Date: Sun, 04 Nov 2012 06:11:50 -0800 From: Manfred Antar <null@pozo.com> To: Dimitry Andric <dimitry@andric.com> Cc: Adrian Chadd <adrian@freebsd.org>, freebsd-current@freebsd.org, Andre Oppermann <andre@freebsd.org> Subject: Re: weird network problems on current since 10/28/2012 Message-ID: <201211041411.qA4EBtab006509@pozo.com> In-Reply-To: <50964FBB.4010600@andric.com> References: <201211031740.qA3HeqVX001622@pozo.com> <CAJ-VmomAR8N8ovhC7La3ttG=7Qu_%2BVwD30tPxFBpzC37eg9CHA@mail.gmail.com> <201211040113.qA41DfLn001577@pozo.com> <50964FBB.4010600@andric.com>
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At 03:21 AM 11/4/2012, Dimitry Andric wrote: >On 2012-11-04 02:13, Manfred Antar wrote: >>At 03:29 PM 11/3/2012, Adrian Chadd wrote: >>>On 3 November 2012 10:40, Manfred Antar <null@pozo.com> wrote: >>>>i have problem connecting to freebsd box on local network since last sunday. >>>>the last kernel that works: >>>> FreeBSD 10.0-CURRENT #0: Sun Oct 28 12:14:38 PDT 2012 >>>>anything after that, sometimes i can connect, other times just hangs. >>>>any network connection hangs ===== pop httpd ssh etc etc. >>>>anyone have any ideas ? >>>>i can checkout different sources and see if i can locate the changes that cause this. >>> >>>Please do! >... >>Here is what I found doing : >>setenv CVSROOT /usr/home/ncvs >> >>cvs co -D"October 28, 2012 12:14:38 PDT" sys >> >>A kernel from that time works fine. >> >>doing: >> >>cvs up -D"October 28, 2012 13:14:38 PDT" sys 1 hour later >>the following files were changed: >>sys/netinet/tcp_input.c >>sys/netinet/tcp_timer.c >>sys/netinet/tcp_var.h >> >>Building a kernel from these new files is when the problem starts. > >So, your problems seem to have been introduced by this commit by Andre: > > http://svn.freebsd.org/changeset/base/242266 > > Increase the initial CWND to 10 segments as defined in IETF TCPM > draft-ietf-tcpm-initcwnd-05. It explains why the increased initial > window improves the overall performance of many web services without > risking congestion collapse. > > As long as it remains a draft it is placed under a sysctl marking it > as experimental: > net.inet.tcp.experimental.initcwnd10 = 1 > When it becomes an official RFC soon the sysctl will be changed to > the RFC number and moved to net.inet.tcp. > > This implementation differs from the RFC draft in that it is a bit > more conservative in the case of packet loss on SYN or SYN|ACK because > we haven't reduced the default RTO to 1 second yet. Also the restart > window isn't yet increased as allowed. Both will be adjusted with > upcoming changes. > > Is is enabled by default. In Linux it is enabled since kernel 3.0. > >After the commit, there was a small discussion thread on svn-src-head@ >about the possible problems with the approach. Maybe you are >experiencing those? > >As the commit message says, you should be able to turn the feature off >using: > > sysctl net.inet.tcp.experimental.initcwnd10=0 > >Can you please try that, and see if the problems go away? I read the commit log and tried that. It didn't change. I will try the patch from Andre and enable the debug log. Manfred ======================== || null@pozo.com || || Ph. (415) 681-6235 || ======================== -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.
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