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/init.h> 17 #include <linux/errno.h> 18 #include <linux/kernel.h> 19 #include <linux/skbuff.h> 20 #include <linux/slab.h> 21 22 #include <net/sock.h> 23 24 static struct kmem_cache *dccp_ackvec_slab; 25 static struct kmem_cache *dccp_ackvec_record_slab; 26 27 static struct dccp_ackvec_record *dccp_ackvec_record_new(void) 28 { 29 struct dccp_ackvec_record *avr = 30 kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC); 31 32 if (avr != NULL) 33 INIT_LIST_HEAD(&avr->avr_node); 34 35 return avr; 36 } 37 38 static void dccp_ackvec_record_delete(struct dccp_ackvec_record *avr) 39 { 40 if (unlikely(avr == NULL)) 41 return; 42 /* Check if deleting a linked record */ 43 WARN_ON(!list_empty(&avr->avr_node)); 44 kmem_cache_free(dccp_ackvec_record_slab, avr); 45 } 46 47 static void dccp_ackvec_insert_avr(struct dccp_ackvec *av, 48 struct dccp_ackvec_record *avr) 49 { 50 /* 51 * AVRs are sorted by seqno. Since we are sending them in order, we 52 * just add the AVR at the head of the list. 53 * -sorbo. 54 */ 55 if (!list_empty(&av->av_records)) { 56 const struct dccp_ackvec_record *head = 57 list_entry(av->av_records.next, 58 struct dccp_ackvec_record, 59 avr_node); 60 BUG_ON(before48(avr->avr_ack_seqno, head->avr_ack_seqno)); 61 } 62 63 list_add(&avr->avr_node, &av->av_records); 64 } 65 66 int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb) 67 { 68 struct dccp_sock *dp = dccp_sk(sk); 69 struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec; 70 /* Figure out how many options do we need to represent the ackvec */ 71 const u16 nr_opts = DIV_ROUND_UP(av->av_vec_len, DCCP_MAX_ACKVEC_OPT_LEN); 72 u16 len = av->av_vec_len + 2 * nr_opts, i; 73 u32 elapsed_time; 74 const unsigned char *tail, *from; 75 unsigned char *to; 76 struct dccp_ackvec_record *avr; 77 suseconds_t delta; 78 79 if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) 80 return -1; 81 82 delta = ktime_us_delta(ktime_get_real(), av->av_time); 83 elapsed_time = delta / 10; 84 85 if (elapsed_time != 0 && 86 dccp_insert_option_elapsed_time(sk, skb, elapsed_time)) 87 return -1; 88 89 avr = dccp_ackvec_record_new(); 90 if (avr == NULL) 91 return -1; 92 93 DCCP_SKB_CB(skb)->dccpd_opt_len += len; 94 95 to = skb_push(skb, len); 96 len = av->av_vec_len; 97 from = av->av_buf + av->av_buf_head; 98 tail = av->av_buf + DCCP_MAX_ACKVEC_LEN; 99 100 for (i = 0; i < nr_opts; ++i) { 101 int copylen = len; 102 103 if (len > DCCP_MAX_ACKVEC_OPT_LEN) 104 copylen = DCCP_MAX_ACKVEC_OPT_LEN; 105 106 *to++ = DCCPO_ACK_VECTOR_0; 107 *to++ = copylen + 2; 108 109 /* Check if buf_head wraps */ 110 if (from + copylen > tail) { 111 const u16 tailsize = tail - from; 112 113 memcpy(to, from, tailsize); 114 to += tailsize; 115 len -= tailsize; 116 copylen -= tailsize; 117 from = av->av_buf; 118 } 119 120 memcpy(to, from, copylen); 121 from += copylen; 122 to += copylen; 123 len -= copylen; 124 } 125 126 /* 127 * From RFC 4340, A.2: 128 * 129 * For each acknowledgement it sends, the HC-Receiver will add an 130 * acknowledgement record. ack_seqno will equal the HC-Receiver 131 * sequence number it used for the ack packet; ack_ptr will equal 132 * buf_head; ack_ackno will equal buf_ackno; and ack_nonce will 133 * equal buf_nonce. 134 */ 135 avr->avr_ack_seqno = DCCP_SKB_CB(skb)->dccpd_seq; 136 avr->avr_ack_ptr = av->av_buf_head; 137 avr->avr_ack_ackno = av->av_buf_ackno; 138 avr->avr_ack_nonce = av->av_buf_nonce; 139 avr->avr_sent_len = av->av_vec_len; 140 141 dccp_ackvec_insert_avr(av, avr); 142 143 dccp_pr_debug("%s ACK Vector 0, len=%d, ack_seqno=%llu, " 144 "ack_ackno=%llu\n", 145 dccp_role(sk), avr->avr_sent_len, 146 (unsigned long long)avr->avr_ack_seqno, 147 (unsigned long long)avr->avr_ack_ackno); 148 return 0; 149 } 150 151 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority) 152 { 153 struct dccp_ackvec *av = kmem_cache_alloc(dccp_ackvec_slab, priority); 154 155 if (av != NULL) { 156 av->av_buf_head = DCCP_MAX_ACKVEC_LEN - 1; 157 av->av_buf_ackno = UINT48_MAX + 1; 158 av->av_buf_nonce = 0; 159 av->av_time = ktime_set(0, 0); 160 av->av_vec_len = 0; 161 INIT_LIST_HEAD(&av->av_records); 162 } 163 164 return av; 165 } 166 167 void dccp_ackvec_free(struct dccp_ackvec *av) 168 { 169 if (unlikely(av == NULL)) 170 return; 171 172 if (!list_empty(&av->av_records)) { 173 struct dccp_ackvec_record *avr, *next; 174 175 list_for_each_entry_safe(avr, next, &av->av_records, avr_node) { 176 list_del_init(&avr->avr_node); 177 dccp_ackvec_record_delete(avr); 178 } 179 } 180 181 kmem_cache_free(dccp_ackvec_slab, av); 182 } 183 184 static inline u8 dccp_ackvec_state(const struct dccp_ackvec *av, 185 const u32 index) 186 { 187 return av->av_buf[index] & DCCP_ACKVEC_STATE_MASK; 188 } 189 190 static inline u8 dccp_ackvec_len(const struct dccp_ackvec *av, 191 const u32 index) 192 { 193 return av->av_buf[index] & DCCP_ACKVEC_LEN_MASK; 194 } 195 196 /* 197 * If several packets are missing, the HC-Receiver may prefer to enter multiple 198 * bytes with run length 0, rather than a single byte with a larger run length; 199 * this simplifies table updates if one of the missing packets arrives. 200 */ 201 static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av, 202 const unsigned int packets, 203 const unsigned char state) 204 { 205 unsigned int gap; 206 long new_head; 207 208 if (av->av_vec_len + packets > DCCP_MAX_ACKVEC_LEN) 209 return -ENOBUFS; 210 211 gap = packets - 1; 212 new_head = av->av_buf_head - packets; 213 214 if (new_head < 0) { 215 if (gap > 0) { 216 memset(av->av_buf, DCCP_ACKVEC_STATE_NOT_RECEIVED, 217 gap + new_head + 1); 218 gap = -new_head; 219 } 220 new_head += DCCP_MAX_ACKVEC_LEN; 221 } 222 223 av->av_buf_head = new_head; 224 225 if (gap > 0) 226 memset(av->av_buf + av->av_buf_head + 1, 227 DCCP_ACKVEC_STATE_NOT_RECEIVED, gap); 228 229 av->av_buf[av->av_buf_head] = state; 230 av->av_vec_len += packets; 231 return 0; 232 } 233 234 /* 235 * Implements the RFC 4340, Appendix A 236 */ 237 int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk, 238 const u64 ackno, const u8 state) 239 { 240 /* 241 * Check at the right places if the buffer is full, if it is, tell the 242 * caller to start dropping packets till the HC-Sender acks our ACK 243 * vectors, when we will free up space in av_buf. 244 * 245 * We may well decide to do buffer compression, etc, but for now lets 246 * just drop. 247 * 248 * From Appendix A.1.1 (`New Packets'): 249 * 250 * Of course, the circular buffer may overflow, either when the 251 * HC-Sender is sending data at a very high rate, when the 252 * HC-Receiver's acknowledgements are not reaching the HC-Sender, 253 * or when the HC-Sender is forgetting to acknowledge those acks 254 * (so the HC-Receiver is unable to clean up old state). In this 255 * case, the HC-Receiver should either compress the buffer (by 256 * increasing run lengths when possible), transfer its state to 257 * a larger buffer, or, as a last resort, drop all received 258 * packets, without processing them whatsoever, until its buffer 259 * shrinks again. 260 */ 261 262 /* See if this is the first ackno being inserted */ 263 if (av->av_vec_len == 0) { 264 av->av_buf[av->av_buf_head] = state; 265 av->av_vec_len = 1; 266 } else if (after48(ackno, av->av_buf_ackno)) { 267 const u64 delta = dccp_delta_seqno(av->av_buf_ackno, ackno); 268 269 /* 270 * Look if the state of this packet is the same as the 271 * previous ackno and if so if we can bump the head len. 272 */ 273 if (delta == 1 && 274 dccp_ackvec_state(av, av->av_buf_head) == state && 275 dccp_ackvec_len(av, av->av_buf_head) < DCCP_ACKVEC_LEN_MASK) 276 av->av_buf[av->av_buf_head]++; 277 else if (dccp_ackvec_set_buf_head_state(av, delta, state)) 278 return -ENOBUFS; 279 } else { 280 /* 281 * A.1.2. Old Packets 282 * 283 * When a packet with Sequence Number S <= buf_ackno 284 * arrives, the HC-Receiver will scan the table for 285 * the byte corresponding to S. (Indexing structures 286 * could reduce the complexity of this scan.) 287 */ 288 u64 delta = dccp_delta_seqno(ackno, av->av_buf_ackno); 289 u32 index = av->av_buf_head; 290 291 while (1) { 292 const u8 len = dccp_ackvec_len(av, index); 293 const u8 av_state = dccp_ackvec_state(av, index); 294 /* 295 * valid packets not yet in av_buf have a reserved 296 * entry, with a len equal to 0. 297 */ 298 if (av_state == DCCP_ACKVEC_STATE_NOT_RECEIVED && 299 len == 0 && delta == 0) { /* Found our 300 reserved seat! */ 301 dccp_pr_debug("Found %llu reserved seat!\n", 302 (unsigned long long)ackno); 303 av->av_buf[index] = state; 304 goto out; 305 } 306 /* len == 0 means one packet */ 307 if (delta < len + 1) 308 goto out_duplicate; 309 310 delta -= len + 1; 311 if (++index == DCCP_MAX_ACKVEC_LEN) 312 index = 0; 313 } 314 } 315 316 av->av_buf_ackno = ackno; 317 av->av_time = ktime_get_real(); 318 out: 319 return 0; 320 321 out_duplicate: 322 /* Duplicate packet */ 323 dccp_pr_debug("Received a dup or already considered lost " 324 "packet: %llu\n", (unsigned long long)ackno); 325 return -EILSEQ; 326 } 327 328 static void dccp_ackvec_throw_record(struct dccp_ackvec *av, 329 struct dccp_ackvec_record *avr) 330 { 331 struct dccp_ackvec_record *next; 332 333 /* sort out vector length */ 334 if (av->av_buf_head <= avr->avr_ack_ptr) 335 av->av_vec_len = avr->avr_ack_ptr - av->av_buf_head; 336 else 337 av->av_vec_len = DCCP_MAX_ACKVEC_LEN - 1 - 338 av->av_buf_head + avr->avr_ack_ptr; 339 340 /* free records */ 341 list_for_each_entry_safe_from(avr, next, &av->av_records, avr_node) { 342 list_del_init(&avr->avr_node); 343 dccp_ackvec_record_delete(avr); 344 } 345 } 346 347 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk, 348 const u64 ackno) 349 { 350 struct dccp_ackvec_record *avr; 351 352 /* 353 * If we traverse backwards, it should be faster when we have large 354 * windows. We will be receiving ACKs for stuff we sent a while back 355 * -sorbo. 356 */ 357 list_for_each_entry_reverse(avr, &av->av_records, avr_node) { 358 if (ackno == avr->avr_ack_seqno) { 359 dccp_pr_debug("%s ACK packet 0, len=%d, ack_seqno=%llu, " 360 "ack_ackno=%llu, ACKED!\n", 361 dccp_role(sk), 1, 362 (unsigned long long)avr->avr_ack_seqno, 363 (unsigned long long)avr->avr_ack_ackno); 364 dccp_ackvec_throw_record(av, avr); 365 break; 366 } else if (avr->avr_ack_seqno > ackno) 367 break; /* old news */ 368 } 369 } 370 371 static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av, 372 struct sock *sk, u64 *ackno, 373 const unsigned char len, 374 const unsigned char *vector) 375 { 376 unsigned char i; 377 struct dccp_ackvec_record *avr; 378 379 /* Check if we actually sent an ACK vector */ 380 if (list_empty(&av->av_records)) 381 return; 382 383 i = len; 384 /* 385 * XXX 386 * I think it might be more efficient to work backwards. See comment on 387 * rcv_ackno. -sorbo. 388 */ 389 avr = list_entry(av->av_records.next, struct dccp_ackvec_record, avr_node); 390 while (i--) { 391 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK; 392 u64 ackno_end_rl; 393 394 dccp_set_seqno(&ackno_end_rl, *ackno - rl); 395 396 /* 397 * If our AVR sequence number is greater than the ack, go 398 * forward in the AVR list until it is not so. 399 */ 400 list_for_each_entry_from(avr, &av->av_records, avr_node) { 401 if (!after48(avr->avr_ack_seqno, *ackno)) 402 goto found; 403 } 404 /* End of the av_records list, not found, exit */ 405 break; 406 found: 407 if (between48(avr->avr_ack_seqno, ackno_end_rl, *ackno)) { 408 const u8 state = *vector & DCCP_ACKVEC_STATE_MASK; 409 if (state != DCCP_ACKVEC_STATE_NOT_RECEIVED) { 410 dccp_pr_debug("%s ACK vector 0, len=%d, " 411 "ack_seqno=%llu, ack_ackno=%llu, " 412 "ACKED!\n", 413 dccp_role(sk), len, 414 (unsigned long long) 415 avr->avr_ack_seqno, 416 (unsigned long long) 417 avr->avr_ack_ackno); 418 dccp_ackvec_throw_record(av, avr); 419 break; 420 } 421 /* 422 * If it wasn't received, continue scanning... we might 423 * find another one. 424 */ 425 } 426 427 dccp_set_seqno(ackno, ackno_end_rl - 1); 428 ++vector; 429 } 430 } 431 432 int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb, 433 u64 *ackno, const u8 opt, const u8 *value, const u8 len) 434 { 435 if (len > DCCP_MAX_ACKVEC_OPT_LEN) 436 return -1; 437 438 /* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */ 439 dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk, 440 ackno, len, value); 441 return 0; 442 } 443 444 int __init dccp_ackvec_init(void) 445 { 446 dccp_ackvec_slab = kmem_cache_create("dccp_ackvec", 447 sizeof(struct dccp_ackvec), 0, 448 SLAB_HWCACHE_ALIGN, NULL); 449 if (dccp_ackvec_slab == NULL) 450 goto out_err; 451 452 dccp_ackvec_record_slab = 453 kmem_cache_create("dccp_ackvec_record", 454 sizeof(struct dccp_ackvec_record), 455 0, SLAB_HWCACHE_ALIGN, NULL); 456 if (dccp_ackvec_record_slab == NULL) 457 goto out_destroy_slab; 458 459 return 0; 460 461 out_destroy_slab: 462 kmem_cache_destroy(dccp_ackvec_slab); 463 dccp_ackvec_slab = NULL; 464 out_err: 465 DCCP_CRIT("Unable to create Ack Vector slab cache"); 466 return -ENOBUFS; 467 } 468 469 void dccp_ackvec_exit(void) 470 { 471 if (dccp_ackvec_slab != NULL) { 472 kmem_cache_destroy(dccp_ackvec_slab); 473 dccp_ackvec_slab = NULL; 474 } 475 if (dccp_ackvec_record_slab != NULL) { 476 kmem_cache_destroy(dccp_ackvec_record_slab); 477 dccp_ackvec_record_slab = NULL; 478 } 479 } 480