| 1 | /* |
| 2 | * net/dccp/ackvec.c |
| 3 | * |
| 4 | * An implementation of Ack Vectors for the DCCP protocol |
| 5 | * Copyright (c) 2007 University of Aberdeen, Scotland, UK |
| 6 | * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net> |
| 7 | * |
| 8 | * This program is free software; you can redistribute it and/or modify it |
| 9 | * under the terms of the GNU General Public License as published by the |
| 10 | * Free Software Foundation; version 2 of the License; |
| 11 | */ |
| 12 | |
| 13 | #include "ackvec.h" |
| 14 | #include "dccp.h" |
| 15 | |
| 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 | struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority) |
| 28 | { |
| 29 | struct dccp_ackvec *av = kmem_cache_zalloc(dccp_ackvec_slab, priority); |
| 30 | |
| 31 | if (av != NULL) { |
| 32 | av->av_buf_head = DCCPAV_MAX_ACKVEC_LEN - 1; |
| 33 | INIT_LIST_HEAD(&av->av_records); |
| 34 | } |
| 35 | return av; |
| 36 | } |
| 37 | |
| 38 | static void dccp_ackvec_purge_records(struct dccp_ackvec *av) |
| 39 | { |
| 40 | struct dccp_ackvec_record *cur, *next; |
| 41 | |
| 42 | list_for_each_entry_safe(cur, next, &av->av_records, avr_node) |
| 43 | kmem_cache_free(dccp_ackvec_record_slab, cur); |
| 44 | INIT_LIST_HEAD(&av->av_records); |
| 45 | } |
| 46 | |
| 47 | void dccp_ackvec_free(struct dccp_ackvec *av) |
| 48 | { |
| 49 | if (likely(av != NULL)) { |
| 50 | dccp_ackvec_purge_records(av); |
| 51 | kmem_cache_free(dccp_ackvec_slab, av); |
| 52 | } |
| 53 | } |
| 54 | |
| 55 | /** |
| 56 | * dccp_ackvec_update_records - Record information about sent Ack Vectors |
| 57 | * @av: Ack Vector records to update |
| 58 | * @seqno: Sequence number of the packet carrying the Ack Vector just sent |
| 59 | * @nonce_sum: The sum of all buffer nonces contained in the Ack Vector |
| 60 | */ |
| 61 | int dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seqno, u8 nonce_sum) |
| 62 | { |
| 63 | struct dccp_ackvec_record *avr; |
| 64 | |
| 65 | avr = kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC); |
| 66 | if (avr == NULL) |
| 67 | return -ENOBUFS; |
| 68 | |
| 69 | avr->avr_ack_seqno = seqno; |
| 70 | avr->avr_ack_ptr = av->av_buf_head; |
| 71 | avr->avr_ack_ackno = av->av_buf_ackno; |
| 72 | avr->avr_ack_nonce = nonce_sum; |
| 73 | avr->avr_ack_runlen = dccp_ackvec_runlen(av->av_buf + av->av_buf_head); |
| 74 | /* |
| 75 | * Since GSS is incremented for each packet, the list is automatically |
| 76 | * arranged in descending order of @ack_seqno. |
| 77 | */ |
| 78 | list_add(&avr->avr_node, &av->av_records); |
| 79 | |
| 80 | dccp_pr_debug("Added Vector, ack_seqno=%llu, ack_ackno=%llu (rl=%u)\n", |
| 81 | (unsigned long long)avr->avr_ack_seqno, |
| 82 | (unsigned long long)avr->avr_ack_ackno, |
| 83 | avr->avr_ack_runlen); |
| 84 | return 0; |
| 85 | } |
| 86 | |
| 87 | /* |
| 88 | * If several packets are missing, the HC-Receiver may prefer to enter multiple |
| 89 | * bytes with run length 0, rather than a single byte with a larger run length; |
| 90 | * this simplifies table updates if one of the missing packets arrives. |
| 91 | */ |
| 92 | static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av, |
| 93 | const unsigned int packets, |
| 94 | const unsigned char state) |
| 95 | { |
| 96 | long gap; |
| 97 | long new_head; |
| 98 | |
| 99 | if (av->av_vec_len + packets > DCCPAV_MAX_ACKVEC_LEN) |
| 100 | return -ENOBUFS; |
| 101 | |
| 102 | gap = packets - 1; |
| 103 | new_head = av->av_buf_head - packets; |
| 104 | |
| 105 | if (new_head < 0) { |
| 106 | if (gap > 0) { |
| 107 | memset(av->av_buf, DCCPAV_NOT_RECEIVED, |
| 108 | gap + new_head + 1); |
| 109 | gap = -new_head; |
| 110 | } |
| 111 | new_head += DCCPAV_MAX_ACKVEC_LEN; |
| 112 | } |
| 113 | |
| 114 | av->av_buf_head = new_head; |
| 115 | |
| 116 | if (gap > 0) |
| 117 | memset(av->av_buf + av->av_buf_head + 1, |
| 118 | DCCPAV_NOT_RECEIVED, gap); |
| 119 | |
| 120 | av->av_buf[av->av_buf_head] = state; |
| 121 | av->av_vec_len += packets; |
| 122 | return 0; |
| 123 | } |
| 124 | |
| 125 | /* |
| 126 | * Implements the RFC 4340, Appendix A |
| 127 | */ |
| 128 | int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk, |
| 129 | const u64 ackno, const u8 state) |
| 130 | { |
| 131 | u8 *cur_head = av->av_buf + av->av_buf_head, |
| 132 | *buf_end = av->av_buf + DCCPAV_MAX_ACKVEC_LEN; |
| 133 | /* |
| 134 | * Check at the right places if the buffer is full, if it is, tell the |
| 135 | * caller to start dropping packets till the HC-Sender acks our ACK |
| 136 | * vectors, when we will free up space in av_buf. |
| 137 | * |
| 138 | * We may well decide to do buffer compression, etc, but for now lets |
| 139 | * just drop. |
| 140 | * |
| 141 | * From Appendix A.1.1 (`New Packets'): |
| 142 | * |
| 143 | * Of course, the circular buffer may overflow, either when the |
| 144 | * HC-Sender is sending data at a very high rate, when the |
| 145 | * HC-Receiver's acknowledgements are not reaching the HC-Sender, |
| 146 | * or when the HC-Sender is forgetting to acknowledge those acks |
| 147 | * (so the HC-Receiver is unable to clean up old state). In this |
| 148 | * case, the HC-Receiver should either compress the buffer (by |
| 149 | * increasing run lengths when possible), transfer its state to |
| 150 | * a larger buffer, or, as a last resort, drop all received |
| 151 | * packets, without processing them whatsoever, until its buffer |
| 152 | * shrinks again. |
| 153 | */ |
| 154 | |
| 155 | /* See if this is the first ackno being inserted */ |
| 156 | if (av->av_vec_len == 0) { |
| 157 | *cur_head = state; |
| 158 | av->av_vec_len = 1; |
| 159 | } else if (after48(ackno, av->av_buf_ackno)) { |
| 160 | const u64 delta = dccp_delta_seqno(av->av_buf_ackno, ackno); |
| 161 | |
| 162 | /* |
| 163 | * Look if the state of this packet is the same as the |
| 164 | * previous ackno and if so if we can bump the head len. |
| 165 | */ |
| 166 | if (delta == 1 && dccp_ackvec_state(cur_head) == state && |
| 167 | dccp_ackvec_runlen(cur_head) < DCCPAV_MAX_RUNLEN) |
| 168 | *cur_head += 1; |
| 169 | else if (dccp_ackvec_set_buf_head_state(av, delta, state)) |
| 170 | return -ENOBUFS; |
| 171 | } else { |
| 172 | /* |
| 173 | * A.1.2. Old Packets |
| 174 | * |
| 175 | * When a packet with Sequence Number S <= buf_ackno |
| 176 | * arrives, the HC-Receiver will scan the table for |
| 177 | * the byte corresponding to S. (Indexing structures |
| 178 | * could reduce the complexity of this scan.) |
| 179 | */ |
| 180 | u64 delta = dccp_delta_seqno(ackno, av->av_buf_ackno); |
| 181 | |
| 182 | while (1) { |
| 183 | const u8 len = dccp_ackvec_runlen(cur_head); |
| 184 | /* |
| 185 | * valid packets not yet in av_buf have a reserved |
| 186 | * entry, with a len equal to 0. |
| 187 | */ |
| 188 | if (*cur_head == DCCPAV_NOT_RECEIVED && delta == 0) { |
| 189 | dccp_pr_debug("Found %llu reserved seat!\n", |
| 190 | (unsigned long long)ackno); |
| 191 | *cur_head = state; |
| 192 | goto out; |
| 193 | } |
| 194 | /* len == 0 means one packet */ |
| 195 | if (delta < len + 1) |
| 196 | goto out_duplicate; |
| 197 | |
| 198 | delta -= len + 1; |
| 199 | if (++cur_head == buf_end) |
| 200 | cur_head = av->av_buf; |
| 201 | } |
| 202 | } |
| 203 | |
| 204 | av->av_buf_ackno = ackno; |
| 205 | out: |
| 206 | return 0; |
| 207 | |
| 208 | out_duplicate: |
| 209 | /* Duplicate packet */ |
| 210 | dccp_pr_debug("Received a dup or already considered lost " |
| 211 | "packet: %llu\n", (unsigned long long)ackno); |
| 212 | return -EILSEQ; |
| 213 | } |
| 214 | |
| 215 | static void dccp_ackvec_throw_record(struct dccp_ackvec *av, |
| 216 | struct dccp_ackvec_record *avr) |
| 217 | { |
| 218 | struct dccp_ackvec_record *next; |
| 219 | |
| 220 | /* sort out vector length */ |
| 221 | if (av->av_buf_head <= avr->avr_ack_ptr) |
| 222 | av->av_vec_len = avr->avr_ack_ptr - av->av_buf_head; |
| 223 | else |
| 224 | av->av_vec_len = DCCPAV_MAX_ACKVEC_LEN - 1 - |
| 225 | av->av_buf_head + avr->avr_ack_ptr; |
| 226 | |
| 227 | /* free records */ |
| 228 | list_for_each_entry_safe_from(avr, next, &av->av_records, avr_node) { |
| 229 | list_del(&avr->avr_node); |
| 230 | kmem_cache_free(dccp_ackvec_record_slab, avr); |
| 231 | } |
| 232 | } |
| 233 | |
| 234 | void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk, |
| 235 | const u64 ackno) |
| 236 | { |
| 237 | struct dccp_ackvec_record *avr; |
| 238 | |
| 239 | /* |
| 240 | * If we traverse backwards, it should be faster when we have large |
| 241 | * windows. We will be receiving ACKs for stuff we sent a while back |
| 242 | * -sorbo. |
| 243 | */ |
| 244 | list_for_each_entry_reverse(avr, &av->av_records, avr_node) { |
| 245 | if (ackno == avr->avr_ack_seqno) { |
| 246 | dccp_pr_debug("%s ACK packet 0, len=%d, ack_seqno=%llu, " |
| 247 | "ack_ackno=%llu, ACKED!\n", |
| 248 | dccp_role(sk), avr->avr_ack_runlen, |
| 249 | (unsigned long long)avr->avr_ack_seqno, |
| 250 | (unsigned long long)avr->avr_ack_ackno); |
| 251 | dccp_ackvec_throw_record(av, avr); |
| 252 | break; |
| 253 | } else if (avr->avr_ack_seqno > ackno) |
| 254 | break; /* old news */ |
| 255 | } |
| 256 | } |
| 257 | |
| 258 | static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av, |
| 259 | struct sock *sk, u64 *ackno, |
| 260 | const unsigned char len, |
| 261 | const unsigned char *vector) |
| 262 | { |
| 263 | unsigned char i; |
| 264 | struct dccp_ackvec_record *avr; |
| 265 | |
| 266 | /* Check if we actually sent an ACK vector */ |
| 267 | if (list_empty(&av->av_records)) |
| 268 | return; |
| 269 | |
| 270 | i = len; |
| 271 | /* |
| 272 | * XXX |
| 273 | * I think it might be more efficient to work backwards. See comment on |
| 274 | * rcv_ackno. -sorbo. |
| 275 | */ |
| 276 | avr = list_entry(av->av_records.next, struct dccp_ackvec_record, avr_node); |
| 277 | while (i--) { |
| 278 | const u8 rl = dccp_ackvec_runlen(vector); |
| 279 | u64 ackno_end_rl; |
| 280 | |
| 281 | dccp_set_seqno(&ackno_end_rl, *ackno - rl); |
| 282 | |
| 283 | /* |
| 284 | * If our AVR sequence number is greater than the ack, go |
| 285 | * forward in the AVR list until it is not so. |
| 286 | */ |
| 287 | list_for_each_entry_from(avr, &av->av_records, avr_node) { |
| 288 | if (!after48(avr->avr_ack_seqno, *ackno)) |
| 289 | goto found; |
| 290 | } |
| 291 | /* End of the av_records list, not found, exit */ |
| 292 | break; |
| 293 | found: |
| 294 | if (between48(avr->avr_ack_seqno, ackno_end_rl, *ackno)) { |
| 295 | if (dccp_ackvec_state(vector) != DCCPAV_NOT_RECEIVED) { |
| 296 | dccp_pr_debug("%s ACK vector 0, len=%d, " |
| 297 | "ack_seqno=%llu, ack_ackno=%llu, " |
| 298 | "ACKED!\n", |
| 299 | dccp_role(sk), len, |
| 300 | (unsigned long long) |
| 301 | avr->avr_ack_seqno, |
| 302 | (unsigned long long) |
| 303 | avr->avr_ack_ackno); |
| 304 | dccp_ackvec_throw_record(av, avr); |
| 305 | break; |
| 306 | } |
| 307 | /* |
| 308 | * If it wasn't received, continue scanning... we might |
| 309 | * find another one. |
| 310 | */ |
| 311 | } |
| 312 | |
| 313 | dccp_set_seqno(ackno, ackno_end_rl - 1); |
| 314 | ++vector; |
| 315 | } |
| 316 | } |
| 317 | |
| 318 | int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb, |
| 319 | u64 *ackno, const u8 opt, const u8 *value, const u8 len) |
| 320 | { |
| 321 | if (len > DCCP_SINGLE_OPT_MAXLEN) |
| 322 | return -1; |
| 323 | |
| 324 | /* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */ |
| 325 | dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk, |
| 326 | ackno, len, value); |
| 327 | return 0; |
| 328 | } |
| 329 | |
| 330 | int __init dccp_ackvec_init(void) |
| 331 | { |
| 332 | dccp_ackvec_slab = kmem_cache_create("dccp_ackvec", |
| 333 | sizeof(struct dccp_ackvec), 0, |
| 334 | SLAB_HWCACHE_ALIGN, NULL); |
| 335 | if (dccp_ackvec_slab == NULL) |
| 336 | goto out_err; |
| 337 | |
| 338 | dccp_ackvec_record_slab = kmem_cache_create("dccp_ackvec_record", |
| 339 | sizeof(struct dccp_ackvec_record), |
| 340 | 0, SLAB_HWCACHE_ALIGN, NULL); |
| 341 | if (dccp_ackvec_record_slab == NULL) |
| 342 | goto out_destroy_slab; |
| 343 | |
| 344 | return 0; |
| 345 | |
| 346 | out_destroy_slab: |
| 347 | kmem_cache_destroy(dccp_ackvec_slab); |
| 348 | dccp_ackvec_slab = NULL; |
| 349 | out_err: |
| 350 | DCCP_CRIT("Unable to create Ack Vector slab cache"); |
| 351 | return -ENOBUFS; |
| 352 | } |
| 353 | |
| 354 | void dccp_ackvec_exit(void) |
| 355 | { |
| 356 | if (dccp_ackvec_slab != NULL) { |
| 357 | kmem_cache_destroy(dccp_ackvec_slab); |
| 358 | dccp_ackvec_slab = NULL; |
| 359 | } |
| 360 | if (dccp_ackvec_record_slab != NULL) { |
| 361 | kmem_cache_destroy(dccp_ackvec_record_slab); |
| 362 | dccp_ackvec_record_slab = NULL; |
| 363 | } |
| 364 | } |