[DCCP] ccid3: Consistently update t_nom, t_ipi, t_delta
This patch:
* consolidates updating of parameters (t_nom, t_ipi, t_delta) which
need to be updated at the same time, since they are inter-dependent
* removes two inline functions which are no longer needed as a result of
the above consolidation
* resolves a FIXME regarding the re-calculation of t_ipi within the nofeedback
timer, in the state where no feedback has previously been received
* ties updating these parameters to updating the sending rate X, exploiting
that all three parameters in turn depend on X; and using a small optimisation
which can reduce the number of required instructions: only update the three
parameters when X really changes
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 9297fca..4342caf 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -100,19 +100,24 @@
hctx->ccid3hctx_state = state;
}
-/* Calculate new t_ipi (inter packet interval) by t_ipi = s / X_inst */
-static inline void ccid3_calc_new_t_ipi(struct ccid3_hc_tx_sock *hctx)
+/*
+ * Recalculate scheduled nominal send time t_nom, inter-packet interval
+ * t_ipi, and delta value. Should be called after each change to X.
+ */
+static inline void ccid3_update_send_time(struct ccid3_hc_tx_sock *hctx)
{
- hctx->ccid3hctx_t_ipi = usecs_div(hctx->ccid3hctx_s, hctx->ccid3hctx_x);
-}
+ timeval_sub_usecs(&hctx->ccid3hctx_t_nom, hctx->ccid3hctx_t_ipi);
-/* Calculate new delta by delta = min(t_ipi / 2, t_gran / 2) */
-static inline void ccid3_calc_new_delta(struct ccid3_hc_tx_sock *hctx)
-{
+ /* Calculate new t_ipi (inter packet interval) by t_ipi = s / X_inst */
+ hctx->ccid3hctx_t_ipi = usecs_div(hctx->ccid3hctx_s, hctx->ccid3hctx_x);
+
+ /* Update nominal send time with regard to the new t_ipi */
+ timeval_add_usecs(&hctx->ccid3hctx_t_nom, hctx->ccid3hctx_t_ipi);
+
+ /* Calculate new delta by delta = min(t_ipi / 2, t_gran / 2) */
hctx->ccid3hctx_delta = min_t(u32, hctx->ccid3hctx_t_ipi / 2,
TFRC_OPSYS_HALF_TIME_GRAN);
}
-
/*
* Update X by
* If (p > 0)
@@ -126,6 +131,7 @@
static void ccid3_hc_tx_update_x(struct sock *sk)
{
struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
+ const __u32 old_x = hctx->ccid3hctx_x;
/* To avoid large error in calcX */
if (hctx->ccid3hctx_p >= TFRC_SMALLEST_P) {
@@ -149,6 +155,8 @@
hctx->ccid3hctx_t_ld = now;
}
}
+ if (hctx->ccid3hctx_x != old_x)
+ ccid3_update_send_time(hctx);
}
static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
@@ -184,11 +192,7 @@
/* The value of R is still undefined and so we can not recompute
* the timout value. Keep initial value as per [RFC 4342, 5]. */
next_tmout = TFRC_INITIAL_TIMEOUT;
- /*
- * FIXME - not sure above calculation is correct. See section
- * 5 of CCID3 11 should adjust tx_t_ipi and double that to
- * achieve it really
- */
+ ccid3_update_send_time(hctx);
break;
case TFRC_SSTATE_FBACK:
/*
@@ -479,17 +483,9 @@
/* unschedule no feedback timer */
sk_stop_timer(sk, &hctx->ccid3hctx_no_feedback_timer);
- /* Update sending rate */
+ /* Update sending rate (and likely t_ipi, t_nom, and delta) */
ccid3_hc_tx_update_x(sk);
- /* Update next send time */
- timeval_sub_usecs(&hctx->ccid3hctx_t_nom,
- hctx->ccid3hctx_t_ipi);
- ccid3_calc_new_t_ipi(hctx);
- timeval_add_usecs(&hctx->ccid3hctx_t_nom,
- hctx->ccid3hctx_t_ipi);
- ccid3_calc_new_delta(hctx);
-
/* remove all packets older than the one acked from history */
dccp_tx_hist_purge_older(ccid3_tx_hist,
&hctx->ccid3hctx_hist, packet);