1 /* 2 * Codel - The Controlled-Delay Active Queue Management algorithm. 3 * 4 * $FreeBSD$ 5 * 6 * Copyright (C) 2016 Centre for Advanced Internet Architectures, 7 * Swinburne University of Technology, Melbourne, Australia. 8 * Portions of this code were made possible in part by a gift from 9 * The Comcast Innovation Fund. 10 * Implemented by Rasool Al-Saadi <ralsaadi@swin.edu.au> 11 * 12 * Copyright (C) 2011-2014 Kathleen Nichols <nichols@pollere.com>. 13 * 14 * Redistribution and use in source and binary forms, with or without 15 * modification, are permitted provided that the following conditions 16 * are met: 17 * 18 * o Redistributions of source code must retain the above copyright 19 * notice, this list of conditions, and the following disclaimer, 20 * without modification. 21 * 22 * o Redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in 24 * the documentation and/or other materials provided with the 25 * distribution. 26 * 27 * o The names of the authors may not be used to endorse or promote 28 * products derived from this software without specific prior written 29 * permission. 30 * 31 * Alternatively, provided that this notice is retained in full, this 32 * software may be distributed under the terms of the GNU General Public 33 * License ("GPL") version 2, in which case the provisions of the GPL 34 * apply INSTEAD OF those given above. 35 36 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 37 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 38 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 39 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 40 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 41 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 42 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 43 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 44 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 45 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 46 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 47 */ 48 49 #ifndef _IP_DN_SCHED_FQ_CODEL_HELPER_H 50 #define _IP_DN_SCHED_FQ_CODEL_HELPER_H 51 52 __inline static struct mbuf * 53 fqc_dodequeue(struct fq_codel_flow *q, aqm_time_t now, uint16_t *ok_to_drop, 54 struct fq_codel_si *si) 55 { 56 struct mbuf * m; 57 struct fq_codel_schk *schk = (struct fq_codel_schk *)(si->_si.sched+1); 58 aqm_time_t pkt_ts, sojourn_time; 59 60 *ok_to_drop = 0; 61 m = fq_codel_extract_head(q, &pkt_ts, si); 62 63 if (m == NULL) { 64 /*queue is empty - we can't be above target*/ 65 q->cst.first_above_time= 0; 66 return m; 67 } 68 69 /* To span a large range of bandwidths, CoDel runs two 70 * different AQMs in parallel. One is sojourn-time-based 71 * and takes effect when the time to send an MTU-sized 72 * packet is less than target. The 1st term of the "if" 73 * below does this. The other is backlog-based and takes 74 * effect when the time to send an MTU-sized packet is >= 75 * target. The goal here is to keep the output link 76 * utilization high by never allowing the queue to get 77 * smaller than the amount that arrives in a typical 78 * interarrival time (MTU-sized packets arriving spaced 79 * by the amount of time it takes to send such a packet on 80 * the bottleneck). The 2nd term of the "if" does this. 81 */ 82 sojourn_time = now - pkt_ts; 83 if (sojourn_time < schk->cfg.ccfg.target || q->stats.len_bytes <= q->cst.maxpkt_size) { 84 /* went below - stay below for at least interval */ 85 q->cst.first_above_time = 0; 86 } else { 87 if (q->cst.first_above_time == 0) { 88 /* just went above from below. if still above at 89 * first_above_time, will say it's ok to drop. */ 90 q->cst.first_above_time = now + schk->cfg.ccfg.interval; 91 } else if (now >= q->cst.first_above_time) { 92 *ok_to_drop = 1; 93 } 94 } 95 return m; 96 } 97 98 /* Codel dequeue function */ 99 __inline static struct mbuf * 100 fqc_codel_dequeue(struct fq_codel_flow *q, struct fq_codel_si *si) 101 { 102 struct mbuf *m; 103 struct dn_aqm_codel_parms *cprms; 104 struct codel_status *cst; 105 aqm_time_t now; 106 uint16_t ok_to_drop; 107 struct fq_codel_schk *schk = (struct fq_codel_schk *)(si->_si.sched+1); 108 109 cst = &q->cst; 110 cprms = &schk->cfg.ccfg; 111 112 now = AQM_UNOW; 113 m = fqc_dodequeue(q, now, &ok_to_drop, si); 114 115 if (cst->dropping) { 116 if (!ok_to_drop) { 117 /* sojourn time below target - leave dropping state */ 118 cst->dropping = false; 119 } 120 121 /* Time for the next drop. Drop current packet and dequeue 122 * next. If the dequeue doesn't take us out of dropping 123 * state, schedule the next drop. A large backlog might 124 * result in drop rates so high that the next drop should 125 * happen now, hence the 'while' loop. 126 */ 127 while (now >= cst->drop_next_time && cst->dropping) { 128 129 /* mark the packet */ 130 if (cprms->flags & CODEL_ECN_ENABLED && ecn_mark(m)) { 131 cst->count++; 132 /* schedule the next mark. */ 133 cst->drop_next_time = control_law(cst, cprms, cst->drop_next_time); 134 return m; 135 } 136 137 /* drop the packet */ 138 fq_update_stats(q, si, 0, 1); 139 m_freem(m); 140 m = fqc_dodequeue(q, now, &ok_to_drop, si); 141 142 if (!ok_to_drop) { 143 /* leave dropping state */ 144 cst->dropping = false; 145 } else { 146 cst->count++; 147 /* schedule the next drop. */ 148 cst->drop_next_time = control_law(cst, cprms, cst->drop_next_time); 149 } 150 } 151 /* If we get here we're not in dropping state. The 'ok_to_drop' 152 * return from dodequeue means that the sojourn time has been 153 * above 'target' for 'interval' so enter dropping state. 154 */ 155 } else if (ok_to_drop) { 156 157 /* if ECN option is disabled or the packet cannot be marked, 158 * drop the packet and extract another. 159 */ 160 if (!(cprms->flags & CODEL_ECN_ENABLED) || !ecn_mark(m)) { 161 fq_update_stats(q, si, 0, 1); 162 m_freem(m); 163 m = fqc_dodequeue(q, now, &ok_to_drop,si); 164 } 165 166 cst->dropping = true; 167 168 /* If min went above target close to when it last went 169 * below, assume that the drop rate that controlled the 170 * queue on the last cycle is a good starting point to 171 * control it now. ('drop_next' will be at most 'interval' 172 * later than the time of the last drop so 'now - drop_next' 173 * is a good approximation of the time from the last drop 174 * until now.) 175 */ 176 cst->count = (cst->count > 2 && ((aqm_stime_t)now - 177 (aqm_stime_t)cst->drop_next_time) < 8* cprms->interval)? cst->count - 2 : 1; 178 179 /* we don't have to set initial guess for Newton's method isqrt as 180 * we initilaize isqrt in control_law function when count == 1 */ 181 cst->drop_next_time = control_law(cst, cprms, now); 182 } 183 184 return m; 185 } 186 187 #endif 188