libnetlink: reduce size of message sent to kernel

Fixes commit 246f57c4086d99fa ("ip link: Add support for kernel
side filtering").

This patch reduce the size of message sent to kernel space. Before this
patch, for command: 'ip link show', we will sent 1056 bytes. With this
patch, we only need to send 40 bytes.

Signed-off-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
1 file changed