Split ZIP replies properly

atalk/zip/query_reply.go

@@ -66,7 +66,7 @@ func UnmarshalQueryPacket(data []byte) (*QueryPacket, error) {
 type ReplyPacket struct {
 	// Function = 2 or 8
 	Extended     bool
-	// NetworkCount uint8
+	NetworkCount uint8
 	// "Replies contain the number of zones lists indicated in the Reply header"
 	// and
 	// "Extended Replies can contain only one zones list. ...
@@ -94,16 +94,12 @@ func (p *ReplyPacket) Marshal() ([]byte, error) {
 		b.WriteByte(FunctionExtendedReply)
 	} else {
 		b.WriteByte(FunctionReply)
-		b.WriteByte(byte(len(p.Networks)))
 	}
+	b.WriteByte(p.NetworkCount)
 	for n, zs := range p.Networks {
-		if p.Extended {
-			if len(zs) > 255 {
+		if p.Extended && len(zs) > 255 {
 			return nil, fmt.Errorf("too many zone names [%d > 255]", len(zs))
 		}
-			// TODO: handle spreading extended replies across multiple packets
-			b.WriteByte(byte(len(zs)))
-		}
 		for _, z := range zs {
 			if len(z) > 32 {
 				return nil, fmt.Errorf("len(%q) > 32", z)

zip.go

@@ -132,26 +132,120 @@ func handleZIP(pcapHandle *pcap.Handle, srcHWAddr, myHWAddr ethernet.Addr, myAdd
 			return err
 		}
 
-		var resp interface {
-			Marshal() ([]byte, error)
-		}
-
 		switch zipkt := zipkt.(type) {
 		case *zip.QueryPacket:
 			log.Printf("ZIP: Got Query for networks %v", zipkt.Networks)
-			// TODO: multiple packets
 			networks := zones.Query(zipkt.Networks)
-			resp = &zip.ReplyPacket{
-				Extended: false,
-				Networks: networks,
+
+			sendReply := func(resp *zip.ReplyPacket) error {
+				respRaw, err := resp.Marshal()
+				if err != nil {
+					return fmt.Errorf("couldn't marshal %T: %w", resp, err)
 				}
+				outDDP := ddp.ExtPacket{
+					ExtHeader: ddp.ExtHeader{
+						Size:      uint16(len(respRaw)) + atalk.DDPExtHeaderSize,
+						Cksum:     0,
+						DstNet:    ddpkt.SrcNet,
+						DstNode:   ddpkt.SrcNode,
+						DstSocket: ddpkt.SrcSocket,
+						SrcNet:    myAddr.Proto.Network,
+						SrcNode:   myAddr.Proto.Node,
+						SrcSocket: 6,
+						Proto:     ddp.ProtoZIP,
+					},
+					Data: respRaw,
+				}
+
+				outFrame, err := ethertalk.AppleTalk(myHWAddr, outDDP)
+				if err != nil {
+					return fmt.Errorf("couldn't create EtherTalk frame: %w", err)
+				}
+				// Unicast reply.
+				outFrame.Dst = srcHWAddr
+				outFrameRaw, err := ethertalk.Marshal(*outFrame)
+				if err != nil {
+					return fmt.Errorf("couldn't marshal EtherTalk frame: %w", err)
+				}
+				if err := pcapHandle.WritePacketData(outFrameRaw); err != nil {
+					return fmt.Errorf("couldn't write packet data: %w", err)
+				}
+				return nil
+			}
+
+			// Inside AppleTalk SE, pp 8-11:
+			//
+			// "Replies (but not Extended Replies) can contain any number of
+			// zones lists, as long as the zones list for each network is
+			// entirely contained in the Reply packet."
+			//
+			// and
+			//
+			// "The zones list for a given network must be contiguous in the
+			// packet, with each zone name in that list preceded by the first
+			// network number in the range of the requested network."
+			size := 2
+			for _, zl := range networks {
+				for _, z := range zl {
+					size += 3 + len(z) // Network number, length byte, string
+				}
+			}
+
+			if size <= atalk.DDPMaxDataSize {
+				// Send one non-extended reply packet with all the data
 				log.Printf("ZIP: Replying with non-extended Reply: %v", networks)
+				return sendReply(&zip.ReplyPacket{
+					Extended: false,
+					// "Replies contain the number of zones lists indicated in
+					// the Reply header."
+					NetworkCount: uint8(len(networks)),
+					Networks:     networks,
+				})
+			}
+
+			// Send Extended Reply packets, 1 or more for each network
+			//
+			// "Extended Replies can contain only one zones list."
+			for nn, zl := range networks {
+				rem := zl // rem: remaining zone names to send for this network
+				for len(rem) > 0 {
+					size := 2
+					var chunk []string // chunk: zone names to send now
+					for _, z := range rem {
+						size += 3 + len(z)
+						if size > atalk.DDPMaxDataSize {
+							break
+						}
+						chunk = append(chunk, z)
+					}
+					rem = rem[len(chunk):]
+
+					nets := map[ddp.Network][]string{
+						nn: chunk,
+					}
+					log.Printf("ZIP: Replying with Extended Reply: %v", nets)
+					err := sendReply(&zip.ReplyPacket{
+						Extended: true,
+						// "The network count in the header indicates, not the
+						// number of zones names in the packet, but the number
+						// of zone names in the entire zones list for the
+						// requested network, which may span more than one
+						// packet."
+						NetworkCount: uint8(len(zl)),
+						Networks:     nets,
+					})
+					if err != nil {
+						return err
+					}
+				}
+			}
+			return nil
 
 		case *zip.GetNetInfoPacket:
 			log.Printf("ZIP: Got GetNetInfo for zone %q", zipkt.ZoneName)
 
 			// Only running a network with one zone for now.
-			gnir := &zip.GetNetInfoReplyPacket{
+			resp := &zip.GetNetInfoReplyPacket{
 				ZoneInvalid:     zipkt.ZoneName != cfg.EtherTalk.ZoneName,
 				UseBroadcast:    false,
 				OnlyOneZone:     true,
@@ -161,16 +255,8 @@ func handleZIP(pcapHandle *pcap.Handle, srcHWAddr, myHWAddr ethernet.Addr, myAdd
 				MulticastAddr:   atalk.MulticastAddr(cfg.EtherTalk.ZoneName),
 				DefaultZoneName: cfg.EtherTalk.ZoneName,
 			}
-			log.Printf("ZIP: Replying with GetNetInfo-Reply: %+v", gnir)
-			resp = gnir
+			log.Printf("ZIP: Replying with GetNetInfo-Reply: %+v", resp)
 
-		default:
-			return fmt.Errorf("TODO: handle type %T", zipkt)
-		}
-
-		if resp == nil {
-			return nil
-		}
 			respRaw, err := resp.Marshal()
 			if err != nil {
 				return fmt.Errorf("couldn't marshal %T: %w", resp, err)
@@ -222,6 +308,10 @@ func handleZIP(pcapHandle *pcap.Handle, srcHWAddr, myHWAddr ethernet.Addr, myAdd
 			}
 			return nil
 
+		default:
+			return fmt.Errorf("TODO: handle type %T", zipkt)
+		}
+
 	default:
 		return fmt.Errorf("invalid DDP type %d on socket 6", ddpkt.Proto)
 	}