1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Copyright (c) 2007 The University of Aberdeen, Scotland, UK 4 * Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand. 5 * Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz> 6 * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br> 7 */ 8 #include <net/sock.h> 9 #include "tfrc.h" 10 11 static struct kmem_cache *tfrc_lh_slab __read_mostly; 12 /* Loss Interval weights from [RFC 3448, 5.4], scaled by 10 */ 13 static const int tfrc_lh_weights[NINTERVAL] = { 10, 10, 10, 10, 8, 6, 4, 2 }; 14 15 /* implements LIFO semantics on the array */ 16 static inline u8 LIH_INDEX(const u8 ctr) 17 { 18 return LIH_SIZE - 1 - (ctr % LIH_SIZE); 19 } 20 21 /* the `counter' index always points at the next entry to be populated */ 22 static inline struct tfrc_loss_interval *tfrc_lh_peek(struct tfrc_loss_hist *lh) 23 { 24 return lh->counter ? lh->ring[LIH_INDEX(lh->counter - 1)] : NULL; 25 } 26 27 /* given i with 0 <= i <= k, return I_i as per the rfc3448bis notation */ 28 static inline u32 tfrc_lh_get_interval(struct tfrc_loss_hist *lh, const u8 i) 29 { 30 BUG_ON(i >= lh->counter); 31 return lh->ring[LIH_INDEX(lh->counter - i - 1)]->li_length; 32 } 33 34 /* 35 * On-demand allocation and de-allocation of entries 36 */ 37 static struct tfrc_loss_interval *tfrc_lh_demand_next(struct tfrc_loss_hist *lh) 38 { 39 if (lh->ring[LIH_INDEX(lh->counter)] == NULL) 40 lh->ring[LIH_INDEX(lh->counter)] = kmem_cache_alloc(tfrc_lh_slab, 41 GFP_ATOMIC); 42 return lh->ring[LIH_INDEX(lh->counter)]; 43 } 44 45 void tfrc_lh_cleanup(struct tfrc_loss_hist *lh) 46 { 47 if (!tfrc_lh_is_initialised(lh)) 48 return; 49 50 for (lh->counter = 0; lh->counter < LIH_SIZE; lh->counter++) 51 if (lh->ring[LIH_INDEX(lh->counter)] != NULL) { 52 kmem_cache_free(tfrc_lh_slab, 53 lh->ring[LIH_INDEX(lh->counter)]); 54 lh->ring[LIH_INDEX(lh->counter)] = NULL; 55 } 56 } 57 58 static void tfrc_lh_calc_i_mean(struct tfrc_loss_hist *lh) 59 { 60 u32 i_i, i_tot0 = 0, i_tot1 = 0, w_tot = 0; 61 int i, k = tfrc_lh_length(lh) - 1; /* k is as in rfc3448bis, 5.4 */ 62 63 if (k <= 0) 64 return; 65 66 for (i = 0; i <= k; i++) { 67 i_i = tfrc_lh_get_interval(lh, i); 68 69 if (i < k) { 70 i_tot0 += i_i * tfrc_lh_weights[i]; 71 w_tot += tfrc_lh_weights[i]; 72 } 73 if (i > 0) 74 i_tot1 += i_i * tfrc_lh_weights[i-1]; 75 } 76 77 lh->i_mean = max(i_tot0, i_tot1) / w_tot; 78 } 79 80 /** 81 * tfrc_lh_update_i_mean - Update the `open' loss interval I_0 82 * @lh: histogram to update 83 * @skb: received socket triggering loss interval update 84 * 85 * For recomputing p: returns `true' if p > p_prev <=> 1/p < 1/p_prev 86 */ 87 u8 tfrc_lh_update_i_mean(struct tfrc_loss_hist *lh, struct sk_buff *skb) 88 { 89 struct tfrc_loss_interval *cur = tfrc_lh_peek(lh); 90 u32 old_i_mean = lh->i_mean; 91 s64 len; 92 93 if (cur == NULL) /* not initialised */ 94 return 0; 95 96 len = dccp_delta_seqno(cur->li_seqno, DCCP_SKB_CB(skb)->dccpd_seq) + 1; 97 98 if (len - (s64)cur->li_length <= 0) /* duplicate or reordered */ 99 return 0; 100 101 if (SUB16(dccp_hdr(skb)->dccph_ccval, cur->li_ccval) > 4) 102 /* 103 * Implements RFC 4342, 10.2: 104 * If a packet S (skb) exists whose seqno comes `after' the one 105 * starting the current loss interval (cur) and if the modulo-16 106 * distance from C(cur) to C(S) is greater than 4, consider all 107 * subsequent packets as belonging to a new loss interval. This 108 * test is necessary since CCVal may wrap between intervals. 109 */ 110 cur->li_is_closed = 1; 111 112 if (tfrc_lh_length(lh) == 1) /* due to RFC 3448, 6.3.1 */ 113 return 0; 114 115 cur->li_length = len; 116 tfrc_lh_calc_i_mean(lh); 117 118 return lh->i_mean < old_i_mean; 119 } 120 121 /* Determine if `new_loss' does begin a new loss interval [RFC 4342, 10.2] */ 122 static inline u8 tfrc_lh_is_new_loss(struct tfrc_loss_interval *cur, 123 struct tfrc_rx_hist_entry *new_loss) 124 { 125 return dccp_delta_seqno(cur->li_seqno, new_loss->tfrchrx_seqno) > 0 && 126 (cur->li_is_closed || SUB16(new_loss->tfrchrx_ccval, cur->li_ccval) > 4); 127 } 128 129 /** 130 * tfrc_lh_interval_add - Insert new record into the Loss Interval database 131 * @lh: Loss Interval database 132 * @rh: Receive history containing a fresh loss event 133 * @calc_first_li: Caller-dependent routine to compute length of first interval 134 * @sk: Used by @calc_first_li in caller-specific way (subtyping) 135 * 136 * Updates I_mean and returns 1 if a new interval has in fact been added to @lh. 137 */ 138 int tfrc_lh_interval_add(struct tfrc_loss_hist *lh, struct tfrc_rx_hist *rh, 139 u32 (*calc_first_li)(struct sock *), struct sock *sk) 140 { 141 struct tfrc_loss_interval *cur = tfrc_lh_peek(lh), *new; 142 143 if (cur != NULL && !tfrc_lh_is_new_loss(cur, tfrc_rx_hist_loss_prev(rh))) 144 return 0; 145 146 new = tfrc_lh_demand_next(lh); 147 if (unlikely(new == NULL)) { 148 DCCP_CRIT("Cannot allocate/add loss record."); 149 return 0; 150 } 151 152 new->li_seqno = tfrc_rx_hist_loss_prev(rh)->tfrchrx_seqno; 153 new->li_ccval = tfrc_rx_hist_loss_prev(rh)->tfrchrx_ccval; 154 new->li_is_closed = 0; 155 156 if (++lh->counter == 1) 157 lh->i_mean = new->li_length = (*calc_first_li)(sk); 158 else { 159 cur->li_length = dccp_delta_seqno(cur->li_seqno, new->li_seqno); 160 new->li_length = dccp_delta_seqno(new->li_seqno, 161 tfrc_rx_hist_last_rcv(rh)->tfrchrx_seqno) + 1; 162 if (lh->counter > (2*LIH_SIZE)) 163 lh->counter -= LIH_SIZE; 164 165 tfrc_lh_calc_i_mean(lh); 166 } 167 return 1; 168 } 169 170 int __init tfrc_li_init(void) 171 { 172 tfrc_lh_slab = kmem_cache_create("tfrc_li_hist", 173 sizeof(struct tfrc_loss_interval), 0, 174 SLAB_HWCACHE_ALIGN, NULL); 175 return tfrc_lh_slab == NULL ? -ENOBUFS : 0; 176 } 177 178 void tfrc_li_exit(void) 179 { 180 if (tfrc_lh_slab != NULL) { 181 kmem_cache_destroy(tfrc_lh_slab); 182 tfrc_lh_slab = NULL; 183 } 184 } 185