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authorGerrit Renker <gerrit@erg.abdn.ac.uk>2008-07-13 06:51:40 -0400
committerGerrit Renker <gerrit@erg.abdn.ac.uk>2008-07-13 06:51:40 -0400
commit2013c7e35aeba39777f9b3eef8a70207b3931152 (patch)
tree5d63ce9f8c512ffd17b8084002e6dc0e0f998b84 /net/dccp
parent79d16385c7f287a33ea771c4dbe60ae43f791b49 (diff)
dccp ccid-3: Fix error in loss detection
The TFRC loss detection code used the wrong loss condition (RFC 4340, 7.7.1): * the difference between sequence numbers s1 and s2 instead of * the number of packets missing between s1 and s2 (one less than the distance). Since this condition appears in many places of the code, it has been put into a separate function, dccp_loss_free(). Further changes: ---------------- * tidied up incorrect typing (it was using `int' for u64/s64 types); * optimised conditional statements for common case of non-reordered packets; * rewrote comments/documentation to match the changes. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Diffstat (limited to 'net/dccp')
-rw-r--r--net/dccp/ccids/lib/packet_history.c73
-rw-r--r--net/dccp/dccp.h15
2 files changed, 43 insertions, 45 deletions
diff --git a/net/dccp/ccids/lib/packet_history.c b/net/dccp/ccids/lib/packet_history.c
index 20af1a693427..8b5c41ec7ee1 100644
--- a/net/dccp/ccids/lib/packet_history.c
+++ b/net/dccp/ccids/lib/packet_history.c
@@ -215,22 +215,19 @@ static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2
215 u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno, 215 u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
216 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno, 216 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
217 s2 = DCCP_SKB_CB(skb)->dccpd_seq; 217 s2 = DCCP_SKB_CB(skb)->dccpd_seq;
218 int n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp,
219 d12 = dccp_delta_seqno(s1, s2), d2;
220 218
221 if (d12 > 0) { /* S1 < S2 */ 219 if (likely(dccp_delta_seqno(s1, s2) > 0)) { /* S1 < S2 */
222 h->loss_count = 2; 220 h->loss_count = 2;
223 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n2); 221 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n2);
224 return; 222 return;
225 } 223 }
226 224
227 /* S0 < S2 < S1 */ 225 /* S0 < S2 < S1 */
228 d2 = dccp_delta_seqno(s0, s2);
229 226
230 if (d2 == 1 || n2 >= d2) { /* S2 is direct successor of S0 */ 227 if (dccp_loss_free(s0, s2, n2)) {
231 int d21 = -d12; 228 u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp;
232 229
233 if (d21 == 1 || n1 >= d21) { 230 if (dccp_loss_free(s2, s1, n1)) {
234 /* hole is filled: S0, S2, and S1 are consecutive */ 231 /* hole is filled: S0, S2, and S1 are consecutive */
235 h->loss_count = 0; 232 h->loss_count = 0;
236 h->loss_start = tfrc_rx_hist_index(h, 1); 233 h->loss_start = tfrc_rx_hist_index(h, 1);
@@ -238,9 +235,9 @@ static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2
238 /* gap between S2 and S1: just update loss_prev */ 235 /* gap between S2 and S1: just update loss_prev */
239 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n2); 236 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n2);
240 237
241 } else { /* hole between S0 and S2 */ 238 } else { /* gap between S0 and S2 */
242 /* 239 /*
243 * Reorder history to insert S2 between S0 and s1 240 * Reorder history to insert S2 between S0 and S1
244 */ 241 */
245 tfrc_rx_hist_swap(h, 0, 3); 242 tfrc_rx_hist_swap(h, 0, 3);
246 h->loss_start = tfrc_rx_hist_index(h, 3); 243 h->loss_start = tfrc_rx_hist_index(h, 3);
@@ -256,22 +253,18 @@ static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3)
256 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno, 253 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
257 s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno, 254 s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
258 s3 = DCCP_SKB_CB(skb)->dccpd_seq; 255 s3 = DCCP_SKB_CB(skb)->dccpd_seq;
259 int n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp,
260 d23 = dccp_delta_seqno(s2, s3), d13, d3, d31;
261 256
262 if (d23 > 0) { /* S2 < S3 */ 257 if (likely(dccp_delta_seqno(s2, s3) > 0)) { /* S2 < S3 */
263 h->loss_count = 3; 258 h->loss_count = 3;
264 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 3), skb, n3); 259 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 3), skb, n3);
265 return 1; 260 return 1;
266 } 261 }
267 262
268 /* S3 < S2 */ 263 /* S3 < S2 */
269 d13 = dccp_delta_seqno(s1, s3);
270 264
271 if (d13 > 0) { 265 if (dccp_delta_seqno(s1, s3) > 0) { /* S1 < S3 < S2 */
272 /* 266 /*
273 * The sequence number order is S1, S3, S2 267 * Reorder history to insert S3 between S1 and S2
274 * Reorder history to insert entry between S1 and S2
275 */ 268 */
276 tfrc_rx_hist_swap(h, 2, 3); 269 tfrc_rx_hist_swap(h, 2, 3);
277 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n3); 270 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n3);
@@ -280,17 +273,15 @@ static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3)
280 } 273 }
281 274
282 /* S0 < S3 < S1 */ 275 /* S0 < S3 < S1 */
283 d31 = -d13;
284 d3 = dccp_delta_seqno(s0, s3);
285 276
286 if (d3 == 1 || n3 >= d3) { /* S3 is a successor of S0 */ 277 if (dccp_loss_free(s0, s3, n3)) {
278 u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp;
287 279
288 if (d31 == 1 || n1 >= d31) { 280 if (dccp_loss_free(s3, s1, n1)) {
289 /* hole between S0 and S1 filled by S3 */ 281 /* hole between S0 and S1 filled by S3 */
290 int d2 = dccp_delta_seqno(s1, s2), 282 u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp;
291 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp;
292 283
293 if (d2 == 1 || n2 >= d2) { 284 if (dccp_loss_free(s1, s2, n2)) {
294 /* entire hole filled by S0, S3, S1, S2 */ 285 /* entire hole filled by S0, S3, S1, S2 */
295 h->loss_start = tfrc_rx_hist_index(h, 2); 286 h->loss_start = tfrc_rx_hist_index(h, 2);
296 h->loss_count = 0; 287 h->loss_count = 0;
@@ -307,8 +298,8 @@ static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3)
307 } 298 }
308 299
309 /* 300 /*
310 * The remaining case: S3 is not a successor of S0. 301 * The remaining case: S0 < S3 < S1 < S2; gap between S0 and S3
311 * Sequence order is S0, S3, S1, S2; reorder to insert between S0 and S1 302 * Reorder history to insert S3 between S0 and S1.
312 */ 303 */
313 tfrc_rx_hist_swap(h, 0, 3); 304 tfrc_rx_hist_swap(h, 0, 3);
314 h->loss_start = tfrc_rx_hist_index(h, 3); 305 h->loss_start = tfrc_rx_hist_index(h, 3);
@@ -318,33 +309,25 @@ static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3)
318 return 1; 309 return 1;
319} 310}
320 311
321/* return the signed modulo-2^48 sequence number distance from entry e1 to e2 */
322static s64 tfrc_rx_hist_delta_seqno(struct tfrc_rx_hist *h, u8 e1, u8 e2)
323{
324 DCCP_BUG_ON(e1 > h->loss_count || e2 > h->loss_count);
325
326 return dccp_delta_seqno(tfrc_rx_hist_entry(h, e1)->tfrchrx_seqno,
327 tfrc_rx_hist_entry(h, e2)->tfrchrx_seqno);
328}
329
330/* recycle RX history records to continue loss detection if necessary */ 312/* recycle RX history records to continue loss detection if necessary */
331static void __three_after_loss(struct tfrc_rx_hist *h) 313static void __three_after_loss(struct tfrc_rx_hist *h)
332{ 314{
333 /* 315 /*
334 * The distance between S0 and S1 is always greater than 1 and the NDP 316 * At this stage we know already that there is a gap between S0 and S1
335 * count of S1 is smaller than this distance. Otherwise there would 317 * (since S0 was the highest sequence number received before detecting
336 * have been no loss. Hence it is only necessary to see whether there 318 * the loss). To recycle the loss record, it is thus only necessary to
337 * are further missing data packets between S1/S2 and S2/S3. 319 * check for other possible gaps between S1/S2 and between S2/S3.
338 */ 320 */
339 int d2 = tfrc_rx_hist_delta_seqno(h, 1, 2), 321 u64 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
340 d3 = tfrc_rx_hist_delta_seqno(h, 2, 3), 322 s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
341 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp, 323 s3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_seqno;
324 u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp,
342 n3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_ndp; 325 n3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_ndp;
343 326
344 if (d2 == 1 || n2 >= d2) { /* S2 is successor to S1 */ 327 if (dccp_loss_free(s1, s2, n2)) {
345 328
346 if (d3 == 1 || n3 >= d3) { 329 if (dccp_loss_free(s2, s3, n3)) {
347 /* S3 is successor of S2: entire hole is filled */ 330 /* no gap between S2 and S3: entire hole is filled */
348 h->loss_start = tfrc_rx_hist_index(h, 3); 331 h->loss_start = tfrc_rx_hist_index(h, 3);
349 h->loss_count = 0; 332 h->loss_count = 0;
350 } else { 333 } else {
@@ -353,7 +336,7 @@ static void __three_after_loss(struct tfrc_rx_hist *h)
353 h->loss_count = 1; 336 h->loss_count = 1;
354 } 337 }
355 338
356 } else { /* gap between S1 and S2 */ 339 } else { /* gap between S1 and S2 */
357 h->loss_start = tfrc_rx_hist_index(h, 1); 340 h->loss_start = tfrc_rx_hist_index(h, 1);
358 h->loss_count = 2; 341 h->loss_count = 2;
359 } 342 }
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 1b2cea244e12..32617e0576cb 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -153,6 +153,21 @@ static inline u64 max48(const u64 seq1, const u64 seq2)
153 return after48(seq1, seq2) ? seq1 : seq2; 153 return after48(seq1, seq2) ? seq1 : seq2;
154} 154}
155 155
156/**
157 * dccp_loss_free - Evaluates condition for data loss from RFC 4340, 7.7.1
158 * @s1: start sequence number
159 * @s2: end sequence number
160 * @ndp: NDP count on packet with sequence number @s2
161 * Returns true if the sequence range s1...s2 has no data loss.
162 */
163static inline bool dccp_loss_free(const u64 s1, const u64 s2, const u64 ndp)
164{
165 s64 delta = dccp_delta_seqno(s1, s2);
166
167 BUG_TRAP(delta >= 0);
168 return (u64)delta <= ndp + 1;
169}
170
156enum { 171enum {
157 DCCP_MIB_NUM = 0, 172 DCCP_MIB_NUM = 0,
158 DCCP_MIB_ACTIVEOPENS, /* ActiveOpens */ 173 DCCP_MIB_ACTIVEOPENS, /* ActiveOpens */