Date: Fri, 27 Feb 2015 13:07:33 -0500 From: John Baldwin <jhb@freebsd.org> To: Adrian Chadd <adrian@freebsd.org> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, "Quattlebaum, Ryan" <Ryan.Quattlebaum@netapp.com> Subject: Re: Accessing socket APIs soon after accept Message-ID: <4083712.jb7qREZuG6@ralph.baldwin.cx> In-Reply-To: <CAJ-VmonSgpDMiCTvdyaHpKX7ahLYAo9FZ0k1OfzK2TesfYLEvQ@mail.gmail.com> References: <1421339375968.94209@netapp.com> <1425050565215.33356@netapp.com> <CAJ-VmonSgpDMiCTvdyaHpKX7ahLYAo9FZ0k1OfzK2TesfYLEvQ@mail.gmail.com>
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On Friday, February 27, 2015 10:03:33 AM Adrian Chadd wrote: > Is this also a bug on -9 and -10? Yes. I may merge just the tcp_syncache.c part of this change down to stable branches. > > -a > > > On 27 February 2015 at 07:22, Quattlebaum, Ryan > > <Ryan.Quattlebaum@netapp.com> wrote: > > Thanks, John. That's almost exactly the approach we were considering. > > > > - Ryan Q > > ________________________________________ > > From: John Baldwin <jhb@freebsd.org> > > Sent: Friday, February 27, 2015 10:20 AM > > To: freebsd-net@freebsd.org > > Cc: Quattlebaum, Ryan; Adrian Chadd > > Subject: Re: Accessing socket APIs soon after accept > > > > On Friday, January 16, 2015 05:07:28 PM Quattlebaum, Ryan wrote: > >> Hi, Adrian. Thanks for taking a look at this. > >> > >> We're using FreeBSD 8.2 and httpd-2.4.10 with arp-1.5.1 and > >> apr-util-1.5.4. > >> > >> The problem we're seeing is pretty intermittent, so I hope this test case > >> can shine a little bit of light on > >> the > >> problem. We tried debugging this on our own by adding calls to > >> getsockname() right after the accept call (in > >> srclib/apr/network_io/unix/sockets.c: apr_socket_accept()) and logging > >> the > >> output. That's where we saw invalid data. > >> > >> I took a look at the source code for the TCP syncache module and the > >> accept > >> syscall. It looks like the new child socket is available for the > >> application to accept after the call to sonewconn returns, but the > >> address > >> information isn't set until further down in the function. Wouldn't this > >> open a window where an application could accept on a socket that the > >> syncache code isn't done configuring? > > > > This is a bug in 8.x it seems. It was fixed in HEAD in this commit: > > > > ------------------------------------------------------------------------ > > r261242 | gnn | 2014-01-28 15:28:32 -0500 (Tue, 28 Jan 2014) | 10 lines > > > > Decrease lock contention within the TCP accept case by removing > > the INP_INFO lock from tcp_usr_accept. As the PR/patch states > > this was following the advice already in the code. > > See the PR below for a full disucssion of this change and its > > measured effects. > > > > PR: 183659 > > Submitted by: Julian Charbon > > Reviewed by: jhb > > > > In particular, that commit changed the syncache code to not place the > > socket in the queue until the end of the function via soisconnected(). > > > > You can probably merge the tcp_syncache.c portion of that change back to > > 8.x without any ill effects and it should fix your problem. > > > > -- > > John Baldwin -- John Baldwin
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