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Diffstat (limited to 'net/ipv4/tcp_lp.c')
| -rw-r--r-- | net/ipv4/tcp_lp.c | 347 |
1 files changed, 347 insertions, 0 deletions
diff --git a/net/ipv4/tcp_lp.c b/net/ipv4/tcp_lp.c new file mode 100644 index 000000000..8c643a4ff --- /dev/null +++ b/net/ipv4/tcp_lp.c @@ -0,0 +1,347 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * TCP Low Priority (TCP-LP) + * + * TCP Low Priority is a distributed algorithm whose goal is to utilize only + * the excess network bandwidth as compared to the ``fair share`` of + * bandwidth as targeted by TCP. + * + * As of 2.6.13, Linux supports pluggable congestion control algorithms. + * Due to the limitation of the API, we take the following changes from + * the original TCP-LP implementation: + * o We use newReno in most core CA handling. Only add some checking + * within cong_avoid. + * o Error correcting in remote HZ, therefore remote HZ will be keeped + * on checking and updating. + * o Handling calculation of One-Way-Delay (OWD) within rtt_sample, since + * OWD have a similar meaning as RTT. Also correct the buggy formular. + * o Handle reaction for Early Congestion Indication (ECI) within + * pkts_acked, as mentioned within pseudo code. + * o OWD is handled in relative format, where local time stamp will in + * tcp_time_stamp format. + * + * Original Author: + * Aleksandar Kuzmanovic <akuzma@northwestern.edu> + * Available from: + * http://www.ece.rice.edu/~akuzma/Doc/akuzma/TCP-LP.pdf + * Original implementation for 2.4.19: + * http://www-ece.rice.edu/networks/TCP-LP/ + * + * 2.6.x module Authors: + * Wong Hoi Sing, Edison <hswong3i@gmail.com> + * Hung Hing Lun, Mike <hlhung3i@gmail.com> + * SourceForge project page: + * http://tcp-lp-mod.sourceforge.net/ + */ + +#include <linux/module.h> +#include <net/tcp.h> + +/* resolution of owd */ +#define LP_RESOL TCP_TS_HZ + +/** + * enum tcp_lp_state + * @LP_VALID_RHZ: is remote HZ valid? + * @LP_VALID_OWD: is OWD valid? + * @LP_WITHIN_THR: are we within threshold? + * @LP_WITHIN_INF: are we within inference? + * + * TCP-LP's state flags. + * We create this set of state flag mainly for debugging. + */ +enum tcp_lp_state { + LP_VALID_RHZ = (1 << 0), + LP_VALID_OWD = (1 << 1), + LP_WITHIN_THR = (1 << 3), + LP_WITHIN_INF = (1 << 4), +}; + +/** + * struct lp + * @flag: TCP-LP state flag + * @sowd: smoothed OWD << 3 + * @owd_min: min OWD + * @owd_max: max OWD + * @owd_max_rsv: resrved max owd + * @remote_hz: estimated remote HZ + * @remote_ref_time: remote reference time + * @local_ref_time: local reference time + * @last_drop: time for last active drop + * @inference: current inference + * + * TCP-LP's private struct. + * We get the idea from original TCP-LP implementation where only left those we + * found are really useful. + */ +struct lp { + u32 flag; + u32 sowd; + u32 owd_min; + u32 owd_max; + u32 owd_max_rsv; + u32 remote_hz; + u32 remote_ref_time; + u32 local_ref_time; + u32 last_drop; + u32 inference; +}; + +/** + * tcp_lp_init + * + * Init all required variables. + * Clone the handling from Vegas module implementation. + */ +static void tcp_lp_init(struct sock *sk) +{ + struct lp *lp = inet_csk_ca(sk); + + lp->flag = 0; + lp->sowd = 0; + lp->owd_min = 0xffffffff; + lp->owd_max = 0; + lp->owd_max_rsv = 0; + lp->remote_hz = 0; + lp->remote_ref_time = 0; + lp->local_ref_time = 0; + lp->last_drop = 0; + lp->inference = 0; +} + +/** + * tcp_lp_cong_avoid + * + * Implementation of cong_avoid. + * Will only call newReno CA when away from inference. + * From TCP-LP's paper, this will be handled in additive increasement. + */ +static void tcp_lp_cong_avoid(struct sock *sk, u32 ack, u32 acked) +{ + struct lp *lp = inet_csk_ca(sk); + + if (!(lp->flag & LP_WITHIN_INF)) + tcp_reno_cong_avoid(sk, ack, acked); +} + +/** + * tcp_lp_remote_hz_estimator + * + * Estimate remote HZ. + * We keep on updating the estimated value, where original TCP-LP + * implementation only guest it for once and use forever. + */ +static u32 tcp_lp_remote_hz_estimator(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct lp *lp = inet_csk_ca(sk); + s64 rhz = lp->remote_hz << 6; /* remote HZ << 6 */ + s64 m = 0; + + /* not yet record reference time + * go away!! record it before come back!! */ + if (lp->remote_ref_time == 0 || lp->local_ref_time == 0) + goto out; + + /* we can't calc remote HZ with no different!! */ + if (tp->rx_opt.rcv_tsval == lp->remote_ref_time || + tp->rx_opt.rcv_tsecr == lp->local_ref_time) + goto out; + + m = TCP_TS_HZ * + (tp->rx_opt.rcv_tsval - lp->remote_ref_time) / + (tp->rx_opt.rcv_tsecr - lp->local_ref_time); + if (m < 0) + m = -m; + + if (rhz > 0) { + m -= rhz >> 6; /* m is now error in remote HZ est */ + rhz += m; /* 63/64 old + 1/64 new */ + } else + rhz = m << 6; + + out: + /* record time for successful remote HZ calc */ + if ((rhz >> 6) > 0) + lp->flag |= LP_VALID_RHZ; + else + lp->flag &= ~LP_VALID_RHZ; + + /* record reference time stamp */ + lp->remote_ref_time = tp->rx_opt.rcv_tsval; + lp->local_ref_time = tp->rx_opt.rcv_tsecr; + + return rhz >> 6; +} + +/** + * tcp_lp_owd_calculator + * + * Calculate one way delay (in relative format). + * Original implement OWD as minus of remote time difference to local time + * difference directly. As this time difference just simply equal to RTT, when + * the network status is stable, remote RTT will equal to local RTT, and result + * OWD into zero. + * It seems to be a bug and so we fixed it. + */ +static u32 tcp_lp_owd_calculator(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct lp *lp = inet_csk_ca(sk); + s64 owd = 0; + + lp->remote_hz = tcp_lp_remote_hz_estimator(sk); + + if (lp->flag & LP_VALID_RHZ) { + owd = + tp->rx_opt.rcv_tsval * (LP_RESOL / lp->remote_hz) - + tp->rx_opt.rcv_tsecr * (LP_RESOL / TCP_TS_HZ); + if (owd < 0) + owd = -owd; + } + + if (owd > 0) + lp->flag |= LP_VALID_OWD; + else + lp->flag &= ~LP_VALID_OWD; + + return owd; +} + +/** + * tcp_lp_rtt_sample + * + * Implementation or rtt_sample. + * Will take the following action, + * 1. calc OWD, + * 2. record the min/max OWD, + * 3. calc smoothed OWD (SOWD). + * Most ideas come from the original TCP-LP implementation. + */ +static void tcp_lp_rtt_sample(struct sock *sk, u32 rtt) +{ + struct lp *lp = inet_csk_ca(sk); + s64 mowd = tcp_lp_owd_calculator(sk); + + /* sorry that we don't have valid data */ + if (!(lp->flag & LP_VALID_RHZ) || !(lp->flag & LP_VALID_OWD)) + return; + + /* record the next min owd */ + if (mowd < lp->owd_min) + lp->owd_min = mowd; + + /* always forget the max of the max + * we just set owd_max as one below it */ + if (mowd > lp->owd_max) { + if (mowd > lp->owd_max_rsv) { + if (lp->owd_max_rsv == 0) + lp->owd_max = mowd; + else + lp->owd_max = lp->owd_max_rsv; + lp->owd_max_rsv = mowd; + } else + lp->owd_max = mowd; + } + + /* calc for smoothed owd */ + if (lp->sowd != 0) { + mowd -= lp->sowd >> 3; /* m is now error in owd est */ + lp->sowd += mowd; /* owd = 7/8 owd + 1/8 new */ + } else + lp->sowd = mowd << 3; /* take the measured time be owd */ +} + +/** + * tcp_lp_pkts_acked + * + * Implementation of pkts_acked. + * Deal with active drop under Early Congestion Indication. + * Only drop to half and 1 will be handle, because we hope to use back + * newReno in increase case. + * We work it out by following the idea from TCP-LP's paper directly + */ +static void tcp_lp_pkts_acked(struct sock *sk, const struct ack_sample *sample) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct lp *lp = inet_csk_ca(sk); + u32 now = tcp_time_stamp(tp); + u32 delta; + + if (sample->rtt_us > 0) + tcp_lp_rtt_sample(sk, sample->rtt_us); + + /* calc inference */ + delta = now - tp->rx_opt.rcv_tsecr; + if ((s32)delta > 0) + lp->inference = 3 * delta; + + /* test if within inference */ + if (lp->last_drop && (now - lp->last_drop < lp->inference)) + lp->flag |= LP_WITHIN_INF; + else + lp->flag &= ~LP_WITHIN_INF; + + /* test if within threshold */ + if (lp->sowd >> 3 < + lp->owd_min + 15 * (lp->owd_max - lp->owd_min) / 100) + lp->flag |= LP_WITHIN_THR; + else + lp->flag &= ~LP_WITHIN_THR; + + pr_debug("TCP-LP: %05o|%5u|%5u|%15u|%15u|%15u\n", lp->flag, + tp->snd_cwnd, lp->remote_hz, lp->owd_min, lp->owd_max, + lp->sowd >> 3); + + if (lp->flag & LP_WITHIN_THR) + return; + + /* FIXME: try to reset owd_min and owd_max here + * so decrease the chance the min/max is no longer suitable + * and will usually within threshold when whithin inference */ + lp->owd_min = lp->sowd >> 3; + lp->owd_max = lp->sowd >> 2; + lp->owd_max_rsv = lp->sowd >> 2; + + /* happened within inference + * drop snd_cwnd into 1 */ + if (lp->flag & LP_WITHIN_INF) + tp->snd_cwnd = 1U; + + /* happened after inference + * cut snd_cwnd into half */ + else + tp->snd_cwnd = max(tp->snd_cwnd >> 1U, 1U); + + /* record this drop time */ + lp->last_drop = now; +} + +static struct tcp_congestion_ops tcp_lp __read_mostly = { + .init = tcp_lp_init, + .ssthresh = tcp_reno_ssthresh, + .undo_cwnd = tcp_reno_undo_cwnd, + .cong_avoid = tcp_lp_cong_avoid, + .pkts_acked = tcp_lp_pkts_acked, + + .owner = THIS_MODULE, + .name = "lp" +}; + +static int __init tcp_lp_register(void) +{ + BUILD_BUG_ON(sizeof(struct lp) > ICSK_CA_PRIV_SIZE); + return tcp_register_congestion_control(&tcp_lp); +} + +static void __exit tcp_lp_unregister(void) +{ + tcp_unregister_congestion_control(&tcp_lp); +} + +module_init(tcp_lp_register); +module_exit(tcp_lp_unregister); + +MODULE_AUTHOR("Wong Hoi Sing Edison, Hung Hing Lun Mike"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("TCP Low Priority"); |