct dccp_sock *dp = dccp_sk(sk);
48 		struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
49 		struct dccp_hdr *dh;
50 		/* XXX For now we're using only 48 bits sequence numbers */
51 		const u32 dccp_header_size = sizeof(*dh) +
52 					     sizeof(struct dccp_hdr_ext) +
53 					  dccp_packet_hdr_len(dcb->dccpd_type);
54 		int err, set_ack = 1;
55 		u64 ackno = dp->dccps_gsr;
56 
57 		dccp_inc_seqno(&dp->dccps_gss);
58 
59 		switch (dcb->dccpd_type) {
60 		case DCCP_PKT_DATA:
61 			set_ack = 0;
62 			/* fall through */
63 		case DCCP_PKT_DATAACK:
64 			break;
65 
66 		case DCCP_PKT_REQUEST:
67 			set_ack = 0;
68 			/* fall through */
69 
70 		case DCCP_PKT_SYNC:
71 		case DCCP_PKT_SYNCACK:
72 			ackno = dcb->dccpd_seq;
73 			/* fall through */
74 		default:
75 			/*
76 			 * Only data packets should come through with skb->sk
77 			 * set.
78 			 */
79 			WARN_ON(skb->sk);
80 			skb_set_owner_w(skb, sk);
81 			break;
82 		}
83 
84 		dcb->dccpd_seq = dp->dccps_gss;
85 
86 		if (dccp_insert_options(sk, skb)) {
87 			kfree_skb(skb);
88 			return -EPROTO;
89 		}
90 
91 
92 		/* Build DCCP header and checksum it. */
93 		dh = dccp_zeroed_hdr(skb, dccp_header_size);
94 		dh->dccph_type	= dcb->dccpd_type;
95 		dh->dccph_sport	= inet->sport;
96 		dh->dccph_dport	= inet->dport;
97 		dh->dccph_doff	= (dccp_header_size + dcb->dccpd_opt_len) / 4;
98 		dh->dccph_ccval	= dcb->dccpd_ccval;
99 		dh->dccph_cscov = dp->dccps_pcslen;
100 		/* XXX For now we're using only 48 bits sequence numbers */
101 		dh->dccph_x	= 1;
102 
103 		dp->dccps_awh = dp->dccps_gss;
104 		dccp_hdr_set_seq(dh, dp->dccps_gss);
105 		if (set_ack)
106 			dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);
107 
108 		switch (dcb->dccpd_type) {
109 		case DCCP_PKT_REQUEST:
110 			dccp_hdr_request(skb)->dccph_req_service =
111 							dp->dccps_service;
112 			break;
113 		case DCCP_PKT_RESET:
114 			dccp_hdr_reset(skb)->dccph_reset_code =
115 							dcb->dccpd_reset_code;
116 			break;
117 		}
118 
119 		icsk->icsk_af_ops->send_check(sk, 0, skb);
120 
121 		if (set_ack)
122 			dccp_event_ack_sent(sk);
123 
124 		DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
125 
126 		memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
127 		err = icsk->icsk_af_ops->queue_xmit(skb, 0);
128 		return net_xmit_eval(err);
129 	}
130 	return -ENOBUFS;
131 }
132 
133 unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
134 {
135 	struct inet_connection_sock *icsk = inet_csk(sk);
136 	struct dccp_sock *dp = dccp_sk(sk);
137 	int mss_now = (pmtu - icsk->icsk_af_ops->net_header_len -
138 		       sizeof(struct dccp_hdr) - sizeof(struct dccp_hdr_ext));
139 
140 	/* Now subtract optional transport overhead */
141 	mss_now -= icsk->icsk_ext_hdr_len;
142 
143 	/*
144 	 * FIXME: this should come from the CCID infrastructure, where, say,
145 	 * TFRC will say it wants TIMESTAMPS, ELAPSED time, etc, for now lets
146 	 * put a rough estimate for NDP + TIMESTAMP + TIMESTAMP_ECHO + ELAPSED
147 	 * TIME + TFRC_OPT_LOSS_EVENT_RATE + TFRC_OPT_RECEIVE_RATE + padding to
148 	 * make it a multiple of 4
149 	 */
150 
151 	mss_now -= ((5 + 6 + 10 + 6 + 6 + 6 + 3) / 4) * 4;
152 
153 	/* And store cached results */
154 	icsk->icsk_pmtu_cookie = pmtu;
155 	dp->dccps_mss_cache = mss_now;
156 
157 	return mss_now;
158 }
159 
160 EXPORT_SYMBOL_GPL(dccp_sync_mss);
161 
162 void dccp_write_space(struct sock *sk)
163 {
164 	read_lock(&sk->sk_callback_lock);
165 
166 	if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
167 		wake_up_interruptible(sk->sk_sleep);
168 	/* Should agree with poll, otherwise some programs break */
169 	if (sock_writeable(sk))
170 		sk_wake_async(sk, 2, POLL_OUT);
171 
172 	read_unlock(&sk->sk_callback_lock);
173 }
174 
175 /**
176  * dccp_wait_for_ccid - Wait for ccid to tell us we can send a packet
177  * @sk: socket to wait for
178  */
179 static int dccp_wait_for_ccid(struct sock *sk, struct sk_buff *skb)
180 {
181 	struct dccp_sock *dp = dccp_sk(sk);
182 	DEFINE_WAIT(wait);
183 	unsigned long delay;
184 	int rc;
185 
186 	while (1) {
187 		prepare_to_wait(sk->sk_sleep, &wait, TASK_INTERRUPTIBLE);
188 
189 		if (sk->sk_err)
190 			goto do_error;
191 		if (signal_pending(current))
192 			goto do_interrupted;
193 
194 		rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
195 		if (rc <= 0)
196 			break;
197 		dccp_pr_debug("delayed send by %d msec\n", rc);
198 		delay = msecs_to_jiffies(rc);
199 		sk->sk_write_pending++;
200 		release_sock(sk);
201 		schedule_timeout(delay);
202 		lock_sock(sk);
203 		sk->sk_write_pending--;
204 	}
205 out:
206 	finish_wait(sk->sk_sleep, &wait);
207 	return rc;
208 
209 do_error:
210 	rc = -EPIPE;
211 	goto out;
212 do_interrupted:
213 	rc = -EINTR;
214 	goto out;
215 }
216 
217 void dccp_write_xmit(struct sock *sk, int block)
218 {
219 	struct dccp_sock *dp = dccp_sk(sk);
220 	struct sk_buff *skb;
221 
222 	while ((skb = skb_peek(&sk->sk_write_queue))) {
223 		int err = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
224 
225 		if (err > 0) {
226 			if (!block) {
227 				sk_reset_timer(sk, &dp->dccps_xmit_timer,
228 						msecs_to_jiffies(err)+jiffies);
229 				break;
230 			} else
231 				err = dccp_wait_for_ccid(sk, skb);
232 			if (err && err != -EINTR)
233 				DCCP_BUG("err=%d after dccp_wait_for_ccid", err);
234 		}
235 
236 		skb_dequeue(&sk->sk_write_queue);
237 		if (err == 0) {
238 			struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
239 			const int len = skb->len;
240 
241 			if (sk->sk_state == DCCP_PARTOPEN) {
242 				/* See 8.1.5.  Handshake Completion */
243 				inet_csk_schedule_ack(sk);
244 				inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
245 						  inet_csk(sk)->icsk_rto,
246 						  DCCP_RTO_MAX);
247 				dcb->dccpd_type = DCCP_PKT_DATAACK;
248 			} else if (dccp_ack_pending(sk))
249 				dcb->dccpd_type = DCCP_PKT_DATAACK;
250 			else
251 				dcb->dccpd_type = DCCP_PKT_DATA;
252 
253 			err = dccp_transmit_skb(sk, skb);
254 			ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, 0, len);
255 			if (err)
256 				DCCP_BUG("err=%d after ccid_hc_tx_packet_sent",
257 					 err);
258 		} else {
259 			dccp_pr_debug("packet discarded due to err=%d\n", err);
260 			kfree_skb(skb);
261 		}
262 	}
263 }
264 
265 int dccp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
266 {
267 	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
268 		return -EHOSTUNREACH; /* Routing failure or similar. */
269 
270 	return dccp_transmit_skb(sk, (skb_cloned(skb) ?
271 				      pskb_copy(skb, GFP_ATOMIC):
272 				      skb_clone(skb, GFP_ATOMIC)));
273 }
274 
275 struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
276 				   struct request_sock *req)
277 {
278 	struct dccp_hdr *dh;
279 	struct dccp_request_sock *dreq;
280 	const u32 dccp_header_size = sizeof(struct dccp_hdr) +
281 				     sizeof(struct dccp_hdr_ext) +
282 				     sizeof(struct dccp_hdr_response);
283 	struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
284 					   GFP_ATOMIC);
285 	if (skb == NULL)
286 		return NULL;
287 
288 	/* Reserve space for headers. */
289 	skb_reserve(skb, sk->sk_prot->max_header);
290 
291 	skb->dst = dst_clone(dst);
292 
293 	dreq = dccp_rsk(req);
294 	if (inet_rsk(req)->acked)	/* increase ISS upon retransmission */
295 		dccp_inc_seqno(&dreq->dreq_iss);
296 	DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
297 	DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_iss;
298 
299 	if (dccp_insert_options(sk, skb)) {
300 		kfree_skb(skb);
301 		return NULL;
302 	}
303 
304 	/* Build and checksum header */
305 	dh = dccp_zeroed_hdr(skb, dccp_header_size);
306 
307 	dh->dccph_sport	= inet_sk(sk)->sport;
308 	dh->dccph_dport	= inet_rsk(req)->rmt_port;
309 	dh->dccph_doff	= (dccp_header_size +
310 			   DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
311 	dh->dccph_type	= DCCP_PKT_RESPONSE;
312 	dh->dccph_x	= 1;
313 	dccp_hdr_set_seq(dh, dreq->dreq_iss);
314 	dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_isr);
315 	dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
316 
317 	dccp_csum_outgoing(skb);
318 
319 	/* We use `acked' to remember that a Response was already sent. */
320 	inet_rsk(req)->acked = 1;
321 	DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
322 	return skb;
323 }
324 
325 EXPORT_SYMBOL_GPL(dccp_make_response);
326 
327 static struct sk_buff *dccp_make_reset(struct sock *sk, struct dst_entry *dst,
328 				       const enum dccp_reset_codes code)
329 {
330 	struct dccp_hdr *dh;
331 	struct dccp_sock *dp = dccp_sk(sk);
332 	const u32 dccp_header_size = sizeof(struct dccp_hdr) +
333 				     sizeof(struct dccp_hdr_ext) +
334 				     sizeof(struct dccp_hdr_reset);
335 	struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
336 					   GFP_ATOMIC);
337 	if (skb == NULL)
338 		return NULL;
339 
340 	/* Reserve space for headers. */
341 	skb_reserve(skb, sk->sk_prot->max_header);
342 
343 	skb->dst = dst_clone(dst);
344 
345 	dccp_inc_seqno(&dp->dccps_gss);
346 
347 	DCCP_SKB_CB(skb)->dccpd_reset_code = code;
348 	DCCP_SKB_CB(skb)->dccpd_type	   = DCCP_PKT_RESET;
349 	DCCP_SKB_CB(skb)->dccpd_seq	   = dp->dccps_gss;
350 
351 	if (dccp_insert_options(sk, skb)) {
352 		kfree_skb(skb);
353 		return NULL;
354 	}
355 
356 	dh = dccp_zeroed_hdr(skb, dccp_header_size);
357 
358 	dh->dccph_sport	= inet_sk(sk)->sport;
359 	dh->dccph_dport	= inet_sk(sk)->dport;
360 	dh->dccph_doff	= (dccp_header_size +
361 			   DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
362 	dh->dccph_type	= DCCP_PKT_RESET;
363 	dh->dccph_x	= 1;
364 	dccp_hdr_set_seq(dh, dp->dccps_gss);
365 	dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dp->dccps_gsr);
366 
367 	dccp_hdr_reset(skb)->dccph_reset_code = code;
368 	inet_csk(sk)->icsk_af_ops->send_check(sk, 0, skb);
369 
370 	DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
371 	return skb;
372 }
373 
374 int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
375 {
376 	/*
377 	 * FIXME: what if rebuild_header fails?
378 	 * Should we be doing a rebuild_header here?
379 	 */
380 	int err = inet_sk_rebuild_header(sk);
381 
382 	if (err == 0) {
383 		struct sk_buff *skb = dccp_make_reset(sk, sk->sk_dst_cache,
384 						      code);
385 		if (skb != NULL) {
386 			memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
387 			err = inet_csk(sk)->icsk_af_ops->queue_xmit(skb, 0);
388 			return net_xmit_eval(err);
389 		}
390 	}
391 
392 	return err;
393 }
394 
395 /*
396  * Do all connect socket setups that can be done AF independent.
397  */
398 static inline void dccp_connect_init(struct sock *sk)
399 {
400 	struct dccp_sock *dp = dccp_sk(sk);
401 	struct dst_entry *dst = __sk_dst_get(sk);
402 	struct inet_connection_sock *icsk = inet_csk(sk);
403 
404 	sk->sk_err = 0;
405 	sock_reset_flag(sk, SOCK_DONE);
406 
407 	dccp_sync_mss(sk, dst_mtu(dst));
408 
409 	/*
410 	 * SWL and AWL are initially adjusted so that they are not less than
411 	 * the initial Sequence Numbers received and sent, respectively:
412 	 *	SWL := max(GSR + 1 - floor(W/4), ISR),
413 	 *	AWL := max(GSS - W' + 1, ISS).
414 	 * These adjustments MUST be applied only at the beginning of the
415 	 * connection.
416 	 */
417 	dccp_update_gss(sk, dp->dccps_iss);
418 	dccp_set_seqno(&dp->dccps_awl, max48(dp->dccps_awl, dp->dccps_iss));
419 
420 	/* S.GAR - greatest valid acknowledgement number received on a non-Sync;
421 	 *         initialized to S.ISS (sec. 8.5)                            */
422 	dp->dccps_gar = dp->dccps_iss;
423 
424 	icsk->icsk_retransmits = 0;
425 }
426 
427 int dccp_connect(struct sock *sk)
428 {
429 	struct sk_buff *skb;
430 	struct inet_connection_sock *icsk = inet_csk(sk);
431 
432 	dccp_connect_init(sk);
433 
434 	skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
435 	if (unlikely(skb == NULL))
436 		return -ENOBUFS;
437 
438 	/* Reserve space for headers. */
439 	skb_reserve(skb, sk->sk_prot->max_header);
440 
441 	DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
442 
443 	dccp_skb_entail(sk, skb);
444 	dccp_transmit_skb(sk, skb_clone(skb, GFP_KERNEL));
445 	DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
446 
447 	/* Timer for repeating the REQUEST until an answer. */
448 	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
449 				  icsk->icsk_rto, DCCP_RTO_MAX);
450 	return 0;
451 }
452 
453 EXPORT_SYMBOL_GPL(dccp_connect);
454 
455 void dccp_send_ack(struct sock *sk)
456 {
457 	/* If we have been reset, we may not send again. */
458 	if (sk->sk_state != DCCP_CLOSED) {
459 		struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header,
460 						GFP_ATOMIC);
461 
462 		if (skb == NULL) {
463 			inet_csk_schedule_ack(sk);
464 			inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
465 			inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
466 						  TCP_DELACK_MAX,
467 						  DCCP_RTO_MAX);
468 			return;
469 		}
470 
471 		/* Reserve space for headers */
472 		skb_reserve(skb, sk->sk_prot->max_header);
473 		DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
474 		dccp_transmit_skb(sk, skb);
475 	}
476 }
477 
478 EXPORT_SYMBOL_GPL(dccp_send_ack);
479 
480 void dccp_send_delayed_ack(struct sock *sk)
481 {
482 	struct inet_connection_sock *icsk = inet_csk(sk);
483 	/*
484 	 * FIXME: tune this timer. elapsed time fixes the skew, so no problem
485 	 * with using 2s, and active senders also piggyback the ACK into a
486 	 * DATAACK packet, so this is really for quiescent senders.
487 	 */
488 	unsigned long timeout = jiffies + 2 * HZ;
489 
490 	/* Use new timeout only if there wasn't a older one earlier. */
491 	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
492 		/* If delack timer was blocked or is about to expire,
493 		 * send ACK now.
494 		 *
495 		 * FIXME: check the "about to expire" part
496 		 */
497 		if (icsk->icsk_ack.blocked) {
498 			dccp_send_ack(sk);
499 			return;
500 		}
501 
502 		if (!time_before(timeout, icsk->icsk_ack.timeout))
503 			timeout = icsk->icsk_ack.timeout;
504 	}
505 	icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
506 	icsk->icsk_ack.timeout = timeout;
507 	sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
508 }
509 
510 void dccp_send_sync(struct sock *sk, const u64 seq,
511 		    const enum dccp_pkt_type pkt_type)
512 {
513 	/*
514 	 * We are not putting this on the write queue, so
515 	 * dccp_transmit_skb() will set the ownership to this
516 	 * sock.
517 	 */
518 	struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
519 
520 	if (skb == NULL)
521 		/* FIXME: how to make sure the sync is sent? */
522 		return;
523 
524 	/* Reserve space for headers and prepare control bits. */
525 	skb_reserve(skb, sk->sk_prot->max_header);
526 	DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
527 	DCCP_SKB_CB(skb)->dccpd_seq = seq;
528 
529 	dccp_transmit_skb(sk, skb);
530 }
531 
532 EXPORT_SYMBOL_GPL(dccp_send_sync);
533 
534 /*
535  * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This
536  * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
537  * any circumstances.
538  */
539 void dccp_send_close(struct sock *sk, const int active)
540 {
541 	struct dccp_sock *dp = dccp_sk(sk);
542 	struct sk_buff *skb;
543 	const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC;
544 
545 	skb = alloc_skb(sk->sk_prot->max_header, prio);
546 	if (skb == NULL)
547 		return;
548 
549 	/* Reserve space for headers and prepare control bits. */
550 	skb_reserve(skb, sk->sk_prot->max_header);
551 	DCCP_SKB_CB(skb)->dccpd_type = dp->dccps_role == DCCP_ROLE_CLIENT ?
552 					DCCP_PKT_CLOSE : DCCP_PKT_CLOSEREQ;
553 
554 	if (active) {
555 		dccp_write_xmit(sk, 1);
556 		dccp_skb_entail(sk, skb);
557 		dccp_transmit_skb(sk, skb_clone(skb, prio));
558 		/* FIXME do we need a retransmit timer here? */
559 	} else
560 		dccp_transmit_skb(sk, skb);
561 }
562