3 files changed, 38 insertions, 57 deletions

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index e9ca0983ac58..b2ddd205d438 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -370,6 +370,7 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 {
 	struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
 	struct ccid3_options_received *opt_recv = &hc->tx_options_received;
+	struct tfrc_tx_hist_entry *acked;
 	ktime_t now;
 	unsigned long t_nfb;
 	u32 pinv, r_sample;
@@ -383,17 +384,24 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 	    hc->tx_state != TFRC_SSTATE_NO_FBACK)
 		return;
 
-	now = ktime_get_real();
-
-	/* Estimate RTT from history if ACK number is valid */
-	r_sample = tfrc_tx_hist_rtt(hc->tx_hist,
-				    DCCP_SKB_CB(skb)->dccpd_ack_seq, now);
-	if (r_sample == 0) {
-		DCCP_WARN("%s(%p): %s with bogus ACK-%llu\n", dccp_role(sk), sk,
-			  dccp_packet_name(DCCP_SKB_CB(skb)->dccpd_type),
-			  (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq);
+	/*
+	 * Locate the acknowledged packet in the TX history.
+	 *
+	 * Returning "entry not found" here can for instance happen when
+	 *  - the host has not sent out anything (e.g. a passive server),
+	 *  - the Ack is outdated (packet with higher Ack number was received),
+	 *  - it is a bogus Ack (for a packet not sent on this connection).
+	 */
+	acked = tfrc_tx_hist_find_entry(hc->tx_hist, dccp_hdr_ack_seq(skb));
+	if (acked == NULL)
 		return;
-	}
+	/* For the sake of RTT sampling, ignore/remove all older entries */
+	tfrc_tx_hist_purge(&acked->next);
+
+	/* Update the moving average for the RTT estimate (RFC 3448, 4.3) */
+	now	  = ktime_get_real();
+	r_sample  = dccp_sample_rtt(sk, ktime_us_delta(now, acked->stamp));
+	hc->tx_rtt = tfrc_ewma(hc->tx_rtt, r_sample, 9);
 
 	/* Update receive rate in units of 64 * bytes/second */
 	hc->tx_x_recv = opt_recv->ccid3or_receive_rate;
@@ -405,11 +413,7 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 		hc->tx_p = 0;
 	else				       /* can not exceed 100% */
 		hc->tx_p = scaled_div(1, pinv);
-	/*
-	 * Validate new RTT sample and update moving average
-	 */
-	r_sample = dccp_sample_rtt(sk, r_sample);
-	hc->tx_rtt = tfrc_ewma(hc->tx_rtt, r_sample, 9);
+
 	/*
 	 * Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3
 	 */
diff --git a/net/dccp/ccids/lib/packet_history.c b/net/dccp/ccids/lib/packet_history.c
index 3a4f414e94a0..de8fe294bf0b 100644
--- a/net/dccp/ccids/lib/packet_history.c
+++ b/net/dccp/ccids/lib/packet_history.c
@@ -38,18 +38,6 @@
 #include "packet_history.h"
 #include "../../dccp.h"
 
-/**
- *  tfrc_tx_hist_entry  -  Simple singly-linked TX history list
- *  @next:  next oldest entry (LIFO order)
- *  @seqno: sequence number of this entry
- *  @stamp: send time of packet with sequence number @seqno
- */
-struct tfrc_tx_hist_entry {
-	struct tfrc_tx_hist_entry *next;
-	u64			  seqno;
-	ktime_t			  stamp;
-};
-
 /*
  * Transmitter History Routines
  */
@@ -71,15 +59,6 @@ void tfrc_tx_packet_history_exit(void)
 	}
 }
 
-static struct tfrc_tx_hist_entry *
-	tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
-{
-	while (head != NULL && head->seqno != seqno)
-		head = head->next;
-
-	return head;
-}
-
 int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno)
 {
 	struct tfrc_tx_hist_entry *entry = kmem_cache_alloc(tfrc_tx_hist_slab, gfp_any());
@@ -107,24 +86,6 @@ void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp)
 	*headp = NULL;
 }
 
-u32 tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head, const u64 seqno,
-		     const ktime_t now)
-{
-	u32 rtt = 0;
-	struct tfrc_tx_hist_entry *packet = tfrc_tx_hist_find_entry(head, seqno);
-
-	if (packet != NULL) {
-		rtt = ktime_us_delta(now, packet->stamp);
-		/*
-		 * Garbage-collect older (irrelevant) entries:
-		 */
-		tfrc_tx_hist_purge(&packet->next);
-	}
-
-	return rtt;
-}
-
-
 /*
  *	Receiver History Routines
  */
diff --git a/net/dccp/ccids/lib/packet_history.h b/net/dccp/ccids/lib/packet_history.h
index 7df6c5299999..7ee4a9d9d335 100644
--- a/net/dccp/ccids/lib/packet_history.h
+++ b/net/dccp/ccids/lib/packet_history.h
@@ -40,12 +40,28 @@
 #include <linux/slab.h>
 #include "tfrc.h"
 
-struct tfrc_tx_hist_entry;
+/**
+ *  tfrc_tx_hist_entry  -  Simple singly-linked TX history list
+ *  @next:  next oldest entry (LIFO order)
+ *  @seqno: sequence number of this entry
+ *  @stamp: send time of packet with sequence number @seqno
+ */
+struct tfrc_tx_hist_entry {
+	struct tfrc_tx_hist_entry *next;
+	u64			  seqno;
+	ktime_t			  stamp;
+};
+
+static inline struct tfrc_tx_hist_entry *
+	tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
+{
+	while (head != NULL && head->seqno != seqno)
+		head = head->next;
+	return head;
+}
 
 extern int  tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno);
 extern void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp);
-extern u32  tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head,
-			     const u64 seqno, const ktime_t now);
 
 /* Subtraction a-b modulo-16, respects circular wrap-around */
 #define SUB16(a, b) (((a) + 16 - (b)) & 0xF)