[patch] tcpdump/libpcap pcap_platform_finddevs broken

[mjw]

pcap_platform_finddevs implementation modifies internal libpcap structures when adding devices to the device list. However, libpcap expects the device list to be ordered in a subtle way: the first device in the list should not be a loopback device.

When tcpdump was run on my machine without any arguments, the loopback device ended up as the first device in the list, which caused tcpdump to exit immediately complaining that there were no suitable devices found.

This patch adds devices to the device list using pcap_add_if() to ensure the device list is suitably ordered. tcpdump can now be executed without any arguments to make it listen on a default device.

I have also added suitable defines to that "tcpdump -D" will now show the list of available devices.

[axeld]

How could I miss pcap_add_if()? I was already wondering what I was doing back there :-) It definitely worked when I tested it, though; apparently the order of the interfaces might have differed in my configuration. I made some minor changes to your patch, and applied it in hrev25601. Thanks a lot!