1 files changed, 21 insertions, 2 deletions

diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c
index 9c5b6c73f7c9..a901202ada64 100644
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -224,8 +224,6 @@ static void ccid2_hc_tx_rto_expire(unsigned long data)
         hctx->ccid2hctx_sent    = 0;
 
         /* clear ack ratio state. */
-        hctx->ccid2hctx_arsent   = 0;
-        hctx->ccid2hctx_ackloss  = 0;
         hctx->ccid2hctx_rpseq    = 0;
         hctx->ccid2hctx_rpdupack = -1;
         ccid2_change_l_ack_ratio(sk, 1);
@@ -289,6 +287,26 @@ static void ccid2_hc_tx_packet_sent(struct sock *sk, int more, unsigned int len)
 
         hctx->ccid2hctx_sent++;
 
+        /*
+         * FIXME: The code below is broken and the variables have been removed
+         * from the socket struct. The `ackloss' variable was always set to 0,
+         * and with arsent there are several problems:
+         *  (i) it doesn't just count the number of Acks, but all sent packets;
+         *  (ii) it is expressed in # of packets, not # of windows, so the
+         *  comparison below uses the wrong formula: Appendix A of RFC 4341
+         *  comes up with the number K = cwnd / (R^2 - R) of consecutive windows
+         *  of data with no lost or marked Ack packets. If arsent were the # of
+         *  consecutive Acks received without loss, then Ack Ratio needs to be
+         *  decreased by 1 when
+         *            arsent >=  K * cwnd / R  =  cwnd^2 / (R^3 - R^2)
+         *  where cwnd / R is the number of Acks received per window of data
+         *  (cf. RFC 4341, App. A). The problems are that
+         *  - arsent counts other packets as well;
+         *  - the comparison uses a formula different from RFC 4341;
+         *  - computing a cubic/quadratic equation each time is too complicated.
+         *  Hence a different algorithm is needed.
+         */
+#if 0
         /* Ack Ratio.  Need to maintain a concept of how many windows we sent */
         hctx->ccid2hctx_arsent++;
         /* We had an ack loss in this window... */
@@ -316,6 +334,7 @@ static void ccid2_hc_tx_packet_sent(struct sock *sk, int more, unsigned int len)
                         hctx->ccid2hctx_arsent = 0; /* or maybe set it to cwnd*/
                 }
         }
+#endif
 
         /* setup RTO timer */
         if (!timer_pending(&hctx->ccid2hctx_rtotimer))