Date: Tue, 4 Dec 2018 22:10:09 +0000 (UTC) From: Michael Tuexen <tuexen@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r341498 - in stable/12/sys/netinet: . tcp_stacks Message-ID: <201812042210.wB4MA9rk093449@repo.freebsd.org>
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Author: tuexen Date: Tue Dec 4 22:10:09 2018 New Revision: 341498 URL: https://svnweb.freebsd.org/changeset/base/341498 Log: MFC r340774: 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@ Sponsored by: Netflix, Inc. Differential Revision: https://reviews.freebsd.org/D17949 Modified: stable/12/sys/netinet/tcp_output.c stable/12/sys/netinet/tcp_stacks/rack.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/netinet/tcp_output.c ============================================================================== --- stable/12/sys/netinet/tcp_output.c Tue Dec 4 22:05:36 2018 (r341497) +++ stable/12/sys/netinet/tcp_output.c Tue Dec 4 22:10:09 2018 (r341498) @@ -1171,14 +1171,18 @@ 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: stable/12/sys/netinet/tcp_stacks/rack.c ============================================================================== --- stable/12/sys/netinet/tcp_stacks/rack.c Tue Dec 4 22:05:36 2018 (r341497) +++ stable/12/sys/netinet/tcp_stacks/rack.c Tue Dec 4 22:10:09 2018 (r341498) @@ -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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