1 files changed, 413 insertions, 0 deletions
diff --git a/pkg/ipstack/ipstack.go b/pkg/ipstack/ipstack.go
new file mode 100644
index 0000000..be8bc1e
--- /dev/null
+++ b/pkg/ipstack/ipstack.go
@@ -0,0 +1,413 @@
+package ipstack
+
+import (
+	"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"
+)
+
+const (
+	MAX_IP_PACKET_SIZE        = 1400
+	LOCAL_COST         uint32 = 0
+	STATIC_COST        uint32 = 4294967295 // 2^32 - 1
+)
+
+// STRUCTS ---------------------------------------------------------------------
+type Interface struct {
+	Name     string
+	IpPrefix netip.Prefix
+	UdpAddr  netip.AddrPort
+
+	RecvSocket    net.UDPConn
+	SocketChannel chan bool
+	State         bool
+}
+
+type Neighbor struct {
+	VipAddr netip.Addr
+	UdpAddr netip.AddrPort
+
+	SendSocket    net.UDPConn
+	SocketChannel chan bool
+}
+
+type RIPMessage struct {
+	command    uint8
+	numEntries uint8
+	entries    []RIPEntry
+}
+
+type RIPEntry struct {
+	addr netip.Addr
+	cost uint32
+	mask netip.Prefix
+}
+
+type Hop struct {
+	Cost     uint32
+	VipAsStr string
+}
+
+// GLOBAL VARIABLES (data structures) ------------------------------------------
+var myVIP netip.Addr
+var myInterfaces []*Interface
+var myNeighbors = make(map[string][]*Neighbor)
+
+// var myRIPNeighbors = make(map[string]Neighbor)
+type HandlerFunc func(int, string, *[]byte) error
+
+var protocolHandlers = make(map[uint16]HandlerFunc)
+
+// var routingTable = routingtable.New()
+var routingTable = make(map[netip.Prefix]Hop)
+
+// reference: https://github.com/brown-csci1680/lecture-examples/blob/main/ip-demo/cmd/udp-ip-recv/main.go
+func createUDPConn(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 {
+	//if len(os.Args) != 2 {
+	//	fmt.Printf("Usage:  %s <configFile>\n", os.Args[0])
+	//	os.Exit(1)
+	//}
+	//lnxFilePath := os.Args[1]
+
+	// Parse the file
+	lnxConfig, err := lnxconfig.ParseConfig(lnxFilePath)
+	if err != nil {
+		return errors.WithMessage(err, "Error parsing config file->\t"+lnxFilePath)
+	}
+
+	// 1) initialize the interfaces on this node here and into the routing table
+	static := false
+	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:         false,
+		}
+
+		err := createUDPConn(iface.UDPAddr, &i.RecvSocket)
+		if err != nil {
+			return errors.WithMessage(err, "Error creating UDP socket for interface->\t"+iface.Name)
+		}
+		go InterfaceListenerRoutine(i.RecvSocket, i.SocketChannel)
+		myInterfaces = append(myInterfaces, i)
+
+		// TODO: (FOR HOSTS ONLY)
+		// add STATIC to routing table
+		if !static {
+			ifacePrefix := netip.MustParsePrefix("0.0.0.0/0")
+			routingTable[ifacePrefix] = Hop{STATIC_COST, iface.Name}
+			static = true
+		}
+	}
+
+	// 2) initialize the neighbors connected to the node and into the routing table
+	for _, neighbor := range lnxConfig.Neighbors {
+		n := &Neighbor{
+			VipAddr:       neighbor.DestAddr,
+			UdpAddr:       neighbor.UDPAddr,
+			SendSocket:    net.UDPConn{},
+			SocketChannel: make(chan bool),
+		}
+
+		err := createUDPConn(neighbor.UDPAddr, &n.SendSocket)
+		if err != nil {
+			return errors.WithMessage(err, "Error creating UDP socket for neighbor->\t"+neighbor.DestAddr.String())
+		}
+
+		myNeighbors[neighbor.InterfaceName] = append(myNeighbors[neighbor.InterfaceName], n)
+
+		// add to routing table
+		// TODO: REVISIT AND SEE IF "24" IS CORRECT
+		neighborPrefix := netip.PrefixFrom(neighbor.DestAddr, 24)
+		routingTable[neighborPrefix] = Hop{LOCAL_COST, neighbor.InterfaceName}
+	}
+
+	return nil
+}
+
+func InterfaceListenerRoutine(socket net.UDPConn, signal <-chan bool) {
+	isUp := false
+	closed := false
+
+	// go routine that hangs on the recv
+	fmt.Println("MAKING GO ROUTINE TO LISTEN:\t", socket.LocalAddr().String())
+	go func() {
+		defer func() { // on close, set isUp to false
+			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(socket, &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
+		}
+	}
+}
+
+func InterfaceUp(iface *Interface) {
+	iface.State = true
+	iface.SocketChannel <- true
+}
+
+func InterfaceDown(iface *Interface) {
+	iface.SocketChannel <- false
+	iface.State = false
+}
+
+func GetInterfaceByName(ifaceName string) (*Interface, error) {
+	for _, iface := range myInterfaces {
+		if iface.Name == ifaceName {
+			return iface, nil
+		}
+	}
+
+	return nil, errors.Errorf("No interface with name %s", ifaceName)
+}
+
+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 SprintInterfaces() string {
+	buf := ""
+	for _, iface := range myInterfaces {
+		buf += fmt.Sprintf("%s\t%s\t%t\n", iface.Name, iface.IpPrefix.String(), iface.State)
+	}
+	return buf
+}
+
+func SprintNeighbors() string {
+	buf := ""
+	for ifaceName, neighbor := range myNeighbors {
+		for _, n := range neighbor {
+			buf += fmt.Sprintf("%s\t%s\t%s\n", ifaceName, n.UdpAddr.String(), n.VipAddr.String())
+		}
+	}
+	return buf
+}
+
+func SprintRoutingTable() string {
+	buf := ""
+	for prefix, hop := range routingTable {
+		buf += fmt.Sprintf("%s\t%s\t%d\n", prefix.String(), hop.VipAsStr, hop.Cost)
+	}
+	return buf
+}
+
+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())
+		}
+	}
+}
+
+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
+		}
+	}
+
+	// go through the neighbors, pop thread & close the UDP FDs
+	for _, neighbor := range myNeighbors {
+		for _, n := range neighbor {
+			if n.SocketChannel != nil {
+				close(n.SocketChannel)
+			}
+			err := n.SendSocket.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 Interface, dest Neighbor, protocolNum int, message []byte) error {
+	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.IpPrefix.Addr(),
+		Dst:      dest.VipAddr,
+		Options:  []byte{},
+	}
+
+	// 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)
+	}
+
+	bytesToSend := make([]byte, 0, len(headerBytes)+len(message))
+	bytesToSend = append(bytesToSend, headerBytes...)
+	bytesToSend = append(bytesToSend, []byte(message)...)
+
+	// Send the message to the "link-layer" addr:port on UDP
+	listenAddr, err := net.ResolveUDPAddr("udp4", dest.UdpAddr.String())
+	if err != nil {
+		return err
+	}
+	bytesWritten, err := dest.SendSocket.WriteToUDP(bytesToSend, listenAddr)
+	if err != nil {
+		return err
+	}
+	fmt.Printf("Sent %d bytes to %s\n", bytesWritten, listenAddr.String())
+
+	return nil
+}
+
+func RecvIP(conn net.UDPConn, isOpen *bool) error {
+	buffer := make([]byte, MAX_IP_PACKET_SIZE) // TODO: fix wordking
+
+	// Read on the UDP port
+	fmt.Println("wating to read from UDP socket")
+	_, sourceAddr, 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
+	message := buffer[headerSize:]
+
+	// Finally, print everything out
+	fmt.Printf("Received IP packet from %s\nHeader:  %v\nChecksum:  %s\nMessage:  %s\n",
+		sourceAddr.String(), hdr, checksumState, string(message))
+
+	// TODO:  handle the message
+	// 1) check if the TTL & checksum is valid
+	// 2) check if the message is for me, if so, sendUP (aka call the correct handler)
+	// if not, need to forward the packer to a neighbor or check the table
+	// after decrementing TTL and updating checksum
+	// 3) check if message is for a neighbor, if so, sendIP there
+	// 4) check if message is for a neighbor, if so, forward to the neighbor with that VIP
+
+	return nil
+}
+
+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
+}