iproute: Make it possible to specify index on link creation

The RTM_NEWLINK message accepts ifi_index non-zero value and lets
creation of links with given index (if it's free, or course). This
functionality is available since linux-v3.5.

This patch makes this API available via ip tool.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
3 files changed