| /* |
| * 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, sicne |
| * 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 1000 |
| |
| /** |
| * 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 in_flight) |
| { |
| struct lp *lp = inet_csk_ca(sk); |
| |
| if (!(lp->flag & LP_WITHIN_INF)) |
| tcp_reno_cong_avoid(sk, ack, in_flight); |
| } |
| |
| /** |
| * 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 = 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 / 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, u32 num_acked, s32 rtt_us) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| struct lp *lp = inet_csk_ca(sk); |
| |
| if (rtt_us > 0) |
| tcp_lp_rtt_sample(sk, rtt_us); |
| |
| /* calc inference */ |
| if (tcp_time_stamp > tp->rx_opt.rcv_tsecr) |
| lp->inference = 3 * (tcp_time_stamp - tp->rx_opt.rcv_tsecr); |
| |
| /* test if within inference */ |
| if (lp->last_drop && (tcp_time_stamp - 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 = tcp_time_stamp; |
| } |
| |
| static struct tcp_congestion_ops tcp_lp __read_mostly = { |
| .flags = TCP_CONG_RTT_STAMP, |
| .init = tcp_lp_init, |
| .ssthresh = tcp_reno_ssthresh, |
| .cong_avoid = tcp_lp_cong_avoid, |
| .min_cwnd = tcp_reno_min_cwnd, |
| .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"); |