This patch allows modification of link attributes by the interface name,
avoids the requirement of translating a name to an ifindex first, and
provides better atomicity to userspace.  It works by setting the ifindex
to a negative number and provide the interface name via the IFLA_IFNAME
TLV and let the kernel lookup the device by name instead of ifindex. Changing
the interface name will not work using this method because IFLA_IFNAME also
transports the new interface name.  The patch also fixes a possible source for
bugs if IFNAMSIZ is ever changed to a number not aligned to RTA_ALIGNTO.
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>