1 files changed, 183 insertions, 0 deletions
diff --git a/pkg/protocol.go b/pkg/protocol.go
new file mode 100644
index 0000000..10cf058
--- /dev/null
+++ b/pkg/protocol.go
@@ -0,0 +1,183 @@
+package protocol
+
+import (
+	"net"
+	"net/netip"
+	"fmt"
+	"os"
+	"bufio"
+	"time"
+	"github.com/brown-cs1680-f23/iptcp-jailpt2/pkg/lnxconfig"
+)
+
+const (
+	MAX_IP_PACKET_SIZE = 1400
+)
+
+type Interface struct {
+	Name           string
+	AssignedIP     netip.Addr
+	AssignedPrefix netip.Prefix
+
+	UDPAddr netip.AddrPort
+	State uint8_t
+}
+
+
+type Neighbor struct{
+	DestAddr netip.Addr
+	UDPAddr  netip.AddrPort
+
+	InterfaceName string
+}
+
+type RIPMessage struct {
+	command uint8_t;
+	numEntries uint8_t;
+	entries []RIPEntry;
+}
+
+type RIPEntry struct {
+	addr netip.Addr;
+	cost uint16_t;
+	mask netip.Prefix;
+}
+
+myInterfaces := make([]Interface);
+myNeighbors :=  make(map[string]Neighbor)
+myRIPNeighbors := make(map[string]Neighbor)
+protocolHandlers := make(map[uint16]HandlerFunc)
+// routingTable := make(map[Address]Routing)
+
+func Initialize(config IpConfig) (error) {
+	if len(os.Args) != 2 {
+		fmt.Printf("Usage:  %s <configFile>\n", os.Args[0])
+		os.Exit(1)
+	}
+	fileName := os.Args[1]
+
+	// Parse the file
+	lnxConfig, err := lnxconfig.ParseConfig(fileName)
+	if err != nil {
+		panic(err)
+	}
+
+	// populate routing table
+	for _, iface := range lnxConfig.Interfaces {
+		myInterfaces = append(myInterfaces, Interface{iface.Name, iface.AssignedIP, iface.AssignedPrefix, iface.UDPAddr, 0})
+	}
+
+	for _, neighbor := range lnxConfig.Neighbors {
+		myNeighbors[neighbor.DestAddr.String()] = Neighbor{neighbor.DestAddr, neighbor.UDPAddr, neighbor.InterfaceName}
+	}
+
+	// add RIP neighbors
+	for _, neighbor := range lnxConfig.RipNeighbors {
+		myRIPNeighbors[neighbor.DestAddr.String()] = Neighbor{neighbor.DestAddr, neighbor.UDPAddr, neighbor.InterfaceName}
+	}
+}
+
+func RecvIp(data []byte) (error) {
+	// deconstruct packet
+
+	// check ip checksum
+	checksum := netip.Checksum(data)
+	if checksum != 0 {
+		return errors.Errorf("Checksum failed: %d", checksum)
+	}
+
+	// check ttl
+	ttl := data[8]
+	if ttl == 0 {
+		return errors.Errorf("TTL is 0")
+	}
+
+	destAddr := netip.AddrFrom(data[16:20])
+	protocolNum := data[9]
+
+	// decrement ttl and update checksum
+	data[8] = ttl - 1
+	data[10] = 0
+	data[11] = 0
+	newChecksum := netip.Checksum(data)
+	data[10] = newChecksum >> 8
+	data[11] = newChecksum & 0xff
+
+	SendIp(destAddr, protocolNum, data)
+}
+
+func SendIp(dst netip.Addr, protocolNum uint16, data []byte) (error) {
+	// check if dst is local
+	islocal := false
+	for _, iface := range myNeighbors {
+		if iface.addr == dst {
+			islocal = true
+			break
+		}
+	}
+
+	if islocal {
+		// send to local handler
+		protocolHandlers[protocolNum](data)
+	} else {
+		// send to forwarding table
+		// lookup forwarding table
+		// toHop, err := lookupForwardingTable(dst)
+		// if err != nil {
+		// 	routeRip()
+		// }
+
+		// // send to toHop interface
+		// for _, iface := range myInterfaces {
+		// 	if iface.addr == toHop {
+		// 		iface.udp.Write(data)
+		// 		break
+		// 	}
+		// }
+}
+
+type HandlerFunc = func help(*Packet, []interface{}) (error) {
+
+	// do smth with packet
+}
+
+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 PrintNeighbors() {
+	for _, iface := range myNeighbors {
+		fmt.Printf("%s\n", iface.addr.String())
+	}
+}
+
+func PrintInterfaces() {
+	for _, iface := range myInterfaces {
+		fmt.Printf("%s\n", iface.addr.String())
+	}
+}
+func GetNeighbors() ([]netip.Addr) {
+	return myNeighbors
+}
+