[CCID3]: Handle Idle and Application-Limited periods
This updates the code with regard to handling idle and application-limited
periods as specified in [RFC 4342, 5.1].
Background:
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 8d33a09..35123c1 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -133,12 +133,23 @@
{
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;
+ /*
+ * Handle IDLE periods: do not reduce below RFC3390 initial sending rate
+ * when idling [RFC 4342, 5.1]. See also draft-ietf-dccp-rfc3448bis.
+ * For consistency with X and X_recv, min_rate is also scaled by 2^6.
+ */
+ if (unlikely(hctx->ccid3hctx_idle)) {
+ min_rate = rfc3390_initial_rate(sk);
+ min_rate = max(min_rate, 2 * hctx->ccid3hctx_x_recv);
+ }
+
if (hctx->ccid3hctx_p > 0) {
hctx->ccid3hctx_x = min(((__u64)hctx->ccid3hctx_x_calc) << 6,
- hctx->ccid3hctx_x_recv * 2);
+ min_rate);
hctx->ccid3hctx_x = max(hctx->ccid3hctx_x,
(((__u64)hctx->ccid3hctx_s) << 6) /
TFRC_T_MBI);
@@ -147,7 +158,7 @@
(suseconds_t)hctx->ccid3hctx_rtt >= 0) {
hctx->ccid3hctx_x =
- max(2 * min(hctx->ccid3hctx_x, hctx->ccid3hctx_x_recv),
+ max(min(2 * hctx->ccid3hctx_x, min_rate),
scaled_div(((__u64)hctx->ccid3hctx_s) << 6,
hctx->ccid3hctx_rtt));
hctx->ccid3hctx_t_ld = *now;
@@ -209,6 +220,7 @@
{
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);
@@ -221,6 +233,8 @@
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 */
@@ -239,49 +253,33 @@
break;
case TFRC_SSTATE_FBACK:
/*
- * Check if IDLE since last timeout and recv rate is less than
- * 4 packets (in units of 64*bytes/sec) per RTT
+ * Modify the cached value of X_recv [RFC 3448, 4.4]
+ *
+ * If (p == 0 || X_calc > 2 * X_recv)
+ * X_recv = max(X_recv / 2, s / (2 * t_mbi));
+ * Else
+ * X_recv = X_calc / 4;
+ *
+ * Note that X_recv is scaled by 2^6 while X_calc is not
*/
- if (!hctx->ccid3hctx_idle ||
- (hctx->ccid3hctx_x_recv >= 4 *
- scaled_div(((__u64)hctx->ccid3hctx_s) << 6,
- hctx->ccid3hctx_rtt))) {
- struct timeval now;
+ BUG_ON(hctx->ccid3hctx_p && !hctx->ccid3hctx_x_calc);
- ccid3_pr_debug("%s(%p, state=%s), not idle\n",
- dccp_role(sk), sk,
- ccid3_tx_state_name(hctx->ccid3hctx_state));
+ if (hctx->ccid3hctx_p == 0 ||
+ (hctx->ccid3hctx_x_calc > (hctx->ccid3hctx_x_recv >> 5))) {
- /*
- * Modify the cached value of X_recv [RFC 3448, 4.4]
- *
- * If (p == 0 || X_calc > 2 * X_recv)
- * X_recv = max(X_recv / 2, s / (2 * t_mbi));
- * Else
- * X_recv = X_calc / 4;
- *
- * Note that X_recv is scaled by 2^6 while X_calc is not
- */
- BUG_ON(hctx->ccid3hctx_p && !hctx->ccid3hctx_x_calc);
+ hctx->ccid3hctx_x_recv =
+ max(hctx->ccid3hctx_x_recv / 2,
+ (((__u64)hctx->ccid3hctx_s) << 6) /
+ (2 * TFRC_T_MBI));
- if (hctx->ccid3hctx_p == 0 ||
- (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 {
- 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);
+ if (hctx->ccid3hctx_p == 0)
+ dccp_timestamp(sk, &now);
+ } 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);
/*
* Schedule no feedback timer to expire in
* max(t_RTO, 2 * s/X) = max(t_RTO, 2 * t_ipi)
@@ -296,8 +294,6 @@
goto out;
}
- hctx->ccid3hctx_idle = 1;
-
restart_timer:
sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
jiffies + usecs_to_jiffies(t_nfb));
@@ -377,6 +373,7 @@
/* 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 */
timeval_add_usecs(&hctx->ccid3hctx_t_nom, hctx->ccid3hctx_t_ipi);
@@ -407,7 +404,6 @@
packet->dccphtx_seqno = dccp_sk(sk)->dccps_gss;
packet->dccphtx_rtt = hctx->ccid3hctx_rtt;
packet->dccphtx_sent = 1;
- hctx->ccid3hctx_idle = 0;
}
static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)