The IP Total Length field includes the IP header and data.  Make sure it
is valid and does not exceed the Ethernet payload size.
Reported-by: N朱东海(启路) <donghai.zdh@alibaba-inc.com>
Reviewed-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>