Re: [Qemu-devel] Re: qemu port

[Juergen Lock]

On Thu, Jun 03, 2004 at 12:21:27AM +0000, Bartosz Fabianowski wrote:
> > OK, I've now taken this and the other FreeBSD patches, added a few 
> > small ones of my own and made a port [...]
> 
> Awesome! A port was my original idea and the reason for why I started
> tinkering with QEMU in the first place.
> 
> > - needs to run as root in order to use /dev/tap* networking (why?)
> 
> I haven't looked at your port yet, but my own compilation of QEMU has
> the same problem.  ...

Problem solved: its a redundant(?) uid check in the if_tap module
(btw at least on 4.9 i have to cycle thru the available /dev/tap[0123]
device nodes myself, see patch-bt)

> > - using physical media doesn't work on 4.x hosts (missing
> > DIOCGMEDIASIZE ioctl)
> 
> This is the place where it's actually used:
> 
> if (ioctl(fd, DIOCGMEDIASIZE, (off_t *)&size))
>      size = lseek(fd, 0LL, SEEK_END);
> 
> This ioctl checks whether the total size of the medium can be retrieved
> and thus only succeeds if there is a medium in the drive. So the ioctl
> effectively just checks whether there is a medium. The size is then
> retrieved separately using lseek.
>...

 Heh. :)  No.  ioctl() returns 0 on success not on failure, so
only if the ioctl fails is the size retrieved via lseek (and this
lseek method doesnt work on pyhsical devices, therefore the ioctl.)

        Juergen