dccp ccid-3: Remove ugly RTT-sampling history lookup

[linux-2.6-omap-h63xx.git] / net / dccp / ccids / ccid3.c

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index eb1bda08eeb2e734bbc31c59120c9f7aca90e7eb..f74e58d9793f11c31c38a525ef1b8a186cdb5f57 100644 (file)
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -371,6 +371,7 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 {
        struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
        struct ccid3_options_received *opt_recv = &hctx->options_received;
+       struct tfrc_tx_hist_entry *acked;
        ktime_t now;
        unsigned long t_nfb;
        u32 pinv, r_sample;
@@ -384,17 +385,24 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
            hctx->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(hctx->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+        *  - the Ack is outdated (packet with higher Ack number was received),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(hctx->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));
+       hctx->rtt = tfrc_ewma(hctx->rtt, r_sample, 9);
 
        /* Update receive rate in units of 64 * bytes/second */
        hctx->x_recv = opt_recv->ccid3or_receive_rate;
@@ -406,11 +414,7 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
                hctx->p = 0;
        else                                   /* can not exceed 100% */
                hctx->p = scaled_div(1, pinv);
-       /*
-        * Validate new RTT sample and update moving average
-        */
-       r_sample = dccp_sample_rtt(sk, r_sample);
-       hctx->rtt = tfrc_ewma(hctx->rtt, r_sample, 9);
+
        /*
         * Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3
         */