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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 | // SPDX-License-Identifier: GPL-2.0-only /* * TCP Veno congestion control * * This is based on the congestion detection/avoidance scheme described in * C. P. Fu, S. C. Liew. * "TCP Veno: TCP Enhancement for Transmission over Wireless Access Networks." * IEEE Journal on Selected Areas in Communication, * Feb. 2003. * See https://www.ie.cuhk.edu.hk/fileadmin/staff_upload/soung/Journal/J3.pdf */ #include <linux/mm.h> #include <linux/module.h> #include <linux/skbuff.h> #include <linux/inet_diag.h> #include <net/tcp.h> /* Default values of the Veno variables, in fixed-point representation * with V_PARAM_SHIFT bits to the right of the binary point. */ #define V_PARAM_SHIFT 1 static const int beta = 3 << V_PARAM_SHIFT; /* Veno variables */ struct veno { u8 doing_veno_now; /* if true, do veno for this rtt */ u16 cntrtt; /* # of rtts measured within last rtt */ u32 minrtt; /* min of rtts measured within last rtt (in usec) */ u32 basertt; /* the min of all Veno rtt measurements seen (in usec) */ u32 inc; /* decide whether to increase cwnd */ u32 diff; /* calculate the diff rate */ }; /* There are several situations when we must "re-start" Veno: * * o when a connection is established * o after an RTO * o after fast recovery * o when we send a packet and there is no outstanding * unacknowledged data (restarting an idle connection) * */ static inline void veno_enable(struct sock *sk) { struct veno *veno = inet_csk_ca(sk); /* turn on Veno */ veno->doing_veno_now = 1; veno->minrtt = 0x7fffffff; } static inline void veno_disable(struct sock *sk) { struct veno *veno = inet_csk_ca(sk); /* turn off Veno */ veno->doing_veno_now = 0; } static void tcp_veno_init(struct sock *sk) { struct veno *veno = inet_csk_ca(sk); veno->basertt = 0x7fffffff; veno->inc = 1; veno_enable(sk); } /* Do rtt sampling needed for Veno. */ static void tcp_veno_pkts_acked(struct sock *sk, const struct ack_sample *sample) { struct veno *veno = inet_csk_ca(sk); u32 vrtt; if (sample->rtt_us < 0) return; /* Never allow zero rtt or baseRTT */ vrtt = sample->rtt_us + 1; /* Filter to find propagation delay: */ if (vrtt < veno->basertt) veno->basertt = vrtt; /* Find the min rtt during the last rtt to find * the current prop. delay + queuing delay: */ veno->minrtt = min(veno->minrtt, vrtt); veno->cntrtt++; } static void tcp_veno_state(struct sock *sk, u8 ca_state) { if (ca_state == TCP_CA_Open) veno_enable(sk); else veno_disable(sk); } /* * If the connection is idle and we are restarting, * then we don't want to do any Veno calculations * until we get fresh rtt samples. So when we * restart, we reset our Veno state to a clean * state. After we get acks for this flight of * packets, _then_ we can make Veno calculations * again. */ static void tcp_veno_cwnd_event(struct sock *sk, enum tcp_ca_event event) { if (event == CA_EVENT_CWND_RESTART || event == CA_EVENT_TX_START) tcp_veno_init(sk); } static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, u32 acked) { struct tcp_sock *tp = tcp_sk(sk); struct veno *veno = inet_csk_ca(sk); if (!veno->doing_veno_now) { tcp_reno_cong_avoid(sk, ack, acked); return; } /* limited by applications */ if (!tcp_is_cwnd_limited(sk)) return; /* We do the Veno calculations only if we got enough rtt samples */ if (veno->cntrtt <= 2) { /* We don't have enough rtt samples to do the Veno * calculation, so we'll behave like Reno. */ tcp_reno_cong_avoid(sk, ack, acked); } else { u64 target_cwnd; u32 rtt; /* We have enough rtt samples, so, using the Veno * algorithm, we determine the state of the network. */ rtt = veno->minrtt; target_cwnd = (u64)tcp_snd_cwnd(tp) * veno->basertt; target_cwnd <<= V_PARAM_SHIFT; do_div(target_cwnd, rtt); veno->diff = (tcp_snd_cwnd(tp) << V_PARAM_SHIFT) - target_cwnd; if (tcp_in_slow_start(tp)) { /* Slow start. */ acked = tcp_slow_start(tp, acked); if (!acked) goto done; } /* Congestion avoidance. */ if (veno->diff < beta) { /* In the "non-congestive state", increase cwnd * every rtt. */ tcp_cong_avoid_ai(tp, tcp_snd_cwnd(tp), acked); } else { /* In the "congestive state", increase cwnd * every other rtt. */ if (tp->snd_cwnd_cnt >= tcp_snd_cwnd(tp)) { if (veno->inc && tcp_snd_cwnd(tp) < tp->snd_cwnd_clamp) { tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + 1); veno->inc = 0; } else veno->inc = 1; tp->snd_cwnd_cnt = 0; } else tp->snd_cwnd_cnt += acked; } done: if (tcp_snd_cwnd(tp) < 2) tcp_snd_cwnd_set(tp, 2); else if (tcp_snd_cwnd(tp) > tp->snd_cwnd_clamp) tcp_snd_cwnd_set(tp, tp->snd_cwnd_clamp); } /* Wipe the slate clean for the next rtt. */ /* veno->cntrtt = 0; */ veno->minrtt = 0x7fffffff; } /* Veno MD phase */ static u32 tcp_veno_ssthresh(struct sock *sk) { const struct tcp_sock *tp = tcp_sk(sk); struct veno *veno = inet_csk_ca(sk); if (veno->diff < beta) /* in "non-congestive state", cut cwnd by 1/5 */ return max(tcp_snd_cwnd(tp) * 4 / 5, 2U); else /* in "congestive state", cut cwnd by 1/2 */ return max(tcp_snd_cwnd(tp) >> 1U, 2U); } static struct tcp_congestion_ops tcp_veno __read_mostly = { .init = tcp_veno_init, .ssthresh = tcp_veno_ssthresh, .undo_cwnd = tcp_reno_undo_cwnd, .cong_avoid = tcp_veno_cong_avoid, .pkts_acked = tcp_veno_pkts_acked, .set_state = tcp_veno_state, .cwnd_event = tcp_veno_cwnd_event, .owner = THIS_MODULE, .name = "veno", }; static int __init tcp_veno_register(void) { BUILD_BUG_ON(sizeof(struct veno) > ICSK_CA_PRIV_SIZE); tcp_register_congestion_control(&tcp_veno); return 0; } static void __exit tcp_veno_unregister(void) { tcp_unregister_congestion_control(&tcp_veno); } module_init(tcp_veno_register); module_exit(tcp_veno_unregister); MODULE_AUTHOR("Bin Zhou, Cheng Peng Fu"); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("TCP Veno"); |