Merge branch 'fix-DCTCP-delayed-ACK'

Yuchung Cheng says:

====================
fix DCTCP delayed ACK

This patch series addresses the issue that sometimes DCTCP
fail to acknowledge the latest sequence and result in sender timeout
if inflight is small.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 4 insertions, 33 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index af3ec72d5d41..3482d13d655b 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -912,8 +912,6 @@ enum tcp_ca_event {
         CA_EVENT_LOSS,          /* loss timeout */
         CA_EVENT_ECN_NO_CE,     /* ECT set, but not CE marked */
         CA_EVENT_ECN_IS_CE,     /* received CE marked IP packet */
-        CA_EVENT_DELAYED_ACK,   /* Delayed ack is sent */
-        CA_EVENT_NON_DELAYED_ACK,
 };
 
 /* Information about inbound ACK, passed to cong_ops->in_ack_event() */
diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c
index 5f5e5936760e..5869f89ca656 100644
--- a/net/ipv4/tcp_dctcp.c
+++ b/net/ipv4/tcp_dctcp.c
@@ -55,7 +55,6 @@ struct dctcp {
         u32 dctcp_alpha;
         u32 next_seq;
         u32 ce_state;
-        u32 delayed_ack_reserved;
         u32 loss_cwnd;
 };
 
@@ -96,7 +95,6 @@ static void dctcp_init(struct sock *sk)
 
                 ca->dctcp_alpha = min(dctcp_alpha_on_init, DCTCP_MAX_ALPHA);
 
-                ca->delayed_ack_reserved = 0;
                 ca->loss_cwnd = 0;
                 ca->ce_state = 0;
 
@@ -134,7 +132,8 @@ static void dctcp_ce_state_0_to_1(struct sock *sk)
         /* State has changed from CE=0 to CE=1 and delayed
          * ACK has not sent yet.
          */
-        if (!ca->ce_state && ca->delayed_ack_reserved) {
+        if (!ca->ce_state &&
+            inet_csk(sk)->icsk_ack.pending & ICSK_ACK_TIMER) {
                 u32 tmp_rcv_nxt;
 
                 /* Save current rcv_nxt. */
@@ -164,7 +163,8 @@ static void dctcp_ce_state_1_to_0(struct sock *sk)
         /* State has changed from CE=1 to CE=0 and delayed
          * ACK has not sent yet.
          */
-        if (ca->ce_state && ca->delayed_ack_reserved) {
+        if (ca->ce_state &&
+            inet_csk(sk)->icsk_ack.pending & ICSK_ACK_TIMER) {
                 u32 tmp_rcv_nxt;
 
                 /* Save current rcv_nxt. */
@@ -248,25 +248,6 @@ static void dctcp_state(struct sock *sk, u8 new_state)
         }
 }
 
-static void dctcp_update_ack_reserved(struct sock *sk, enum tcp_ca_event ev)
-{
-        struct dctcp *ca = inet_csk_ca(sk);
-
-        switch (ev) {
-        case CA_EVENT_DELAYED_ACK:
-                if (!ca->delayed_ack_reserved)
-                        ca->delayed_ack_reserved = 1;
-                break;
-        case CA_EVENT_NON_DELAYED_ACK:
-                if (ca->delayed_ack_reserved)
-                        ca->delayed_ack_reserved = 0;
-                break;
-        default:
-                /* Don't care for the rest. */
-                break;
-        }
-}
-
 static void dctcp_cwnd_event(struct sock *sk, enum tcp_ca_event ev)
 {
         switch (ev) {
@@ -276,10 +257,6 @@ static void dctcp_cwnd_event(struct sock *sk, enum tcp_ca_event ev)
         case CA_EVENT_ECN_NO_CE:
                 dctcp_ce_state_1_to_0(sk);
                 break;
-        case CA_EVENT_DELAYED_ACK:
-        case CA_EVENT_NON_DELAYED_ACK:
-                dctcp_update_ack_reserved(sk, ev);
-                break;
         default:
                 /* Don't care for the rest. */
                 break;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 8e08b409c71e..00e5a300ddb9 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3523,8 +3523,6 @@ void tcp_send_delayed_ack(struct sock *sk)
         int ato = icsk->icsk_ack.ato;
         unsigned long timeout;
 
-        tcp_ca_event(sk, CA_EVENT_DELAYED_ACK);
-
         if (ato > TCP_DELACK_MIN) {
                 const struct tcp_sock *tp = tcp_sk(sk);
                 int max_ato = HZ / 2;
@@ -3581,8 +3579,6 @@ void tcp_send_ack(struct sock *sk)
         if (sk->sk_state == TCP_CLOSE)
                 return;
 
-        tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK);
-
         /* We are not putting this on the write queue, so
          * tcp_transmit_skb() will set the ownership to this
          * sock.