Re: [Qemu-devel] [Bug 1814352] Re: SIOCGIFNAME takes a struct ifreq not an integer

[Peter Maydell]

On Wed, 10 Apr 2019 at 01:26, Erik Kline <address@hidden> wrote:
> Sure.  Looking at HEAD, and even the surrounding the lines, I think I
> should have tried STRUCT_short_ifreq instead of STRUCT_int_ifreq, though
> I'm not sure what the real difference would be.

The multiple STRUCT_*_ifreq are working around the fact that
our MK_STRUCT infrastructure can't handle unions. The struct
ifreq is a char array followed by a union whose members are
various different types. You should use the STRUCT_*_ifreq
corresponding to whatever type the union field used by this
particular ioctl is. For SIOCGIFNAME the ifr_ifindex is read,
and that's an int, so you want STRUCT_int_ifreq. (If you used
the 'short' version by mistake this would probably break for the
case of big-endian guest and little-endian host or vice-versa
because we'd swap the wrong amount of data.)

thanks
-- PMM