dccp ccid-2: Separate internals of Ack Vectors from option-parsing code
[linux-2.6.git] / net / dccp / ackvec.c
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 }