datasource: use opaque object instead of string

Rather than serializing the network config into a string and then later
deserializing it, just pass the object through directly.

network/digitalocean.go

@@ -15,7 +15,6 @@
 package network
 
 import (
-	"encoding/json"
 	"fmt"
 	"log"
 	"net"
@@ -23,26 +22,18 @@ import (
 	"github.com/coreos/coreos-cloudinit/datasource/metadata/digitalocean"
 )
 
-func ProcessDigitalOceanNetconf(config []byte) ([]InterfaceGenerator, error) {
+func ProcessDigitalOceanNetconf(config digitalocean.Metadata) ([]InterfaceGenerator, error) {
 	log.Println("Processing DigitalOcean network config")
-	if len(config) == 0 {
-		return nil, nil
-	}
-
-	var cfg digitalocean.Metadata
-	if err := json.Unmarshal(config, &cfg); err != nil {
-		return nil, err
-	}
 
 	log.Println("Parsing nameservers")
-	nameservers, err := parseNameservers(cfg.DNS)
+	nameservers, err := parseNameservers(config.DNS)
 	if err != nil {
 		return nil, err
 	}
 	log.Printf("Parsed %d nameservers\n", len(nameservers))
 
 	log.Println("Parsing interfaces")
-	generators, err := parseInterfaces(cfg.Interfaces, nameservers)
+	generators, err := parseInterfaces(config.Interfaces, nameservers)
 	if err != nil {
 		return nil, err
 	}
@@ -52,9 +43,9 @@ func ProcessDigitalOceanNetconf(config []byte) ([]InterfaceGenerator, error) {
 	return generators, nil
 }
 
-func parseNameservers(cfg digitalocean.DNS) ([]net.IP, error) {
-	nameservers := make([]net.IP, 0, len(cfg.Nameservers))
-	for _, ns := range cfg.Nameservers {
+func parseNameservers(config digitalocean.DNS) ([]net.IP, error) {
+	nameservers := make([]net.IP, 0, len(config.Nameservers))
+	for _, ns := range config.Nameservers {
 		if ip := net.ParseIP(ns); ip == nil {
 			return nil, fmt.Errorf("could not parse %q as nameserver IP address", ns)
 		} else {
@@ -64,16 +55,16 @@ func parseNameservers(cfg digitalocean.DNS) ([]net.IP, error) {
 	return nameservers, nil
 }
 
-func parseInterfaces(cfg digitalocean.Interfaces, nameservers []net.IP) ([]InterfaceGenerator, error) {
-	generators := make([]InterfaceGenerator, 0, len(cfg.Public)+len(cfg.Private))
-	for _, iface := range cfg.Public {
+func parseInterfaces(config digitalocean.Interfaces, nameservers []net.IP) ([]InterfaceGenerator, error) {
+	generators := make([]InterfaceGenerator, 0, len(config.Public)+len(config.Private))
+	for _, iface := range config.Public {
 		if generator, err := parseInterface(iface, nameservers, true); err == nil {
 			generators = append(generators, &physicalInterface{*generator})
 		} else {
 			return nil, err
 		}
 	}
-	for _, iface := range cfg.Private {
+	for _, iface := range config.Private {
 		if generator, err := parseInterface(iface, []net.IP{}, false); err == nil {
 			generators = append(generators, &physicalInterface{*generator})
 		} else {

network/digitalocean_test.go

@@ -358,27 +358,37 @@ func TestParseInterfaces(t *testing.T) {
 
 func TestProcessDigitalOceanNetconf(t *testing.T) {
 	for _, tt := range []struct {
-		cfg    string
+		cfg    digitalocean.Metadata
 		ifaces []InterfaceGenerator
 		err    error
 	}{
 		{
-			cfg: ``,
-		},
-		{
-			cfg: `{"dns":{"nameservers":["bad"]}}`,
+			cfg: digitalocean.Metadata{
+				DNS: digitalocean.DNS{
+					Nameservers: []string{"bad"},
+				},
+			},
 			err: errors.New("could not parse \"bad\" as nameserver IP address"),
 		},
 		{
-			cfg: `{"interfaces":{"public":[{"ipv4":{"ip_address":"bad"}}]}}`,
+			cfg: digitalocean.Metadata{
+				Interfaces: digitalocean.Interfaces{
+					Public: []digitalocean.Interface{
+						digitalocean.Interface{
+							IPv4: &digitalocean.Address{
+								IPAddress: "bad",
+							},
+						},
+					},
+				},
+			},
 			err: errors.New("could not parse \"bad\" as IPv4 address"),
 		},
 		{
-			cfg:    `{}`,
 			ifaces: []InterfaceGenerator{},
 		},
 	} {
-		ifaces, err := ProcessDigitalOceanNetconf([]byte(tt.cfg))
+		ifaces, err := ProcessDigitalOceanNetconf(tt.cfg)
 		if !errorsEqual(tt.err, err) {
 			t.Fatalf("bad error (%q): want %q, got %q", tt.cfg, tt.err, err)
 		}

network/packet.go

@@ -15,18 +15,12 @@
 package network
 
 import (
-	"encoding/json"
 	"net"
 
 	"github.com/coreos/coreos-cloudinit/datasource/metadata/packet"
 )
 
-func ProcessPacketNetconf(config []byte) ([]InterfaceGenerator, error) {
-	var netdata packet.NetworkData
-	if err := json.Unmarshal(config, &netdata); err != nil {
-		return nil, err
-	}
-
+func ProcessPacketNetconf(netdata packet.NetworkData) ([]InterfaceGenerator, error) {
 	var nameservers []net.IP
 	if netdata.DNS != nil {
 		nameservers = netdata.DNS