[PATCH] tcp: extend window to fit all restored unacked data in a send queue

From: Andrey Vagin
Date: Tue May 31 2016 - 11:03:05 EST

Data from a send queue is sent only if there is enough space in a
window, so when we restore unacked data, we need to expand a window to
fit this data.

Currently we don't do this and tcp_acceptable_seq() returns
tcp_wnd_end(tp) instead of tp->snd_nxt. The other side drops packets
with this seq, becuse tcp_sequence() returns false (seq < tp->rcv_nxt).

Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Alexey Kuznetsov <kuznet@xxxxxxxxxxxxx>
Cc: James Morris <jmorris@xxxxxxxxx>
Cc: Hideaki YOSHIFUJI <yoshfuji@xxxxxxxxxxxxxx>
Cc: Patrick McHardy <kaber@xxxxxxxxx>
Signed-off-by: Andrey Vagin <avagin@xxxxxxxxxx>
net/ipv4/tcp_output.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 79a03b8..b36f968 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -75,6 +75,10 @@ static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb)
tcp_advance_send_head(sk, skb);
tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;

+ /* All sent data have to fit into the window */
+ if (unlikely(tp->repair) && before(tcp_wnd_end(tp), tp->snd_nxt))
+ tp->snd_wnd = tp->snd_nxt - tp->snd_una;
tp->packets_out += tcp_skb_pcount(skb);
if (!prior_packets || icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {