1 files changed, 66 insertions, 18 deletions

diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c
index 0462040fc818..67164bb6ae4d 100644
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -85,7 +85,6 @@ static int ccid2_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
 
 static void ccid2_change_l_ack_ratio(struct sock *sk, u32 val)
 {
-        struct dccp_sock *dp = dccp_sk(sk);
         u32 max_ratio = DIV_ROUND_UP(ccid2_hc_tx_sk(sk)->tx_cwnd, 2);
 
         /*
@@ -98,14 +97,33 @@ static void ccid2_change_l_ack_ratio(struct sock *sk, u32 val)
                 DCCP_WARN("Limiting Ack Ratio (%u) to %u\n", val, max_ratio);
                 val = max_ratio;
         }
-        if (val > DCCPF_ACK_RATIO_MAX)
-                val = DCCPF_ACK_RATIO_MAX;
+        dccp_feat_signal_nn_change(sk, DCCPF_ACK_RATIO,
+                                   min_t(u32, val, DCCPF_ACK_RATIO_MAX));
+}
 
-        if (val == dp->dccps_l_ack_ratio)
-                return;
+static void ccid2_check_l_ack_ratio(struct sock *sk)
+{
+        struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
 
-        ccid2_pr_debug("changing local ack ratio to %u\n", val);
-        dp->dccps_l_ack_ratio = val;
+        /*
+         * After a loss, idle period, application limited period, or RTO we
+         * need to check that the ack ratio is still less than the congestion
+         * window. Otherwise, we will send an entire congestion window of
+         * packets and got no response because we haven't sent ack ratio
+         * packets yet.
+         * If the ack ratio does need to be reduced, we reduce it to half of
+         * the congestion window (or 1 if that's zero) instead of to the
+         * congestion window. This prevents problems if one ack is lost.
+         */
+        if (dccp_feat_nn_get(sk, DCCPF_ACK_RATIO) > hc->tx_cwnd)
+                ccid2_change_l_ack_ratio(sk, hc->tx_cwnd/2 ? : 1U);
+}
+
+static void ccid2_change_l_seq_window(struct sock *sk, u64 val)
+{
+        dccp_feat_signal_nn_change(sk, DCCPF_SEQUENCE_WINDOW,
+                                   clamp_val(val, DCCPF_SEQ_WMIN,
+                                                  DCCPF_SEQ_WMAX));
 }
 
 static void ccid2_hc_tx_rto_expire(unsigned long data)
@@ -187,6 +205,8 @@ static void ccid2_cwnd_application_limited(struct sock *sk, const u32 now)
         }
         hc->tx_cwnd_used  = 0;
         hc->tx_cwnd_stamp = now;
+
+        ccid2_check_l_ack_ratio(sk);
 }
 
 /* This borrows the code of tcp_cwnd_restart() */
@@ -205,6 +225,8 @@ static void ccid2_cwnd_restart(struct sock *sk, const u32 now)
 
         hc->tx_cwnd_stamp = now;
         hc->tx_cwnd_used  = 0;
+
+        ccid2_check_l_ack_ratio(sk);
 }
 
 static void ccid2_hc_tx_packet_sent(struct sock *sk, unsigned int len)
@@ -405,17 +427,37 @@ static void ccid2_new_ack(struct sock *sk, struct ccid2_seq *seqp,
                           unsigned int *maxincr)
 {
         struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
-
-        if (hc->tx_cwnd < hc->tx_ssthresh) {
-                if (*maxincr > 0 && ++hc->tx_packets_acked == 2) {
+        struct dccp_sock *dp = dccp_sk(sk);
+        int r_seq_used = hc->tx_cwnd / dp->dccps_l_ack_ratio;
+
+        if (hc->tx_cwnd < dp->dccps_l_seq_win &&
+            r_seq_used < dp->dccps_r_seq_win) {
+                if (hc->tx_cwnd < hc->tx_ssthresh) {
+                        if (*maxincr > 0 && ++hc->tx_packets_acked >= 2) {
+                                hc->tx_cwnd += 1;
+                                *maxincr    -= 1;
+                                hc->tx_packets_acked = 0;
+                        }
+                } else if (++hc->tx_packets_acked >= hc->tx_cwnd) {
                         hc->tx_cwnd += 1;
-                        *maxincr    -= 1;
                         hc->tx_packets_acked = 0;
                 }
-        } else if (++hc->tx_packets_acked >= hc->tx_cwnd) {
-                        hc->tx_cwnd += 1;
-                        hc->tx_packets_acked = 0;
         }
+
+        /*
+         * Adjust the local sequence window and the ack ratio to allow about
+         * 5 times the number of packets in the network (RFC 4340 7.5.2)
+         */
+        if (r_seq_used * CCID2_WIN_CHANGE_FACTOR >= dp->dccps_r_seq_win)
+                ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio * 2);
+        else if (r_seq_used * CCID2_WIN_CHANGE_FACTOR < dp->dccps_r_seq_win/2)
+                ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio / 2 ? : 1U);
+
+        if (hc->tx_cwnd * CCID2_WIN_CHANGE_FACTOR >= dp->dccps_l_seq_win)
+                ccid2_change_l_seq_window(sk, dp->dccps_l_seq_win * 2);
+        else if (hc->tx_cwnd * CCID2_WIN_CHANGE_FACTOR < dp->dccps_l_seq_win/2)
+                ccid2_change_l_seq_window(sk, dp->dccps_l_seq_win / 2);
+
         /*
          * FIXME: RTT is sampled several times per acknowledgment (for each
          * entry in the Ack Vector), instead of once per Ack (as in TCP SACK).
@@ -441,9 +483,7 @@ static void ccid2_congestion_event(struct sock *sk, struct ccid2_seq *seqp)
         hc->tx_cwnd      = hc->tx_cwnd / 2 ? : 1U;
         hc->tx_ssthresh  = max(hc->tx_cwnd, 2U);
 
-        /* Avoid spurious timeouts resulting from Ack Ratio > cwnd */
-        if (dccp_sk(sk)->dccps_l_ack_ratio > hc->tx_cwnd)
-                ccid2_change_l_ack_ratio(sk, hc->tx_cwnd);
+        ccid2_check_l_ack_ratio(sk);
 }
 
 static int ccid2_hc_tx_parse_options(struct sock *sk, u8 packet_type,
@@ -494,8 +534,16 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
                         if (hc->tx_rpdupack >= NUMDUPACK) {
                                 hc->tx_rpdupack = -1; /* XXX lame */
                                 hc->tx_rpseq    = 0;
-
+#ifdef __CCID2_COPES_GRACEFULLY_WITH_ACK_CONGESTION_CONTROL__
+                                /*
+                                 * FIXME: Ack Congestion Control is broken; in
+                                 * the current state instabilities occurred with
+                                 * Ack Ratios greater than 1; causing hang-ups
+                                 * and long RTO timeouts. This needs to be fixed
+                                 * before opening up dynamic changes. -- gerrit
+                                 */
                                 ccid2_change_l_ack_ratio(sk, 2 * dp->dccps_l_ack_ratio);
+#endif
                         }
                 }
         }