Routes to neighbour subnets should be provided via DHCP

[Alexey I. Froloff]

As RFC3442 says:

   In some cases more than one IP subnet may be configured on a link.
   In such cases, a host whose IP address is in one IP subnet in the
   link could communicate directly with a host whose IP address is in a
   different IP subnet on the same link. In cases where a client is
   being assigned an IP address on an IP subnet on such a link, for each
   IP subnet in the link other than the IP subnet on which the client
   has been assigned the DHCP server MAY be configured to specify a
   router IP address of 0.0.0.0.

When network contains more that one IPv4 subnets, routes to these subnets should also be reported in 'classless-static-routes' DHCP option.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/125043

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/125043
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=6dce817c7c210b0c0862463384221ba5730cb8f3
Submitter: Jenkins
Branch: master

commit 6dce817c7c210b0c0862463384221ba5730cb8f3
Author: Alexey I. Froloff <email address hidden>
Date: Tue Sep 30 17:01:15 2014 +0400

    Provide routes for neighbor IPv4 subnets

    Network may contain several Subnets. In this case all these subnets are
    accessible via same link and two VMs with addresses from different
    Subnets may talk to each other directly, bypassing default router. For
    this to work, "neighbour Subnets" should have entry in VM's routing
    tables. RFC3442 describes this situation:

       In some cases more than one IP subnet may be configured on a link.
       In such cases, a host whose IP address is in one IP subnet in the
       link could communicate directly with a host whose IP address is in a
       different IP subnet on the same link. In cases where a client is
       being assigned an IP address on an IP subnet on such a link, for each
       IP subnet in the link other than the IP subnet on which the client
       has been assigned the DHCP server MAY be configured to specify a
       router IP address of 0.0.0.0.

    When network contains more that one IPv4 subnets, report these subnets
    in 'classless-static-routes' DHCP option.

    DocImpact

    Change-Id: Ifcf1d99e0f0136bf52b8d13675b7ccfd48005fab
    Closes-Bug: #1372885

[OpenStack Infra (hudson-openstack)]

Change abandoned by Quan Tian (<email address hidden>) on branch: master
Review: https://review.openstack.org/352530