1 files changed, 53 insertions, 31 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 25a89eaa669d..5d083855c111 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -355,6 +355,12 @@ static void tcp_fixup_rcvbuf(struct sock *sk)
 	rcvmem = 2 * SKB_TRUESIZE(mss + MAX_TCP_HEADER) *
 		 tcp_default_init_rwnd(mss);
 
+	/* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency
+	 * Allow enough cushion so that sender is not limited by our window
+	 */
+	if (sysctl_tcp_moderate_rcvbuf)
+		rcvmem <<= 2;
+
 	if (sk->sk_rcvbuf < rcvmem)
 		sk->sk_rcvbuf = min(rcvmem, sysctl_tcp_rmem[2]);
 }
@@ -373,6 +379,8 @@ void tcp_init_buffer_space(struct sock *sk)
 		tcp_fixup_sndbuf(sk);
 
 	tp->rcvq_space.space = tp->rcv_wnd;
+	tp->rcvq_space.time = tcp_time_stamp;
+	tp->rcvq_space.seq = tp->copied_seq;
 
 	maxwin = tcp_full_space(sk);
 
@@ -512,48 +520,62 @@ void tcp_rcv_space_adjust(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	int time;
-	int space;
-
-	if (tp->rcvq_space.time == 0)
-		goto new_measure;
+	int copied;
 
 	time = tcp_time_stamp - tp->rcvq_space.time;
 	if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0)
 		return;
 
-	space = 2 * (tp->copied_seq - tp->rcvq_space.seq);
+	/* Number of bytes copied to user in last RTT */
+	copied = tp->copied_seq - tp->rcvq_space.seq;
+	if (copied <= tp->rcvq_space.space)
+		goto new_measure;
+
+	/* A bit of theory :
+	 * copied = bytes received in previous RTT, our base window
+	 * To cope with packet losses, we need a 2x factor
+	 * To cope with slow start, and sender growing its cwin by 100 %
+	 * every RTT, we need a 4x factor, because the ACK we are sending
+	 * now is for the next RTT, not the current one :
+	 * <prev RTT . ><current RTT .. ><next RTT .... >
+	 */
+
+	if (sysctl_tcp_moderate_rcvbuf &&
+	    !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
+		int rcvwin, rcvmem, rcvbuf;
 
-	space = max(tp->rcvq_space.space, space);
+		/* minimal window to cope with packet losses, assuming
+		 * steady state. Add some cushion because of small variations.
+		 */
+		rcvwin = (copied << 1) + 16 * tp->advmss;
 
-	if (tp->rcvq_space.space != space) {
-		int rcvmem;
+		/* If rate increased by 25%,
+		 *	assume slow start, rcvwin = 3 * copied
+		 * If rate increased by 50%,
+		 *	assume sender can use 2x growth, rcvwin = 4 * copied
+		 */
+		if (copied >=
+		    tp->rcvq_space.space + (tp->rcvq_space.space >> 2)) {
+			if (copied >=
+			    tp->rcvq_space.space + (tp->rcvq_space.space >> 1))
+				rcvwin <<= 1;
+			else
+				rcvwin += (rcvwin >> 1);
+		}
 
-		tp->rcvq_space.space = space;
+		rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER);
+		while (tcp_win_from_space(rcvmem) < tp->advmss)
+			rcvmem += 128;
 
-		if (sysctl_tcp_moderate_rcvbuf &&
-		    !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
-			int new_clamp = space;
+		rcvbuf = min(rcvwin / tp->advmss * rcvmem, sysctl_tcp_rmem[2]);
+		if (rcvbuf > sk->sk_rcvbuf) {
+			sk->sk_rcvbuf = rcvbuf;
 
-			/* Receive space grows, normalize in order to
-			 * take into account packet headers and sk_buff
-			 * structure overhead.
-			 */
-			space /= tp->advmss;
-			if (!space)
-				space = 1;
-			rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER);
-			while (tcp_win_from_space(rcvmem) < tp->advmss)
-				rcvmem += 128;
-			space *= rcvmem;
-			space = min(space, sysctl_tcp_rmem[2]);
-			if (space > sk->sk_rcvbuf) {
-				sk->sk_rcvbuf = space;
-
-				/* Make the window clamp follow along.  */
-				tp->window_clamp = new_clamp;
-			}
+			/* Make the window clamp follow along.  */
+			tp->window_clamp = rcvwin;
 		}
 	}
+	tp->rcvq_space.space = copied;
 
 new_measure:
 	tp->rcvq_space.seq = tp->copied_seq;
@@ -5674,8 +5696,8 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 			tcp_init_congestion_control(sk);
 
 			tcp_mtup_init(sk);
-			tcp_init_buffer_space(sk);
 			tp->copied_seq = tp->rcv_nxt;
+			tcp_init_buffer_space(sk);
 		}
 		smp_mb();
 		tcp_set_state(sk, TCP_ESTABLISHED);