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dccp tfrc: Perform early loss detection 

This enables the TFRC code to begin loss detection (as soon as the module
is loaded), using the latest updates from rfc3448bis-06, 6.3.1:

 * when the first data packet(s) are lost or marked, set
 * X_target = s/(2*R) => f(p) = s/(R * X_target) = 2,
 * corresponding to a loss rate of ~ 20.64%.

The handle_loss() function is now called right at the begin of rx_packet_recv()
and thus no longer protected against duplicates: hence a call to rx_duplicate()
has been added.  Such a call makes sense now, as the previous patch initialises
the first entry with a sequence number of GSR.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
This commit is contained in:
Gerrit Renker 2008-09-04 07:30:19 +02:00
parent 24b8d34321
commit d20ed95f8b
2 changed files with 42 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
net/dccp/ccids/ccid3.c
View File

@ -577,6 +577,28 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk,
hcrx->p_inverse = ~0U; /* see RFC 4342, 8.5 */
break;
case CCID3_FBACK_PARAM_CHANGE:
if (unlikely(hcrx->state == TFRC_RSTATE_NO_DATA)) {
/*
* rfc3448bis-06, 6.3.1: First packet(s) lost or marked
* FIXME: in rfc3448bis the receiver returns X_recv=0
* here as it normally would in the first feedback packet.
* However this is not possible yet, since the code still
* uses RFC 3448, i.e.
* If (p > 0)
* Calculate X_calc using the TCP throughput equation.
* X = max(min(X_calc, 2*X_recv), s/t_mbi);
* would bring X down to s/t_mbi. That is why we return
* X_recv according to rfc3448bis-06 for the moment.
*/
u32 rtt = hcrx->rtt ? : DCCP_FALLBACK_RTT, s = hcrx->s;
if (s == 0) {
DCCP_WARN("No sample for s, using fallback\n");
s = TCP_MIN_RCVMSS;
}
hcrx->x_recv = scaled_div32(s, 2 * rtt);
break;
}
/*
* When parameters change (new loss or p > p_prev), we do not
* have a reliable estimate for R_m of [RFC 3448, 6.2] and so
@ -650,6 +672,14 @@ static u32 ccid3_first_li(struct sock *sk)
u32 x_recv, p, delta;
u64 fval;
/*
* rfc3448bis-06, 6.3.1: First data packet(s) are marked or lost. Set p
* to give the equivalent of X_target = s/(2*R). Thus fval = 2 and so p
* is about 20.64%. This yields an interval length of 4.84 (rounded up).
*/
if (unlikely(hcrx->state == TFRC_RSTATE_NO_DATA))
return 5;
if (hcrx->rtt == 0) {
DCCP_WARN("No RTT estimate available, using fallback RTT\n");
hcrx->rtt = DCCP_FALLBACK_RTT;
@ -683,6 +713,15 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
const u64 ndp = dccp_sk(sk)->dccps_options_received.dccpor_ndp;
const bool is_data_packet = dccp_data_packet(skb);
/*
* Perform loss detection and handle pending losses
*/
if (tfrc_rx_handle_loss(&hcrx->hist, &hcrx->li_hist,
skb, ndp, ccid3_first_li, sk)) {
do_feedback = CCID3_FBACK_PARAM_CHANGE;
goto done_receiving;
}
if (unlikely(hcrx->state == TFRC_RSTATE_NO_DATA)) {
if (is_data_packet) {
const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
@ -710,15 +749,6 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
hcrx->bytes_recv += payload;
}
/*
* Perform loss detection and handle pending losses
*/
if (tfrc_rx_handle_loss(&hcrx->hist, &hcrx->li_hist,
skb, ndp, ccid3_first_li, sk)) {
do_feedback = CCID3_FBACK_PARAM_CHANGE;
goto done_receiving;
}
if (tfrc_rx_hist_loss_pending(&hcrx->hist))
return; /* done receiving */

3
net/dccp/ccids/lib/packet_history.c
View File

@ -335,6 +335,9 @@ int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
{
int is_new_loss = 0;
if (tfrc_rx_hist_duplicate(h, skb))
return 0;
if (h->loss_count == 0) {
__do_track_loss(h, skb, ndp);
} else if (h->loss_count == 1) {