xref: /openbmc/linux/net/dccp/ackvec.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
1 /*
2  *  net/dccp/ackvec.c
3  *
4  *  An implementation of the DCCP protocol
5  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
6  *
7  *      This program is free software; you can redistribute it and/or modify it
8  *      under the terms of the GNU General Public License as published by the
9  *      Free Software Foundation; version 2 of the License;
10  */
11 
12 #include "ackvec.h"
13 #include "dccp.h"
14 
15 #include <linux/dccp.h>
16 #include <linux/skbuff.h>
17 
18 #include <net/sock.h>
19 
20 int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
21 {
22 	struct dccp_sock *dp = dccp_sk(sk);
23 	struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
24 	int len = av->dccpav_vec_len + 2;
25 	struct timeval now;
26 	u32 elapsed_time;
27 	unsigned char *to, *from;
28 
29 	dccp_timestamp(sk, &now);
30 	elapsed_time = timeval_delta(&now, &av->dccpav_time) / 10;
31 
32 	if (elapsed_time != 0)
33 		dccp_insert_option_elapsed_time(sk, skb, elapsed_time);
34 
35 	if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
36 		return -1;
37 
38 	/*
39 	 * XXX: now we have just one ack vector sent record, so
40 	 * we have to wait for it to be cleared.
41 	 *
42 	 * Of course this is not acceptable, but this is just for
43 	 * basic testing now.
44 	 */
45 	if (av->dccpav_ack_seqno != DCCP_MAX_SEQNO + 1)
46 		return -1;
47 
48 	DCCP_SKB_CB(skb)->dccpd_opt_len += len;
49 
50 	to    = skb_push(skb, len);
51 	*to++ = DCCPO_ACK_VECTOR_0;
52 	*to++ = len;
53 
54 	len  = av->dccpav_vec_len;
55 	from = av->dccpav_buf + av->dccpav_buf_head;
56 
57 	/* Check if buf_head wraps */
58 	if (av->dccpav_buf_head + len > av->dccpav_vec_len) {
59 		const u32 tailsize = (av->dccpav_vec_len - av->dccpav_buf_head);
60 
61 		memcpy(to, from, tailsize);
62 		to   += tailsize;
63 		len  -= tailsize;
64 		from = av->dccpav_buf;
65 	}
66 
67 	memcpy(to, from, len);
68 	/*
69 	 *	From draft-ietf-dccp-spec-11.txt:
70 	 *
71 	 *	For each acknowledgement it sends, the HC-Receiver will add an
72 	 *	acknowledgement record.  ack_seqno will equal the HC-Receiver
73 	 *	sequence number it used for the ack packet; ack_ptr will equal
74 	 *	buf_head; ack_ackno will equal buf_ackno; and ack_nonce will
75 	 *	equal buf_nonce.
76 	 *
77 	 * This implemention uses just one ack record for now.
78 	 */
79 	av->dccpav_ack_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
80 	av->dccpav_ack_ptr   = av->dccpav_buf_head;
81 	av->dccpav_ack_ackno = av->dccpav_buf_ackno;
82 	av->dccpav_ack_nonce = av->dccpav_buf_nonce;
83 	av->dccpav_sent_len  = av->dccpav_vec_len;
84 
85 	dccp_pr_debug("%sACK Vector 0, len=%d, ack_seqno=%llu, "
86 		      "ack_ackno=%llu\n",
87 		      debug_prefix, av->dccpav_sent_len,
88 		      (unsigned long long)av->dccpav_ack_seqno,
89 		      (unsigned long long)av->dccpav_ack_ackno);
90 	return -1;
91 }
92 
93 struct dccp_ackvec *dccp_ackvec_alloc(const unsigned int len,
94 				      const gfp_t priority)
95 {
96 	struct dccp_ackvec *av = kmalloc(sizeof(*av) + len, priority);
97 
98 	if (av != NULL) {
99 		av->dccpav_buf_len	= len;
100 		av->dccpav_buf_head	=
101 			av->dccpav_buf_tail = av->dccpav_buf_len - 1;
102 		av->dccpav_buf_ackno	=
103 			av->dccpav_ack_ackno = av->dccpav_ack_seqno = ~0LLU;
104 		av->dccpav_buf_nonce = av->dccpav_buf_nonce = 0;
105 		av->dccpav_ack_ptr	= 0;
106 		av->dccpav_time.tv_sec	= 0;
107 		av->dccpav_time.tv_usec	= 0;
108 		av->dccpav_sent_len	= av->dccpav_vec_len = 0;
109 	}
110 
111 	return av;
112 }
113 
114 void dccp_ackvec_free(struct dccp_ackvec *av)
115 {
116 	kfree(av);
117 }
118 
119 static inline u8 dccp_ackvec_state(const struct dccp_ackvec *av,
120 				   const unsigned int index)
121 {
122 	return av->dccpav_buf[index] & DCCP_ACKVEC_STATE_MASK;
123 }
124 
125 static inline u8 dccp_ackvec_len(const struct dccp_ackvec *av,
126 				 const unsigned int index)
127 {
128 	return av->dccpav_buf[index] & DCCP_ACKVEC_LEN_MASK;
129 }
130 
131 /*
132  * If several packets are missing, the HC-Receiver may prefer to enter multiple
133  * bytes with run length 0, rather than a single byte with a larger run length;
134  * this simplifies table updates if one of the missing packets arrives.
135  */
136 static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
137 						 const unsigned int packets,
138 						  const unsigned char state)
139 {
140 	unsigned int gap;
141 	signed long new_head;
142 
143 	if (av->dccpav_vec_len + packets > av->dccpav_buf_len)
144 		return -ENOBUFS;
145 
146 	gap	 = packets - 1;
147 	new_head = av->dccpav_buf_head - packets;
148 
149 	if (new_head < 0) {
150 		if (gap > 0) {
151 			memset(av->dccpav_buf, DCCP_ACKVEC_STATE_NOT_RECEIVED,
152 			       gap + new_head + 1);
153 			gap = -new_head;
154 		}
155 		new_head += av->dccpav_buf_len;
156 	}
157 
158 	av->dccpav_buf_head = new_head;
159 
160 	if (gap > 0)
161 		memset(av->dccpav_buf + av->dccpav_buf_head + 1,
162 		       DCCP_ACKVEC_STATE_NOT_RECEIVED, gap);
163 
164 	av->dccpav_buf[av->dccpav_buf_head] = state;
165 	av->dccpav_vec_len += packets;
166 	return 0;
167 }
168 
169 /*
170  * Implements the draft-ietf-dccp-spec-11.txt Appendix A
171  */
172 int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
173 		    const u64 ackno, const u8 state)
174 {
175 	/*
176 	 * Check at the right places if the buffer is full, if it is, tell the
177 	 * caller to start dropping packets till the HC-Sender acks our ACK
178 	 * vectors, when we will free up space in dccpav_buf.
179 	 *
180 	 * We may well decide to do buffer compression, etc, but for now lets
181 	 * just drop.
182 	 *
183 	 * From Appendix A:
184 	 *
185 	 *	Of course, the circular buffer may overflow, either when the
186 	 *	HC-Sender is sending data at a very high rate, when the
187 	 *	HC-Receiver's acknowledgements are not reaching the HC-Sender,
188 	 *	or when the HC-Sender is forgetting to acknowledge those acks
189 	 *	(so the HC-Receiver is unable to clean up old state). In this
190 	 *	case, the HC-Receiver should either compress the buffer (by
191 	 *	increasing run lengths when possible), transfer its state to
192 	 *	a larger buffer, or, as a last resort, drop all received
193 	 *	packets, without processing them whatsoever, until its buffer
194 	 *	shrinks again.
195 	 */
196 
197 	/* See if this is the first ackno being inserted */
198 	if (av->dccpav_vec_len == 0) {
199 		av->dccpav_buf[av->dccpav_buf_head] = state;
200 		av->dccpav_vec_len = 1;
201 	} else if (after48(ackno, av->dccpav_buf_ackno)) {
202 		const u64 delta = dccp_delta_seqno(av->dccpav_buf_ackno,
203 						   ackno);
204 
205 		/*
206 		 * Look if the state of this packet is the same as the
207 		 * previous ackno and if so if we can bump the head len.
208 		 */
209 		if (delta == 1 &&
210 		    dccp_ackvec_state(av, av->dccpav_buf_head) == state &&
211 		    (dccp_ackvec_len(av, av->dccpav_buf_head) <
212 		     DCCP_ACKVEC_LEN_MASK))
213 			av->dccpav_buf[av->dccpav_buf_head]++;
214 		else if (dccp_ackvec_set_buf_head_state(av, delta, state))
215 			return -ENOBUFS;
216 	} else {
217 		/*
218 		 * A.1.2.  Old Packets
219 		 *
220 		 *	When a packet with Sequence Number S arrives, and
221 		 *	S <= buf_ackno, the HC-Receiver will scan the table
222 		 *	for the byte corresponding to S. (Indexing structures
223 		 *	could reduce the complexity of this scan.)
224 		 */
225 		u64 delta = dccp_delta_seqno(ackno, av->dccpav_buf_ackno);
226 		unsigned int index = av->dccpav_buf_head;
227 
228 		while (1) {
229 			const u8 len = dccp_ackvec_len(av, index);
230 			const u8 state = dccp_ackvec_state(av, index);
231 			/*
232 			 * valid packets not yet in dccpav_buf have a reserved
233 			 * entry, with a len equal to 0.
234 			 */
235 			if (state == DCCP_ACKVEC_STATE_NOT_RECEIVED &&
236 			    len == 0 && delta == 0) { /* Found our
237 							 reserved seat! */
238 				dccp_pr_debug("Found %llu reserved seat!\n",
239 					      (unsigned long long)ackno);
240 				av->dccpav_buf[index] = state;
241 				goto out;
242 			}
243 			/* len == 0 means one packet */
244 			if (delta < len + 1)
245 				goto out_duplicate;
246 
247 			delta -= len + 1;
248 			if (++index == av->dccpav_buf_len)
249 				index = 0;
250 		}
251 	}
252 
253 	av->dccpav_buf_ackno = ackno;
254 	dccp_timestamp(sk, &av->dccpav_time);
255 out:
256 	dccp_pr_debug("");
257 	return 0;
258 
259 out_duplicate:
260 	/* Duplicate packet */
261 	dccp_pr_debug("Received a dup or already considered lost "
262 		      "packet: %llu\n", (unsigned long long)ackno);
263 	return -EILSEQ;
264 }
265 
266 #ifdef CONFIG_IP_DCCP_DEBUG
267 void dccp_ackvector_print(const u64 ackno, const unsigned char *vector, int len)
268 {
269 	if (!dccp_debug)
270 		return;
271 
272 	printk("ACK vector len=%d, ackno=%llu |", len,
273 	       (unsigned long long)ackno);
274 
275 	while (len--) {
276 		const u8 state = (*vector & DCCP_ACKVEC_STATE_MASK) >> 6;
277 		const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
278 
279 		printk("%d,%d|", state, rl);
280 		++vector;
281 	}
282 
283 	printk("\n");
284 }
285 
286 void dccp_ackvec_print(const struct dccp_ackvec *av)
287 {
288 	dccp_ackvector_print(av->dccpav_buf_ackno,
289 			     av->dccpav_buf + av->dccpav_buf_head,
290 			     av->dccpav_vec_len);
291 }
292 #endif
293 
294 static void dccp_ackvec_trow_away_ack_record(struct dccp_ackvec *av)
295 {
296 	/*
297 	 * As we're keeping track of the ack vector size (dccpav_vec_len) and
298 	 * the sent ack vector size (dccpav_sent_len) we don't need
299 	 * dccpav_buf_tail at all, but keep this code here as in the future
300 	 * we'll implement a vector of ack records, as suggested in
301 	 * draft-ietf-dccp-spec-11.txt Appendix A. -acme
302 	 */
303 #if 0
304 	av->dccpav_buf_tail = av->dccpav_ack_ptr + 1;
305 	if (av->dccpav_buf_tail >= av->dccpav_vec_len)
306 		av->dccpav_buf_tail -= av->dccpav_vec_len;
307 #endif
308 	av->dccpav_vec_len -= av->dccpav_sent_len;
309 }
310 
311 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
312 				 const u64 ackno)
313 {
314 	/* Check if we actually sent an ACK vector */
315 	if (av->dccpav_ack_seqno == DCCP_MAX_SEQNO + 1)
316 		return;
317 
318 	if (ackno == av->dccpav_ack_seqno) {
319 #ifdef CONFIG_IP_DCCP_DEBUG
320 		struct dccp_sock *dp = dccp_sk(sk);
321 		const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
322 					"CLIENT rx ack: " : "server rx ack: ";
323 #endif
324 		dccp_pr_debug("%sACK packet 0, len=%d, ack_seqno=%llu, "
325 			      "ack_ackno=%llu, ACKED!\n",
326 			      debug_prefix, 1,
327 			      (unsigned long long)av->dccpav_ack_seqno,
328 			      (unsigned long long)av->dccpav_ack_ackno);
329 		dccp_ackvec_trow_away_ack_record(av);
330 		av->dccpav_ack_seqno = DCCP_MAX_SEQNO + 1;
331 	}
332 }
333 
334 static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
335 					    struct sock *sk, u64 ackno,
336 					    const unsigned char len,
337 					    const unsigned char *vector)
338 {
339 	unsigned char i;
340 
341 	/* Check if we actually sent an ACK vector */
342 	if (av->dccpav_ack_seqno == DCCP_MAX_SEQNO + 1)
343 		return;
344 	/*
345 	 * We're in the receiver half connection, so if the received an ACK
346 	 * vector ackno (e.g. 50) before dccpav_ack_seqno (e.g. 52), we're
347 	 * not interested.
348 	 *
349 	 * Extra explanation with example:
350 	 *
351 	 * if we received an ACK vector with ackno 50, it can only be acking
352 	 * 50, 49, 48, etc, not 52 (the seqno for the ACK vector we sent).
353 	 */
354 	/* dccp_pr_debug("is %llu < %llu? ", ackno, av->dccpav_ack_seqno); */
355 	if (before48(ackno, av->dccpav_ack_seqno)) {
356 		/* dccp_pr_debug_cat("yes\n"); */
357 		return;
358 	}
359 	/* dccp_pr_debug_cat("no\n"); */
360 
361 	i = len;
362 	while (i--) {
363 		const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
364 		u64 ackno_end_rl;
365 
366 		dccp_set_seqno(&ackno_end_rl, ackno - rl);
367 
368 		/*
369 		 * dccp_pr_debug("is %llu <= %llu <= %llu? ", ackno_end_rl,
370 		 * av->dccpav_ack_seqno, ackno);
371 		 */
372 		if (between48(av->dccpav_ack_seqno, ackno_end_rl, ackno)) {
373 			const u8 state = (*vector &
374 					  DCCP_ACKVEC_STATE_MASK) >> 6;
375 			/* dccp_pr_debug_cat("yes\n"); */
376 
377 			if (state != DCCP_ACKVEC_STATE_NOT_RECEIVED) {
378 #ifdef CONFIG_IP_DCCP_DEBUG
379 				struct dccp_sock *dp = dccp_sk(sk);
380 				const char *debug_prefix =
381 					dp->dccps_role == DCCP_ROLE_CLIENT ?
382 					"CLIENT rx ack: " : "server rx ack: ";
383 #endif
384 				dccp_pr_debug("%sACK vector 0, len=%d, "
385 					      "ack_seqno=%llu, ack_ackno=%llu, "
386 					      "ACKED!\n",
387 					      debug_prefix, len,
388 					      (unsigned long long)
389 					      av->dccpav_ack_seqno,
390 					      (unsigned long long)
391 					      av->dccpav_ack_ackno);
392 				dccp_ackvec_trow_away_ack_record(av);
393 			}
394 			/*
395 			 * If dccpav_ack_seqno was not received, no problem
396 			 * we'll send another ACK vector.
397 			 */
398 			av->dccpav_ack_seqno = DCCP_MAX_SEQNO + 1;
399 			break;
400 		}
401 		/* dccp_pr_debug_cat("no\n"); */
402 
403 		dccp_set_seqno(&ackno, ackno_end_rl - 1);
404 		++vector;
405 	}
406 }
407 
408 int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
409 		      const u8 opt, const u8 *value, const u8 len)
410 {
411 	if (len > DCCP_MAX_ACKVEC_LEN)
412 		return -1;
413 
414 	/* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
415 	dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk,
416 					DCCP_SKB_CB(skb)->dccpd_ack_seq,
417 				        len, value);
418 	return 0;
419 }
420