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Diffstat (limited to '')
| -rw-r--r-- | net/ipv4/tcp_hybla.c | 193 |
1 files changed, 193 insertions, 0 deletions
diff --git a/net/ipv4/tcp_hybla.c b/net/ipv4/tcp_hybla.c new file mode 100644 index 000000000..0f7175c33 --- /dev/null +++ b/net/ipv4/tcp_hybla.c @@ -0,0 +1,193 @@ +/* + * TCP HYBLA + * + * TCP-HYBLA Congestion control algorithm, based on: + * C.Caini, R.Firrincieli, "TCP-Hybla: A TCP Enhancement + * for Heterogeneous Networks", + * International Journal on satellite Communications, + * September 2004 + * Daniele Lacamera + * root at danielinux.net + */ + +#include <linux/module.h> +#include <net/tcp.h> + +/* Tcp Hybla structure. */ +struct hybla { + bool hybla_en; + u32 snd_cwnd_cents; /* Keeps increment values when it is <1, <<7 */ + u32 rho; /* Rho parameter, integer part */ + u32 rho2; /* Rho * Rho, integer part */ + u32 rho_3ls; /* Rho parameter, <<3 */ + u32 rho2_7ls; /* Rho^2, <<7 */ + u32 minrtt_us; /* Minimum smoothed round trip time value seen */ +}; + +/* Hybla reference round trip time (default= 1/40 sec = 25 ms), in ms */ +static int rtt0 = 25; +module_param(rtt0, int, 0644); +MODULE_PARM_DESC(rtt0, "reference rout trip time (ms)"); + +/* This is called to refresh values for hybla parameters */ +static inline void hybla_recalc_param (struct sock *sk) +{ + struct hybla *ca = inet_csk_ca(sk); + + ca->rho_3ls = max_t(u32, + tcp_sk(sk)->srtt_us / (rtt0 * USEC_PER_MSEC), + 8U); + ca->rho = ca->rho_3ls >> 3; + ca->rho2_7ls = (ca->rho_3ls * ca->rho_3ls) << 1; + ca->rho2 = ca->rho2_7ls >> 7; +} + +static void hybla_init(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct hybla *ca = inet_csk_ca(sk); + + ca->rho = 0; + ca->rho2 = 0; + ca->rho_3ls = 0; + ca->rho2_7ls = 0; + ca->snd_cwnd_cents = 0; + ca->hybla_en = true; + tp->snd_cwnd = 2; + tp->snd_cwnd_clamp = 65535; + + /* 1st Rho measurement based on initial srtt */ + hybla_recalc_param(sk); + + /* set minimum rtt as this is the 1st ever seen */ + ca->minrtt_us = tp->srtt_us; + tp->snd_cwnd = ca->rho; +} + +static void hybla_state(struct sock *sk, u8 ca_state) +{ + struct hybla *ca = inet_csk_ca(sk); + + ca->hybla_en = (ca_state == TCP_CA_Open); +} + +static inline u32 hybla_fraction(u32 odds) +{ + static const u32 fractions[] = { + 128, 139, 152, 165, 181, 197, 215, 234, + }; + + return (odds < ARRAY_SIZE(fractions)) ? fractions[odds] : 128; +} + +/* TCP Hybla main routine. + * This is the algorithm behavior: + * o Recalc Hybla parameters if min_rtt has changed + * o Give cwnd a new value based on the model proposed + * o remember increments <1 + */ +static void hybla_cong_avoid(struct sock *sk, u32 ack, u32 acked) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct hybla *ca = inet_csk_ca(sk); + u32 increment, odd, rho_fractions; + int is_slowstart = 0; + + /* Recalculate rho only if this srtt is the lowest */ + if (tp->srtt_us < ca->minrtt_us) { + hybla_recalc_param(sk); + ca->minrtt_us = tp->srtt_us; + } + + if (!tcp_is_cwnd_limited(sk)) + return; + + if (!ca->hybla_en) { + tcp_reno_cong_avoid(sk, ack, acked); + return; + } + + if (ca->rho == 0) + hybla_recalc_param(sk); + + rho_fractions = ca->rho_3ls - (ca->rho << 3); + + if (tcp_in_slow_start(tp)) { + /* + * slow start + * INC = 2^RHO - 1 + * This is done by splitting the rho parameter + * into 2 parts: an integer part and a fraction part. + * Inrement<<7 is estimated by doing: + * [2^(int+fract)]<<7 + * that is equal to: + * (2^int) * [(2^fract) <<7] + * 2^int is straightly computed as 1<<int, + * while we will use hybla_slowstart_fraction_increment() to + * calculate 2^fract in a <<7 value. + */ + is_slowstart = 1; + increment = ((1 << min(ca->rho, 16U)) * + hybla_fraction(rho_fractions)) - 128; + } else { + /* + * congestion avoidance + * INC = RHO^2 / W + * as long as increment is estimated as (rho<<7)/window + * it already is <<7 and we can easily count its fractions. + */ + increment = ca->rho2_7ls / tp->snd_cwnd; + if (increment < 128) + tp->snd_cwnd_cnt++; + } + + odd = increment % 128; + tp->snd_cwnd += increment >> 7; + ca->snd_cwnd_cents += odd; + + /* check when fractions goes >=128 and increase cwnd by 1. */ + while (ca->snd_cwnd_cents >= 128) { + tp->snd_cwnd++; + ca->snd_cwnd_cents -= 128; + tp->snd_cwnd_cnt = 0; + } + /* check when cwnd has not been incremented for a while */ + if (increment == 0 && odd == 0 && tp->snd_cwnd_cnt >= tp->snd_cwnd) { + tp->snd_cwnd++; + tp->snd_cwnd_cnt = 0; + } + /* clamp down slowstart cwnd to ssthresh value. */ + if (is_slowstart) + tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); + + tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp); +} + +static struct tcp_congestion_ops tcp_hybla __read_mostly = { + .init = hybla_init, + .ssthresh = tcp_reno_ssthresh, + .undo_cwnd = tcp_reno_undo_cwnd, + .cong_avoid = hybla_cong_avoid, + .set_state = hybla_state, + + .owner = THIS_MODULE, + .name = "hybla" +}; + +static int __init hybla_register(void) +{ + BUILD_BUG_ON(sizeof(struct hybla) > ICSK_CA_PRIV_SIZE); + return tcp_register_congestion_control(&tcp_hybla); +} + +static void __exit hybla_unregister(void) +{ + tcp_unregister_congestion_control(&tcp_hybla); +} + +module_init(hybla_register); +module_exit(hybla_unregister); + +MODULE_AUTHOR("Daniele Lacamera"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("TCP Hybla"); |