Add support for rfc8572 DHCP option encoding.

dhcp/dhcp.go

@@ -40,8 +40,8 @@ const confTemplate = `
 server6:
    plugins:
      - server_id: LL {{ .IntfMacAddr }}
-     {{ if .BootzURL }}
-     - bootz: {{ .BootzURL }}
+     {{ if .BootzURLs }}
+     - bootz: {{ .BootzURLs }}
      {{ end }}
      {{ if .DNSv6 }}
      - DNS: {{ .DNSv6 }}
@@ -53,8 +53,8 @@ server4:
   plugins:
     - lease_time: 3600s
     - server_id: {{ .IntfIPAddr }}
-    {{ if .BootzURL }}
-    - bootz: {{ .BootzURL }}
+    {{ if .BootzURLs }}
+    - bootz: {{ .BootzURLs }}
     {{ end }}
     {{ if .DNSv4 }}
     - DNS: {{ .DNSv4 }}
@@ -77,7 +77,7 @@ type Config struct {
 	Interface  string
 	DNS        []string
 	AddressMap map[string]*Entry
-	BootzURL   string
+	BootzURLs  []string
 }
 
 // Entry represents a dhcp record.
@@ -158,7 +158,7 @@ func generateConfigFile(conf *Config) (string, error) {
 
 	intf, err := net.InterfaceByName(conf.Interface)
 	if err != nil {
-		return "", fmt.Errorf("unknown interface %v", *intf)
+		return "", fmt.Errorf("unknown interface %v: %v", conf.Interface, err)
 	}
 
 	IPv4Addr := getIPv4Address(intf)
@@ -191,15 +191,15 @@ func generateConfigFile(conf *Config) (string, error) {
 		DNSv6       string
 		IPv4Leases  string
 		IPv6Leases  string
-		BootzURL    string
+		BootzURLs   string
 	}{
 		IntfIPAddr:  IPv4Addr.String(),
 		IntfMacAddr: intf.HardwareAddr.String(),
 		DNSv4:       strings.Join(DNSv4, " "),
 		DNSv6:       strings.Join(DNSv6, " "),
 		IPv4Leases:  strings.Join(v4Records, " "),
 		IPv6Leases:  strings.Join(v6Records, " "),
-		BootzURL:    conf.BootzURL,
+		BootzURLs:   strings.Join(conf.BootzURLs, " "),
 	}); err != nil {
 		return "", fmt.Errorf("error generating configuration template: %v", err)
 	}

dhcp/main/dhcp.go

@@ -29,7 +29,7 @@ var (
 	intf    = flag.String("i", "eth7", "Network interface to use for dhcp server.")
 	records = flag.String("records", "4c:5d:3c:ef:de:60,5.78.26.27/16,5.78.0.1;FOX2506P2QT,5::10/64", "List of dhcp records separated by a semi-colon.")
 	dns     = flag.String("dns", "5.38.4.124", "List of dns servers separated by a semi-colon.")
-	bootz   = flag.String("bootz_url", "bootz://dev-mgbl-lnx6.cisco.com:50052/grpc", "Bootz server URL.")
+	bootz   = flag.String("bootz_urls", "bootz://dev-mgbl-lnx6.cisco.com:50052/grpc;bootz://dev-mgbl-lnx2.cisco.com:50052/grpc", "List of Bootz server URLs separated by a semi-colon.")
 )
 
 func main() {
@@ -57,7 +57,7 @@ func main() {
 		Interface:  *intf,
 		DNS:        strings.Split(*dns, ";"),
 		AddressMap: addressMap,
-		BootzURL:   *bootz,
+		BootzURLs:  strings.Split(*bootz, ";"),
 	}
 
 	go func() {

dhcp/plugins/bootz/bootz.go

@@ -16,6 +16,7 @@
 package bootz
 
 import (
+	"encoding/binary"
 	"fmt"
 	"net/url"
 
@@ -44,33 +45,60 @@ var (
 	ztpV6Opt dhcpv6.Option
 )
 
-func parseArgs(args ...string) (*url.URL, error) {
-	if len(args) != 1 {
-		return nil, fmt.Errorf("exactly one argument must be passed to BootZ plugin, got %d", len(args))
+func encodeBootstrapServerList(urls []string) []byte {
+	// From RFC 8572 section 8.3:
+	//
+	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
+	// |       uri-length              |          URI                  |
+	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
+	//
+	// * uri-length: 2 octets long; specifies the length of the URI data.
+	// * URI: URI of the SZTP bootstrap server.
+	b := []byte{}
+	for _, u := range urls {
+		b = binary.BigEndian.AppendUint16(b, uint16(len(u)))
+		b = append(b, []byte(u)...)
 	}
-	return url.Parse(args[0])
+	return b
+}
+
+// Verifies that the passed Bootz servers are valid URLs and returns them as a list of strings.
+func parseArgs(args ...string) ([]string, error) {
+	if len(args) < 1 {
+		return nil, fmt.Errorf("at least one argument must be passed to BootZ plugin, got %d", len(args))
+	}
+	urls := make([]string, len(args))
+	for i, arg := range args {
+		u, err := url.Parse(arg)
+		if err != nil {
+			return nil, err
+		}
+		urls[i] = u.String()
+	}
+	return urls, nil
 }
 
 func setup4(args ...string) (handler.Handler4, error) {
-	url, err := parseArgs(args...)
+	urls, err := parseArgs(args...)
 	if err != nil {
 		return nil, err
 	}
+
 	ztpV4Opt = &dhcpv4.Option{
 		Code:  dhcpv4.GenericOptionCode(OPTION_V4_SZTP_REDIRECT),
-		Value: dhcpv4.String(url.String()),
+		Value: dhcpv4.String(string(encodeBootstrapServerList(urls))),
 	}
 	return handler4, nil
 }
 
 func setup6(args ...string) (handler.Handler6, error) {
-	url, err := parseArgs(args...)
+	urls, err := parseArgs(args...)
 	if err != nil {
 		return nil, err
 	}
 	ztpV6Opt = &dhcpv6.OptionGeneric{
 		OptionCode: dhcpv6.OptionCode(OPTION_V6_SZTP_REDIRECT),
-		OptionData: []byte(url.String()),
+		OptionData: encodeBootstrapServerList(urls),
 	}
 	return handler6, nil
 }