[TCP]: Two RFC3465 Appropriate Byte Count fixes.

1) fix slow start after retransmit timeout
2) fix case of L=2*SMSS acked bytes comparison

Signed-off-by: Daikichi Osuga <osugad@s1.nttdocomo.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 8 insertions, 3 deletions

diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 5765f9d0317..7ff2e4273a7 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -189,7 +189,7 @@ void tcp_slow_start(struct tcp_sock *tp)
                         return;
 
                 /* We MAY increase by 2 if discovered delayed ack */
-                if (sysctl_tcp_abc > 1 && tp->bytes_acked > 2*tp->mss_cache) {
+                if (sysctl_tcp_abc > 1 && tp->bytes_acked >= 2*tp->mss_cache) {
                         if (tp->snd_cwnd < tp->snd_cwnd_clamp)
                                 tp->snd_cwnd++;
                 }
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 104af5d5bcb..111ff39a08c 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2505,8 +2505,13 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
         if (before(ack, prior_snd_una))
                 goto old_ack;
 
-        if (sysctl_tcp_abc && icsk->icsk_ca_state < TCP_CA_CWR)
-                tp->bytes_acked += ack - prior_snd_una;
+        if (sysctl_tcp_abc) {
+                if (icsk->icsk_ca_state < TCP_CA_CWR)
+                        tp->bytes_acked += ack - prior_snd_una;
+                else if (icsk->icsk_ca_state == TCP_CA_Loss)
+                        /* we assume just one segment left network */
+                        tp->bytes_acked += min(ack - prior_snd_una, tp->mss_cache);
+        }
 
         if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
                 /* Window is constant, pure forward advance.