[PATCH 12/29] Use t_RTO as indicator for feedback reception

[Arnaldo Carvalho de Melo <acme@ghostprotocols.net>]

 This patch uses t_RTO instead of ccid3hctx_state to check whether upon
 expiry of the nofeedback timer feedback has been received yet.

 Justification:

  Functionally, there is no change yet using this patch, but it is necessary
  for the support of nofeedback handling as per rfc3448bis (subsequent patch).

  The main advantage is that ccid3hctx_state can now be used to toggle between
  the reception of feedback and no feedback as in "the nofeedback timer has
  expired". This is more efficient, since the state "packet sent but no initial
  feedback" happens only once during the lifetime of a connection, whereas the
  other state change (feedback <-> nofeedback timer expires) happens often.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
---
 net/dccp/ccids/ccid3.c |   19 ++++++++++---------
 1 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index e166f5c..471db59 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -244,9 +244,6 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
 			       "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 timout value. Keep initial value as per [RFC 4342, 5]. */
-		t_nfb = TFRC_INITIAL_TIMEOUT;
 		ccid3_update_send_interval(hctx);
 		break;
 	case TFRC_SSTATE_FBACK:
@@ -278,12 +275,6 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
 		}
 		/* 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)
-		 * 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);
@@ -294,6 +285,15 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
 
 	hctx->ccid3hctx_idle = 1;
 
+	/*
+	 * 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,
 			   jiffies + usecs_to_jiffies(t_nfb));
@@ -631,6 +631,7 @@ static int ccid3_hc_tx_init(struct ccid *ccid, struct sock *sk)
 
 	hctx->ccid3hctx_s     = 0;
 	hctx->ccid3hctx_rtt   = 0;
+	hctx->ccid3hctx_t_rto = 0;
 	hctx->ccid3hctx_state = TFRC_SSTATE_NO_SENT;
 	INIT_LIST_HEAD(&hctx->ccid3hctx_hist);
 
-- 
1.5.0.6