implement recvip and sendip, with tests to know it's working

1 files changed, 142 insertions, 128 deletions

diff --git a/pkg/ipstack/ipstack.go b/pkg/ipstack/ipstack.go
index 5546e32..2063c67 100644
--- a/pkg/ipstack/ipstack.go
+++ b/pkg/ipstack/ipstack.go
@@ -2,8 +2,11 @@ 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"
@@ -17,9 +20,9 @@ const (
 
 // STRUCTS ---------------------------------------------------------------------
 type Interface struct {
-	Name     string
-	IpPrefix netip.Prefix
-
+	Name          string
+	IpPrefix      netip.Prefix
+	UdpAddr       netip.AddrPort
 	RecvSocket    net.UDPConn
 	SocketChannel chan bool
 	State         bool
@@ -51,6 +54,7 @@ type Hop struct {
 }
 
 // GLOBAL VARIABLES (data structures) ------------------------------------------
+var myVIP netip.Addr
 var myInterfaces []*Interface
 var myNeighbors = make(map[string][]*Neighbor)
 
@@ -98,6 +102,7 @@ func Initialize(lnxFilePath string) error {
 		i := &Interface{
 			Name:          iface.Name,
 			IpPrefix:      prefix,
+			UdpAddr:       iface.UDPAddr,
 			RecvSocket:    net.UDPConn{},
 			SocketChannel: make(chan bool),
 			State:         false,
@@ -137,6 +142,7 @@ func Initialize(lnxFilePath string) error {
 		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}
 	}
@@ -171,10 +177,13 @@ func InterfaceListenerRoutine(socket net.UDPConn, signal <-chan bool) {
 			if !isUp { // don't call the listeners if interface is down
 				continue
 			}
-
-			fmt.Println("no activity, actively listening on ", socket.LocalAddr().String())
-			// TODO: remove these training wheels, call the listener function
+			// 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
+			}
 		}
 	}()
 
@@ -205,126 +214,6 @@ func InterfaceDown(iface *Interface) {
 	iface.State = false
 }
 
-/*
-
-func ListerToInterfaces() {
-	for _, iface := range myInterfaces {
-		go RecvIp(iface)
-	}
-}
-func ValidateChecksum(b []byte, fromHeader uint16) uint16 {
-	checksum := header.Checksum(b, fromHeader)
-
-	return checksum
-}
-
-func SendIp(dst netip.Addr, port uint16, protocolNum uint16, data []byte, iface Interface) error {
-	bindLocalAddr, err := net.ResolveUDPAddr("udp4", iface.UDPAddr.String())
-	if err != nil {
-		log.Panicln("Error resolving address:  ", err)
-	}
-
-	addrString := fmt.Sprintf("%s:%s", dst, port)
-	remoteAddr, err := net.ResolveUDPAddr("udp4", addrString)
-	if err != nil {
-		log.Panicln("Error resolving address:  ", err)
-	}
-
-	fmt.Printf("Sending to %s:%d\n",
-		remoteAddr.IP.String(), remoteAddr.Port)
-
-	// Bind on the local UDP port:  this sets the source port
-	// and creates a conn
-	conn, err := net.ListenUDP("udp4", bindLocalAddr)
-	if err != nil {
-		log.Panicln("Dial: ", err)
-	}
-
-	// Start filling in the header
-	message := data[20:]
-	hdr := ipv4header.IPv4Header{
-		Version:  data[0] >> 4,
-		Len:      20, // Header length is always 20 when no IP options
-		TOS:      data[1],
-		TotalLen: ipv4header.HeaderLen + len(message),
-		ID:       data[4],
-		Flags:    data[6] >> 5,
-		FragOff:  data[6] & 0x1f,
-		TTL:      data[8],
-		Protocol: data[9],
-		Checksum: 0, // Should be 0 until checksum is computed
-		Src:      netip.MustParseAddr(iface.addr.String()),
-		Dst:      netip.MustParseAddr(dst.String()),
-		Options:  []byte{},
-	}
-
-	// Assemble the header into a byte array
-	headerBytes, err := hdr.Marshal()
-	if err != nil {
-		log.Fatalln("Error marshalling header:  ", 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
-	bytesWritten, err := conn.WriteToUDP(bytesToSend, remoteAddr)
-	if err != nil {
-		log.Panicln("Error writing to socket: ", err)
-	}
-	fmt.Printf("Sent %d bytes\n", bytesWritten)
-}
-
-func ComputeChecksum(b []byte) uint16 {
-	checksum := header.Checksum(b, 0)
-	checksumInv := checksum ^ 0xffff
-
-	return checksumInv
-}
-
-func ForwardIP(data []byte) error {
-}
-
-func AddRecvHandler(protocolNum uint8, callbackFunc HandlerFunc) error {
-	if protocolHandlers[protocolNum] != nil {
-		fmt.Printf("Warning: Handler for protocol %d already exists", protocolNum)
-	}
-	protocolHandlers[protocolNum] = callbackFunc
-	return nil
-}
-
-func RemoveRecvHandler(protocolNum uint8) error {
-	// consider error
-	if protocolHandlers[protocolNum] == nil {
-		return errors.Errorf("No handler for protocol %d", protocolNum)
-	}
-	delete(protocolHandlers, protocolNum)
-	return nil
-}
-
-// func routeRip(data []byte) (error) {
-// 	// deconstruct packet
-// 	newRIPMessage := RIPMessage{}
-// 	newRIPMessage.command = data[0]
-// 	newRIPMessage.numEntries = data[1]
-// 	newRIPMessage.entries = make([]RIPEntry, newRIPMessage.numEntries)
-// }
-
-func GetNeighbors() []netip.Addr {
-	return myNeighbors
-}
-*/
-
 func GetInterfaceByName(ifaceName string) (*Interface, error) {
 	for _, iface := range myInterfaces {
 		if iface.Name == ifaceName {
@@ -335,6 +224,14 @@ func GetInterfaceByName(ifaceName string) (*Interface, error) {
 	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 {
@@ -376,7 +273,10 @@ func CleanUp() {
 		if iface.SocketChannel != nil {
 			close(iface.SocketChannel)
 		}
-		iface.RecvSocket.Close()
+		err := iface.RecvSocket.Close()
+		if err != nil {
+			continue
+		}
 	}
 
 	// go through the neighbors, pop thread & close the UDP FDs
@@ -385,7 +285,10 @@ func CleanUp() {
 			if n.SocketChannel != nil {
 				close(n.SocketChannel)
 			}
-			n.SendSocket.Close()
+			err := n.SendSocket.Close()
+			if err != nil {
+				continue
+			}
 		}
 	}
 
@@ -398,3 +301,114 @@ func CleanUp() {
 
 	time.Sleep(5 * time.Millisecond)
 }
+
+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))
+
+	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
+}