LinkByName: using IFLA_ALT_IFNAME incorrectly and thus without effect

[thediveo]

The Linux kernel's rtnl_dev_get implementation prefers IFLA_IFNAME over IFLA_ALT_IFNAME (6.1, but probably for a long time). LinkByName(name) always produces an IFLA_IFNAME in its query, and adds an IFLA_ALT_IFNAME in case the specified name is longer than 15 bytes. However, based on the kernel's rtnl_dev_get implementation, this is without effect.

LinkByName needs to produce IFLA_ALT_IFNAME in lieu of IFLA_IFNAME when the specified name is longer than 15 bytes.