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Send consistent SEG.WIN when using timewait codepath for TCP.

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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
This commit is contained in:
Michael Tuexen 2018-07-30 21:13:42 +00:00
parent 22e56aea3f
commit e2662978b8
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=336937
1 changed files with 11 additions and 5 deletions
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16
sys/netinet/tcp_timewait.c
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@ -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;