[CCID 3]: 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 34484 is 4 years old)
* concepts in rfc3448bis arose from a real, working implementation (cf. sec. 12)
Further Changes:
----------------
1. The CCID 3 state now changes from FBACK back to NO_FBACK when the nofeedback timer
expires - this is required for updating X when feedback is received (cf. draft
rfc3448bis, 4.2); and better reflects that no feedback was heard since the time has
been started; the corresponding support for X is implemented in subsequent patch.
2. Two more irrelevant states are removed (as in earlier patch for packet_sent):
o TFRC_SSTATE_NO_SENT (logically not possible), and
o TFRC_SSTATE_TERM (irrelevant, since terminating anyway).
Signed-off-by: Gerrit Renker <gerrit@xxxxxxxxxxxxxx>
---
net/dccp/ccids/ccid3.c | 48 ++++++++++++++++++++----------------------------
1 file changed, 20 insertions(+), 28 deletions(-)
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -220,7 +220,6 @@ static void ccid3_hc_tx_no_feedback_time
{
struct sock *sk = (struct sock *)data;
struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
- struct timeval now;
unsigned long t_nfb = USEC_PER_SEC / 5;
bh_lock_sock(sk);
@@ -233,24 +232,27 @@ 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));
- 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, 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));
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;
@@ -259,29 +261,19 @@ static void ccid3_hc_tx_no_feedback_time
*/
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));
-
- if (hctx->ccid3hctx_p == 0)
- dccp_timestamp(sk, &now);
- } 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, &now);
- 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_hc_tx_update_x(sk, NULL);
}
+ ccid3_pr_debug("Reduced X to %llu/64 bytes/sec\n",
+ (unsigned long long)hctx->ccid3hctx_x);
/*
* Set new timeout for the nofeedback timer.
-
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