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+         *  - the Ack is outdated (packet with higher Ack number was received),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)