Re: [PATCH] accept4 tests: fix specified flags

[Pádraig Brady]

On 12/10/15 12:18, Pino Toscano wrote:
> On Friday 09 October 2015 15:41:47 Pádraig Brady wrote:
>> On 09/10/15 14:38, Pino Toscano wrote:
>>> On Thursday 08 October 2015 15:46:42 Pádraig Brady wrote:
>>>> On 08/10/15 13:47, Pino Toscano wrote:
>>>>> Pass only SOCK_* flags to accept4, as they are the only documented
>>>>> ones, and passing others may trigger EINVAL.
>>>>> * tests/test-accept4.c: (main): Pass SOCK_CLOEXEC instead of
>>>>> O_CLOEXEC | O_BINARY to accept4.
>>>>> ---
>>>>>  ChangeLog            | 7 +++++++
>>>>>  tests/test-accept4.c | 4 ++--
>>>>>  2 files changed, 9 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/ChangeLog b/ChangeLog
>>>>> index 02d8bf8..3601eda 100644
>>>>> --- a/ChangeLog
>>>>> +++ b/ChangeLog
>>>>> @@ -1,3 +1,10 @@
>>>>> +2015-10-08  Pino Toscano  <address@hidden>
>>>>> +
>>>>> + Pass only SOCK_* flags to accept4, as they are the only documented
>>>>> + ones, and passing others may trigger EINVAL.
>>>>> + * tests/test-accept4.c: (main): Pass SOCK_CLOEXEC instead of
>>>>> + O_CLOEXEC | O_BINARY to accept4.
>>>>> +
>>>>>  2015-10-06  Pavel Raiskup  <address@hidden>
>>>>>  
>>>>>   gnulib-tool: fix tests of 'extensions' module
>>>>> diff --git a/tests/test-accept4.c b/tests/test-accept4.c
>>>>> index b24af0b..b2e6fa8 100644
>>>>> --- a/tests/test-accept4.c
>>>>> +++ b/tests/test-accept4.c
>>>>> @@ -43,7 +43,7 @@ main (void)
>>>>>  
>>>>>      errno = 0;
>>>>>      ASSERT (accept4 (-1, (struct sockaddr *) &addr, &addrlen,
>>>>> -                     O_CLOEXEC | O_BINARY)
>>>>> +                     SOCK_CLOEXEC)
>>>>>              == -1);
>>>>>      ASSERT (errno == EBADF);
>>>>>    }
>>>>> @@ -54,7 +54,7 @@ main (void)
>>>>>      close (99);
>>>>>      errno = 0;
>>>>>      ASSERT (accept4 (99, (struct sockaddr *) &addr, &addrlen,
>>>>> -                     O_CLOEXEC | O_BINARY)
>>>>> +                     SOCK_CLOEXEC)
>>>>>              == -1);
>>>>>      ASSERT (errno == EBADF);
>>>>>    }
>>>>
>>>> That change looks good, though it also suggests that
>>>> the implementation doesn't assume the availability of SOCK_CLOEXEC etc.
>>>> I think we also may need the following included in your patch,
>>>> to ensure the test compiles on all platforms, and that those
>>>> constants are defined appropriately on all platforms?
>>>
>>> The idea seems ok -- should I merge it with my patch, or can/should it
>>> go as separate patch?
>>>
>>>> diff --git a/lib/accept4.c b/lib/accept4.c
>>>> index adf0989..992dfd0 100644
>>>> --- a/lib/accept4.c
>>>> +++ b/lib/accept4.c
>>>> @@ -24,10 +24,6 @@
>>>>  #include "binary-io.h"
>>>>  #include "msvc-nothrow.h"
>>>>
>>>> -#ifndef SOCK_CLOEXEC
>>>> -# define SOCK_CLOEXEC 0
>>>> -#endif
>>>> -
>>>>  int
>>>>  accept4 (int sockfd, struct sockaddr *addr, socklen_t *addrlen, int flags)
>>>>  {
>>>> diff --git a/lib/sys_socket.in.h b/lib/sys_socket.in.h
>>>> index d29cc09..2d9df45 100644
>>>> --- a/lib/sys_socket.in.h
>>>> +++ b/lib/sys_socket.in.h
>>>> @@ -654,10 +654,16 @@ _GL_WARN_ON_USE (shutdown, "shutdown is not always 
>>>> POSIX compliant - "
>>>>
>>>>  #if @GNULIB_ACCEPT4@
>>>>  /* Accept a connection on a socket, with specific opening flags.
>>>> -   The flags are a bitmask, possibly including O_CLOEXEC (defined in 
>>>> <fcntl.h>)
>>>> -   and O_TEXT, O_BINARY (defined in "binary-io.h").
>>>> +   The flags are a bitmask, possibly including SOCK_NONBLOCK,
>>>> +   SOCK_CLOEXEC, and O_TEXT, O_BINARY (defined in "binary-io.h").
>>>>     See also the Linux man page at
>>>>     
>>>> <http://www.kernel.org/doc/man-pages/online/pages/man2/accept4.2.html>.  */
>>>> +# ifndef SOCK_CLOEXEC
>>>> +#  define SOCK_CLOEXEC O_CLOEXEC
>>>> +# endif
>>>> +# ifndef SOCK_NONBLOCK
>>>> +#  define SOCK_NONBLOCK O_NONBLOCK
>>>> +# endif
>>>>  # if @HAVE_ACCEPT4@
>>>>  #  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
>>>>  #   define accept4 rpl_accept4
>>>
>>> SOCK_CLOEXEC is used only in src/accept4.c, so that seems ok.
>>> OTOH, SOCK_NONBLOCK is checked in tests/test-nonblocking.c, where it
>>> would enable the code passing extra flags to the socket type; defining
>>> could make that check failing in case the OS does not implement accept4
>>> (and thus we are providing SOCK_*). What do you think?
>>
>> Yes good point.
>>
>> accept4() makes no sense without SOCK_CLOEXEC or SOCK_NONBLOCK,
>> so my change to define make sense in that respect.
>> Defining them to non zero will ensure for example EINVAL is
>> returned for SOCK_NONBLOCK on platforms where we replace accept4()
>> (though I suppose we could simulate that also).
> 
> True: if gnulib is providing accept4 to some platform which does not
> provide it, then SOCK_CLOEXEC and SOCK_NONBLOCK ought to be provided
> too, as they are part of the interface.
> 
>> However SOCK_CLOEXEC and SOCK_NONBLOCK may not be defined
>> on platforms with select(), and we probably shouldn't define
>> as user space may be doing:
>>
>>   #ifdef SOCK_CLOEXEC
>>     socket(..., SOCK_CLOEXEC);
>>   #else
>>     socket();
>>     fcntl(..., FD_CLOEXEC);
>>   #endif
> 
> One workaround to that, albeit local to gnulib, would be to define
> something like GNULIB_DEFINED_SOCK_NONBLOCK, and adapt
> tests/test-nonblocking.c to
> # if defined(SOCK_NONBLOCK) && !defined(GNULIB_DEFINED_SOCK_NONBLOCK)
> or, even better, add some configure check to test whether
> socket(.., .. | SOCK_NONBLOCK) works.
> 
> However, the above would not work with 3rd party code doing that check;
> one could think that such code may be broken already, as the underlying
> kernel could not support those extra flags for socket.
> 
>> So let's forget my adjustment and instead I suggest
>> merging this into your change:
>>
>> diff --git a/doc/glibc-functions/accept4.texi 
>> b/doc/glibc-functions/accept4.texi
>> index 20386e9..b4114db 100644
>> --- a/doc/glibc-functions/accept4.texi
>> +++ b/doc/glibc-functions/accept4.texi
>> @@ -16,4 +16,7 @@ programs that spawn child processes.
>>
>>  Portability problems not fixed by Gnulib:
>>  @itemize
>> address@hidden
>> +SOCK_CLOEXEC and SOCK_NONBLOCK may not be defined
>> +as they're also significant to the socket() function.
>>  @end itemize
>> diff --git a/tests/test-accept4.c b/tests/test-accept4.c
>> index b24af0b..5a29680 100644
>> --- a/tests/test-accept4.c
>> +++ b/tests/test-accept4.c
>> @@ -31,6 +31,10 @@ SIGNATURE_CHECK (accept4, int, (int, struct sockaddr *, 
>> socklen_t *, int));
>>
>>  #include "macros.h"
>>
>> +#ifndef SOCK_CLOEXEC
>> +# define SOCK_CLOEXEC 0
>> +#endif
>> +
> 
> I was not unsure about this, but then I noticed we do the same also in
> lib/accept4.c itself, so it will not make things worse (platforms
> without accept4 and SOCK_* flags already have an accept4 implementation
> which basically works like socket).
> 
> Should I merge the above bit in my patch? What about authorship of it?

Done at:
http://git.sv.gnu.org/gitweb/?p=gnulib.git;a=commit;h=f982bc8d

thanks,
Pádraig.