Date: Thu, 21 May 2020 16:31:57 -0700 (PDT) From: "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net> To: Richard Scheffenegger <rscheff@freebsd.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: Re: svn commit: r361340 - in stable/12/sys/netinet: . tcp_stacks Message-ID: <202005212331.04LNVvac018957@gndrsh.dnsmgr.net> In-Reply-To: <202005211941.04LJfPQ0023810@repo.freebsd.org>
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> Author: rscheff > Date: Thu May 21 19:41:25 2020 > New Revision: 361340 > URL: https://svnweb.freebsd.org/changeset/base/361340 > > Log: > MFC r360479: Prevent premature shrinking of the scaled receive window > > which can cause a TCP client to use invalid or stale TCP sequence numbers for ACK packets. > > Packets with old sequence numbers are ignored and not used to update the send window size. > This might cause the TCP session to hang indefinitely under some circumstances. There should of been a note here: This does NOT contain the merge of the change to bbrv1 since at this time that code does not exist in stable/12, and there is no plan to merge that code to stable/12. > Reported by: Cui Cheng > Reviewed by: tuexen (mentor), rgrimes (mentor, blanket) > Approved by: tuexen (mentor), rgrimes (mentor, blanket) > MFC after: 3 weeks > Sponsored by: NetApp, Inc. > Differential Revision: https://reviews.freebsd.org/D24515 > > 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 Thu May 21 18:50:05 2020 (r361339) > +++ stable/12/sys/netinet/tcp_output.c Thu May 21 19:41:25 2020 (r361340) > @@ -1206,8 +1206,11 @@ send: > if (flags & TH_SYN) > th->th_win = htons((u_short) > (min(sbspace(&so->so_rcv), TCP_MAXWIN))); > - else > + else { > + /* Avoid shrinking window with window scaling. */ > + recwin = roundup2(recwin, 1 << tp->rcv_scale); > th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); > + } > > /* > * Adjust the RXWIN0SENT flag - indicate that we have advertised > > Modified: stable/12/sys/netinet/tcp_stacks/rack.c > ============================================================================== > --- stable/12/sys/netinet/tcp_stacks/rack.c Thu May 21 18:50:05 2020 (r361339) > +++ stable/12/sys/netinet/tcp_stacks/rack.c Thu May 21 19:41:25 2020 (r361340) > @@ -8355,8 +8355,11 @@ send: > if (flags & TH_SYN) > th->th_win = htons((u_short) > (min(sbspace(&so->so_rcv), TCP_MAXWIN))); > - else > + else { > + /* Avoid shrinking window with window scaling. */ > + recwin = roundup2(recwin, 1 << tp->rcv_scale); > th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); > + } > /* > * Adjust the RXWIN0SENT flag - indicate that we have advertised a 0 > * window. This may cause the remote transmitter to stall. This > -- Rod Grimes rgrimes@freebsd.org
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