From: "Cui, Cheng" <cheng....@netapp.com> Date: Tue, 14 Feb 2017 23:14:59 +0000
> This updates tcp_acceptable_seq(), one of the oldest functions since 2.4.0, by > preventing 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. > > RFC7323 page 10 (Chapter 2.4. Addressing Window Retraction) specifies sender > side responsibility to handle the sequence number out of window: >> On the sender side: >> >> 3) The initial transmission MUST be within the window announced by >> the most recent <ACK>. > > Some related discussion can be found at the IETF [tcpm] mailing list: > https://mailarchive.ietf.org/arch/msg/tcpm/pPO7cYxtky27Qto9b30eaHB_RQI > > The issue has been reproduced and the patch has been verified by scp a 20GB > file > from a Linux box using kernel version 4.4.48 to a FreeBSD 11.0 box. > > [ I mainly want feedback to see if everyone is OK with the approach. ] > > Cc: "David S. Miller" <da...@davemloft.net> > Cc: Alexey Kuznetsov <kuz...@ms2.inr.ac.ru> > Cc: James Morris <jmor...@namei.org> > Cc: Hideaki YOSHIFUJI <yoshf...@linux-ipv6.org> > Cc: Patrick McHardy <ka...@trash.net> > Signed-off-by: Cheng Cui <cheng....@netapp.com> Patch looks fine to me, but too much parenthesis in the initial conditional and it's easier to see to high level structure if you format the check like this; 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)))) THanks.
