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Commit a4ecb15a authored by Cui, Cheng's avatar Cui, Cheng Committed by David S. Miller
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tcp: accommodate sequence number to a peer's shrunk receive window caused by... 


tcp: accommodate sequence number to a peer's shrunk receive window caused by precision loss in window scaling

Prevent sending out a left-shifted sequence number from a Linux sender in
response to a peer's shrunk receive-window caused by losing least significant
bits in window-scaling.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: James Morris <jmorris@namei.org>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: Patrick McHardy <kaber@trash.net>
Signed-off-by: default avatarCheng Cui <Cheng.Cui@netapp.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e606519e

net/ipv4/tcp_output.c

+5 −2
Original line number Diff line number Diff line
@@ -83,7 +83,8 @@ static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb) 
		      tcp_skb_pcount(skb));

}



/* SND.NXT, if window was not shrunk.

/* SND.NXT, if window was not shrunk or the amount of shrunk was less than one

 * window scaling factor due to loss of precision.

 * If window has been shrunk, what should we make? It is not clear at all.

 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(

 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
@@ -93,7 +94,9 @@ static inline __u32 tcp_acceptable_seq(const struct sock *sk) 
{

	const struct tcp_sock *tp = tcp_sk(sk);



	if (!before(tcp_wnd_end(tp), tp->snd_nxt))

	if (!before(tcp_wnd_end(tp), tp->snd_nxt) ||

	    (tp->rx_opt.wscale_ok &&

	     ((tp->snd_nxt - tcp_wnd_end(tp)) < (1 << tp->rx_opt.rcv_wscale))))

		return tp->snd_nxt;

	else

		return tcp_wnd_end(tp);