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From Jeff Trawick <traw...@gmail.com>
Subject Re: Issue with apr-1.5.0 on FreeBSD 10beta3
Date Sun, 08 Dec 2013 18:32:03 GMT
On Sun, Dec 8, 2013 at 8:56 AM, Jeff Trawick <trawick@gmail.com> wrote:

> On Tue, Nov 26, 2013 at 4:01 PM, Rainer Jung <rainer.jung@kippdata.de>wrote:
>
>> On 26.11.2013 15:58, olli hauer wrote:
>> > On 2013-11-25 23:25, Jeff Trawick wrote:
>>
>> >> See if this brings any happiness:
>> >>
>> >> Index: network_io/unix/sockets.c
>> >> ===================================================================
>> >> --- network_io/unix/sockets.c (revision 1545394)
>> >> +++ network_io/unix/sockets.c (working copy)
>> >> @@ -273,7 +273,7 @@
>> >>  #endif /* TCP_NODELAY_INHERITED */
>> >>  #if APR_O_NONBLOCK_INHERITED
>> >>      if (apr_is_option_set(sock, APR_SO_NONBLOCK) == 1) {
>> >> -        apr_set_option(*new, APR_SO_NONBLOCK, 1);
>> >> +        /* apr_set_option(*new, APR_SO_NONBLOCK, 1); */
>> >>      }
>> >>  #endif /* APR_O_NONBLOCK_INHERITED */
>> >
>> >
>> > I can confirm after removing the line in apr-1.5.0 apache24 no longer
>> hangs.
>> > (tested with apache-2.4.6 / 2.4.7)
>> >
>> > I seen now why this is triggered by comparing apr.h after `./configure',
>> >
>> >> grep APR_O_NONBLOCK_INHERITED work/apr-1.4.8/include/apr.h
>> > ./work/apr-1.4.8/include/apr.h:#define APR_O_NONBLOCK_INHERITED 0
>> >
>> >> grep APR_O_NONBLOCK_INHERITED work/apr-1.5.0/include/apr.h
>> > work/apr-1.5.0/include/apr.h:#define APR_O_NONBLOCK_INHERITED 1
>> >
>> >
>> >> There are some APR 1.5 autoconf changes to consider at
>> >>
>> http://svn.apache.org/viewvc/apr/apr/branches/1.5.x/build/apr_network.m4?view=log
>> >
>> > OK, backing out the changes from r1502805 seems to do the trick on 10b3
>> > http://svn.apache.org/viewvc?view=revision&revision=1502805
>> >
>> >> grep APR_O_NONBLOCK_INHERITED work/apr-1.5.0/include/apr.h
>> > work/apr-1.5.0/include/apr.h:#define APR_O_NONBLOCK_INHERITED 0
>>
>> But acking out that change simply breaks the configure test on any
>> platform, because the resulting detection program no longer compiles.
>>
>> So the real culprit, is that the detection isn't doing the right thing.
>>
>> The test was changed before the compilation fix in the following revision:
>>
>>
>> http://svn.apache.org/viewvc/apr/apr/branches/1.5.x/build/apr_network.m4?r1=887002&r2=1449569&pathrev=1502805&diff_format=h
>>
>> That was due to the fact that I saw the test providing unreliable
>> results on a busy machine.
>>
>> So the question to me is: is the O_NONBLOCK setting inherited from a
>> listening socket on FreeBSD 10 - that's what the test tries to detect -
>> and how can we fix this feature test?
>>
>
> O_NONBLOCK is inherited from either an IPv6 listener or IPv4 listener in
> the obvious case on FreeBSD (9 and 10 tested), where "obvious" = V6ONLY in
> default setting (clearly ON), IPv6 client socket used to connect to IPv6
> server socket, IPv4 client socket used to connect to IPv4 server socket.
>  If I set V6ONLY to OFF, I still see O_NONBLOCK inherited.
>
> This is with a pure sockets program, ruling out APR.
>
>
>>
>> Or: is the test correct, but it previously failed for systems, where the
>> Apache or APR code does not do the right thing if the test would have
>> succeeded.
>>
>
> I guess something about the real world scenario in httpd (combination of
> other settings on the socket or presence of another listener on the port or
> something else unexpected) is breaking this.  But I suppose there is other
> code that could be broken and needs to be tested for completeness, such as
> failing to set non-blocking in the listener but managing to set the flag in
> the APR socket.
>

I forgot that FreeBSD is a real OS (has source code for kernel installed) :)

To make a long story short, FreeBSD 10 introduces accept4().  APR uses
accept4() where it can find it.  accept4() on Linux and FreeBSD 10 both
have a SOCK_NONBLOCK flag, but on FreeBSD 10 the SOCK_NONBLOCK is the sole
determiner of whether or not the connected socket is non-blocking.

(Recall that my binaries built on FreeBSD 9 worked fine.)

So APR's use of accept4() was broken w.r.t. inherited non-blocking on
FreeBSD 10 but for a while we still worked because the configure-time check
didn't work right with clang (the normal compiler on FreeBSD 10).

Once the clang issue was resolved, we hit the bad use of
accept4()-on-FreeBSD 10.

I guess when calling accept4() and SOCK_NONBLOCK is defined we need to set
the SOCK_NONBLOCK flag if the listen socket is non-blocking, and not worry
about the more detailed semantics of accept4().

(untested as of yet, though I'm sure that will change in the next couple of
days)

--/--

This is separate from the httpd issue -- fixing the FreeBSD version check
for --{enable|disable}-v6mapped, for which there is a patch earlier in this
thread.


>
>
>
>>
>> Regards,
>>
>> Rainer
>>
>
>
>
> --
> Born in Roswell... married an alien...
> http://emptyhammock.com/
>



-- 
Born in Roswell... married an alien...
http://emptyhammock.com/

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