---

yaml
---
r: 111501
b: refs/heads/master
c: 535c55d
h: refs/heads/master
i:
  111499: 111c05f
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 3306c781ff13aea89606435c134ec84e3c608681
+refs/heads/master: 535c55df136ad2783d444e54d518a8fae8bdbf79

trunk/net/dccp/ccids/ccid3.c

@@ -410,10 +410,10 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 
 	/* Update loss event rate (which is scaled by 1e6) */
 	pinv = opt_recv->ccid3or_loss_event_rate;
-	if (pinv == ~0U || pinv == 0)	       /* see RFC 4342, 8.5   */
+	if (pinv == 0)
 		hctx->p = 0;
-	else				       /* can not exceed 100% */
-		hctx->p = scaled_div(1, pinv);
+	else
+		hctx->p = tfrc_invert_loss_event_rate(pinv);
 
 	/*
 	 * Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3
@@ -854,8 +854,7 @@ static int ccid3_hc_rx_getsockopt(struct sock *sk, const int optname, int len,
 			return -EINVAL;
 		rx_info.tfrcrx_x_recv = hcrx->x_recv;
 		rx_info.tfrcrx_rtt    = hcrx->rtt;
-		rx_info.tfrcrx_p      = hcrx->p_inverse == 0 ? ~0U :
-					   scaled_div(1, hcrx->p_inverse);
+		rx_info.tfrcrx_p      = tfrc_invert_loss_event_rate(hcrx->p_inverse);
 		len = sizeof(rx_info);
 		val = &rx_info;
 		break;

trunk/net/dccp/ccids/lib/tfrc.h

@@ -58,6 +58,7 @@ static inline u32 tfrc_ewma(const u32 avg, const u32 newval, const u8 weight)
 
 extern u32  tfrc_calc_x(u16 s, u32 R, u32 p);
 extern u32  tfrc_calc_x_reverse_lookup(u32 fvalue);
+extern u32  tfrc_invert_loss_event_rate(u32 loss_event_rate);
 
 extern int  tfrc_tx_packet_history_init(void);
 extern void tfrc_tx_packet_history_exit(void);

trunk/net/dccp/ccids/lib/tfrc_equation.c

@@ -658,7 +658,6 @@ u32 tfrc_calc_x(u16 s, u32 R, u32 p)
 	result = scaled_div(s, R);
 	return scaled_div32(result, f);
 }
-
 EXPORT_SYMBOL_GPL(tfrc_calc_x);
 
 /**
@@ -693,5 +692,19 @@ u32 tfrc_calc_x_reverse_lookup(u32 fvalue)
 	index = tfrc_binsearch(fvalue, 0);
 	return (index + 1) * 1000000 / TFRC_CALC_X_ARRSIZE;
 }
-
 EXPORT_SYMBOL_GPL(tfrc_calc_x_reverse_lookup);
+
+/**
+ * tfrc_invert_loss_event_rate  -  Compute p so that 10^6 corresponds to 100%
+ * When @loss_event_rate is large, there is a chance that p is truncated to 0.
+ * To avoid re-entering slow-start in that case, we set p = TFRC_SMALLEST_P > 0.
+ */
+u32 tfrc_invert_loss_event_rate(u32 loss_event_rate)
+{
+	if (loss_event_rate == UINT_MAX)		/* see RFC 4342, 8.5 */
+		return 0;
+	if (unlikely(loss_event_rate == 0))		/* map 1/0 into 100% */
+		return 1000000;
+	return max_t(u32, scaled_div(1, loss_event_rate), TFRC_SMALLEST_P);
+}
+EXPORT_SYMBOL_GPL(tfrc_invert_loss_event_rate);