-/*
- * TCP Westwood+
- */
-
-/*
- * @init_westwood
- * This function initializes fields used in TCP Westwood+. We can't
- * get no information about RTTmin at this time so we simply set it to
- * TCP_WESTWOOD_INIT_RTT. This value was chosen to be too conservative
- * since in this way we're sure it will be updated in a consistent
- * way as soon as possible. It will reasonably happen within the first
- * RTT period of the connection lifetime.
- */
-
-static void init_westwood(struct sock *sk)
-{
- struct tcp_opt *tp = tcp_sk(sk);
-
- tp->westwood.bw_ns_est = 0;
- tp->westwood.bw_est = 0;
- tp->westwood.accounted = 0;
- tp->westwood.cumul_ack = 0;
- tp->westwood.rtt_win_sx = tcp_time_stamp;
- tp->westwood.rtt = TCP_WESTWOOD_INIT_RTT;
- tp->westwood.rtt_min = TCP_WESTWOOD_INIT_RTT;
- tp->westwood.snd_una = tp->snd_una;
-}
-
-/*
- * @westwood_do_filter
- * Low-pass filter. Implemented using constant coeffients.
- */
-
-static inline __u32 westwood_do_filter(__u32 a, __u32 b)
-{
- return (((7 * a) + b) >> 3);
-}
-
-static void westwood_filter(struct sock *sk, __u32 delta)
-{
- struct tcp_opt *tp = tcp_sk(sk);
-
- tp->westwood.bw_ns_est =
- westwood_do_filter(tp->westwood.bw_ns_est,
- tp->westwood.bk / delta);
- tp->westwood.bw_est =
- westwood_do_filter(tp->westwood.bw_est,
- tp->westwood.bw_ns_est);
-}
-
-/*
- * @westwood_update_rttmin
- * It is used to update RTTmin. In this case we MUST NOT use
- * WESTWOOD_RTT_MIN minimum bound since we could be on a LAN!
- */
-
-static inline __u32 westwood_update_rttmin(struct sock *sk)
-{
- struct tcp_opt *tp = tcp_sk(sk);
- __u32 rttmin = tp->westwood.rtt_min;
-
- if (tp->westwood.rtt == 0)
- return(rttmin);
-
- if (tp->westwood.rtt < tp->westwood.rtt_min || !rttmin)
- rttmin = tp->westwood.rtt;
-
- return(rttmin);
-}
-
-/*
- * @westwood_acked
- * Evaluate increases for dk.
- */
-
-static inline __u32 westwood_acked(struct sock *sk)
-{
- struct tcp_opt *tp = tcp_sk(sk);
-
- return ((tp->snd_una) - (tp->westwood.snd_una));
-}
-
-/*
- * @westwood_new_window
- * It evaluates if we are receiving data inside the same RTT window as
- * when we started.
- * Return value:
- * It returns 0 if we are still evaluating samples in the same RTT
- * window, 1 if the sample has to be considered in the next window.
- */
-
-static int westwood_new_window(struct sock *sk)
-{
- struct tcp_opt *tp = tcp_sk(sk);
- __u32 left_bound;
- __u32 rtt;
- int ret = 0;
-
- left_bound = tp->westwood.rtt_win_sx;
- rtt = max(tp->westwood.rtt, (u32) TCP_WESTWOOD_RTT_MIN);
-
- /*
- * A RTT-window has passed. Be careful since if RTT is less than
- * 50ms we don't filter but we continue 'building the sample'.
- * This minimum limit was choosen since an estimation on small
- * time intervals is better to avoid...
- * Obvioulsy on a LAN we reasonably will always have
- * right_bound = left_bound + WESTWOOD_RTT_MIN
- */
-
- if ((left_bound + rtt) < tcp_time_stamp)
- ret = 1;
-
- return ret;
-}
-
-/*
- * @westwood_update_window
- * It updates RTT evaluation window if it is the right moment to do
- * it. If so it calls filter for evaluating bandwidth.
- */
-
-static void __westwood_update_window(struct sock *sk, __u32 now)
-{
- struct tcp_opt *tp = tcp_sk(sk);
- __u32 delta = now - tp->westwood.rtt_win_sx;
-
- if (!delta)
- return;
-
- if (tp->westwood.rtt)
- westwood_filter(sk, delta);
-
- tp->westwood.bk = 0;
- tp->westwood.rtt_win_sx = tcp_time_stamp;
-}
-
-
-static void westwood_update_window(struct sock *sk, __u32 now)
-{
- if (westwood_new_window(sk))
- __westwood_update_window(sk, now);
-}
-
-/*
- * @__tcp_westwood_fast_bw
- * It is called when we are in fast path. In particular it is called when
- * header prediction is successfull. In such case infact update is
- * straight forward and doesn't need any particular care.
- */
-
-void __tcp_westwood_fast_bw(struct sock *sk, struct sk_buff *skb)
-{
- struct tcp_opt *tp = tcp_sk(sk);
-
- westwood_update_window(sk, tcp_time_stamp);
-
- tp->westwood.bk += westwood_acked(sk);
- tp->westwood.snd_una = tp->snd_una;
- tp->westwood.rtt_min = westwood_update_rttmin(sk);
-}
-
-
-/*
- * @westwood_dupack_update
- * It updates accounted and cumul_ack when receiving a dupack.
- */
-
-static void westwood_dupack_update(struct sock *sk)
-{
- struct tcp_opt *tp = tcp_sk(sk);
-
- tp->westwood.accounted += tp->mss_cache;
- tp->westwood.cumul_ack = tp->mss_cache;
-}
-
-static inline int westwood_may_change_cumul(struct tcp_opt *tp)
-{
- return ((tp->westwood.cumul_ack) > tp->mss_cache);
-}
-
-static inline void westwood_partial_update(struct tcp_opt *tp)
-{
- tp->westwood.accounted -= tp->westwood.cumul_ack;
- tp->westwood.cumul_ack = tp->mss_cache;
-}
-
-static inline void westwood_complete_update(struct tcp_opt *tp)
-{
- tp->westwood.cumul_ack -= tp->westwood.accounted;
- tp->westwood.accounted = 0;
-}
-
-/*
- * @westwood_acked_count
- * This function evaluates cumul_ack for evaluating dk in case of
- * delayed or partial acks.
- */
-
-static __u32 westwood_acked_count(struct sock *sk)
-{
- struct tcp_opt *tp = tcp_sk(sk);
-
- tp->westwood.cumul_ack = westwood_acked(sk);
-
- /* If cumul_ack is 0 this is a dupack since it's not moving
- * tp->snd_una.
- */
- if (!(tp->westwood.cumul_ack))
- westwood_dupack_update(sk);
-
- if (westwood_may_change_cumul(tp)) {
- /* Partial or delayed ack */
- if ((tp->westwood.accounted) >= (tp->westwood.cumul_ack))
- westwood_partial_update(tp);
- else
- westwood_complete_update(tp);
- }
-
- tp->westwood.snd_una = tp->snd_una;
-
- return tp->westwood.cumul_ack;
-}
-
-
-/*
- * @__tcp_westwood_slow_bw
- * It is called when something is going wrong..even if there could
- * be no problems! Infact a simple delayed packet may trigger a
- * dupack. But we need to be careful in such case.
- */
-
-void __tcp_westwood_slow_bw(struct sock *sk, struct sk_buff *skb)
-{
- struct tcp_opt *tp = tcp_sk(sk);
-
- westwood_update_window(sk, tcp_time_stamp);
-
- tp->westwood.bk += westwood_acked_count(sk);
- tp->westwood.rtt_min = westwood_update_rttmin(sk);
-}
-