Add prefix delegation configuration for onmetal (#213)

* Make prefix delegation length configurable

* Update readme

* Fix some lint findings

README.md

@@ -48,9 +48,14 @@ Further, as a second parameter, a comma-separated list of subnet names shall be
 - depends on [IPAM operator](https://github.com/ironcore-dev/ipam)
 
 ## OnMetal
-The OnMetal plugin leases a [non temporary IPv6 address](https://datatracker.ietf.org/doc/html/rfc8415#section-6.2) to an in-band client, based on the algorithm described above.
+The OnMetal plugin leases a [non temporary IPv6 address](https://datatracker.ietf.org/doc/html/rfc8415#section-6.2) to an in-band client, based on the algorithm described above. Additionally, when requested from the client, a prefix delegation with preconfigured length is leased. Currently multiple prefix delegations are not supported, client prefix delegation length proposals are ignored completely. The prefix delegation length should be in the range 1 <= length <= 127.
 ### Configuration
-No configuration is needed
+The onmetal configuration consists of the prefix delegation length only.
+Providing the length in `onmetal_config.yaml` goes as follows:
+```yaml
+prefixDelegation:
+  length: 64
+```
 ### Notes
 - supports only IPv6
 - IPv6 relays are mandatory

example/config.yaml

@@ -12,7 +12,7 @@ server6:
         # add leased IPs to ironcore's IPAM
         - ipam: ipam-ns ipam-subnet1,ipam-subnet2,some-other-subnet
         # lease IPs based on /127 subnets coming from relays running on the switches
-        - onmetal:
+        - onmetal: onmetal_config.yaml
         # announce DNS servers per DHCP
         - dns: 2001:4860:4860::6464 2001:4860:4860::64
         # implement (i)PXE boot

example/onmetal_config.yaml

@@ -0,0 +1,2 @@
+prefixDelegation:
+    length: 64

internal/api/onmetal_config.go

@@ -0,0 +1,12 @@
+// SPDX-FileCopyrightText: 2023 SAP SE or an SAP affiliate company and IronCore contributors
+// SPDX-License-Identifier: MIT
+
+package api
+
+type PrefixDelegation struct {
+	Length int `yaml:"length"`
+}
+
+type OnMetalConfig struct {
+	PrefixDelegation PrefixDelegation `yaml:"prefixDelegation"`
+}

plugins/onmetal/plugin.go

@@ -6,8 +6,12 @@ package onmetal
 import (
 	"fmt"
 	"net"
+	"os"
 	"time"
 
+	"github.com/ironcore-dev/fedhcp/internal/api"
+	"gopkg.in/yaml.v3"
+
 	"github.com/coredhcp/coredhcp/handler"
 	"github.com/coredhcp/coredhcp/logger"
 	"github.com/coredhcp/coredhcp/plugins"
@@ -21,19 +25,52 @@ var Plugin = plugins.Plugin{
 	Setup6: setup6,
 }
 
-var mask80 = net.CIDRMask(prefixLength, 128)
+var prefixLength int
 
 const (
-	preferredLifeTime = 24 * time.Hour
-	validLifeTime     = 24 * time.Hour
-	prefixLength      = 80
+	preferredLifeTime         = 24 * time.Hour
+	validLifeTime             = 24 * time.Hour
+	prefixDelegationLengthMin = 1
+	prefixDelegationLengthMax = 127
 )
 
+// args[0] = path to config file
+func parseArgs(args ...string) (string, error) {
+	if len(args) != 1 {
+		return "", fmt.Errorf("exactly one argument must be passed to the onmetal plugin, got %d", len(args))
+	}
+	return args[0], nil
+}
+
+func loadConfig(args ...string) (*api.OnMetalConfig, error) {
+	path, err := parseArgs(args...)
+	if err != nil {
+		return nil, fmt.Errorf("invalid configuration: %v", err)
+	}
+
+	log.Debugf("Reading metal config file %s", path)
+	configData, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read config file: %v", err)
+	}
+
+	config := &api.OnMetalConfig{}
+	if err = yaml.Unmarshal(configData, config); err != nil {
+		return nil, fmt.Errorf("failed to parse config file: %v", err)
+	}
+	return config, nil
+}
+
 func setup6(args ...string) (handler.Handler6, error) {
-	if len(args) != 0 {
-		return nil, fmt.Errorf("no arguments expected, got %d", len(args))
+	onMetalConfig, err := loadConfig(args...)
+	if err != nil {
+		return nil, err
+	}
+
+	prefixLength = onMetalConfig.PrefixDelegation.Length
+	if prefixLength < prefixDelegationLengthMin || prefixLength > prefixDelegationLengthMax {
+		return nil, fmt.Errorf("invalid prefix length: %d", prefixLength)
 	}
-	log.Printf("loaded onmetal plugin for DHCPv6.")
 
 	return handler6, nil
 }
@@ -79,6 +116,7 @@ func handler6(req, resp dhcpv6.DHCPv6) (dhcpv6.DHCPv6, bool) {
 	optIAPD := m.Options.OneIAPD()
 	T1 := preferredLifeTime
 	T2 := validLifeTime
+	var mask80 = net.CIDRMask(prefixLength, 128)
 
 	if optIAPD != nil {
 		if optIAPD.T1 != 0 {

plugins/onmetal/plugin_test.go

@@ -5,8 +5,12 @@ package onmetal
 
 import (
 	"net"
+	"os"
 	"testing"
 
+	"github.com/ironcore-dev/fedhcp/internal/api"
+	"gopkg.in/yaml.v3"
+
 	"github.com/insomniacslk/dhcp/dhcpv6"
 )
 
@@ -17,23 +21,46 @@ const (
 )
 
 var (
-	expectedIPAddress6 = net.IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2}
-	expectedIAID       = [4]byte{1, 2, 3, 4}
-	expectedPrefix     = "2001:db8:1111:2222:3333::/80"
+	expectedIAID = [4]byte{1, 2, 3, 4}
 )
 
 func Init6() {
-	_, err := setup6()
+	data := api.OnMetalConfig{
+		PrefixDelegation: api.PrefixDelegation{
+			Length: 80,
+		},
+	}
+
+	configData, _ := yaml.Marshal(data)
+
+	file, _ := os.CreateTemp("", "config.yaml")
+	defer func() {
+		_ = file.Close()
+		_ = os.Remove(file.Name())
+	}()
+	_ = os.WriteFile(file.Name(), configData, 0644)
+
+	_, err := setup6(file.Name())
 	if err != nil {
 		log.Fatal(err)
 	}
 }
 
 /* parametrization */
 func TestWrongNumberArgs(t *testing.T) {
-	_, err := setup6("not-needed-arg")
+	_, err := setup6()
 	if err == nil {
-		t.Fatal("no error occurred when providing wrong number of args (1), but it should have")
+		t.Fatal("no error occurred when not providing a configuration file path, but it should have")
+	}
+
+	_, err = setup6("non-existing.yaml")
+	if err == nil {
+		t.Fatal("no error occurred when providing non existing configuration path, but it should have")
+	}
+
+	_, err = setup6("foo", "bar")
+	if err == nil {
+		t.Fatal("no error occurred when providing wrong number of args (2), but it should have")
 	}
 }
 
@@ -91,6 +118,7 @@ func TestIPAddressRequested6(t *testing.T) {
 		t.Errorf("expected IAID %d, got %d", expectedIAID, iana.IaId)
 	}
 
+	expectedIPAddress6 := net.IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2}
 	if !addr.Equal(expectedIPAddress6) {
 		t.Errorf("expected IPv6 address %v, got %v", expectedIPAddress6, iana.Options.OneAddress().IPv6Addr)
 	}
@@ -217,6 +245,7 @@ func TestPrefixDelegationRequested6(t *testing.T) {
 		t.Errorf("expected IAID %d, got %d", expectedIAID, iapd.IaId)
 	}
 
+	expectedPrefix := "2001:db8:1111:2222:3333::/80"
 	if pref.String() != expectedPrefix {
 		t.Errorf("expected prefix %v, got %v", expectedPrefix, pref)
 	}
@@ -257,3 +286,26 @@ func TestPrefixDelegationNotRequested6(t *testing.T) {
 		t.Fatalf("Expected %d IAPD option, got %d: %v", optionDisabled, len(opts), opts)
 	}
 }
+
+func TestPrefixDelegationNotRequested7(t *testing.T) {
+	prefixDelegationLengthOutOfBounds := 128
+	data := api.OnMetalConfig{
+		PrefixDelegation: api.PrefixDelegation{
+			Length: prefixDelegationLengthOutOfBounds,
+		},
+	}
+
+	configData, _ := yaml.Marshal(data)
+
+	file, _ := os.CreateTemp("", "config.yaml")
+	defer func() {
+		_ = file.Close()
+		_ = os.Remove(file.Name())
+	}()
+	_ = os.WriteFile(file.Name(), configData, 0644)
+
+	_, err := setup6(file.Name())
+	if err == nil {
+		t.Fatal("no error occurred when providing wrong prefix delegation length, but it should have")
+	}
+}