Bitfields and removing/modifying help

[lanman92]

I've been hooking my packets and trying to modify their flags(which are bitfields), but I'm having issues checking if the flag has a value. Here's an example of a log...

Normal:
Movement:  DA   0  674B0C9    -10612.121094    1109.751221  38.010147
Bad:
Movement:  DA   800    674E225  -10612.121094  1109.751221 38.010147

The code I'm using is...

if(mp->flags & 0x800)
{
      mp->flags &= ~0x800;
}

Any help?