Implement zone multicast

atalk/strings.go

@@ -0,0 +1,102 @@
+/*
+   Copyright 2024 Josh Deprez
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package atalk
+
+import (
+	"math/bits"
+
+	"github.com/sfiera/multitalk/pkg/ethernet"
+)
+
+// Inside AppleTalk, appendix D
+var toUpperMap = []byte{
+	// The alphabet
+	0x61: 0x41,
+	0x62: 0x42,
+	0x63: 0x43,
+	0x64: 0x44,
+	0x65: 0x45,
+	0x66: 0x46,
+	0x67: 0x47,
+	0x68: 0x48,
+	0x69: 0x49,
+	0x6A: 0x4A,
+	0x6B: 0x4B,
+	0x6C: 0x4C,
+	0x6D: 0x4D,
+	0x6E: 0x4E,
+	0x6F: 0x4F,
+	0x70: 0x50,
+	0x71: 0x51,
+	0x72: 0x52,
+	0x73: 0x53,
+	0x74: 0x54,
+	0x75: 0x55,
+	0x76: 0x56,
+	0x77: 0x57,
+	0x78: 0x58,
+	0x79: 0x59,
+	0x7A: 0x5A,
+
+	// Letters with diacritics, etc
+	0x88: 0xCB,
+	0x8A: 0x80,
+	0x8B: 0xCC,
+	0x8C: 0x81,
+	0x8D: 0x82,
+	0x8E: 0x83,
+	0x96: 0x84,
+	0x9A: 0x85,
+	0x9B: 0xCD,
+	0x9F: 0x86,
+	0xBE: 0xAE,
+	0xBF: 0xAF,
+	0xCF: 0xCE,
+}
+
+func Checksum(s string) uint16 {
+	// Inside AppleTalk, pp 4-17 and pp 8-18
+	var cksum uint16
+	for _, b := range []byte(s) {
+		cksum += uint16(b)
+		cksum = bits.RotateLeft16(cksum, -1)
+	}
+	if cksum == 0 {
+		cksum = 0xFFFF
+	}
+	return cksum
+}
+
+func ToUpper(s string) string {
+	// Inside Appletalk, appendix D
+	sb := []byte(s)
+	out := make([]byte, len(sb))
+	for i, b := range sb {
+		if u := toUpperMap[b]; u != 0 {
+			out[i] = u
+		} else {
+			out[i] = b
+		}
+	}
+	return string(out)
+}
+
+func MulticastAddr(zone string) ethernet.Addr {
+	// Inside AppleTalk, pp 3-10 and pp 8-18
+	h := Checksum(ToUpper(zone))
+	return ethernet.Addr{0x09, 0x00, 0x07, 0x00, 0x00, byte(h % 0xFD)}
+}

atalk/zip/getnetinfo.go

@@ -57,9 +57,9 @@ type GetNetInfoReplyPacket struct {
 	// DDP type = 6
 	// ---
 	// ZIP command = 6
-	ZoneInvalid  bool // 0x80
+	ZoneInvalid  bool // 0x80 - "set if the zone name in the request is invalid for the network from which the request was sent"
-	UseBroadcast bool // 0x40
+	UseBroadcast bool // 0x40 - "set for data links that do not support multicast"
-	OnlyOneZone  bool // 0x20
+	OnlyOneZone  bool // 0x20 - "set if the network's zone list contains only one zone name"
 	// Remainder of flags reserved
 	NetStart ddp.Network
 	NetEnd   ddp.Network

main.go

@@ -205,6 +205,9 @@ func main() {
 				continue
 			}
 
+			// TODO: filter ethFrame.Dst to myHWAddr, the broadcast address,
+			// or the relevant zone multicast address
+
 			switch ethFrame.SNAPProto {
 			case ethertalk.AARPProto:
 				// log.Print("Got an AARP frame")

nbp.go

@@ -100,6 +100,10 @@ func handleNBP(pcapHandle *pcap.Handle, myHWAddr, srcHWAddr ethernet.Addr, myAdd
 	case nbp.FunctionBrRq:
 		// There must be 1!
 		tuple := &nbpkt.Tuples[0]
+		ethDst := ethertalk.AppleTalkBroadcast
+		if tuple.Zone != "*" && tuple.Zone != "" {
+			ethDst = atalk.MulticastAddr(tuple.Zone)
+		}
 
 		zones := zoneTable.LookupName(tuple.Zone)
 		for _, z := range zones {
@@ -112,7 +116,6 @@ func handleNBP(pcapHandle *pcap.Handle, myHWAddr, srcHWAddr ethernet.Addr, myAdd
 				// lookups in their own zone will receive LkUp packets from themselves
 				// (actually sent by a router). The node's NBP process should expect to
 				// receive these packets and must reply to them."
-				// TODO: use zone-specific multicast
 				nbpkt.Function = nbp.FunctionLkUp
 				nbpRaw, err := nbpkt.Marshal()
 				if err != nil {
@@ -128,6 +131,7 @@ func handleNBP(pcapHandle *pcap.Handle, myHWAddr, srcHWAddr ethernet.Addr, myAdd
 				if err != nil {
 					return err
 				}
+				outFrame.Dst = ethDst
 				outFrameRaw, err := ethertalk.Marshal(*outFrame)
 				if err != nil {
 					return err

nbp_aurp.go

@@ -20,6 +20,7 @@ import (
 	"fmt"
 	"log"
 
+	"gitea.drjosh.dev/josh/jrouter/atalk"
 	"gitea.drjosh.dev/josh/jrouter/atalk/nbp"
 	"github.com/google/gopacket/pcap"
 	"github.com/sfiera/multitalk/pkg/ddp"
@@ -43,11 +44,11 @@ func handleNBPInAURP(pcapHandle *pcap.Handle, myHWAddr ethernet.Addr, ddpkt *ddp
 	if len(nbpkt.Tuples) < 1 {
 		return fmt.Errorf("no tuples in NBP packet")
 	}
+	tuple := &nbpkt.Tuples[0]
 
-	log.Printf("NBP/DDP/AURP: Converting FwdReq to LkUp (%v)", nbpkt.Tuples[0])
+	log.Printf("NBP/DDP/AURP: Converting FwdReq to LkUp (%v)", tuple)
 
 	// Convert it to a LkUp and broadcast on EtherTalk
-	// TODO: use zone-specific multicast
 	nbpkt.Function = nbp.FunctionLkUp
 	nbpRaw, err := nbpkt.Marshal()
 	if err != nil {
@@ -66,7 +67,9 @@ func handleNBPInAURP(pcapHandle *pcap.Handle, myHWAddr ethernet.Addr, ddpkt *ddp
 	if err != nil {
 		return err
 	}
-	// TODO: outFrame.Dst = zone-specific multicast address
+	if tuple.Zone != "*" && tuple.Zone != "" {
+		outFrame.Dst = atalk.MulticastAddr(tuple.Zone)
+	}
 	outFrameRaw, err := ethertalk.Marshal(*outFrame)
 	if err != nil {
 		return err

zip.go

@@ -126,12 +126,12 @@ func handleZIP(pcapHandle *pcap.Handle, srcHWAddr, myHWAddr ethernet.Addr, myAdd
 			// Only running a network with one zone for now.
 			gnir := &zip.GetNetInfoReplyPacket{
 				ZoneInvalid:     zipkt.ZoneName != cfg.EtherTalk.ZoneName,
-				UseBroadcast:    true, // TODO: add multicast addr computation
+				UseBroadcast:    false,
 				OnlyOneZone:     true,
 				NetStart:        cfg.EtherTalk.NetStart,
 				NetEnd:          cfg.EtherTalk.NetEnd,
 				ZoneName:        zipkt.ZoneName, // has to match request
-				MulticastAddr:   ethertalk.AppleTalkBroadcast,
+				MulticastAddr:   atalk.MulticastAddr(cfg.EtherTalk.ZoneName),
 				DefaultZoneName: cfg.EtherTalk.ZoneName,
 			}
 			log.Printf("ZIP: Replying with GetNetInfo-Reply: %+v", gnir)