1 /* 2 * net/dccp/ccids/lib/loss_interval.c 3 * 4 * Copyright (c) 2007 The University of Aberdeen, Scotland, UK 5 * Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand. 6 * Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz> 7 * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br> 8 * 9 * This program is free software; you can redistribute it and/or modify 10 * it under the terms of the GNU General Public License as published by 11 * the Free Software Foundation; either version 2 of the License, or 12 * (at your option) any later version. 13 */ 14 #include <net/sock.h> 15 #include "tfrc.h" 16 17 static struct kmem_cache *tfrc_lh_slab __read_mostly; 18 /* Loss Interval weights from [RFC 3448, 5.4], scaled by 10 */ 19 static const int tfrc_lh_weights[NINTERVAL] = { 10, 10, 10, 10, 8, 6, 4, 2 }; 20 21 /* implements LIFO semantics on the array */ 22 static inline u8 LIH_INDEX(const u8 ctr) 23 { 24 return (LIH_SIZE - 1 - (ctr % LIH_SIZE)); 25 } 26 27 /* the `counter' index always points at the next entry to be populated */ 28 static inline struct tfrc_loss_interval *tfrc_lh_peek(struct tfrc_loss_hist *lh) 29 { 30 return lh->counter ? lh->ring[LIH_INDEX(lh->counter - 1)] : NULL; 31 } 32 33 /* given i with 0 <= i <= k, return I_i as per the rfc3448bis notation */ 34 static inline u32 tfrc_lh_get_interval(struct tfrc_loss_hist *lh, const u8 i) 35 { 36 BUG_ON(i >= lh->counter); 37 return lh->ring[LIH_INDEX(lh->counter - i - 1)]->li_length; 38 } 39 40 /* 41 * On-demand allocation and de-allocation of entries 42 */ 43 static struct tfrc_loss_interval *tfrc_lh_demand_next(struct tfrc_loss_hist *lh) 44 { 45 if (lh->ring[LIH_INDEX(lh->counter)] == NULL) 46 lh->ring[LIH_INDEX(lh->counter)] = kmem_cache_alloc(tfrc_lh_slab, 47 GFP_ATOMIC); 48 return lh->ring[LIH_INDEX(lh->counter)]; 49 } 50 51 void tfrc_lh_cleanup(struct tfrc_loss_hist *lh) 52 { 53 if (!tfrc_lh_is_initialised(lh)) 54 return; 55 56 for (lh->counter = 0; lh->counter < LIH_SIZE; lh->counter++) 57 if (lh->ring[LIH_INDEX(lh->counter)] != NULL) { 58 kmem_cache_free(tfrc_lh_slab, 59 lh->ring[LIH_INDEX(lh->counter)]); 60 lh->ring[LIH_INDEX(lh->counter)] = NULL; 61 } 62 } 63 64 static void tfrc_lh_calc_i_mean(struct tfrc_loss_hist *lh) 65 { 66 u32 i_i, i_tot0 = 0, i_tot1 = 0, w_tot = 0; 67 int i, k = tfrc_lh_length(lh) - 1; /* k is as in rfc3448bis, 5.4 */ 68 69 if (k <= 0) 70 return; 71 72 for (i = 0; i <= k; i++) { 73 i_i = tfrc_lh_get_interval(lh, i); 74 75 if (i < k) { 76 i_tot0 += i_i * tfrc_lh_weights[i]; 77 w_tot += tfrc_lh_weights[i]; 78 } 79 if (i > 0) 80 i_tot1 += i_i * tfrc_lh_weights[i-1]; 81 } 82 83 lh->i_mean = max(i_tot0, i_tot1) / w_tot; 84 } 85 86 /** 87 * tfrc_lh_update_i_mean - Update the `open' loss interval I_0 88 * For recomputing p: returns `true' if p > p_prev <=> 1/p < 1/p_prev 89 */ 90 u8 tfrc_lh_update_i_mean(struct tfrc_loss_hist *lh, struct sk_buff *skb) 91 { 92 struct tfrc_loss_interval *cur = tfrc_lh_peek(lh); 93 u32 old_i_mean = lh->i_mean; 94 s64 len; 95 96 if (cur == NULL) /* not initialised */ 97 return 0; 98 99 len = dccp_delta_seqno(cur->li_seqno, DCCP_SKB_CB(skb)->dccpd_seq) + 1; 100 101 if (len - (s64)cur->li_length <= 0) /* duplicate or reordered */ 102 return 0; 103 104 if (SUB16(dccp_hdr(skb)->dccph_ccval, cur->li_ccval) > 4) 105 /* 106 * Implements RFC 4342, 10.2: 107 * If a packet S (skb) exists whose seqno comes `after' the one 108 * starting the current loss interval (cur) and if the modulo-16 109 * distance from C(cur) to C(S) is greater than 4, consider all 110 * subsequent packets as belonging to a new loss interval. This 111 * test is necessary since CCVal may wrap between intervals. 112 */ 113 cur->li_is_closed = 1; 114 115 if (tfrc_lh_length(lh) == 1) /* due to RFC 3448, 6.3.1 */ 116 return 0; 117 118 cur->li_length = len; 119 tfrc_lh_calc_i_mean(lh); 120 121 return (lh->i_mean < old_i_mean); 122 } 123 124 /* Determine if `new_loss' does begin a new loss interval [RFC 4342, 10.2] */ 125 static inline u8 tfrc_lh_is_new_loss(struct tfrc_loss_interval *cur, 126 struct tfrc_rx_hist_entry *new_loss) 127 { 128 return dccp_delta_seqno(cur->li_seqno, new_loss->tfrchrx_seqno) > 0 && 129 (cur->li_is_closed || SUB16(new_loss->tfrchrx_ccval, cur->li_ccval) > 4); 130 } 131 132 /** tfrc_lh_interval_add - Insert new record into the Loss Interval database 133 * @lh: Loss Interval database 134 * @rh: Receive history containing a fresh loss event 135 * @calc_first_li: Caller-dependent routine to compute length of first interval 136 * @sk: Used by @calc_first_li in caller-specific way (subtyping) 137 * Updates I_mean and returns 1 if a new interval has in fact been added to @lh. 138 */ 139 int tfrc_lh_interval_add(struct tfrc_loss_hist *lh, struct tfrc_rx_hist *rh, 140 u32 (*calc_first_li)(struct sock *), struct sock *sk) 141 { 142 struct tfrc_loss_interval *cur = tfrc_lh_peek(lh), *new; 143 144 if (cur != NULL && !tfrc_lh_is_new_loss(cur, tfrc_rx_hist_loss_prev(rh))) 145 return 0; 146 147 new = tfrc_lh_demand_next(lh); 148 if (unlikely(new == NULL)) { 149 DCCP_CRIT("Cannot allocate/add loss record."); 150 return 0; 151 } 152 153 new->li_seqno = tfrc_rx_hist_loss_prev(rh)->tfrchrx_seqno; 154 new->li_ccval = tfrc_rx_hist_loss_prev(rh)->tfrchrx_ccval; 155 new->li_is_closed = 0; 156 157 if (++lh->counter == 1) 158 lh->i_mean = new->li_length = (*calc_first_li)(sk); 159 else { 160 cur->li_length = dccp_delta_seqno(cur->li_seqno, new->li_seqno); 161 new->li_length = dccp_delta_seqno(new->li_seqno, 162 tfrc_rx_hist_last_rcv(rh)->tfrchrx_seqno) + 1; 163 if (lh->counter > (2*LIH_SIZE)) 164 lh->counter -= LIH_SIZE; 165 166 tfrc_lh_calc_i_mean(lh); 167 } 168 return 1; 169 } 170 171 int __init tfrc_li_init(void) 172 { 173 tfrc_lh_slab = kmem_cache_create("tfrc_li_hist", 174 sizeof(struct tfrc_loss_interval), 0, 175 SLAB_HWCACHE_ALIGN, NULL); 176 return tfrc_lh_slab == NULL ? -ENOBUFS : 0; 177 } 178 179 void tfrc_li_exit(void) 180 { 181 if (tfrc_lh_slab != NULL) { 182 kmem_cache_destroy(tfrc_lh_slab); 183 tfrc_lh_slab = NULL; 184 } 185 } 186