From: Vincent Li <redacted>
Date: Tue, 24 Sep 2013 14:09:48 -0700

the reason for this patch is that we have a multi blade cluster platform 
sharing 'floating management ip' and also that each blade has its own 
management ip on the management interface, so whichever blade in the
cluster becomes primary blade, the 'floating mangaement ip' follows it,
and we want any of our traffic originated from the primary blade source from
the 'floating management ip' for consistency. but in this case, since the local
blade management ip is always the primary ip on the mangaement interface and 
'floating management ip' is always secondary, kernel always choose the primary
ip as source ip address. thus we would like to add the flexibility in kernel to
allow us to specify which ip to be primary or secondary.

You have the flexibility already.

You can specify a specific source address ot use in routes.