[CCID3]: Accurately determine idle & application-limited periods
This fixes/updates the handling of idle and application-limited periods in
CCID3,
which currently is broken: there is no detection as to how long a sender has
been
idle - there is only one flag which is toggled in between function calls.
The patch implements detection of idle/application-limited periods on the basis
of draft rfc3448bis-01, taking into account the time during which the sender
has indeed not sent anything (i.e. has been idle); the condition now is:
If the sender has not sent anything during the last two RTTs,
it gets the bonus of a larger initial window (from RFC 3390).
Further support for this definition of idleness is found in the specification of
CCID 2 (RFC 4341): in section 6.2.1, the timeout interval for detecting
quiescence
(aka idleness) is set to max(0.2 sec, 2 * RTT).
Being obsolete now, the `idle' flag is removed.
Notes:
(1) The use of `idle' flag in no_feedback_timer() was buggy: the `idle' state
was
mistakenly entered before the allowed sending rate X was recomputed, which
messed up
the computation of X in ccid3_hc_tx_update_x. Hence the patch actually
fixes two bugs
(the fix used to be in a separate patch, but was later overridden by this
one).
(2) It uses the timestamp of the last window counter - which keeps the last
RTT/4 update.
Signed-off-by: Gerrit Renker <[EMAIL PROTECTED]>
---
net/dccp/ccids/ccid3.c | 18 ++++++++++--------
net/dccp/ccids/ccid3.h | 2 --
2 files changed, 10 insertions(+), 10 deletions(-)
--- a/net/dccp/ccids/ccid3.h
+++ b/net/dccp/ccids/ccid3.h
@@ -88,7 +88,6 @@ enum ccid3_hc_tx_states {
* @ccid3hctx_t_last_win_count - Timestamp of earliest packet
* with last_win_count value sent
* @ccid3hctx_no_feedback_timer - Handle to no feedback timer
- * @ccid3hctx_idle - Flag indicating that sender is idling
* @ccid3hctx_t_ld - Time last doubled during slow start
* @ccid3hctx_t_nom - Nominal send time of next packet
* @ccid3hctx_delta - Send timer delta (RFC 3448, 4.6) in usecs
@@ -107,7 +106,6 @@ struct ccid3_hc_tx_sock {
u16 ccid3hctx_s;
enum ccid3_hc_tx_states ccid3hctx_state:8;
u8 ccid3hctx_last_win_count;
- u8 ccid3hctx_idle;
ktime_t ccid3hctx_t_last_win_count;
struct timer_list ccid3hctx_no_feedback_timer;
ktime_t ccid3hctx_t_ld;
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -115,6 +115,13 @@ static inline void ccid3_update_send_int
}
+static u32 ccid3_hc_tx_idle_rtt(struct ccid3_hc_tx_sock *hctx, ktime_t now)
+{
+ u32 delta = ktime_delta(now, hctx->ccid3hctx_t_last_win_count);
+
+ return delta/hctx->ccid3hctx_rtt;
+}
+
/**
* ccid3_hc_tx_update_x - Update allowed sending rate X
* @stamp: most recent time if available - can be left NULL.
@@ -135,10 +142,11 @@ static void ccid3_hc_tx_update_x(struct
/*
* Handle IDLE periods: do not reduce below RFC3390 initial sending rate
- * when idling [RFC 4342, 5.1]. See also draft-ietf-dccp-rfc3448bis.
+ * when idling [RFC 4342, 5.1]. Definition of idling is from rfc3448bis:
+ * a sender is idle if it has not sent anything over a 2-RTT-period.
* For consistency with X and X_recv, min_rate is also scaled by 2^6.
*/
- if (unlikely(hctx->ccid3hctx_idle)) {
+ if (ccid3_hc_tx_idle_rtt(hctx, now) >= 2) {
min_rate = rfc3390_initial_rate(sk);
min_rate = max(min_rate, 2 * hctx->ccid3hctx_x_recv);
}
@@ -225,8 +233,6 @@ static void ccid3_hc_tx_no_feedback_time
ccid3_pr_debug("%s(%p, state=%s) - entry \n", dccp_role(sk), sk,
ccid3_tx_state_name(hctx->ccid3hctx_state));
- hctx->ccid3hctx_idle = 1;
-
switch (hctx->ccid3hctx_state) {
case TFRC_SSTATE_NO_FBACK:
/* RFC 3448, 4.4: Halve send rate directly */
@@ -376,7 +382,6 @@ static int ccid3_hc_tx_send_packet(struc
/* prepare to send now (add options etc.) */
dp->dccps_hc_tx_insert_options = 1;
DCCP_SKB_CB(skb)->dccpd_ccval = hctx->ccid3hctx_last_win_count;
- hctx->ccid3hctx_idle = 0;
/* set the nominal send time for the next following packet */
hctx->ccid3hctx_t_nom = ktime_add_ns(hctx->ccid3hctx_t_nom,
@@ -543,9 +548,6 @@ static void ccid3_hc_tx_packet_recv(stru
sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
jiffies + usecs_to_jiffies(t_nfb));
-
- /* set idle flag */
- hctx->ccid3hctx_idle = 1;
break;
case TFRC_SSTATE_NO_SENT: /* fall through */
case TFRC_SSTATE_TERM: /* ignore feedback when closing */
-
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