diff options
Diffstat (limited to 'kernel/net/ipv4/tcp_veno.c')
| -rw-r--r-- | kernel/net/ipv4/tcp_veno.c | 232 |
1 files changed, 232 insertions, 0 deletions
diff --git a/kernel/net/ipv4/tcp_veno.c b/kernel/net/ipv4/tcp_veno.c new file mode 100644 index 000000000..112151eee --- /dev/null +++ b/kernel/net/ipv4/tcp_veno.c @@ -0,0 +1,232 @@ +/* + * 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 http://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, u32 cnt, s32 rtt_us) +{ + struct veno *veno = inet_csk_ca(sk); + u32 vrtt; + + if (rtt_us < 0) + return; + + /* Never allow zero rtt or baseRTT */ + vrtt = 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)tp->snd_cwnd * veno->basertt; + target_cwnd <<= V_PARAM_SHIFT; + do_div(target_cwnd, rtt); + + veno->diff = (tp->snd_cwnd << V_PARAM_SHIFT) - target_cwnd; + + if (tp->snd_cwnd <= tp->snd_ssthresh) { + /* Slow start. */ + tcp_slow_start(tp, acked); + } else { + /* Congestion avoidance. */ + if (veno->diff < beta) { + /* In the "non-congestive state", increase cwnd + * every rtt. + */ + tcp_cong_avoid_ai(tp, tp->snd_cwnd, 1); + } else { + /* In the "congestive state", increase cwnd + * every other rtt. + */ + if (tp->snd_cwnd_cnt >= tp->snd_cwnd) { + if (veno->inc && + tp->snd_cwnd < tp->snd_cwnd_clamp) { + tp->snd_cwnd++; + veno->inc = 0; + } else + veno->inc = 1; + tp->snd_cwnd_cnt = 0; + } else + tp->snd_cwnd_cnt++; + } + } + if (tp->snd_cwnd < 2) + tp->snd_cwnd = 2; + else if (tp->snd_cwnd > tp->snd_cwnd_clamp) + tp->snd_cwnd = 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(tp->snd_cwnd * 4 / 5, 2U); + else + /* in "congestive state", cut cwnd by 1/2 */ + return max(tp->snd_cwnd >> 1U, 2U); +} + +static struct tcp_congestion_ops tcp_veno __read_mostly = { + .init = tcp_veno_init, + .ssthresh = tcp_veno_ssthresh, + .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"); |