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/host-local/backend/allocator/config.go

@@ -42,31 +42,43 @@ type IPAMArgs struct {
 }
 
 type Net struct {
-	Name string      `json:"name"`
-	IPAM *IPAMConfig `json:"ipam"`
+	Name       string      `json:"name"`
+	CNIVersion string      `json:"cniVersion"`
+	IPAM       *IPAMConfig `json:"ipam"`
 }
 
 // NewIPAMConfig creates a NetworkConfig from the given network name.
-func LoadIPAMConfig(bytes []byte, args string) (*IPAMConfig, error) {
+func LoadIPAMConfig(bytes []byte, args string) (*IPAMConfig, string, error) {
 	n := Net{}
 	if err := json.Unmarshal(bytes, &n); err != nil {
-		return nil, err
+		return nil, "", err
 	}
 
 	if args != "" {
 		n.IPAM.Args = &IPAMArgs{}
 		err := types.LoadArgs(args, n.IPAM.Args)
 		if err != nil {
-			return nil, err
+			return nil, "", err
 		}
 	}
 
 	if n.IPAM == nil {
-		return nil, fmt.Errorf("IPAM config missing 'ipam' key")
+		return nil, "", fmt.Errorf("IPAM config missing 'ipam' key")
 	}
 
 	// Copy net name into IPAM so not to drag Net struct around
 	n.IPAM.Name = n.Name
 
-	return n.IPAM, nil
+	return n.IPAM, n.CNIVersion, nil
+}
+
+func convertRoutesToCurrent(routes []types.Route) []*types.Route {
+	var currentRoutes []*types.Route
+	for _, r := range routes {
+		currentRoutes = append(currentRoutes, &types.Route{
+			Dst: r.Dst,
+			GW:  r.GW,
+		})
+	}
+	return currentRoutes
 }