tcp_htcp: last_cong bug fix

This patch fixes a minor bug in tcp_htcp.c which has been
highlighted by Lachlan Andrew and Lawrence Stewart.  Currently, the
time since the last congestion event, which is stored in variable
last_cong, is reset whenever there is a state change into
TCP_CA_Open.  This includes transitions of the type
TCP_CA_Open->TCP_CA_Disorder->TCP_CA_Open which are not associated
with backoff of cwnd.  The patch changes last_cong to be updated
only on transitions into TCP_CA_Open that occur after experiencing
the congestion-related states TCP_CA_Loss, TCP_CA_Recovery,
TCP_CA_CWR.

Signed-off-by: Doug Leith <doug.leith@nuim.ie>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_htcp.c b/net/ipv4/tcp_htcp.c
index af99776146ffc14a4f85cb08ceaaea619d7b8a90..937549b8a9212fa6289964bde303367e2f462d74 100644 (file)
--- a/net/ipv4/tcp_htcp.c
+++ b/net/ipv4/tcp_htcp.c
@@ -69,9 +69,12 @@ static u32 htcp_cwnd_undo(struct sock *sk)
        const struct tcp_sock *tp = tcp_sk(sk);
        struct htcp *ca = inet_csk_ca(sk);
 
-       ca->last_cong = ca->undo_last_cong;
-       ca->maxRTT = ca->undo_maxRTT;
-       ca->old_maxB = ca->undo_old_maxB;
+       if (ca->undo_last_cong) {
+               ca->last_cong = ca->undo_last_cong;
+               ca->maxRTT = ca->undo_maxRTT;
+               ca->old_maxB = ca->undo_old_maxB;
+               ca->undo_last_cong = 0;
+       }
 
        return max(tp->snd_cwnd, (tp->snd_ssthresh << 7) / ca->beta);
 }
@@ -268,7 +271,10 @@ static void htcp_state(struct sock *sk, u8 new_state)
        case TCP_CA_Open:
                {
                        struct htcp *ca = inet_csk_ca(sk);
-                       ca->last_cong = jiffies;
+                       if (ca->undo_last_cong) {
+                               ca->last_cong = jiffies;
+                               ca->undo_last_cong = 0;
+                       }
                }
                break;
        case TCP_CA_CWR: