From e2662978b8351fe9b0f1174099e2603179ff0e9a Mon Sep 17 00:00:00 2001 From: Michael Tuexen Date: Mon, 30 Jul 2018 21:13:42 +0000 Subject: [PATCH] Send consistent SEG.WIN when using timewait codepath for TCP. When sending TCP segments from the timewait code path, a stored value of the last sent window is used. Use the same code for computing this in the timewait code path as in the main code path used in tcp_output() to avoiv inconsistencies. Reviewed by: rrs@ MFC after: 1 month Sponsored by: Netflix, Inc. Differential Revision: https://reviews.freebsd.org/D16503 --- sys/netinet/tcp_timewait.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/sys/netinet/tcp_timewait.c b/sys/netinet/tcp_timewait.c index fa652f39b5fe..0384fc54ca8d 100644 --- a/sys/netinet/tcp_timewait.c +++ b/sys/netinet/tcp_timewait.c @@ -230,6 +230,7 @@ tcp_twstart(struct tcpcb *tp) struct tcptw twlocal, *tw; struct inpcb *inp = tp->t_inpcb; struct socket *so; + uint32_t recwin; bool acknow, local; #ifdef INET6 bool isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6; @@ -292,10 +293,16 @@ tcp_twstart(struct tcpcb *tp) /* * Recover last window size sent. */ - if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) - tw->last_win = (tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale; - else - tw->last_win = 0; + so = inp->inp_socket; + recwin = lmin(lmax(sbspace(&so->so_rcv), 0), + (long)TCP_MAXWIN << tp->rcv_scale); + if (recwin < (so->so_rcv.sb_hiwat / 4) && + recwin < tp->t_maxseg) + recwin = 0; + if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && + recwin < (tp->rcv_adv - tp->rcv_nxt)) + recwin = (tp->rcv_adv - tp->rcv_nxt); + tw->last_win = htons((u_short)(recwin >> tp->rcv_scale)); /* * Set t_recent if timestamps are used on the connection. @@ -332,7 +339,6 @@ tcp_twstart(struct tcpcb *tp) * and might not be needed here any longer. */ tcp_discardcb(tp); - so = inp->inp_socket; soisdisconnected(so); tw->tw_so_options = so->so_options; inp->inp_flags |= INP_TIMEWAIT;