1 /* 2 * Codel - The Controlled-Delay Active Queue Management algorithm. 3 * 4 * Copyright (C) 2016 Centre for Advanced Internet Architectures, 5 * Swinburne University of Technology, Melbourne, Australia. 6 * Portions of this code were made possible in part by a gift from 7 * The Comcast Innovation Fund. 8 * Implemented by Rasool Al-Saadi <ralsaadi@swin.edu.au> 9 * 10 * Copyright (C) 2011-2014 Kathleen Nichols <nichols@pollere.com>. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 16 * o Redistributions of source code must retain the above copyright 17 * notice, this list of conditions, and the following disclaimer, 18 * without modification. 19 * 20 * o Redistributions in binary form must reproduce the above copyright 21 * notice, this list of conditions and the following disclaimer in 22 * the documentation and/or other materials provided with the 23 * distribution. 24 * 25 * o The names of the authors may not be used to endorse or promote 26 * products derived from this software without specific prior written 27 * permission. 28 * 29 * Alternatively, provided that this notice is retained in full, this 30 * software may be distributed under the terms of the GNU General Public 31 * License ("GPL") version 2, in which case the provisions of the GPL 32 * apply INSTEAD OF those given above. 33 34 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 35 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 36 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 37 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 38 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 39 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 40 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 41 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 42 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 43 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 44 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 45 */ 46 47 #ifndef _IP_DN_SCHED_FQ_CODEL_HELPER_H 48 #define _IP_DN_SCHED_FQ_CODEL_HELPER_H 49 50 __inline static struct mbuf * 51 fqc_dodequeue(struct fq_codel_flow *q, aqm_time_t now, uint16_t *ok_to_drop, 52 struct fq_codel_si *si) 53 { 54 struct mbuf * m; 55 struct fq_codel_schk *schk = (struct fq_codel_schk *)(si->_si.sched+1); 56 aqm_time_t pkt_ts, sojourn_time; 57 58 *ok_to_drop = 0; 59 m = fq_codel_extract_head(q, &pkt_ts, si); 60 61 if (m == NULL) { 62 /*queue is empty - we can't be above target*/ 63 q->cst.first_above_time= 0; 64 return m; 65 } 66 67 /* To span a large range of bandwidths, CoDel runs two 68 * different AQMs in parallel. One is sojourn-time-based 69 * and takes effect when the time to send an MTU-sized 70 * packet is less than target. The 1st term of the "if" 71 * below does this. The other is backlog-based and takes 72 * effect when the time to send an MTU-sized packet is >= 73 * target. The goal here is to keep the output link 74 * utilization high by never allowing the queue to get 75 * smaller than the amount that arrives in a typical 76 * interarrival time (MTU-sized packets arriving spaced 77 * by the amount of time it takes to send such a packet on 78 * the bottleneck). The 2nd term of the "if" does this. 79 */ 80 sojourn_time = now - pkt_ts; 81 if (sojourn_time < schk->cfg.ccfg.target || q->stats.len_bytes <= q->cst.maxpkt_size) { 82 /* went below - stay below for at least interval */ 83 q->cst.first_above_time = 0; 84 } else { 85 if (q->cst.first_above_time == 0) { 86 /* just went above from below. if still above at 87 * first_above_time, will say it's ok to drop. */ 88 q->cst.first_above_time = now + schk->cfg.ccfg.interval; 89 } else if (now >= q->cst.first_above_time) { 90 *ok_to_drop = 1; 91 } 92 } 93 return m; 94 } 95 96 /* Codel dequeue function */ 97 __inline static struct mbuf * 98 fqc_codel_dequeue(struct fq_codel_flow *q, struct fq_codel_si *si) 99 { 100 struct mbuf *m; 101 struct dn_aqm_codel_parms *cprms; 102 struct codel_status *cst; 103 aqm_time_t now; 104 uint16_t ok_to_drop; 105 struct fq_codel_schk *schk = (struct fq_codel_schk *)(si->_si.sched+1); 106 107 cst = &q->cst; 108 cprms = &schk->cfg.ccfg; 109 110 now = AQM_UNOW; 111 m = fqc_dodequeue(q, now, &ok_to_drop, si); 112 113 if (cst->dropping) { 114 if (!ok_to_drop) { 115 /* sojourn time below target - leave dropping state */ 116 cst->dropping = false; 117 } 118 119 /* Time for the next drop. Drop current packet and dequeue 120 * next. If the dequeue doesn't take us out of dropping 121 * state, schedule the next drop. A large backlog might 122 * result in drop rates so high that the next drop should 123 * happen now, hence the 'while' loop. 124 */ 125 while (now >= cst->drop_next_time && cst->dropping) { 126 /* mark the packet */ 127 if (cprms->flags & CODEL_ECN_ENABLED && ecn_mark(m)) { 128 cst->count++; 129 /* schedule the next mark. */ 130 cst->drop_next_time = control_law(cst, cprms, cst->drop_next_time); 131 return m; 132 } 133 134 /* drop the packet */ 135 fq_update_stats(q, si, 0, 1); 136 m_freem(m); 137 m = fqc_dodequeue(q, now, &ok_to_drop, si); 138 139 if (!ok_to_drop) { 140 /* leave dropping state */ 141 cst->dropping = false; 142 } else { 143 cst->count++; 144 /* schedule the next drop. */ 145 cst->drop_next_time = control_law(cst, cprms, cst->drop_next_time); 146 } 147 } 148 /* If we get here we're not in dropping state. The 'ok_to_drop' 149 * return from dodequeue means that the sojourn time has been 150 * above 'target' for 'interval' so enter dropping state. 151 */ 152 } else if (ok_to_drop) { 153 /* if ECN option is disabled or the packet cannot be marked, 154 * drop the packet and extract another. 155 */ 156 if (!(cprms->flags & CODEL_ECN_ENABLED) || !ecn_mark(m)) { 157 fq_update_stats(q, si, 0, 1); 158 m_freem(m); 159 m = fqc_dodequeue(q, now, &ok_to_drop,si); 160 } 161 162 cst->dropping = true; 163 164 /* If min went above target close to when it last went 165 * below, assume that the drop rate that controlled the 166 * queue on the last cycle is a good starting point to 167 * control it now. ('drop_next' will be at most 'interval' 168 * later than the time of the last drop so 'now - drop_next' 169 * is a good approximation of the time from the last drop 170 * until now.) 171 */ 172 cst->count = (cst->count > 2 && ((aqm_stime_t)now - 173 (aqm_stime_t)cst->drop_next_time) < 8* cprms->interval)? cst->count - 2 : 1; 174 175 /* we don't have to set initial guess for Newton's method isqrt as 176 * we initilaize isqrt in control_law function when count == 1 */ 177 cst->drop_next_time = control_law(cst, cprms, now); 178 } 179 180 return m; 181 } 182 183 #endif 184