init

.gitignore

@@ -0,0 +1,28 @@
+
+# Created by https://www.toptal.com/developers/gitignore/api/go
+# Edit at https://www.toptal.com/developers/gitignore?templates=go
+
+### Go ###
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, built with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+
+# Dependency directories (remove the comment below to include it)
+# vendor/
+
+### Go Patch ###
+/vendor/
+/Godeps/
+
+# End of https://www.toptal.com/developers/gitignore/api/go
+
+abbel

go.mod

@@ -0,0 +1,5 @@
+module git.freifunk-franken.de/jkimmel/abbel
+
+go 1.15
+
+require golang.org/x/net v0.0.0-20210226172049-e18ecbb05110

go.sum

@@ -0,0 +1,7 @@
+golang.org/x/net v0.0.0-20210226172049-e18ecbb05110 h1:qWPm9rbaAMKs8Bq/9LRpbMqxWRVUAQwMI9fVrssnTfw=
+golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68 h1:nxC68pudNYkKU6jWhgrqdreuFiOQWj1Fs7T3VrH4Pjw=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
+golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=

main.go

@@ -0,0 +1,126 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"net"
+
+	"git.freifunk-franken.de/jkimmel/abbel/tlv"
+	"golang.org/x/net/ipv6"
+)
+
+type options struct {
+	Group net.IP
+	Port  uint16
+	Ifs   []net.Interface
+}
+
+func parseOpts() (options, error) {
+	var opt options
+	var err error
+
+	opt.Group = net.ParseIP("ff02::1:6")
+	opt.Port = 6696
+	ifi, err := net.InterfaceByName("babel")
+	if err != nil {
+		return opt, err
+	}
+	opt.Ifs = []net.Interface{*ifi}
+
+	return opt, err
+}
+
+func run(opt options) error {
+	var err error
+	uc, err := net.ListenUDP("udp6", &net.UDPAddr{Port: int(opt.Port)})
+	if err != nil {
+		return err
+	}
+	defer uc.Close()
+	up := ipv6.NewPacketConn(uc)
+
+	if err := up.SetControlMessage(ipv6.FlagDst, true); err != nil {
+		return err
+	}
+
+	for ifi := range opt.Ifs {
+		if err := up.JoinGroup(&opt.Ifs[ifi], &net.UDPAddr{IP: opt.Group}); err != nil {
+			return err
+		}
+	}
+
+	b := make([]byte, 1500)
+	for {
+		n, rcm, src, err := up.ReadFrom(b)
+		if err != nil {
+			return err
+		}
+
+		_ = rcm
+
+		magic := b[0]
+		version := b[1]
+		length := uint16(b[2])<<8 + uint16(b[3])
+
+		if magic != 42 {
+			continue
+		}
+		if int(length)+4 > n {
+			fmt.Println("invalid length")
+		}
+
+		fmt.Println(src, rcm, magic, version, length, n)
+
+		var u tlv.PacketUpdate
+		var s tlv.PacketDecoder
+		ts := tlv.NewTLVScanner(b[4 : 4+length])
+		for ts.Scan() {
+			t, v := ts.TLV()
+			switch t {
+			case tlv.Update:
+				u, err = s.UpdateFromBytes(v)
+				if err != nil {
+					fmt.Println(u.PacketUpdateHeader, &u.Prefix, err)
+				} else {
+					if u.PacketUpdateHeader.Metric == 0xFFFF {
+						fmt.Print("\x1B[1m")
+					}
+					fmt.Printf("%43s: %+v\x1B[0m\n", &u.Prefix, u.PacketUpdateHeader)
+				}
+			default:
+				fmt.Printf("   T: %12s (%2d), L: %3d\n", t, t, len(v))
+			}
+
+		}
+		if ts.Err() != nil {
+			fmt.Println(err)
+		}
+
+		//{
+		//	var bbuf bytes.Buffer
+		//	lzww := lzw.NewWriter(&bbuf, lzw.LSB, 8)
+		//	lzww.Write(b[:n])
+		//	lzww.Close()
+		//	fmt.Println(n, len(bbuf.Bytes()))
+		//}
+		//{
+		//	var bbuf bytes.Buffer
+		//	gzw, _ := gzip.NewWriterLevel(&bbuf, 9)
+		//	gzw.Write(b[:n])
+		//	gzw.Close()
+		//	fmt.Println(n, len(bbuf.Bytes()))
+		//}
+	}
+
+	return nil
+}
+
+func main() {
+	opt, err := parseOpts()
+	if err != nil {
+		log.Fatal(err)
+	}
+	if err := run(opt); err != nil {
+		log.Fatal(err)
+	}
+}

tlv/tlv.go

@@ -0,0 +1,74 @@
+//go:generate stringer -type=TLV
+package tlv
+
+import "fmt"
+
+type TLV uint8
+
+const (
+	Pad1 TLV = iota
+	PadN
+	AckReq
+	Ack
+	Hello
+	IHU
+	RouterID
+	NextHop
+	Update
+	RouteRequest
+	RouteUpdate
+	TSPC
+	HMAC
+)
+
+type Scanner struct {
+	buf []byte
+	err error
+	t   TLV
+	l   uint8
+}
+
+func NewTLVScanner(buf []byte) *Scanner {
+	return &Scanner{
+		buf: buf,
+	}
+}
+
+func (ts *Scanner) Scan() bool {
+	if ts.err != nil {
+		return false
+	}
+
+	if len(ts.buf) <= int(ts.l) {
+		return false
+	}
+
+	// move beginning of the buffer to the next TLV
+	ts.buf = ts.buf[ts.l:]
+	ts.t, ts.l = TLV(ts.buf[0]), 0
+
+	switch ts.t {
+	case Pad1:
+		ts.buf = ts.buf[1:]
+	default:
+		ts.l = ts.buf[1]
+		if 2+int(ts.l) > len(ts.buf) {
+			ts.err = fmt.Errorf("Invalid length: type %d, length %d, size %d", ts.t, ts.l, len(ts.buf))
+			return false
+		}
+		// move beginning of the buffer behind the header
+		ts.buf = ts.buf[2:]
+	}
+	return true
+}
+
+func (ts *Scanner) Err() error {
+	return ts.err
+}
+
+func (ts *Scanner) TLV() (TLV, []byte) {
+	if ts.err != nil {
+		return 0, nil
+	}
+	return ts.t, ts.buf[:ts.l]
+}

tlv/tlv_string.go

@@ -0,0 +1,35 @@
+// Code generated by "stringer -type=TLV"; DO NOT EDIT.
+
+package tlv
+
+import "strconv"
+
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[Pad1-0]
+	_ = x[PadN-1]
+	_ = x[AckReq-2]
+	_ = x[Ack-3]
+	_ = x[Hello-4]
+	_ = x[IHU-5]
+	_ = x[RouterID-6]
+	_ = x[NextHop-7]
+	_ = x[Update-8]
+	_ = x[RouteRequest-9]
+	_ = x[RouteUpdate-10]
+	_ = x[TSPC-11]
+	_ = x[HMAC-12]
+}
+
+const _TLV_name = "Pad1PadNAckReqAckHelloIHURouterIDNextHopUpdateRouteRequestRouteUpdateTSPCHMAC"
+
+var _TLV_index = [...]uint8{0, 4, 8, 14, 17, 22, 25, 33, 40, 46, 58, 69, 73, 77}
+
+func (i TLV) String() string {
+	if i >= TLV(len(_TLV_index)-1) {
+		return "TLV(" + strconv.FormatInt(int64(i), 10) + ")"
+	}
+	return _TLV_name[_TLV_index[i]:_TLV_index[i+1]]
+}

tlv/update.go

@@ -0,0 +1,64 @@
+package tlv
+
+import (
+	"bytes"
+	"encoding/binary"
+	"net"
+)
+
+type PacketUpdateHeader struct {
+	AE       uint8
+	Flags    uint8
+	Plen     uint8
+	Omitted  uint8
+	Interval uint16
+	Seqno    uint16
+	Metric   uint16
+}
+
+type PacketUpdate struct {
+	PacketUpdateHeader
+	Prefix net.IPNet
+}
+
+type PacketDecoder struct {
+	routerID [8]byte
+	v4       [4]byte
+	v6       [16]byte
+}
+
+func (s *PacketDecoder) UpdateFromBytes(b []byte) (PacketUpdate, error) {
+	var u PacketUpdate
+
+	r := bytes.NewReader(b[:10])
+	err := binary.Read(r, binary.BigEndian, &u.PacketUpdateHeader)
+
+	b = b[10:]
+
+	psize := (u.Plen+7)/8 - u.Omitted
+	switch u.AE {
+	case 0:
+	case 1:
+		u.Prefix.Mask = net.CIDRMask(int(u.Plen), 4*8)
+		u.Prefix.IP = append([]byte{}, s.v4[:]...)
+		copy(u.Prefix.IP[u.Omitted:], b[:psize])
+		if u.Flags&0x80 > 0 {
+			copy(s.v4[:], u.Prefix.IP)
+		}
+	case 2:
+		u.Prefix.Mask = net.CIDRMask(int(u.Plen), 16*8)
+		u.Prefix.IP = append([]byte{}, s.v6[:]...)
+		copy(u.Prefix.IP[u.Omitted:], b[:psize])
+		if u.Flags&0x80 > 0 {
+			copy(s.v6[:], u.Prefix.IP)
+		}
+	case 3:
+		u.Prefix.Mask = net.CIDRMask(8, 16*8)
+		u.Prefix.IP = make([]byte, 16)
+		u.Prefix.IP[0] = 0xfe
+		u.Prefix.IP[1] = 0x80
+		copy(u.Prefix.IP[8:], b[:8])
+	}
+
+	return u, err
+}