rtems_bsdnet_fdToSocket()

[Till Straumann]

Chris Johns wrote:
> Till Straumann wrote:
>> IMHO rtems_bsdnet_fdToSocket() doesn't
>> verify thoroughly enough that the file
>> descriptor passed in is really a socket.
>>
>> If you e.g., try getsockname() on a fd
>> that was opened on a termios device then
>> a crash may result.
>>
>> I propose to let rtems_bsdnet_fdToSocket()
>> test not only that iop->data1 is NULL but
>> to add an additional test.
>>
>> Either
>> 1) add a new flag LIBIO_FLAGS_ISSOCK
>>    which is set by rtems_bsdnet_makeFdForSocket()
>>    and tested by rtems_bsdnet_fdToSocket()
>> 1a) instead of one flag we could use a few
>>    more bits and create a LIBIO_FLAGS_IOP_TYPE
>>    bitmask (in case the need for other special
>>    cases besides sockets arises in the future).
>>    The test would then look like
>>
>>    if ( LIBIO_FLAGS_IOP_TYPE(iop->flags) != LIBIO_FLAGS_IOP_TYPE_SOCK 
>> ) {
>>        errno = ENOTSOCK;
>>        return NULL;
>>    }
>>
>>    Sidenote: IMO, if data1 == NULL then errno should
>>              also be ENOTSOCK instead of EBADF.
>>
>
> The LIBIO flags do not describe the fd rather they deal with what you 
> can do. I do not like the type of fd being added to the flags.
>
> NetBSD has a type field in the fp referenced by the fd:
Problemo being that libio has no such thing. It has
absolutely no knowledge about what is attached to
'data', 'data1', 'file-info'.

Where do you see an equivalent to fp_type in the iop
or how would you propose that, given a iop, the
code can figure out what kind of object
is attached to e.g., 'data1' ?

Do you like testing the 'handlers' better?

T.
>
> int
> getsock(struct filedesc *fdp, int fdes, struct file **fpp)
> {
>         struct file     *fp;
>
>         if ((fp = fd_getfile(fdp, fdes)) == NULL)
>                 return (EBADF);
>
>         FILE_USE(fp);
>
>         if (fp->f_type != DTYPE_SOCKET) {
>                 FILE_UNUSE(fp, NULL);
>                 return (ENOTSOCK);
>         }
>         *fpp = fp;
>         return (0);
> }
>
> I would prefer this.
>
> Regards
> Chris
>
>>
>> 2) alternatively, rtems_bsdnet_fdToSocket() could
>>    test if iop->handlers == socket_handlers.
>>
>>    socket_handlers would then have to become a globally
>>    visible symbol (right now a static variable).
>>
>>    Unfortunately, this would introduce some asymmetry
>>    (fdToSocket() refers to global symbol, makeFdForSocket
>>    gets pointer to handlers passed in).
>>
>> If nobody objects or has a better idea then I would
>> implement 1a), create a PR and commit to 4.9 and HEAD.
>>
>> RFC
>> -Till
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