xref: /openbmc/linux/net/dccp/ccids/ccid3.c (revision 0b609b55)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
4  *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
5  *  Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz>
6  *
7  *  An implementation of the DCCP protocol
8  *
9  *  This code has been developed by the University of Waikato WAND
10  *  research group. For further information please see https://www.wand.net.nz/
11  *
12  *  This code also uses code from Lulea University, rereleased as GPL by its
13  *  authors:
14  *  Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
15  *
16  *  Changes to meet Linux coding standards, to make it meet latest ccid3 draft
17  *  and to make it work as a loadable module in the DCCP stack written by
18  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
19  *
20  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
21  */
22 #include "../dccp.h"
23 #include "ccid3.h"
24 
25 #include <asm/unaligned.h>
26 
27 #ifdef CONFIG_IP_DCCP_CCID3_DEBUG
28 static bool ccid3_debug;
29 #define ccid3_pr_debug(format, a...)	DCCP_PR_DEBUG(ccid3_debug, format, ##a)
30 #else
31 #define ccid3_pr_debug(format, a...)
32 #endif
33 
34 /*
35  *	Transmitter Half-Connection Routines
36  */
37 #ifdef CONFIG_IP_DCCP_CCID3_DEBUG
ccid3_tx_state_name(enum ccid3_hc_tx_states state)38 static const char *ccid3_tx_state_name(enum ccid3_hc_tx_states state)
39 {
40 	static const char *const ccid3_state_names[] = {
41 	[TFRC_SSTATE_NO_SENT]  = "NO_SENT",
42 	[TFRC_SSTATE_NO_FBACK] = "NO_FBACK",
43 	[TFRC_SSTATE_FBACK]    = "FBACK",
44 	};
45 
46 	return ccid3_state_names[state];
47 }
48 #endif
49 
ccid3_hc_tx_set_state(struct sock * sk,enum ccid3_hc_tx_states state)50 static void ccid3_hc_tx_set_state(struct sock *sk,
51 				  enum ccid3_hc_tx_states state)
52 {
53 	struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
54 	enum ccid3_hc_tx_states oldstate = hc->tx_state;
55 
56 	ccid3_pr_debug("%s(%p) %-8.8s -> %s\n",
57 		       dccp_role(sk), sk, ccid3_tx_state_name(oldstate),
58 		       ccid3_tx_state_name(state));
59 	WARN_ON(state == oldstate);
60 	hc->tx_state = state;
61 }
62 
63 /*
64  * Compute the initial sending rate X_init in the manner of RFC 3390:
65  *
66  *	X_init  =  min(4 * s, max(2 * s, 4380 bytes)) / RTT
67  *
68  * Note that RFC 3390 uses MSS, RFC 4342 refers to RFC 3390, and rfc3448bis
69  * (rev-02) clarifies the use of RFC 3390 with regard to the above formula.
70  * For consistency with other parts of the code, X_init is scaled by 2^6.
71  */
rfc3390_initial_rate(struct sock * sk)72 static inline u64 rfc3390_initial_rate(struct sock *sk)
73 {
74 	const struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
75 	const __u32 w_init = clamp_t(__u32, 4380U, 2 * hc->tx_s, 4 * hc->tx_s);
76 
77 	return scaled_div(w_init << 6, hc->tx_rtt);
78 }
79 
80 /**
81  * ccid3_update_send_interval  -  Calculate new t_ipi = s / X_inst
82  * @hc: socket to have the send interval updated
83  *
84  * This respects the granularity of X_inst (64 * bytes/second).
85  */
ccid3_update_send_interval(struct ccid3_hc_tx_sock * hc)86 static void ccid3_update_send_interval(struct ccid3_hc_tx_sock *hc)
87 {
88 	hc->tx_t_ipi = scaled_div32(((u64)hc->tx_s) << 6, hc->tx_x);
89 
90 	DCCP_BUG_ON(hc->tx_t_ipi == 0);
91 	ccid3_pr_debug("t_ipi=%u, s=%u, X=%u\n", hc->tx_t_ipi,
92 		       hc->tx_s, (unsigned int)(hc->tx_x >> 6));
93 }
94 
ccid3_hc_tx_idle_rtt(struct ccid3_hc_tx_sock * hc,ktime_t now)95 static u32 ccid3_hc_tx_idle_rtt(struct ccid3_hc_tx_sock *hc, ktime_t now)
96 {
97 	u32 delta = ktime_us_delta(now, hc->tx_t_last_win_count);
98 
99 	return delta / hc->tx_rtt;
100 }
101 
102 /**
103  * ccid3_hc_tx_update_x  -  Update allowed sending rate X
104  * @sk: socket to be updated
105  * @stamp: most recent time if available - can be left NULL.
106  *
107  * This function tracks draft rfc3448bis, check there for latest details.
108  *
109  * Note: X and X_recv are both stored in units of 64 * bytes/second, to support
110  *       fine-grained resolution of sending rates. This requires scaling by 2^6
111  *       throughout the code. Only X_calc is unscaled (in bytes/second).
112  *
113  */
ccid3_hc_tx_update_x(struct sock * sk,ktime_t * stamp)114 static void ccid3_hc_tx_update_x(struct sock *sk, ktime_t *stamp)
115 {
116 	struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
117 	__u64 min_rate = 2 * hc->tx_x_recv;
118 	const __u64 old_x = hc->tx_x;
119 	ktime_t now = stamp ? *stamp : ktime_get_real();
120 
121 	/*
122 	 * Handle IDLE periods: do not reduce below RFC3390 initial sending rate
123 	 * when idling [RFC 4342, 5.1]. Definition of idling is from rfc3448bis:
124 	 * a sender is idle if it has not sent anything over a 2-RTT-period.
125 	 * For consistency with X and X_recv, min_rate is also scaled by 2^6.
126 	 */
127 	if (ccid3_hc_tx_idle_rtt(hc, now) >= 2) {
128 		min_rate = rfc3390_initial_rate(sk);
129 		min_rate = max(min_rate, 2 * hc->tx_x_recv);
130 	}
131 
132 	if (hc->tx_p > 0) {
133 
134 		hc->tx_x = min(((__u64)hc->tx_x_calc) << 6, min_rate);
135 		hc->tx_x = max(hc->tx_x, (((__u64)hc->tx_s) << 6) / TFRC_T_MBI);
136 
137 	} else if (ktime_us_delta(now, hc->tx_t_ld) - (s64)hc->tx_rtt >= 0) {
138 
139 		hc->tx_x = min(2 * hc->tx_x, min_rate);
140 		hc->tx_x = max(hc->tx_x,
141 			       scaled_div(((__u64)hc->tx_s) << 6, hc->tx_rtt));
142 		hc->tx_t_ld = now;
143 	}
144 
145 	if (hc->tx_x != old_x) {
146 		ccid3_pr_debug("X_prev=%u, X_now=%u, X_calc=%u, "
147 			       "X_recv=%u\n", (unsigned int)(old_x >> 6),
148 			       (unsigned int)(hc->tx_x >> 6), hc->tx_x_calc,
149 			       (unsigned int)(hc->tx_x_recv >> 6));
150 
151 		ccid3_update_send_interval(hc);
152 	}
153 }
154 
155 /**
156  *	ccid3_hc_tx_update_s - Track the mean packet size `s'
157  *	@hc: socket to be updated
158  *	@len: DCCP packet payload size in bytes
159  *
160  *	cf. RFC 4342, 5.3 and  RFC 3448, 4.1
161  */
ccid3_hc_tx_update_s(struct ccid3_hc_tx_sock * hc,int len)162 static inline void ccid3_hc_tx_update_s(struct ccid3_hc_tx_sock *hc, int len)
163 {
164 	const u16 old_s = hc->tx_s;
165 
166 	hc->tx_s = tfrc_ewma(hc->tx_s, len, 9);
167 
168 	if (hc->tx_s != old_s)
169 		ccid3_update_send_interval(hc);
170 }
171 
172 /*
173  *	Update Window Counter using the algorithm from [RFC 4342, 8.1].
174  *	As elsewhere, RTT > 0 is assumed by using dccp_sample_rtt().
175  */
ccid3_hc_tx_update_win_count(struct ccid3_hc_tx_sock * hc,ktime_t now)176 static inline void ccid3_hc_tx_update_win_count(struct ccid3_hc_tx_sock *hc,
177 						ktime_t now)
178 {
179 	u32 delta = ktime_us_delta(now, hc->tx_t_last_win_count),
180 	    quarter_rtts = (4 * delta) / hc->tx_rtt;
181 
182 	if (quarter_rtts > 0) {
183 		hc->tx_t_last_win_count = now;
184 		hc->tx_last_win_count  += min(quarter_rtts, 5U);
185 		hc->tx_last_win_count  &= 0xF;		/* mod 16 */
186 	}
187 }
188 
ccid3_hc_tx_no_feedback_timer(struct timer_list * t)189 static void ccid3_hc_tx_no_feedback_timer(struct timer_list *t)
190 {
191 	struct ccid3_hc_tx_sock *hc = from_timer(hc, t, tx_no_feedback_timer);
192 	struct sock *sk = hc->sk;
193 	unsigned long t_nfb = USEC_PER_SEC / 5;
194 
195 	bh_lock_sock(sk);
196 	if (sock_owned_by_user(sk)) {
197 		/* Try again later. */
198 		/* XXX: set some sensible MIB */
199 		goto restart_timer;
200 	}
201 
202 	ccid3_pr_debug("%s(%p, state=%s) - entry\n", dccp_role(sk), sk,
203 		       ccid3_tx_state_name(hc->tx_state));
204 
205 	/* Ignore and do not restart after leaving the established state */
206 	if ((1 << sk->sk_state) & ~(DCCPF_OPEN | DCCPF_PARTOPEN))
207 		goto out;
208 
209 	/* Reset feedback state to "no feedback received" */
210 	if (hc->tx_state == TFRC_SSTATE_FBACK)
211 		ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
212 
213 	/*
214 	 * Determine new allowed sending rate X as per draft rfc3448bis-00, 4.4
215 	 * RTO is 0 if and only if no feedback has been received yet.
216 	 */
217 	if (hc->tx_t_rto == 0 || hc->tx_p == 0) {
218 
219 		/* halve send rate directly */
220 		hc->tx_x = max(hc->tx_x / 2,
221 			       (((__u64)hc->tx_s) << 6) / TFRC_T_MBI);
222 		ccid3_update_send_interval(hc);
223 	} else {
224 		/*
225 		 *  Modify the cached value of X_recv
226 		 *
227 		 *  If (X_calc > 2 * X_recv)
228 		 *    X_recv = max(X_recv / 2, s / (2 * t_mbi));
229 		 *  Else
230 		 *    X_recv = X_calc / 4;
231 		 *
232 		 *  Note that X_recv is scaled by 2^6 while X_calc is not
233 		 */
234 		if (hc->tx_x_calc > (hc->tx_x_recv >> 5))
235 			hc->tx_x_recv =
236 				max(hc->tx_x_recv / 2,
237 				    (((__u64)hc->tx_s) << 6) / (2*TFRC_T_MBI));
238 		else {
239 			hc->tx_x_recv = hc->tx_x_calc;
240 			hc->tx_x_recv <<= 4;
241 		}
242 		ccid3_hc_tx_update_x(sk, NULL);
243 	}
244 	ccid3_pr_debug("Reduced X to %llu/64 bytes/sec\n",
245 			(unsigned long long)hc->tx_x);
246 
247 	/*
248 	 * Set new timeout for the nofeedback timer.
249 	 * See comments in packet_recv() regarding the value of t_RTO.
250 	 */
251 	if (unlikely(hc->tx_t_rto == 0))	/* no feedback received yet */
252 		t_nfb = TFRC_INITIAL_TIMEOUT;
253 	else
254 		t_nfb = max(hc->tx_t_rto, 2 * hc->tx_t_ipi);
255 
256 restart_timer:
257 	sk_reset_timer(sk, &hc->tx_no_feedback_timer,
258 			   jiffies + usecs_to_jiffies(t_nfb));
259 out:
260 	bh_unlock_sock(sk);
261 	sock_put(sk);
262 }
263 
264 /**
265  * ccid3_hc_tx_send_packet  -  Delay-based dequeueing of TX packets
266  * @sk: socket to send packet from
267  * @skb: next packet candidate to send on @sk
268  *
269  * This function uses the convention of ccid_packet_dequeue_eval() and
270  * returns a millisecond-delay value between 0 and t_mbi = 64000 msec.
271  */
ccid3_hc_tx_send_packet(struct sock * sk,struct sk_buff * skb)272 static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
273 {
274 	struct dccp_sock *dp = dccp_sk(sk);
275 	struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
276 	ktime_t now = ktime_get_real();
277 	s64 delay;
278 
279 	/*
280 	 * This function is called only for Data and DataAck packets. Sending
281 	 * zero-sized Data(Ack)s is theoretically possible, but for congestion
282 	 * control this case is pathological - ignore it.
283 	 */
284 	if (unlikely(skb->len == 0))
285 		return -EBADMSG;
286 
287 	if (hc->tx_state == TFRC_SSTATE_NO_SENT) {
288 		sk_reset_timer(sk, &hc->tx_no_feedback_timer, (jiffies +
289 			       usecs_to_jiffies(TFRC_INITIAL_TIMEOUT)));
290 		hc->tx_last_win_count	= 0;
291 		hc->tx_t_last_win_count = now;
292 
293 		/* Set t_0 for initial packet */
294 		hc->tx_t_nom = now;
295 
296 		hc->tx_s = skb->len;
297 
298 		/*
299 		 * Use initial RTT sample when available: recommended by erratum
300 		 * to RFC 4342. This implements the initialisation procedure of
301 		 * draft rfc3448bis, section 4.2. Remember, X is scaled by 2^6.
302 		 */
303 		if (dp->dccps_syn_rtt) {
304 			ccid3_pr_debug("SYN RTT = %uus\n", dp->dccps_syn_rtt);
305 			hc->tx_rtt  = dp->dccps_syn_rtt;
306 			hc->tx_x    = rfc3390_initial_rate(sk);
307 			hc->tx_t_ld = now;
308 		} else {
309 			/*
310 			 * Sender does not have RTT sample:
311 			 * - set fallback RTT (RFC 4340, 3.4) since a RTT value
312 			 *   is needed in several parts (e.g.  window counter);
313 			 * - set sending rate X_pps = 1pps as per RFC 3448, 4.2.
314 			 */
315 			hc->tx_rtt = DCCP_FALLBACK_RTT;
316 			hc->tx_x   = hc->tx_s;
317 			hc->tx_x <<= 6;
318 		}
319 		ccid3_update_send_interval(hc);
320 
321 		ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
322 
323 	} else {
324 		delay = ktime_us_delta(hc->tx_t_nom, now);
325 		ccid3_pr_debug("delay=%ld\n", (long)delay);
326 		/*
327 		 *	Scheduling of packet transmissions (RFC 5348, 8.3)
328 		 *
329 		 * if (t_now > t_nom - delta)
330 		 *       // send the packet now
331 		 * else
332 		 *       // send the packet in (t_nom - t_now) milliseconds.
333 		 */
334 		if (delay >= TFRC_T_DELTA)
335 			return (u32)delay / USEC_PER_MSEC;
336 
337 		ccid3_hc_tx_update_win_count(hc, now);
338 	}
339 
340 	/* prepare to send now (add options etc.) */
341 	dp->dccps_hc_tx_insert_options = 1;
342 	DCCP_SKB_CB(skb)->dccpd_ccval  = hc->tx_last_win_count;
343 
344 	/* set the nominal send time for the next following packet */
345 	hc->tx_t_nom = ktime_add_us(hc->tx_t_nom, hc->tx_t_ipi);
346 	return CCID_PACKET_SEND_AT_ONCE;
347 }
348 
ccid3_hc_tx_packet_sent(struct sock * sk,unsigned int len)349 static void ccid3_hc_tx_packet_sent(struct sock *sk, unsigned int len)
350 {
351 	struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
352 
353 	ccid3_hc_tx_update_s(hc, len);
354 
355 	if (tfrc_tx_hist_add(&hc->tx_hist, dccp_sk(sk)->dccps_gss))
356 		DCCP_CRIT("packet history - out of memory!");
357 }
358 
ccid3_hc_tx_packet_recv(struct sock * sk,struct sk_buff * skb)359 static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
360 {
361 	struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
362 	struct tfrc_tx_hist_entry *acked;
363 	ktime_t now;
364 	unsigned long t_nfb;
365 	u32 r_sample;
366 
367 	/* we are only interested in ACKs */
368 	if (!(DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_ACK ||
369 	      DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_DATAACK))
370 		return;
371 	/*
372 	 * Locate the acknowledged packet in the TX history.
373 	 *
374 	 * Returning "entry not found" here can for instance happen when
375 	 *  - the host has not sent out anything (e.g. a passive server),
376 	 *  - the Ack is outdated (packet with higher Ack number was received),
377 	 *  - it is a bogus Ack (for a packet not sent on this connection).
378 	 */
379 	acked = tfrc_tx_hist_find_entry(hc->tx_hist, dccp_hdr_ack_seq(skb));
380 	if (acked == NULL)
381 		return;
382 	/* For the sake of RTT sampling, ignore/remove all older entries */
383 	tfrc_tx_hist_purge(&acked->next);
384 
385 	/* Update the moving average for the RTT estimate (RFC 3448, 4.3) */
386 	now	  = ktime_get_real();
387 	r_sample  = dccp_sample_rtt(sk, ktime_us_delta(now, acked->stamp));
388 	hc->tx_rtt = tfrc_ewma(hc->tx_rtt, r_sample, 9);
389 
390 	/*
391 	 * Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3
392 	 */
393 	if (hc->tx_state == TFRC_SSTATE_NO_FBACK) {
394 		ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
395 
396 		if (hc->tx_t_rto == 0) {
397 			/*
398 			 * Initial feedback packet: Larger Initial Windows (4.2)
399 			 */
400 			hc->tx_x    = rfc3390_initial_rate(sk);
401 			hc->tx_t_ld = now;
402 
403 			ccid3_update_send_interval(hc);
404 
405 			goto done_computing_x;
406 		} else if (hc->tx_p == 0) {
407 			/*
408 			 * First feedback after nofeedback timer expiry (4.3)
409 			 */
410 			goto done_computing_x;
411 		}
412 	}
413 
414 	/* Update sending rate (step 4 of [RFC 3448, 4.3]) */
415 	if (hc->tx_p > 0)
416 		hc->tx_x_calc = tfrc_calc_x(hc->tx_s, hc->tx_rtt, hc->tx_p);
417 	ccid3_hc_tx_update_x(sk, &now);
418 
419 done_computing_x:
420 	ccid3_pr_debug("%s(%p), RTT=%uus (sample=%uus), s=%u, "
421 			       "p=%u, X_calc=%u, X_recv=%u, X=%u\n",
422 			       dccp_role(sk), sk, hc->tx_rtt, r_sample,
423 			       hc->tx_s, hc->tx_p, hc->tx_x_calc,
424 			       (unsigned int)(hc->tx_x_recv >> 6),
425 			       (unsigned int)(hc->tx_x >> 6));
426 
427 	/* unschedule no feedback timer */
428 	sk_stop_timer(sk, &hc->tx_no_feedback_timer);
429 
430 	/*
431 	 * As we have calculated new ipi, delta, t_nom it is possible
432 	 * that we now can send a packet, so wake up dccp_wait_for_ccid
433 	 */
434 	sk->sk_write_space(sk);
435 
436 	/*
437 	 * Update timeout interval for the nofeedback timer. In order to control
438 	 * rate halving on networks with very low RTTs (<= 1 ms), use per-route
439 	 * tunable RTAX_RTO_MIN value as the lower bound.
440 	 */
441 	hc->tx_t_rto = max_t(u32, 4 * hc->tx_rtt,
442 				  USEC_PER_SEC/HZ * tcp_rto_min(sk));
443 	/*
444 	 * Schedule no feedback timer to expire in
445 	 * max(t_RTO, 2 * s/X)  =  max(t_RTO, 2 * t_ipi)
446 	 */
447 	t_nfb = max(hc->tx_t_rto, 2 * hc->tx_t_ipi);
448 
449 	ccid3_pr_debug("%s(%p), Scheduled no feedback timer to "
450 		       "expire in %lu jiffies (%luus)\n",
451 		       dccp_role(sk), sk, usecs_to_jiffies(t_nfb), t_nfb);
452 
453 	sk_reset_timer(sk, &hc->tx_no_feedback_timer,
454 			   jiffies + usecs_to_jiffies(t_nfb));
455 }
456 
ccid3_hc_tx_parse_options(struct sock * sk,u8 packet_type,u8 option,u8 * optval,u8 optlen)457 static int ccid3_hc_tx_parse_options(struct sock *sk, u8 packet_type,
458 				     u8 option, u8 *optval, u8 optlen)
459 {
460 	struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
461 	__be32 opt_val;
462 
463 	switch (option) {
464 	case TFRC_OPT_RECEIVE_RATE:
465 	case TFRC_OPT_LOSS_EVENT_RATE:
466 		/* Must be ignored on Data packets, cf. RFC 4342 8.3 and 8.5 */
467 		if (packet_type == DCCP_PKT_DATA)
468 			break;
469 		if (unlikely(optlen != 4)) {
470 			DCCP_WARN("%s(%p), invalid len %d for %u\n",
471 				  dccp_role(sk), sk, optlen, option);
472 			return -EINVAL;
473 		}
474 		opt_val = ntohl(get_unaligned((__be32 *)optval));
475 
476 		if (option == TFRC_OPT_RECEIVE_RATE) {
477 			/* Receive Rate is kept in units of 64 bytes/second */
478 			hc->tx_x_recv = opt_val;
479 			hc->tx_x_recv <<= 6;
480 
481 			ccid3_pr_debug("%s(%p), RECEIVE_RATE=%u\n",
482 				       dccp_role(sk), sk, opt_val);
483 		} else {
484 			/* Update the fixpoint Loss Event Rate fraction */
485 			hc->tx_p = tfrc_invert_loss_event_rate(opt_val);
486 
487 			ccid3_pr_debug("%s(%p), LOSS_EVENT_RATE=%u\n",
488 				       dccp_role(sk), sk, opt_val);
489 		}
490 	}
491 	return 0;
492 }
493 
ccid3_hc_tx_init(struct ccid * ccid,struct sock * sk)494 static int ccid3_hc_tx_init(struct ccid *ccid, struct sock *sk)
495 {
496 	struct ccid3_hc_tx_sock *hc = ccid_priv(ccid);
497 
498 	hc->tx_state = TFRC_SSTATE_NO_SENT;
499 	hc->tx_hist  = NULL;
500 	hc->sk	     = sk;
501 	timer_setup(&hc->tx_no_feedback_timer,
502 		    ccid3_hc_tx_no_feedback_timer, 0);
503 	return 0;
504 }
505 
ccid3_hc_tx_exit(struct sock * sk)506 static void ccid3_hc_tx_exit(struct sock *sk)
507 {
508 	struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
509 
510 	sk_stop_timer(sk, &hc->tx_no_feedback_timer);
511 	tfrc_tx_hist_purge(&hc->tx_hist);
512 }
513 
ccid3_hc_tx_get_info(struct sock * sk,struct tcp_info * info)514 static void ccid3_hc_tx_get_info(struct sock *sk, struct tcp_info *info)
515 {
516 	info->tcpi_rto = ccid3_hc_tx_sk(sk)->tx_t_rto;
517 	info->tcpi_rtt = ccid3_hc_tx_sk(sk)->tx_rtt;
518 }
519 
ccid3_hc_tx_getsockopt(struct sock * sk,const int optname,int len,u32 __user * optval,int __user * optlen)520 static int ccid3_hc_tx_getsockopt(struct sock *sk, const int optname, int len,
521 				  u32 __user *optval, int __user *optlen)
522 {
523 	const struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
524 	struct tfrc_tx_info tfrc;
525 	const void *val;
526 
527 	switch (optname) {
528 	case DCCP_SOCKOPT_CCID_TX_INFO:
529 		if (len < sizeof(tfrc))
530 			return -EINVAL;
531 		memset(&tfrc, 0, sizeof(tfrc));
532 		tfrc.tfrctx_x	   = hc->tx_x;
533 		tfrc.tfrctx_x_recv = hc->tx_x_recv;
534 		tfrc.tfrctx_x_calc = hc->tx_x_calc;
535 		tfrc.tfrctx_rtt	   = hc->tx_rtt;
536 		tfrc.tfrctx_p	   = hc->tx_p;
537 		tfrc.tfrctx_rto	   = hc->tx_t_rto;
538 		tfrc.tfrctx_ipi	   = hc->tx_t_ipi;
539 		len = sizeof(tfrc);
540 		val = &tfrc;
541 		break;
542 	default:
543 		return -ENOPROTOOPT;
544 	}
545 
546 	if (put_user(len, optlen) || copy_to_user(optval, val, len))
547 		return -EFAULT;
548 
549 	return 0;
550 }
551 
552 /*
553  *	Receiver Half-Connection Routines
554  */
555 
556 /* CCID3 feedback types */
557 enum ccid3_fback_type {
558 	CCID3_FBACK_NONE = 0,
559 	CCID3_FBACK_INITIAL,
560 	CCID3_FBACK_PERIODIC,
561 	CCID3_FBACK_PARAM_CHANGE
562 };
563 
564 #ifdef CONFIG_IP_DCCP_CCID3_DEBUG
ccid3_rx_state_name(enum ccid3_hc_rx_states state)565 static const char *ccid3_rx_state_name(enum ccid3_hc_rx_states state)
566 {
567 	static const char *const ccid3_rx_state_names[] = {
568 	[TFRC_RSTATE_NO_DATA] = "NO_DATA",
569 	[TFRC_RSTATE_DATA]    = "DATA",
570 	};
571 
572 	return ccid3_rx_state_names[state];
573 }
574 #endif
575 
ccid3_hc_rx_set_state(struct sock * sk,enum ccid3_hc_rx_states state)576 static void ccid3_hc_rx_set_state(struct sock *sk,
577 				  enum ccid3_hc_rx_states state)
578 {
579 	struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
580 	enum ccid3_hc_rx_states oldstate = hc->rx_state;
581 
582 	ccid3_pr_debug("%s(%p) %-8.8s -> %s\n",
583 		       dccp_role(sk), sk, ccid3_rx_state_name(oldstate),
584 		       ccid3_rx_state_name(state));
585 	WARN_ON(state == oldstate);
586 	hc->rx_state = state;
587 }
588 
ccid3_hc_rx_send_feedback(struct sock * sk,const struct sk_buff * skb,enum ccid3_fback_type fbtype)589 static void ccid3_hc_rx_send_feedback(struct sock *sk,
590 				      const struct sk_buff *skb,
591 				      enum ccid3_fback_type fbtype)
592 {
593 	struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
594 	struct dccp_sock *dp = dccp_sk(sk);
595 	ktime_t now = ktime_get();
596 	s64 delta = 0;
597 
598 	switch (fbtype) {
599 	case CCID3_FBACK_INITIAL:
600 		hc->rx_x_recv = 0;
601 		hc->rx_pinv   = ~0U;   /* see RFC 4342, 8.5 */
602 		break;
603 	case CCID3_FBACK_PARAM_CHANGE:
604 		/*
605 		 * When parameters change (new loss or p > p_prev), we do not
606 		 * have a reliable estimate for R_m of [RFC 3448, 6.2] and so
607 		 * need to  reuse the previous value of X_recv. However, when
608 		 * X_recv was 0 (due to early loss), this would kill X down to
609 		 * s/t_mbi (i.e. one packet in 64 seconds).
610 		 * To avoid such drastic reduction, we approximate X_recv as
611 		 * the number of bytes since last feedback.
612 		 * This is a safe fallback, since X is bounded above by X_calc.
613 		 */
614 		if (hc->rx_x_recv > 0)
615 			break;
616 		fallthrough;
617 	case CCID3_FBACK_PERIODIC:
618 		delta = ktime_us_delta(now, hc->rx_tstamp_last_feedback);
619 		if (delta <= 0)
620 			delta = 1;
621 		hc->rx_x_recv = scaled_div32(hc->rx_bytes_recv, delta);
622 		break;
623 	default:
624 		return;
625 	}
626 
627 	ccid3_pr_debug("Interval %lldusec, X_recv=%u, 1/p=%u\n", delta,
628 		       hc->rx_x_recv, hc->rx_pinv);
629 
630 	hc->rx_tstamp_last_feedback = now;
631 	hc->rx_last_counter	    = dccp_hdr(skb)->dccph_ccval;
632 	hc->rx_bytes_recv	    = 0;
633 
634 	dp->dccps_hc_rx_insert_options = 1;
635 	dccp_send_ack(sk);
636 }
637 
ccid3_hc_rx_insert_options(struct sock * sk,struct sk_buff * skb)638 static int ccid3_hc_rx_insert_options(struct sock *sk, struct sk_buff *skb)
639 {
640 	const struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
641 	__be32 x_recv, pinv;
642 
643 	if (!(sk->sk_state == DCCP_OPEN || sk->sk_state == DCCP_PARTOPEN))
644 		return 0;
645 
646 	if (dccp_packet_without_ack(skb))
647 		return 0;
648 
649 	x_recv = htonl(hc->rx_x_recv);
650 	pinv   = htonl(hc->rx_pinv);
651 
652 	if (dccp_insert_option(skb, TFRC_OPT_LOSS_EVENT_RATE,
653 			       &pinv, sizeof(pinv)) ||
654 	    dccp_insert_option(skb, TFRC_OPT_RECEIVE_RATE,
655 			       &x_recv, sizeof(x_recv)))
656 		return -1;
657 
658 	return 0;
659 }
660 
661 /**
662  * ccid3_first_li  -  Implements [RFC 5348, 6.3.1]
663  * @sk: socket to calculate loss interval for
664  *
665  * Determine the length of the first loss interval via inverse lookup.
666  * Assume that X_recv can be computed by the throughput equation
667  *		    s
668  *	X_recv = --------
669  *		 R * fval
670  * Find some p such that f(p) = fval; return 1/p (scaled).
671  */
ccid3_first_li(struct sock * sk)672 static u32 ccid3_first_li(struct sock *sk)
673 {
674 	struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
675 	u32 x_recv, p;
676 	s64 delta;
677 	u64 fval;
678 
679 	if (hc->rx_rtt == 0) {
680 		DCCP_WARN("No RTT estimate available, using fallback RTT\n");
681 		hc->rx_rtt = DCCP_FALLBACK_RTT;
682 	}
683 
684 	delta = ktime_us_delta(ktime_get(), hc->rx_tstamp_last_feedback);
685 	if (delta <= 0)
686 		delta = 1;
687 	x_recv = scaled_div32(hc->rx_bytes_recv, delta);
688 	if (x_recv == 0) {		/* would also trigger divide-by-zero */
689 		DCCP_WARN("X_recv==0\n");
690 		if (hc->rx_x_recv == 0) {
691 			DCCP_BUG("stored value of X_recv is zero");
692 			return ~0U;
693 		}
694 		x_recv = hc->rx_x_recv;
695 	}
696 
697 	fval = scaled_div(hc->rx_s, hc->rx_rtt);
698 	fval = scaled_div32(fval, x_recv);
699 	p = tfrc_calc_x_reverse_lookup(fval);
700 
701 	ccid3_pr_debug("%s(%p), receive rate=%u bytes/s, implied "
702 		       "loss rate=%u\n", dccp_role(sk), sk, x_recv, p);
703 
704 	return p == 0 ? ~0U : scaled_div(1, p);
705 }
706 
ccid3_hc_rx_packet_recv(struct sock * sk,struct sk_buff * skb)707 static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
708 {
709 	struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
710 	enum ccid3_fback_type do_feedback = CCID3_FBACK_NONE;
711 	const u64 ndp = dccp_sk(sk)->dccps_options_received.dccpor_ndp;
712 	const bool is_data_packet = dccp_data_packet(skb);
713 
714 	if (unlikely(hc->rx_state == TFRC_RSTATE_NO_DATA)) {
715 		if (is_data_packet) {
716 			const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
717 			do_feedback = CCID3_FBACK_INITIAL;
718 			ccid3_hc_rx_set_state(sk, TFRC_RSTATE_DATA);
719 			hc->rx_s = payload;
720 			/*
721 			 * Not necessary to update rx_bytes_recv here,
722 			 * since X_recv = 0 for the first feedback packet (cf.
723 			 * RFC 3448, 6.3) -- gerrit
724 			 */
725 		}
726 		goto update_records;
727 	}
728 
729 	if (tfrc_rx_hist_duplicate(&hc->rx_hist, skb))
730 		return; /* done receiving */
731 
732 	if (is_data_packet) {
733 		const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
734 		/*
735 		 * Update moving-average of s and the sum of received payload bytes
736 		 */
737 		hc->rx_s = tfrc_ewma(hc->rx_s, payload, 9);
738 		hc->rx_bytes_recv += payload;
739 	}
740 
741 	/*
742 	 * Perform loss detection and handle pending losses
743 	 */
744 	if (tfrc_rx_handle_loss(&hc->rx_hist, &hc->rx_li_hist,
745 				skb, ndp, ccid3_first_li, sk)) {
746 		do_feedback = CCID3_FBACK_PARAM_CHANGE;
747 		goto done_receiving;
748 	}
749 
750 	if (tfrc_rx_hist_loss_pending(&hc->rx_hist))
751 		return; /* done receiving */
752 
753 	/*
754 	 * Handle data packets: RTT sampling and monitoring p
755 	 */
756 	if (unlikely(!is_data_packet))
757 		goto update_records;
758 
759 	if (!tfrc_lh_is_initialised(&hc->rx_li_hist)) {
760 		const u32 sample = tfrc_rx_hist_sample_rtt(&hc->rx_hist, skb);
761 		/*
762 		 * Empty loss history: no loss so far, hence p stays 0.
763 		 * Sample RTT values, since an RTT estimate is required for the
764 		 * computation of p when the first loss occurs; RFC 3448, 6.3.1.
765 		 */
766 		if (sample != 0)
767 			hc->rx_rtt = tfrc_ewma(hc->rx_rtt, sample, 9);
768 
769 	} else if (tfrc_lh_update_i_mean(&hc->rx_li_hist, skb)) {
770 		/*
771 		 * Step (3) of [RFC 3448, 6.1]: Recompute I_mean and, if I_mean
772 		 * has decreased (resp. p has increased), send feedback now.
773 		 */
774 		do_feedback = CCID3_FBACK_PARAM_CHANGE;
775 	}
776 
777 	/*
778 	 * Check if the periodic once-per-RTT feedback is due; RFC 4342, 10.3
779 	 */
780 	if (SUB16(dccp_hdr(skb)->dccph_ccval, hc->rx_last_counter) > 3)
781 		do_feedback = CCID3_FBACK_PERIODIC;
782 
783 update_records:
784 	tfrc_rx_hist_add_packet(&hc->rx_hist, skb, ndp);
785 
786 done_receiving:
787 	if (do_feedback)
788 		ccid3_hc_rx_send_feedback(sk, skb, do_feedback);
789 }
790 
ccid3_hc_rx_init(struct ccid * ccid,struct sock * sk)791 static int ccid3_hc_rx_init(struct ccid *ccid, struct sock *sk)
792 {
793 	struct ccid3_hc_rx_sock *hc = ccid_priv(ccid);
794 
795 	hc->rx_state = TFRC_RSTATE_NO_DATA;
796 	tfrc_lh_init(&hc->rx_li_hist);
797 	return tfrc_rx_hist_alloc(&hc->rx_hist);
798 }
799 
ccid3_hc_rx_exit(struct sock * sk)800 static void ccid3_hc_rx_exit(struct sock *sk)
801 {
802 	struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
803 
804 	tfrc_rx_hist_purge(&hc->rx_hist);
805 	tfrc_lh_cleanup(&hc->rx_li_hist);
806 }
807 
ccid3_hc_rx_get_info(struct sock * sk,struct tcp_info * info)808 static void ccid3_hc_rx_get_info(struct sock *sk, struct tcp_info *info)
809 {
810 	info->tcpi_ca_state = ccid3_hc_rx_sk(sk)->rx_state;
811 	info->tcpi_options  |= TCPI_OPT_TIMESTAMPS;
812 	info->tcpi_rcv_rtt  = ccid3_hc_rx_sk(sk)->rx_rtt;
813 }
814 
ccid3_hc_rx_getsockopt(struct sock * sk,const int optname,int len,u32 __user * optval,int __user * optlen)815 static int ccid3_hc_rx_getsockopt(struct sock *sk, const int optname, int len,
816 				  u32 __user *optval, int __user *optlen)
817 {
818 	const struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
819 	struct tfrc_rx_info rx_info;
820 	const void *val;
821 
822 	switch (optname) {
823 	case DCCP_SOCKOPT_CCID_RX_INFO:
824 		if (len < sizeof(rx_info))
825 			return -EINVAL;
826 		rx_info.tfrcrx_x_recv = hc->rx_x_recv;
827 		rx_info.tfrcrx_rtt    = hc->rx_rtt;
828 		rx_info.tfrcrx_p      = tfrc_invert_loss_event_rate(hc->rx_pinv);
829 		len = sizeof(rx_info);
830 		val = &rx_info;
831 		break;
832 	default:
833 		return -ENOPROTOOPT;
834 	}
835 
836 	if (put_user(len, optlen) || copy_to_user(optval, val, len))
837 		return -EFAULT;
838 
839 	return 0;
840 }
841 
842 struct ccid_operations ccid3_ops = {
843 	.ccid_id		   = DCCPC_CCID3,
844 	.ccid_name		   = "TCP-Friendly Rate Control",
845 	.ccid_hc_tx_obj_size	   = sizeof(struct ccid3_hc_tx_sock),
846 	.ccid_hc_tx_init	   = ccid3_hc_tx_init,
847 	.ccid_hc_tx_exit	   = ccid3_hc_tx_exit,
848 	.ccid_hc_tx_send_packet	   = ccid3_hc_tx_send_packet,
849 	.ccid_hc_tx_packet_sent	   = ccid3_hc_tx_packet_sent,
850 	.ccid_hc_tx_packet_recv	   = ccid3_hc_tx_packet_recv,
851 	.ccid_hc_tx_parse_options  = ccid3_hc_tx_parse_options,
852 	.ccid_hc_rx_obj_size	   = sizeof(struct ccid3_hc_rx_sock),
853 	.ccid_hc_rx_init	   = ccid3_hc_rx_init,
854 	.ccid_hc_rx_exit	   = ccid3_hc_rx_exit,
855 	.ccid_hc_rx_insert_options = ccid3_hc_rx_insert_options,
856 	.ccid_hc_rx_packet_recv	   = ccid3_hc_rx_packet_recv,
857 	.ccid_hc_rx_get_info	   = ccid3_hc_rx_get_info,
858 	.ccid_hc_tx_get_info	   = ccid3_hc_tx_get_info,
859 	.ccid_hc_rx_getsockopt	   = ccid3_hc_rx_getsockopt,
860 	.ccid_hc_tx_getsockopt	   = ccid3_hc_tx_getsockopt,
861 };
862 
863 #ifdef CONFIG_IP_DCCP_CCID3_DEBUG
864 module_param(ccid3_debug, bool, 0644);
865 MODULE_PARM_DESC(ccid3_debug, "Enable CCID-3 debug messages");
866 #endif
867