[PATCH net-next] tcp: use TCP_INIT_CWND in tcp_fixup_sndbuf()

[PATCH net-next] tcp: use TCP_INIT_CWND in tcp_fixup_sndbuf()

[Eric Dumazet]

Initial cwnd being 10 (TCP_INIT_CWND) instead of 3, change
tcp_fixup_sndbuf() to get more than 16384 bytes (sysctl_tcp_wmem[1]) in
initial sk_sndbuf

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
I believe a similar change in tcp_fixup_rcvbuf() is needed too.

 net/ipv4/tcp_input.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index c1653fe..1e848b2 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -267,11 +267,9 @@ static void tcp_fixup_sndbuf(struct sock *sk)
 {
 	int sndmem = SKB_TRUESIZE(tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER);
 
-	if (sk->sk_sndbuf < 3 * sndmem) {
-		sk->sk_sndbuf = 3 * sndmem;
-		if (sk->sk_sndbuf > sysctl_tcp_wmem[2])
-			sk->sk_sndbuf = sysctl_tcp_wmem[2];
-	}
+	sndmem *= TCP_INIT_CWND;
+	if (sk->sk_sndbuf < sndmem)
+		sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
 }
 
 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)

Re: [PATCH net-next] tcp: use TCP_INIT_CWND in tcp_fixup_sndbuf()

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Fri, 14 Oct 2011 06:24:42 +0200

> Initial cwnd being 10 (TCP_INIT_CWND) instead of 3, change
> tcp_fixup_sndbuf() to get more than 16384 bytes (sysctl_tcp_wmem[1]) in
> initial sk_sndbuf
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>

Applied, thanks Eric.  Another reason to obliterate all magic constants :-)

> I believe a similar change in tcp_fixup_rcvbuf() is needed too.

And tcp_init_buffer_space() has a similar set of "4 * tp->advmss"
calculations.

And then some "2 * tp->advmss" cases, also having to do with window
clamping.