path: root/pkg/ipstack/ipstack.go

package ipstack

import (
	"encoding/binary"
	"fmt"
	ipv4header "github.com/brown-csci1680/iptcp-headers"
	"github.com/google/netstack/tcpip/header"
	"github.com/pkg/errors"
	"iptcp/pkg/lnxconfig"
	"log"
	"net"
	"net/netip"
	"time"
	// "bytes"
	// "unicode"
)

const (
	MAX_IP_PACKET_SIZE         = 1400
	LOCAL_COST          uint32 = 0
	STATIC_COST         uint32 = 4294967295 // 2^32 - 1
	MaxEntries                 = 64
	INFINITY                   = 15
	SIZE_OF_RIP_ENTRY          = 12
	SIZE_OF_RIP_MESSAGE        = 6
	RIP_PROTOCOL               = 12
	TEST_PROTOCOL              = 0
)

// STRUCTS ---------------------------------------------------------------------
type Interface struct {
	Name     string
	IpPrefix netip.Prefix
	UdpAddr  netip.AddrPort

	RecvSocket    net.UDPConn
	SocketChannel chan bool
	State         bool
}

type Neighbor struct {
	Name    string
	VipAddr netip.Addr
	UdpAddr netip.AddrPort
}

type RIPMessage struct {
	command    uint8
	numEntries uint8
	entries    []RIPEntry
}

type RIPEntry struct {
	address uint32
	cost    uint32
	mask    uint32
}

type Hop struct {
	Cost uint32
	Type string

	Interface *Interface
	VIP       netip.Addr
}

// GLOBAL VARIABLES (data structures) ------------------------------------------
var myVIP Interface
var myInterfaces []*Interface
var myNeighbors = make(map[string][]*Neighbor)

var myRIPNeighbors = make(map[string]bool)

type HandlerFunc func(src *Interface, dest *Neighbor, message []byte, hdr *ipv4header.IPv4Header) error

var protocolHandlers = make(map[int]HandlerFunc)

var routingTable = make(map[netip.Prefix]Hop)

// ************************************** INIT FUNCTIONS **********************************************************
// reference: https://github.com/brown-csci1680/lecture-examples/blob/main/ip-demo/cmd/udp-ip-recv/main.go
func createUDPListener(UdpAddr netip.AddrPort, conn *net.UDPConn) error {
	listenString := UdpAddr.String()
	listenAddr, err := net.ResolveUDPAddr("udp4", listenString)
	if err != nil {
		return errors.WithMessage(err, "Error resolving address->\t"+listenString)
	}
	tmpConn, err := net.ListenUDP("udp4", listenAddr)
	if err != nil {
		return errors.WithMessage(err, "Could not bind to UDP port->\t"+listenString)
	}
	*conn = *tmpConn

	return nil
}

func Initialize(lnxFilePath string) error {
	// Parse the file
	lnxConfig, err := lnxconfig.ParseConfig(lnxFilePath)
	if err != nil {
		return errors.WithMessage(err, "Error parsing config file->\t"+lnxFilePath)
	}

	// 1) add each local if to the routing table, as dictated by its subnet
	for _, iface := range lnxConfig.Interfaces {
		prefix := netip.PrefixFrom(iface.AssignedIP, iface.AssignedPrefix.Bits())
		i := &Interface{
			Name:          iface.Name,
			IpPrefix:      prefix,
			UdpAddr:       iface.UDPAddr,
			RecvSocket:    net.UDPConn{},
			SocketChannel: make(chan bool),
			State:         true,
		}
		// Added this for printing purposes for REPL FYI, if you have a better way lmk

		err := createUDPListener(iface.UDPAddr, &i.RecvSocket)
		if err != nil {
			return errors.WithMessage(err, "Error creating UDP socket for interface->\t"+iface.Name)
		}

		go InterfaceListenerRoutine(i)
		myInterfaces = append(myInterfaces, i)

		routingTable[prefix.Masked()] = Hop{LOCAL_COST, "L", i, prefix.Addr()}
	}

	// 2) add neighbors to if->neighbors map
	for _, neighbor := range lnxConfig.Neighbors {
		n := &Neighbor{
			Name:    neighbor.InterfaceName,
			VipAddr: neighbor.DestAddr,
			UdpAddr: neighbor.UDPAddr,
		}

		myNeighbors[neighbor.InterfaceName] = append(myNeighbors[neighbor.InterfaceName], n)
	}

	// 3) add RIP neighbors to RIP neighbor list
	for _, route := range lnxConfig.RipNeighbors {
		// add to RIP neighbors
		for _, iface := range myInterfaces {
			for _, neighbor := range myNeighbors[iface.Name] {
				if neighbor.VipAddr == route {
					myRIPNeighbors[neighbor.VipAddr.String()] = true
					break
				}
			}
		}
	}

	// 4) add static routes to routing table
	for prefix, addr := range lnxConfig.StaticRoutes {
		// need loops to find the interface that matches the neighbor to send static to
		// hops needs this interface
		for _, iface := range myInterfaces {
			for _, neighbor := range myNeighbors[iface.Name] {
				if neighbor.VipAddr == addr {
					routingTable[prefix] = Hop{STATIC_COST, "S", iface, addr}
					break
				}
			}
		}
	}

	// add protocol handlers
	return nil
}

func InterfaceListenerRoutine(i *Interface) {
	// decompose the interface
	socket := i.RecvSocket
	signal := i.SocketChannel

	// booleans to control listening routine
	isUp := true
	closed := false

	// go routine that hangs on the recv
	fmt.Println("MAKING GO ROUTINE TO LISTEN:\t", socket.LocalAddr().String())
	go func() {
		defer func() {
			fmt.Println("exiting go routine that listens on ", socket.LocalAddr().String())
		}()

		for {
			if closed { // stop this go routine if channel is closed
				return
			}
			if !isUp { // don't call the listeners if interface is down
				continue
			}
			// TODO: remove these "training wheels"
			time.Sleep(1 * time.Millisecond)
			err := RecvIP(i, &isUp)
			if err != nil {
				fmt.Println("Error receiving IP packet", err)
				return
			}
		}
	}()

	for {
		select {
		case sig, ok := <-signal:
			if !ok {
				fmt.Println("channel closed, exiting")
				closed = true
				return
			}
			fmt.Println("received isUP SIGNAL with value", sig)
			isUp = sig
		default:
			continue
		}
	}
}

// ************************************** DOWN/UP FUNCTIONS ******************************************************

func InterfaceUp(iface *Interface) {
	iface.State = true
	iface.SocketChannel <- true
}

func InterfaceUpREPL(ifaceName string) {
	iface, err := GetInterfaceByName(ifaceName)
	if err != nil {
		fmt.Println("Error getting interface by name", err)
		return
	}
	InterfaceUp(iface)
}

// we could do either of these but the REPL results in less work done in router and host

func InterfaceDown(iface *Interface) {
	iface.SocketChannel <- false
	iface.State = false
}

func InterfaceDownREPL(ifaceName string) {
	iface, err := GetInterfaceByName(ifaceName)
	if err != nil {
		fmt.Println("Error getting interface by name", err)
		return
	}
	InterfaceDown(iface)
}

// ************************************** GETTER FUNCTIONS **********************************************************
func GetInterfaceByName(ifaceName string) (*Interface, error) {
	// iterate through the interfaces and return the one with the same name
	for _, iface := range myInterfaces {
		if iface.Name == ifaceName {
			return iface, nil
		}
	}
	return nil, errors.Errorf("No interface with name %s", ifaceName)
}

func GetNeighborByIP(ipAddr string) (*Neighbor, error) {
	// iterate through the neighbors and return the one with the same ipAddr
	for _, neighbors := range myNeighbors {
		for _, neighbor := range neighbors {
			if neighbor.VipAddr.String() == ipAddr {
				return neighbor, nil
			}
		}
	}

	return nil, errors.Errorf("No interface with ip %s", ipAddr)
}

func GetNeighborsToInterface(ifaceName string) ([]*Neighbor, error) {
	if neighbors, ok := myNeighbors[ifaceName]; ok {
		return neighbors, nil
	}

	return nil, errors.Errorf("No interface with name %s", ifaceName)
}

func GetMyVIP() Interface {
	return myVIP
}

func GetInterfaces() []*Interface {
	return myInterfaces
}

func GetNeighbors() map[string][]*Neighbor {
	return myNeighbors
}

func GetRoutes() map[netip.Prefix]Hop {
	return routingTable
}

// ************************************** PRINT FUNCTIONS **********************************************************

func SprintInterfaces() {
	for _, iface := range myInterfaces {
		if iface.State {
			fmt.Printf("%s\t%s\t%s\n", iface.Name, iface.IpPrefix.String(), "UP")
		} else {
			fmt.Printf("%s\t%s\t%s\n", iface.Name, iface.IpPrefix.String(), "DOWN")
		}
	}
}

func SprintNeighbors() {
	for ifaceName, neighbor := range myNeighbors {
		for _, n := range neighbor {
			fmt.Printf("%s\t%s\t%s\n", ifaceName, n.VipAddr.String(), n.UdpAddr.String())
		}
	}
}

func SprintRoutingTable() {
	for prefix, hop := range routingTable {
		if hop.Type == "L" {
			fmt.Printf("%s\t%s\tLOCAL:%s\t%d\n", hop.Type, prefix.String(), hop.Interface.Name, 0)
		} else if hop.Type == "S" {
			fmt.Printf("%s\t%s\t%s\t%s\n", hop.Type, prefix.String(), hop.VIP.String(), "-")
		} else {
			fmt.Printf("%s\t%s\t%s\t%d\n", hop.Type, prefix.String(), hop.VIP.String(), hop.Cost)
		}
	}
}

func DebugNeighbors() {
	for ifaceName, neighbor := range myNeighbors {
		for _, n := range neighbor {
			fmt.Printf("%s\t%s\t%s\n", ifaceName, n.UdpAddr.String(), n.VipAddr.String())
		}
	}
}

// TODO @ MICHAEL:
// func RemoveNeighbor(neighbor Neighbor) {
// 	// TODO: remove from routing table
// 	myRoutes := GetRoutes()
// 	for prefix, hop := range myRoutes {
// 		if hop.VipAsStr == neighbor.VipAddr.String() {
// 			delete(myRoutes, prefix)
// 		}
// 	}

// 	// TODO: remove from myNeighbors
// 	myNeighbors[neighbor.VipAddr.String()] = nil

// 	// TODO: close the UDP socket
// 	err := neighbor.SendSocket.Close()
// 	if err != nil {
// 		fmt.Println("Error closing UDP socket", err)
// 	}

// }
// untested function above

// ************************************** BASIC FUNCTIONS **********************************************************

func CleanUp() {
	fmt.Print("Cleaning up...\n")
	// go through the interfaces, pop thread & close the UDP FDs
	for _, iface := range myInterfaces {
		if iface.SocketChannel != nil {
			close(iface.SocketChannel)
		}
		err := iface.RecvSocket.Close()
		if err != nil {
			continue
		}
	}

	// delete all the neighbors
	myNeighbors = make(map[string][]*Neighbor)
	// delete all the interfaces
	myInterfaces = nil
	// delete the routing table
	routingTable = make(map[netip.Prefix]Hop)

	time.Sleep(5 * time.Millisecond)
}

// TODO: have it take TTL so we can decrement it when forwarding
func SendIP(src *netip.Addr, dest *Neighbor, protocolNum int, message []byte, destIP string, hdr *ipv4header.IPv4Header) error {
	if hdr == nil {
		hdr = &ipv4header.IPv4Header{
			Version:  4,
			Len:      20, // Header length is always 20 when no IP options
			TOS:      0,
			TotalLen: ipv4header.HeaderLen + len(message),
			ID:       0,
			Flags:    0,
			FragOff:  0,
			TTL:      32,
			Protocol: protocolNum,
			Checksum: 0, // Should be 0 until checksum is computed
			Src:      *src,
			Dst:      netip.MustParseAddr(destIP),
			Options:  []byte{},
		}
	} else {
		hdr.TTL--
	}

	// Assemble the header into a byte array
	headerBytes, err := hdr.Marshal()
	if err != nil {
		return err
	}

	// Compute the checksum (see below)
	// Cast back to an int, which is what the Header structure expects
	hdr.Checksum = int(ComputeChecksum(headerBytes))

	headerBytes, err = hdr.Marshal()
	if err != nil {
		log.Fatalln("Error marshalling header:  ", err)
	}

	// Combine the header and the message into a single byte array
	bytesToSend := make([]byte, 0, len(headerBytes)+len(message))
	bytesToSend = append(bytesToSend, headerBytes...)
	bytesToSend = append(bytesToSend, []byte(message)...)

	sendAddr, err := net.ResolveUDPAddr("udp4", dest.UdpAddr.String())
	tmpConn, err := net.DialUDP("udp4", nil, sendAddr)
	if err != nil {
		return errors.WithMessage(err, "Could not bind to UDP port->\t"+dest.UdpAddr.String())
	}

	bytesWritten, err := tmpConn.Write(bytesToSend)
	if err != nil {
		return err
	}

	fmt.Printf("Sent %d bytes to %s\n", bytesWritten, dest.VipAddr.String())

	return nil
}

func RecvIP(iface *Interface, isOpen *bool) error {
	fmt.Printf("Receiving IP packet on %s\n", iface.Name)

	// deconstruct interface
	prefix := iface.IpPrefix
	conn := iface.RecvSocket

	buffer := make([]byte, MAX_IP_PACKET_SIZE) // TODO: fix wordking

	// Read on the UDP port
	// Too much printing so I commented it out
	// fmt.Println("wating to read from UDP socket")
	_, _, err := conn.ReadFromUDP(buffer)
	if err != nil {
		return err
	}

	if !*isOpen {
		return errors.New("interface is down")
	}

	// Marshal the received byte array into a UDP header
	// NOTE:  This does not validate the checksum or check any fields
	// (You'll need to do this part yourself)
	hdr, err := ipv4header.ParseHeader(buffer)
	if err != nil {
		// What should you if the message fails to parse?
		// Your node should not crash or exit when you get a bad message.
		// Instead, simply drop the packet and return to processing.
		fmt.Println("Error parsing header", err)
		return err
	}

	headerSize := hdr.Len
	headerBytes := buffer[:headerSize]
	checksumFromHeader := uint16(hdr.Checksum)
	computedChecksum := ValidateChecksum(headerBytes, checksumFromHeader)

	var checksumState string
	if computedChecksum == checksumFromHeader {
		checksumState = "OK"
	} else {
		checksumState = "FAIL"
	}

	// Next, get the message, which starts after the header
	messageLen := hdr.TotalLen - hdr.Len
	message := buffer[headerSize : messageLen+headerSize]

	// 1) check if the TTL & checksum is valid
	TTL := hdr.TTL
	if TTL == 0 {
		// drop the packet
		return nil
	}

	// check if the checksum is valid
	if checksumState == "FAIL" {
		// drop the packet
		fmt.Println("checksum failed, dropping packet")
		return nil
	}

	// at this point, the packet is valid. next steps consider the forwarding of the packet
	// 2) check if the message is for me, if so, sendUP (aka call the correct handler)
	if hdr.Protocol != RIP_PROTOCOL {
		fmt.Println("I see a non-rip packet")
	}
	if hdr.Dst == prefix.Addr() {
		// see if there is a handler for this protocol
		if handler, ok := protocolHandlers[hdr.Protocol]; ok {
			if hdr.Protocol != RIP_PROTOCOL {
				fmt.Println("this test packet is exactly for me")
			}
			err := handler(iface, nil, message, hdr)
			if err != nil {
				fmt.Println(err)
			}
		}
		return nil
	}

	// 4) check forwarding table.
	// if it's a local hop, send to that iface
	// if it's a RIP hop, send to the neighbor with that VIP
	fmt.Println("checking routing table")
	hop, err := LongestPrefix(hdr.Dst)
	if err == nil { // on no err, found a match
		fmt.Println("found route", hop.VIP)
		if hop.Type == "S" {
			// default, static route
			// drop in this case
			return nil
		}

		// local hop
		if hop.Type == "L" {
			// if it's a local route, then the name is the interface name
			for _, neighbor := range myNeighbors[hop.Interface.Name] {
				if neighbor.VipAddr == hdr.Dst {
					err2 := SendIP(nil, neighbor, hdr.Protocol, message, hdr.Dst.String(), hdr)
					if err2 != nil {
						return err2
					}
				}
			}
		}

		// rip hop
		if hop.Type == "R" {
			// if it's a rip route, then the check is against the hop vip
			for _, neighbor := range myNeighbors[hop.Interface.Name] {
				if neighbor.VipAddr == hop.VIP {
					err2 := SendIP(nil, neighbor, hdr.Protocol, message, hdr.Dst.String(), hdr)
					if err2 != nil {
						return err2
					}
				}
			}
		}
	}

	// if not in table, drop packet
	return nil
}

// ************************************** RIP Routines *******************************************************

func periodicUpdateRoutine() {
	for {
		// for each periodic update, we want to send our nodes in the table
		entries := make([]RIPEntry, len(routingTable))
		for prefix, hop := range routingTable {
			entries = append(entries,
				RIPEntry{
					address: ConvertIPToUint32(prefix.Addr().String()),
					mask:    uint32(prefix.Bits()),
					cost:    hop.Cost,
				})
			// fmt.Printf("Sending RIP update: %s\t%d\t%d\n", prefix.Addr().String(), uint32(prefix.Bits()), hop.Cost)
		}

		// send to each neighbor
		for _, iface := range myInterfaces {
			for _, n := range myNeighbors[iface.Name] {
				_, in := myRIPNeighbors[n.VipAddr.String()]
				if !in {
					continue
				}
				message := NewRIPMessage(2, entries)
				err := SendRIPMessage(*iface, n, message)
				if err != nil {
					// fmt.Printf("Error sending RIP message to %s\n", n.VipAddr.String())
					continue
				}
			}
		}

		// wait 5 sec
		time.Sleep(5 * time.Second)
	}
}

//timeoutTable := make(map[netip.Addr]time.Time)
//func manageTimeoutsRoutine() {
//	for
//}

func startRipRoutines() {
	// send a request to every neighbor
	go func() {
		for _, iface := range myInterfaces {
			for _, neighbor := range myNeighbors[iface.Name] {
				// send a request
				message := NewRIPMessage(1, nil)
				err := SendRIPMessage(*iface, neighbor, message)
				if err != nil {
					return
				}
			}
		}
	}()

	go periodicUpdateRoutine()

	// make a "timeout" table, for each response we add to the table via rip
	// go manageTimeoutsRoutine()

	// start a routine that sends updates every 10 seconds
}

// ************************************** Protocol Handlers *******************************************************

func RegisterProtocolHandler(protocolNum int) bool {
	if protocolNum == RIP_PROTOCOL {
		protocolHandlers[protocolNum] = handleRIP
		go startRipRoutines()
		return true
	}
	if protocolNum == TEST_PROTOCOL {
		protocolHandlers[protocolNum] = handleTestPackets
		return true
	}
	return false
}

func handleRIP(src *Interface, dest *Neighbor, message []byte, hdr *ipv4header.IPv4Header) error {
	command := message[0]
	switch command {
	case 1:
		// request
		// SendUpdates()
		break
	case 2:
		numEntries := message[1]

		// parse the entries
		entries := make([]RIPEntry, 0, numEntries)
		for i := 0; i < int(numEntries); i++ {
			offset := SIZE_OF_RIP_MESSAGE + i*SIZE_OF_RIP_ENTRY

			// each field is 4 bytes
			address := binary.BigEndian.Uint32(message[offset : offset+4])
			mask := binary.BigEndian.Uint32(message[offset+4 : offset+8])
			cost := binary.BigEndian.Uint32(message[offset+8 : offset+12])

			// add to entries
			entries = append(entries, RIPEntry{address: address, mask: mask, cost: cost})
		}

		// add to routing table
		for _, entry := range entries {
			address := fmt.Sprintf("%d.%d.%d.%d", byte(entry.address>>24), byte(entry.address>>16), byte(entry.address>>8), byte(entry.address))
			// fmt.Printf("Received RIP update: %s\t%d\t%d\n", address, entry.mask, entry.cost)

			if address == "0.0.0.0" { // TODO: investigate this
				continue
			}

			prefix := netip.PrefixFrom(netip.MustParseAddr(address), int(entry.mask))
			// fmt.Println(prefix.String())

			// check if the entry is already in the routing table and update if need be
			if node, ok := routingTable[prefix.Masked()]; ok {
				if entry.cost < node.Cost {
					routingTable[prefix.Masked()] = Hop{entry.cost + 1, "R", src, hdr.Src}
				}
				continue
			}

			if entry.cost == 17 {
				routingTable[prefix.Masked()] = Hop{0, "R", src, hdr.Src}
			} else {
				routingTable[prefix.Masked()] = Hop{entry.cost + 1, "R", src, hdr.Src}
			}
		}
	}

	return nil
}

func handleTestPackets(src *Interface, dest *Neighbor, message []byte, hdr *ipv4header.IPv4Header) error {
	fmt.Printf("Received test packet:  Src: %s, Dst: %s, TTL: %d, Data: %s\n",
		hdr.Src.String(), hdr.Dst.String(), hdr.TTL, string(message))
	return nil
}

// ************************************** CHECKSUM FUNCTIONS ******************************************************

func ComputeChecksum(b []byte) uint16 {
	checksum := header.Checksum(b, 0)
	checksumInv := checksum ^ 0xffff

	return checksumInv
}

func ValidateChecksum(b []byte, fromHeader uint16) uint16 {
	checksum := header.Checksum(b, fromHeader)

	return checksum
}

// ************************************** RIP FUNCTIONS **********************************************************

// TODO @ MICHAEL: LONGEST PREFIX MATCHING
func LongestPrefix(src netip.Addr) (Hop, error) {
	possibleBits := [2]int{32, 24}
	for _, bits := range possibleBits {
		cmpPrefix := netip.PrefixFrom(src, bits)
		for prefix, hop := range routingTable {
			if cmpPrefix.Overlaps(prefix) {
				return hop, nil
			}
		}
	}
	return Hop{}, errors.Errorf("No route to ip %s on table.", src)
}

func NewRIPMessage(command uint8, entries []RIPEntry) *RIPMessage {
	return &RIPMessage{
		command:    command,
		numEntries: uint8(len(entries)),
		entries:    entries,
	}
}

func SendRIPMessage(src Interface, dest *Neighbor, message *RIPMessage) error {
	hdr := ipv4header.IPv4Header{
		Version:  4,
		Len:      20, // Header length is always 20 when no IP options
		TOS:      0,
		TotalLen: ipv4header.HeaderLen + 4 + 1 + 1 + len(message.entries)*12,
		ID:       0,
		Flags:    0,
		FragOff:  0,
		TTL:      32,
		Protocol: 12,
		Checksum: 0, // Should be 0 until checksum is computed
		Src:      src.IpPrefix.Addr(),
		Dst:      netip.MustParseAddr(dest.VipAddr.String()),
		Options:  []byte{},
	}

	headerBytes, err := hdr.Marshal()
	if err != nil {
		return err
	}

	hdr.Checksum = int(ComputeChecksum(headerBytes))

	headerBytes, err = hdr.Marshal()
	if err != nil {
		log.Fatalln("Error marshalling header:  ", err)
	}

	bytesToSend := make([]byte, 0, len(headerBytes)+4+1+1+len(message.entries)*12)
	bytesToSend = append(bytesToSend, headerBytes...)

	// make the RIP message
	buf := make([]byte, SIZE_OF_RIP_MESSAGE+len(message.entries)*SIZE_OF_RIP_ENTRY)
	buf[0] = message.command
	buf[1] = message.numEntries

	for i, entry := range message.entries {
		offset := SIZE_OF_RIP_MESSAGE + i*SIZE_OF_RIP_ENTRY
		// each field is 4 bytes
		binary.BigEndian.PutUint32(buf[offset:offset+4], entry.address)
		binary.BigEndian.PutUint32(buf[offset+4:offset+8], entry.mask)
		binary.BigEndian.PutUint32(buf[offset+8:offset+12], entry.cost)
	}

	bytesToSend = append(bytesToSend, buf...)

	// send RIP message
	sendAddr, err := net.ResolveUDPAddr("udp4", dest.UdpAddr.String())
	tmpConn, err := net.DialUDP("udp4", nil, sendAddr)
	if err != nil {
		return errors.WithMessage(err, "Could not bind to UDP port->\t"+dest.UdpAddr.String())
	}
	_, err = tmpConn.Write(bytesToSend)
	if err != nil {
		return err
	}

	return nil
}

//func RequestRip() {
//	// create RIP message
//	message := NewRIPMessage(1, []RIPEntry{})
//
//	// send RIP message to RIP neighbors
//	for _, neighbors := range myNeighbors {
//		for _, neighbor := range neighbors {
//			// check if neighbor is RIP neighbor
//			// if not, continue
//			for _, ripNeighbor := range myRIPNeighbors {
//				if neighbor.VipAddr.String() == ripNeighbor.String() {
//					// send RIP message
//					err := SendRIPMessage(myVIP, neighbor, message)
//					if err != nil {
//						continue
//					}
//				}
//			}
//			continue
//		}
//	}
//}

func BroadcastPeriodicUpdates() {
	// for each periodic update, we want to send our nodes in the table
	entries := make([]RIPEntry, len(routingTable))
	for prefix, hop := range routingTable {
		entries = append(entries,
			RIPEntry{
				address: ConvertIPToUint32(prefix.Addr().String()),
				mask:    uint32(prefix.Bits()),
				cost:    hop.Cost,
			})
	}
	message := NewRIPMessage(2, entries)

	// send to each neighbor
	for _, iface := range myInterfaces {
		for _, n := range myNeighbors[iface.Name] {
			err := SendRIPMessage(*iface, n, message)
			if err != nil {
				fmt.Printf("Error sending RIP message to %s\n", n.VipAddr.String())
				continue
			}
		}
	}

}

// THIS MIGHT BE WRONG...
func SendUpdates() {
	entries := make([]RIPEntry, len(routingTable))
	// create RIP entries from its interfaces to one another
	for _, iface := range myInterfaces {
		for _, iface2 := range myInterfaces {
			if iface.Name == iface2.Name {
				continue
			}
			// TODO @ MICHAEL: fix this
			// hardcoded way to get cost to 0, fix if you want a better way
			entry := &RIPEntry{
				address: ConvertIPToUint32(iface2.IpPrefix.Addr().String()),
				cost:    17,
				mask:    ConvertIPToUint32(iface.IpPrefix.Addr().String()),
			}
			entries = append(entries, *entry)

			entry = &RIPEntry{
				address: ConvertIPToUint32(iface.IpPrefix.Addr().String()),
				cost:    17,
				mask:    ConvertIPToUint32(iface2.IpPrefix.Addr().String()),
			}
			entries = append(entries, *entry)
		}
	}

	// create RIP entries from its neighbors
	for _, neighbors := range myNeighbors {
		for _, neighbor := range neighbors {
			ipUint32 := ConvertIPToUint32(neighbor.VipAddr.String())
			var neighborUint32 uint32
			for _, interfaces := range myInterfaces {
				if ifaceContainsIP(*interfaces, neighbor.VipAddr) {
					neighborUint32 = ConvertIPToUint32(interfaces.IpPrefix.Addr().String())
					break
				}
			}

			// create RIP entry
			entry := &RIPEntry{
				address: ipUint32,
				cost:    LOCAL_COST,
				mask:    neighborUint32,
			}

			// add to entries and create RIP message
			entries = append(entries, *entry)
			message := NewRIPMessage(2, entries)

			// send RIP message
			for _, Interfaces := range myInterfaces {
				if Interfaces.Name == neighbor.Name {
					err := SendRIPMessage(myVIP, neighbor, message)
					if err != nil {
						continue
					}
				}
			}

		}
	}
}

func ifaceContainsIP(iface Interface, ip netip.Addr) bool {
	// check if the ip is in the interface's prefix
	if iface.IpPrefix.Contains(netip.MustParseAddr(ip.String())) {
		return true
	}
	return false
}

func ConvertIPToUint32(ip string) uint32 {
	netIP := net.ParseIP(ip)
	ipBytes := netIP.To4()
	ipUint32 := uint32(ipBytes[0])<<24 | uint32(ipBytes[1])<<16 | uint32(ipBytes[2])<<8 | uint32(ipBytes[3])
	return ipUint32
}

// TODO @ MICHEAL: Handle links going down and link recovery
// func CheckAndUpdateRoutingTable() {
// 	for {
// 	time.Sleep(12 * time.Second)
// 	for prefix, hop := range routingTable {
// 		// delete route if not refreshed in 12 seconds
// 		// not sure if there is a better way to do this
// 		if hop.Type == "R" {
// 			delete(routingTable, prefix)
// 			SendUpdates()
// 		}
// 	}
// 	}
// }

// TODO @ MICHAEL: Triggered Updates and Split Horizon with Poisoned Reverse