Date: Thu, 22 Nov 2018 19:49:53 +0000 (UTC) From: Michael Tuexen <tuexen@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r340774 - in head/sys/netinet: . tcp_stacks Message-ID: <201811221949.wAMJnrm0078975@repo.freebsd.org>
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Author: tuexen Date: Thu Nov 22 19:49:52 2018 New Revision: 340774 URL: https://svnweb.freebsd.org/changeset/base/340774 Log: Ensure that TCP RST-segments announce consistently a receiver window of zero. This was already done when sending them via tcp_respond(). Reviewed by: rrs@ MFC after: 1 week Sponsored by: Netflix, Inc. Differential Revision: https://reviews.freebsd.org/D17949 Modified: head/sys/netinet/tcp_output.c head/sys/netinet/tcp_stacks/rack.c Modified: head/sys/netinet/tcp_output.c ============================================================================== --- head/sys/netinet/tcp_output.c Thu Nov 22 18:59:05 2018 (r340773) +++ head/sys/netinet/tcp_output.c Thu Nov 22 19:49:52 2018 (r340774) @@ -1172,14 +1172,18 @@ send: /* * Calculate receive window. Don't shrink window, * but avoid silly window syndrome. + * If a RST segment is sent, advertise a window of zero. */ - if (recwin < (so->so_rcv.sb_hiwat / 4) && - recwin < tp->t_maxseg) + if (flags & TH_RST) { 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); - + } else { + 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); + } /* * According to RFC1323 the window field in a SYN (i.e., a <SYN> * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> Modified: head/sys/netinet/tcp_stacks/rack.c ============================================================================== --- head/sys/netinet/tcp_stacks/rack.c Thu Nov 22 18:59:05 2018 (r340773) +++ head/sys/netinet/tcp_stacks/rack.c Thu Nov 22 19:49:52 2018 (r340774) @@ -8189,15 +8189,20 @@ send: /* * Calculate receive window. Don't shrink window, but avoid silly * window syndrome. + * If a RST segment is sent, advertise a window of zero. */ - if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && - recwin < (long)tp->t_maxseg) + if (flags & TH_RST) { recwin = 0; - if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && - recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) - recwin = (long)(tp->rcv_adv - tp->rcv_nxt); - if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) - recwin = (long)TCP_MAXWIN << tp->rcv_scale; + } else { + if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && + recwin < (long)tp->t_maxseg) + recwin = 0; + if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && + recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) + recwin = (long)(tp->rcv_adv - tp->rcv_nxt); + if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) + recwin = (long)TCP_MAXWIN << tp->rcv_scale; + } /* * According to RFC1323 the window field in a SYN (i.e., a <SYN> or
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