ipv6: Don't create clones of host routes.
ipv6: Don't create clones of host routes.

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=29252
Addresses https://bugzilla.kernel.org/show_bug.cgi?id=30462

In commit d80bc0fd262ef840ed4e82593ad6416fa1ba3fc4 ("ipv6: Always
clone offlink routes.") we forced the kernel to always clone offlink
routes.

The reason we do that is to make sure we never bind an inetpeer to a
prefixed route.

The logic turned on here has existed in the tree for many years,
but was always off due to a protecting CPP define.  So perhaps
it's no surprise that there is a logic bug here.

The problem is that we canot clone a route that is already a
host route (ie. has DST_HOST set).  Because if we do, an identical
entry already exists in the routing tree and therefore the
ip6_rt_ins() call is going to fail.

This sets off a series of failures and high cpu usage, because when
ip6_rt_ins() fails we loop retrying this operation a few times in
order to handle a race between two threads trying to clone and insert
the same host route at the same time.

Fix this by simply using the route as-is when DST_HOST is set.

Reported-by: bee20638eef97e5b5614ed172b3372271af9f5d3@ac.auone-net.jp
Reported-by: Ernst Sjöstrand <19fc1fb05bf28fc9a8a1be50d7f1c695114e7ea6@gmail.com>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs