From a00cc7da6350e3f12730e0789f692aefecc486d6 Mon Sep 17 00:00:00 2001
From: Jim Colderwood <jim.colderwood@pnsol.com>
Date: Wed, 10 Apr 2024 13:59:01 +0100
Subject: [PATCH] Response parsing

---
 main.go            | 45 +++++++++++-----------------------
 ripv2/constants.go |  7 ------
 ripv2/ripv2.go     | 60 +++++++++++++++++++++++++++++++++-------------
 ripv2/types.go     | 33 +++++++++++++++++++++++++
 4 files changed, 91 insertions(+), 54 deletions(-)
 delete mode 100644 ripv2/constants.go
 create mode 100644 ripv2/types.go

diff --git a/main.go b/main.go
index 55140ee..05b4006 100644
--- a/main.go
+++ b/main.go
@@ -25,42 +25,25 @@ func main() {
 	defer conn.Close()
 	buff := make([]byte, 1024)
 
-	/*
-		bytes, err := rip.Request(conn)
+	log.Println("waiting")
+	for {
+		n, UDPAddr, err := conn.ReadFromUDP(buff)
 		if err != nil {
 			log.Fatalln(err)
 		}
+		_ = UDPAddr
 
-		fmt.Println(bytes)
+		if err := rip.MParse(&buff, n); err != nil {
+			log.Fatalln(err)
+		}
 
-
-			RipAddr := net.UDPAddr{
-				Port: 520,
-				IP:   net.ParseIP("224.0.0.9"),
+		/* Just testing the parsing output */
+		for i := 0; i < 24; i++ {
+			if rip.RIP[i].Metric == 0 {
+				break
 			}
-			bw, err := conn.WriteToUDP(bytes, &RipAddr)
-			if err != nil {
-				log.Fatalln(err)
-			}
-
-			log.Printf("wrote %d bytes\n", bw)
-
-	*/
-	log.Println("waiting")
-	n, UDPAddr, err := conn.ReadFromUDP(buff)
-	if err != nil {
-		log.Fatalln(err)
-	}
-	_ = UDPAddr
-	if n == 0 {
-		log.Fatalln("empty")
-	}
-
-	if err := rip.Parse(&buff); err != nil {
-		log.Fatalln(err)
-	}
-	for i := 0; i < 24; i++ {
-		ipa := net.IPv4(byte(rip.RIP[i].Addr), byte(rip.RIP[i].Addr>>8), byte(rip.RIP[i].Addr>>16), byte(rip.RIP[i].Addr>>24))
-		fmt.Printf("Command %d\n%s\t%d\n", rip.Command, ipa.String(), rip.RIP[i].Metric)
+			fmt.Printf("%d\t%s\t%s\t%s\t%d\n", rip.RIP[i].AFI, rip.RIP[i].Addr.String(), rip.RIP[i].Subnet.String(), rip.RIP[i].Nexthop.String(), rip.RIP[i].Metric)
+		}
+		fmt.Println("")
 	}
 }
diff --git a/ripv2/constants.go b/ripv2/constants.go
deleted file mode 100644
index 0dcd568..0000000
--- a/ripv2/constants.go
+++ /dev/null
@@ -1,7 +0,0 @@
-package ripv2
-
-const (
-	ZERO = iota
-	REQUEST
-	RESPONSE
-)
diff --git a/ripv2/ripv2.go b/ripv2/ripv2.go
index 4abd30c..e4b2977 100644
--- a/ripv2/ripv2.go
+++ b/ripv2/ripv2.go
@@ -3,29 +3,57 @@ package ripv2
 import (
 	"bytes"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"net"
 )
 
-type Message struct {
-	Command uint8
-	Version uint8
-	Zero    uint16
-	RIP     [25]RIP
-}
-
-type RIP struct {
-	AFI     uint16
-	Zero    uint16
-	Addr    uint32
-	Packing uint64
-	Metric  uint32
-}
-
 func New() Message {
 	return Message{}
 }
 
+func (m *Message) MParse(b *[]byte, n int) error {
+	if n == 0 {
+		return errors.New("can't parse empty data")
+	}
+
+	if (n-4)/20 > 25 {
+		return errors.New("rip table exceeds limit")
+	}
+
+	data := (*b)
+	m.Command = Command(data[0])
+	m.Version = Version(data[1])
+
+	if m.Version > RIPv2 {
+		return errors.New("unknown version")
+	}
+
+	var indexA, indexB = 4, 25
+	ripentry := data[indexA:indexB]
+	switch m.Command {
+	case REQUEST:
+		return nil
+	case RESPONSE:
+		for i := 0; i < (n-4)/20; i++ {
+			m.RIP[i].AFI = binary.BigEndian.Uint16(ripentry[0:2])
+			m.RIP[i].RouteTag = binary.BigEndian.Uint16(ripentry[2:4])
+			m.RIP[i].Addr = net.IPv4(ripentry[4], ripentry[5], ripentry[6], ripentry[7])
+			m.RIP[i].Subnet = net.IPv4Mask(ripentry[8], ripentry[9], ripentry[10], ripentry[11])
+			m.RIP[i].Nexthop = net.IPv4(ripentry[12], ripentry[13], ripentry[14], ripentry[15])
+			m.RIP[i].Metric = binary.BigEndian.Uint32(ripentry[16:20])
+			indexA += 20
+			indexB += 20
+			ripentry = data[indexA:indexB]
+		}
+	default:
+		return errors.New("unknown command type")
+	}
+
+	return nil
+}
+
+/* Basic parsing */
 func (m *Message) Parse(b *[]byte) error {
 	if len(*b) == 0 {
 		return fmt.Errorf("can't parse empty data")
@@ -33,7 +61,7 @@ func (m *Message) Parse(b *[]byte) error {
 
 	bytes := bytes.NewBuffer(*b)
 
-	if err := binary.Read(bytes, binary.LittleEndian, m); err != nil {
+	if err := binary.Read(bytes, binary.BigEndian, m); err != nil {
 		return err
 	}
 
diff --git a/ripv2/types.go b/ripv2/types.go
new file mode 100644
index 0000000..fbed13d
--- /dev/null
+++ b/ripv2/types.go
@@ -0,0 +1,33 @@
+package ripv2
+
+import "net"
+
+type Command uint8
+type Version uint8
+
+const (
+	ZERO Command = iota
+	REQUEST
+	RESPONSE
+)
+
+const (
+	RIPv1 Version = iota + 1
+	RIPv2
+)
+
+type Message struct {
+	Command Command
+	Version Version
+	Zero    uint16
+	RIP     [25]RIP
+}
+
+type RIP struct {
+	AFI      uint16
+	RouteTag uint16
+	Addr     net.IP
+	Subnet   net.IPMask
+	Nexthop  net.IP
+	Metric   uint32
+}