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authorCui, Cheng <Cheng.Cui@netapp.com>2017-02-17 17:04:55 +0000
committerDavid S. Miller <davem@davemloft.net>2017-02-17 15:30:33 -0500
commita4ecb15a2432880353d0de4a35204ab8b65b8751 (patch)
treedb790c28e3b8fc8d2512f8200e98a2e176f234b9 /net/ipv4
parente606519ec3e7ec294b9c15c6248f9ea51e9eb2cb (diff)
downloadlinux-a4ecb15a2432880353d0de4a35204ab8b65b8751.tar.gz
linux-a4ecb15a2432880353d0de4a35204ab8b65b8751.tar.xz
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: Cheng Cui <Cheng.Cui@netapp.com> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
-rw-r--r--net/ipv4/tcp_output.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 61f272a99a49..22548b5f05cb 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -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);