[CCID3]: Implement rfc3448bis changes to feedback reception

This implements the algorithm to update the allowed sending rate X upon
receiving feedback packets, as described in draft rfc3448bis, 4.2/4.3.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 26 insertions, 21 deletions

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index a93a556ad03d..1156fef17471 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -429,40 +429,46 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
         if (pinv == ~0U || pinv == 0)          /* see RFC 4342, 8.5   */
                 hctx->ccid3hctx_p = 0;
         else                                   /* can not exceed 100% */
-                hctx->ccid3hctx_p = 1000000 / pinv;
+                hctx->ccid3hctx_p = scaled_div(1, pinv);
         /*
          * Validate new RTT sample and update moving average
          */
         r_sample = dccp_sample_rtt(sk, r_sample);
         hctx->ccid3hctx_rtt = tfrc_ewma(hctx->ccid3hctx_rtt, r_sample, 9);
-
+        /*
+         * Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3
+         */
         if (hctx->ccid3hctx_state == TFRC_SSTATE_NO_FBACK) {
-                /*
-                 * Larger Initial Windows [RFC 4342, sec. 5]
-                 */
-                hctx->ccid3hctx_x    = rfc3390_initial_rate(sk);
-                hctx->ccid3hctx_t_ld = now;
+                ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
 
-                ccid3_update_send_interval(hctx);
+                if (hctx->ccid3hctx_t_rto == 0) {
+                        /*
+                         * Initial feedback packet: Larger Initial Windows (4.2)
+                         */
+                        hctx->ccid3hctx_x    = rfc3390_initial_rate(sk);
+                        hctx->ccid3hctx_t_ld = now;
 
-                ccid3_pr_debug("%s(%p), s=%u, MSS=%u, "
-                               "R_sample=%uus, X=%u\n", dccp_role(sk),
-                               sk, hctx->ccid3hctx_s,
-                               dccp_sk(sk)->dccps_mss_cache, r_sample,
-                               (unsigned)(hctx->ccid3hctx_x >> 6));
+                        ccid3_update_send_interval(hctx);
 
-                ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
-        } else {
+                        goto done_computing_x;
+                } else if (hctx->ccid3hctx_p == 0) {
+                        /*
+                         * First feedback after nofeedback timer expiry (4.3)
+                         */
+                        goto done_computing_x;
+                }
+        }
 
-                /* Update sending rate (step 4 of [RFC 3448, 4.3]) */
-                if (hctx->ccid3hctx_p > 0)
-                        hctx->ccid3hctx_x_calc =
+        /* Update sending rate (step 4 of [RFC 3448, 4.3]) */
+        if (hctx->ccid3hctx_p > 0)
+                hctx->ccid3hctx_x_calc =
                                 tfrc_calc_x(hctx->ccid3hctx_s,
                                             hctx->ccid3hctx_rtt,
                                             hctx->ccid3hctx_p);
-                ccid3_hc_tx_update_x(sk, &now);
+        ccid3_hc_tx_update_x(sk, &now);
 
-                ccid3_pr_debug("%s(%p), RTT=%uus (sample=%uus), s=%u, "
+done_computing_x:
+        ccid3_pr_debug("%s(%p), RTT=%uus (sample=%uus), s=%u, "
                                "p=%u, X_calc=%u, X_recv=%u, X=%u\n",
                                dccp_role(sk),
                                sk, hctx->ccid3hctx_rtt, r_sample,
@@ -470,7 +476,6 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
                                hctx->ccid3hctx_x_calc,
                                (unsigned)(hctx->ccid3hctx_x_recv >> 6),
                                (unsigned)(hctx->ccid3hctx_x >> 6));
-        }
 
         /* unschedule no feedback timer */
         sk_stop_timer(sk, &hctx->ccid3hctx_no_feedback_timer);