spec/plugins: return interface details and multiple IP addresses to runtime

Updates the spec and plugins to return an array of interfaces and IP details
to the runtime including:

- interface names and MAC addresses configured by the plugin
- whether the interfaces are sandboxed (container/VM) or host (bridge, veth, etc)
- multiple IP addresses configured by IPAM and which interface they
have been assigned to

Returning interface details is useful for runtimes, as well as allowing
more flexible chaining of CNI plugins themselves.  For example, some
meta plugins may need to know the host-side interface to be able to
apply firewall or traffic shaping rules to the container.

plugins/ipam/dhcp/options.go

@@ -40,17 +40,17 @@ func classfulSubnet(sn net.IP) net.IPNet {
 	}
 }
 
-func parseRoutes(opts dhcp4.Options) []types.Route {
+func parseRoutes(opts dhcp4.Options) []*types.Route {
 	// StaticRoutes format: pairs of:
 	// Dest = 4 bytes; Classful IP subnet
 	// Router = 4 bytes; IP address of router
 
-	routes := []types.Route{}
+	routes := []*types.Route{}
 	if opt, ok := opts[dhcp4.OptionStaticRoute]; ok {
 		for len(opt) >= 8 {
 			sn := opt[0:4]
 			r := opt[4:8]
-			rt := types.Route{
+			rt := &types.Route{
 				Dst: classfulSubnet(sn),
 				GW:  r,
 			}
@@ -62,10 +62,10 @@ func parseRoutes(opts dhcp4.Options) []types.Route {
 	return routes
 }
 
-func parseCIDRRoutes(opts dhcp4.Options) []types.Route {
+func parseCIDRRoutes(opts dhcp4.Options) []*types.Route {
 	// See RFC4332 for format (http://tools.ietf.org/html/rfc3442)
 
-	routes := []types.Route{}
+	routes := []*types.Route{}
 	if opt, ok := opts[dhcp4.OptionClasslessRouteFormat]; ok {
 		for len(opt) >= 5 {
 			width := int(opt[0])
@@ -89,7 +89,7 @@ func parseCIDRRoutes(opts dhcp4.Options) []types.Route {
 
 			gw := net.IP(opt[octets+1 : octets+5])
 
-			rt := types.Route{
+			rt := &types.Route{
 				Dst: net.IPNet{
 					IP:   net.IP(sn),
 					Mask: net.CIDRMask(width, 32),