tcp_veno.c
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上传日期:2015-12-11
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- /* Modified Linux module source code from /home/weixl/linux-2.6.22.6 */
- #define NS_PROTOCOL "tcp_veno.c"
- #include "../ns-linux-c.h"
- #include "../ns-linux-util.h"
- /*
- * 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.ntu.edu.sg/home5/ZHOU0022/papers/CPFu03a.pdf
- */
- /* 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, ktime_t last)
- {
- struct veno *veno = inet_csk_ca(sk);
- u32 vrtt;
- if (ktime_equal(last, net_invalid_timestamp()))
- return;
- /* Never allow zero rtt or baseRTT */
- vrtt = ktime_to_us(net_timedelta(last)) + 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 seq_rtt, u32 in_flight, int flag)
- {
- struct tcp_sock *tp = tcp_sk(sk);
- struct veno *veno = inet_csk_ca(sk);
- if (!veno->doing_veno_now)
- return tcp_reno_cong_avoid(sk, ack, seq_rtt, in_flight, flag);
- /* limited by applications */
- if (!tcp_is_cwnd_limited(sk, in_flight))
- 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, seq_rtt, in_flight, flag);
- } else {
- u32 rtt, target_cwnd;
- /* We have enough rtt samples, so, using the Veno
- * algorithm, we determine the state of the network.
- */
- rtt = veno->minrtt;
- target_cwnd = ((tp->snd_cwnd * veno->basertt)
- << V_PARAM_SHIFT) / rtt;
- veno->diff = (tp->snd_cwnd << V_PARAM_SHIFT) - target_cwnd;
- if (tp->snd_cwnd <= tp->snd_ssthresh) {
- /* Slow start. */
- tcp_slow_start(tp);
- } else {
- /* Congestion avoidance. */
- if (veno->diff < beta) {
- /* In the "non-congestive state", increase cwnd
- * every rtt.
- */
- if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
- if (tp->snd_cwnd < tp->snd_cwnd_clamp)
- tp->snd_cwnd++;
- tp->snd_cwnd_cnt = 0;
- } else
- tp->snd_cwnd_cnt++;
- } 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 = {
- .flags = TCP_CONG_RTT_STAMP,
- .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");
- #undef NS_PROTOCOL