Add management plugin that doesn't need IPAM

Author: maxmoehl

plugins/management/plugin.go

@@ -0,0 +1,139 @@
+// SPDX-FileCopyrightText: 2025 SAP SE or an SAP affiliate company and IronCore contributors
+// SPDX-License-Identifier: MIT
+
+package management
+
+import (
+	"net"
+	"time"
+
+	"github.com/ironcore-dev/fedhcp/internal/printer"
+
+	"github.com/coredhcp/coredhcp/handler"
+	"github.com/coredhcp/coredhcp/logger"
+	"github.com/coredhcp/coredhcp/plugins"
+	"github.com/insomniacslk/dhcp/dhcpv6"
+	"github.com/insomniacslk/dhcp/iana"
+	"github.com/mdlayher/netx/eui64"
+)
+
+var log = logger.GetLogger("plugins/managament")
+
+var Plugin = plugins.Plugin{
+	Name:   "management",
+	Setup6: setup6,
+}
+
+const (
+	preferredLifeTime = 24 * time.Hour
+	validLifeTime     = 24 * time.Hour
+)
+
+func setup6(_ ...string) (handler.Handler6, error) {
+	return handler6, nil
+}
+
+func handler6(req, resp dhcpv6.DHCPv6) (dhcpv6.DHCPv6, bool) {
+	if req == nil {
+		log.Error("Received nil DHCPv6 request")
+		return nil, true
+	}
+
+	printer.VerboseRequest(req, log, printer.IPv6)
+	defer printer.VerboseResponse(req, resp, log, printer.IPv6)
+
+	if !req.IsRelay() {
+		log.Printf("Received non-relay DHCPv6 request, dropping.")
+		return nil, true
+	}
+
+	relayMsg := req.(*dhcpv6.RelayMessage)
+
+	if len(relayMsg.LinkAddr) != 16 {
+		log.Errorf("Received malformed link address of length %d, dropping.", len(relayMsg.LinkAddr))
+		return nil, true
+	}
+
+	mac, err := getMAC(relayMsg)
+	if err != nil {
+		log.Errorf("Failed to obtain MAC, dropping: %s", err.Error())
+		return nil, true
+	}
+
+	if len(mac) != 6 {
+		log.Errorf("Received malformed MAC address of length %d, dropping.", len(mac))
+		return nil, true
+	}
+
+	ipaddr := make(net.IP, len(relayMsg.LinkAddr))
+	copy(ipaddr, relayMsg.LinkAddr)
+
+	feEUI64(ipaddr, mac)
+
+	msg, err := req.GetInnerMessage()
+	if err != nil {
+		log.Errorf("BUG: could not decapsulate: %v", err)
+		return nil, true
+	}
+
+	if msg.Options.OneIANA() == nil {
+		log.Debug("No address requested")
+		return resp, false
+	}
+
+	iana := &dhcpv6.OptIANA{
+		IaId: msg.Options.OneIANA().IaId,
+		Options: dhcpv6.IdentityOptions{
+			Options: []dhcpv6.Option{
+				&dhcpv6.OptIAAddress{
+					IPv6Addr:          ipaddr,
+					PreferredLifetime: preferredLifeTime,
+					ValidLifetime:     validLifeTime,
+				},
+			},
+		},
+	}
+	resp.AddOption(iana)
+	log.Infof("Client %s, added option IA address %s", mac.String(), iana.String())
+
+	return resp, false
+}
+
+func getMAC(relayMsg *dhcpv6.RelayMessage) (net.HardwareAddr, error) {
+	hwType, mac := relayMsg.Options.ClientLinkLayerAddress()
+	if hwType == iana.HWTypeEthernet {
+		return mac, nil
+	}
+
+	log.Infof("failed to retrieve client link layer address, falling back to EUI64 (%s)", relayMsg.PeerAddr.String())
+	_, mac, err := eui64.ParseIP(relayMsg.PeerAddr)
+	if err != nil {
+		log.Errorf("Could not parse peer address: %s", err)
+		return nil, err
+	}
+
+	return mac, nil
+}
+
+// feEUI64 adjusts the given IP address in-place by overwriting the host part
+// using an adaptation of the EUI64 scheme. The two middle bytes are set to 0xfe
+// and the first and last three bytes consist of the corresponding first and
+// last three bytes of the MAC address. Any pre-existing host bits will be
+// overwritten.
+//
+// Example:
+//
+//	ipaddr=2001:db8::
+//	mac=01:23:45:67:89:ab
+//	result=2001:db8::0123:45fe:fe67:89ab
+func feEUI64(ipaddr net.IP, mac net.HardwareAddr) {
+	// 128 bit == 16 byte, 0-7 are left as-is, 8-15 are modified.
+	// 11, 12 get set to 0xfe (EUI64 would use 0xff 0xfe)
+	ipaddr[11] = 0xfe
+	ipaddr[12] = 0xfe
+
+	copy(ipaddr[8:11], mac[0:3])
+	copy(ipaddr[13:16], mac[3:6])
+	// TODO: should we flip the 7th bit as EUI64 does it? To me that is just
+	// confusing so I won't do it for now.
+}

plugins/management/plugin_test.go

@@ -0,0 +1,49 @@
+// SPDX-FileCopyrightText: 2025 SAP SE or an SAP affiliate company and IronCore contributors
+// SPDX-License-Identifier: MIT
+
+package management
+
+import (
+	"fmt"
+	"net"
+	"slices"
+	"testing"
+)
+
+func TestFeEUI64(t *testing.T) {
+	tests := []struct {
+		ip   net.IP
+		mac  net.HardwareAddr
+		want net.IP
+	}{{
+		net.ParseIP("2001:db8::"),
+		parseMAC("aa:bb:cc:dd:ee:ff"),
+		net.ParseIP("2001:db8::aabb:ccfe:fedd:eeff"),
+	}, {
+		net.ParseIP("2001:db8::"),
+		parseMAC("01:23:45:67:89:ab"),
+		net.ParseIP("2001:db8::0123:45fe:fe67:89ab"),
+	}, {
+		net.ParseIP("2001:db8::dead:beef"),
+		parseMAC("aa:bb:cc:dd:ee:ff"),
+		net.ParseIP("2001:db8::aabb:ccfe:fedd:eeff"),
+	}}
+
+	for ti, tt := range tests {
+		t.Run(fmt.Sprintf("#%d", ti), func(t *testing.T) {
+			feEUI64(tt.ip, tt.mac)
+			if !slices.Equal(tt.ip, tt.want) {
+				t.Errorf("got=%s != want=%s", tt.ip.String(), tt.want.String())
+			}
+		})
+	}
+}
+
+func parseMAC(s string) net.HardwareAddr {
+	a, err := net.ParseMAC(s)
+	if err != nil {
+		panic(err.Error())
+	}
+
+	return a
+}