NetworkInterface objects disappear on Mac computers

Question

In our Java 6 program, we are trying to get the Mac address of all the network interfaces on the machine. It calls NetworkInterface.getNetworkInterfaces() to get a list of them. On Windows with the Sun JRE, everything works fine. However, on Mac computers, this method only returns instances of NetworkInterface for interfaces that are active. If the ethernet cable or wireless card are disconnected, the interfaces are no longer returned.
Why would it do this? Running ifconfig still returns all of the interfaces regardless of their state. If I only wanted the active interfaces, I could call isUp() on the returned NetworkInterface instances to find and discard the inactive ones. However, the Apple JRE developers seem to have predetermined that we would never want them.
Is there any way to get the inactive interfaces to show up? I could get it to run ifconfig and parse out the mac addresses, but I don't want users to be able to replace it with a dummy program and fool our application into thinking a nonexistent interface is there.

Answer 1

it's hard to explain every situation but i created an example and as i was doing it i thing i know what's happening but still not sure why.
here is the file i made
download
what i did
1. made a symbol to be used as a mask (the symbol is just a rectangle with a black and white pattern fill)
2. drew a blue rectangle
3. made an opacity mask for the rectangle and placed in the masking symbol
- so far that works as expected. if i make a pdf or print at this point it show up as it should
if i do the following things, the pdf/print goes wrong
1. if i duplicate the blue rectangle containing the masking symbol, the front most blue rectangle does not show up in the pdf or print
2. if i insert an instance of the masking symbol, it too does not show up in the pdf
3. if the masking symbol instance is the bottom object, all the objects containing the mask show up as the masking symbol plus i get an instance of the mask in the bottom left corner of the document
4. if i make a symbol out of the blue squares then i can duplicate the symbol without it disappearing, but all symbols disappear in the pdf if an instance of the mask exist in the bottom most layer of the document.
you can test this situations by changing the layer order of the objects in my document and looking at the icon preview.
it seems like if i use a symbol as a mask, instances of that symbol can't exist in the same space.
i know some of you may ask "why do you want to do this?"
i deal with very complicated patterns and clients want to see them rendered out in different materials with shadows etc.