rtems_bsdnet_fdToSocket()

[Chris Johns]

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:

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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