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[CCID3]: Nofeedback timer according to rfc3448bis 

This implements the changes to the nofeedback timer handling suggested
in draft rfc3448bis00, section 4.4. In particular, these changes mean:

 * better handling of the lossless case (p == 0)
 * the timestamp for computing t_ld becomes obsolete
 * much more recent document (RFC 3448 is almost 5 years old)
 * concepts in rfc3448bis arose from a real, working implementation
   (cf. sec. 12)

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Gerrit Renker 2007-12-17 12:57:43 -02:00 committed by David S. Miller
parent d8d1252f74
commit 52515e77a7
1 changed files with 29 additions and 34 deletions
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63
net/dccp/ccids/ccid3.c
View File

@ -131,12 +131,11 @@ static u32 ccid3_hc_tx_idle_rtt(struct ccid3_hc_tx_sock *hctx, ktime_t now)
*
*/
static void ccid3_hc_tx_update_x(struct sock *sk, ktime_t *stamp)
{
struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
__u64 min_rate = 2 * hctx->ccid3hctx_x_recv;
const __u64 old_x = hctx->ccid3hctx_x;
ktime_t now = stamp? *stamp : ktime_get_real();
ktime_t now = stamp ? *stamp : ktime_get_real();
/*
* Handle IDLE periods: do not reduce below RFC3390 initial sending rate
@ -230,27 +229,27 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
ccid3_pr_debug("%s(%p, state=%s) - entry \n", dccp_role(sk), sk,
ccid3_tx_state_name(hctx->ccid3hctx_state));
switch (hctx->ccid3hctx_state) {
case TFRC_SSTATE_NO_FBACK:
/* RFC 3448, 4.4: Halve send rate directly */
if (hctx->ccid3hctx_state == TFRC_SSTATE_FBACK)
ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
else if (hctx->ccid3hctx_state != TFRC_SSTATE_NO_FBACK)
goto out;
/*
* Determine new allowed sending rate X as per draft rfc3448bis-00, 4.4
*/
if (hctx->ccid3hctx_t_rto == 0 || /* no feedback received yet */
hctx->ccid3hctx_p == 0) {
/* halve send rate directly */
hctx->ccid3hctx_x = max(hctx->ccid3hctx_x / 2,
(((__u64)hctx->ccid3hctx_s) << 6) /
TFRC_T_MBI);
ccid3_pr_debug("%s(%p, state=%s), updated tx rate to %u "
"bytes/s\n", dccp_role(sk), sk,
ccid3_tx_state_name(hctx->ccid3hctx_state),
(unsigned)(hctx->ccid3hctx_x >> 6));
/* The value of R is still undefined and so we can not recompute
* the timeout value. Keep initial value as per [RFC 4342, 5]. */
t_nfb = TFRC_INITIAL_TIMEOUT;
ccid3_update_send_interval(hctx);
break;
case TFRC_SSTATE_FBACK:
} else {
/*
* Modify the cached value of X_recv [RFC 3448, 4.4]
* Modify the cached value of X_recv
*
* If (p == 0 || X_calc > 2 * X_recv)
* If (X_calc > 2 * X_recv)
* X_recv = max(X_recv / 2, s / (2 * t_mbi));
* Else
* X_recv = X_calc / 4;
@ -259,32 +258,28 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
*/
BUG_ON(hctx->ccid3hctx_p && !hctx->ccid3hctx_x_calc);
if (hctx->ccid3hctx_p == 0 ||
(hctx->ccid3hctx_x_calc > (hctx->ccid3hctx_x_recv >> 5))) {
if (hctx->ccid3hctx_x_calc > (hctx->ccid3hctx_x_recv >> 5))
hctx->ccid3hctx_x_recv =
max(hctx->ccid3hctx_x_recv / 2,
(((__u64)hctx->ccid3hctx_s) << 6) /
(2 * TFRC_T_MBI));
} else {
else {
hctx->ccid3hctx_x_recv = hctx->ccid3hctx_x_calc;
hctx->ccid3hctx_x_recv <<= 4;
}
/* Now recalculate X [RFC 3448, 4.3, step (4)] */
ccid3_hc_tx_update_x(sk, NULL);
/*
* Schedule no feedback timer to expire in
* max(t_RTO, 2 * s/X) = max(t_RTO, 2 * t_ipi)
* See comments in packet_recv() regarding the value of t_RTO.
*/
t_nfb = max(hctx->ccid3hctx_t_rto, 2 * hctx->ccid3hctx_t_ipi);
break;
case TFRC_SSTATE_NO_SENT:
DCCP_BUG("%s(%p) - Illegal state NO_SENT", dccp_role(sk), sk);
/* fall through */
case TFRC_SSTATE_TERM:
goto out;
}
ccid3_pr_debug("Reduced X to %llu/64 bytes/sec\n",
(unsigned long long)hctx->ccid3hctx_x);
/*
* Set new timeout for the nofeedback timer.
* See comments in packet_recv() regarding the value of t_RTO.
*/
if (unlikely(hctx->ccid3hctx_t_rto == 0)) /* no feedback yet */
t_nfb = TFRC_INITIAL_TIMEOUT;
else
t_nfb = max(hctx->ccid3hctx_t_rto, 2 * hctx->ccid3hctx_t_ipi);
restart_timer:
sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,