Initial code upload

README.md

@@ -1,2 +1,49 @@
 # nonstd
 Go Language utility to encode/decode ip addresses for the Twister Network
+
+This is a toool I created for the dns seeder for the [Twister P2P network](https://github.com/gombadi/dnsseeder/)
+
+This tool allows you to test a DNS server and check it is returning the correct information.
+
+
+
+> **NOTE:** This repository is under ongoing development and
+is likely to break over time. Use at your own risk.
+
+
+## Installing
+
+Simply use go get to download the code:
+
+    $ go get github.com/gombadi/nonstd
+
+
+## Usage
+
+    $ nonstd -h <dns server to test>
+
+    $ nonstd -i ipaddress -p port // to see an encoded ip for a real ip & port
+
+    $ nonstd -t1 ipaddress -t2 ipaddress // check if these two ip addresses are associated and if so display the port
+
+
+### Command line Options:
+
+```
+
+
+Usage of nonstd:
+  -h string
+        DNS host to query for addresses
+  -i string
+        Real ip to encode
+  -p string
+        Port encode
+  -t1 string
+        Single ip to test. Also needs -t2
+  -t2 string
+        Single ip to test. Also needs -t1
+  -v    Display additional information
+
+```
+

main.go

@@ -0,0 +1,163 @@
+/*
+
+ */
+package main
+
+import (
+	"flag"
+	"fmt"
+	"net"
+	"os"
+	"strconv"
+	"strings"
+)
+
+var host, port, ip, t1, t2 string
+var verbose bool
+
+func main() {
+
+	flag.StringVar(&t1, "t1", "", "Single ip to test. Also needs -t2")
+	flag.StringVar(&t2, "t2", "", "Single ip to test. Also needs -t1")
+	flag.StringVar(&host, "h", "", "DNS host to query for addresses")
+	flag.StringVar(&port, "p", "", "Port encode")
+	flag.StringVar(&ip, "i", "", "Real ip to encode")
+	flag.BoolVar(&verbose, "v", false, "Display additional information")
+	flag.Parse()
+
+	if host != "" && ip != "" {
+		fmt.Printf("Please only select a host with -h OR an ip address with -i\n")
+	}
+
+	if t1 != "" && t2 == "" {
+		fmt.Printf("Please enter both -t1 and -t2 at the same time\n")
+	}
+
+	if t2 != "" && t1 == "" {
+		fmt.Printf("Please enter both -t1 and -t2 at the same time\n")
+	}
+
+	// convert an ip & port to real & encoded addresses
+	if ip != "" {
+		encodeip(ip, port)
+	}
+
+	// pull ip addresses from dns server and decode them
+	if host != "" {
+		var lookuphost string
+		if x := strings.HasPrefix(host, "nonstd."); x == false {
+			lookuphost = "nonstd." + host
+		} else {
+			lookuphost = host
+		}
+		ips, err := net.LookupHost(lookuphost)
+		if err != nil {
+			fmt.Printf("Error - unable to lookup addresses from %s %v\n", host, err)
+		}
+		decodeips(ips)
+	}
+
+	if t1 != "" && t2 != "" {
+		ips := []string{t1, t2}
+		decodeips(ips)
+	}
+
+	fmt.Printf("\nProgram exiting. Bye\n")
+}
+
+// decideips receives a slice of ip addresses and displays information
+// about the ip addresses and ports encoded in them
+func decodeips(ips []string) {
+
+	var match bool
+
+	if verbose && host != "" {
+		fmt.Printf("Received %v addresses from %s\n", len(ips), host)
+	}
+
+	for _, ip := range ips {
+
+		netip := net.ParseIP(ip)
+		netip = netip.To4()
+		if netip == nil {
+			continue
+		}
+		crcAddr := crc16(netip)
+		match = false
+
+		for _, ipport := range ips {
+
+			netipport := net.ParseIP(ipport)
+			netipport = netipport.To4()
+			if netipport == nil {
+				continue
+			}
+			if (netipport[0] == byte(crcAddr>>8)) && (netipport[1] == byte(crcAddr&0xff)) {
+				theport := (uint16(netipport[2]) << 8) + uint16(netipport[3])
+				fmt.Printf("realip: %s\tport: %v\tencodedip: %s\n", ip, theport, ipport)
+				if verbose {
+					fmt.Printf("crcAddr: 0x%x encoded bytes: 0x%x 0x%x 0x%x 0x%x\n", crcAddr, netipport[0], netipport[1], netipport[2], netipport[3])
+				}
+				match = true
+			}
+		}
+		if match == false && verbose {
+			fmt.Printf("No match found for ip: %s\n", ip)
+		}
+	}
+
+}
+
+// encodeip takes an ip address and port strings and displays the encoded
+// ip address they would use
+func encodeip(ip, port string) {
+
+	var netport int
+	if port != "" {
+		netport, _ = strconv.Atoi(port)
+	}
+
+	netip := net.ParseIP(ip)
+	netip = netip.To4()
+	if netip == nil {
+		fmt.Printf("error changing ip: %s to 4 bytes storage\n", ip)
+		os.Exit(0)
+	}
+
+	crcAddr := crc16(netip)
+
+	bs := make([]byte, 4)
+	bs[0] = byte(crcAddr >> 8)
+	bs[1] = byte(crcAddr & 0xff)
+	bs[2] = byte(netport >> 8)
+	bs[3] = byte(netport & 0xff)
+
+	encodedip := net.IPv4(bs[0], bs[1], bs[2], bs[3])
+	if x := encodedip.To4(); x == nil {
+		fmt.Printf("Error checking encoded ip to real ip\n")
+		fmt.Printf("Real ip:   \t%s\n", ip)
+		fmt.Printf("Encoded ip:\t%v.%v.%v.%v\n", bs[0], bs[1], bs[2], bs[3])
+	} else {
+
+		fmt.Printf("crcAddr:\t%#v\n", crcAddr)
+		fmt.Printf("Real ip:   \t%s\n", ip)
+		fmt.Printf("Encoded ip:\t%s\n", encodedip.String())
+	}
+}
+
+func crc16(bs []byte) uint16 {
+	var x, crc uint16
+	crc = 0xffff
+
+	for _, v := range bs {
+
+		x = crc>>8 ^ uint16(v)
+		x ^= x >> 4
+		crc = (crc << 8) ^ (x << 12) ^ (x << 5) ^ x
+	}
+	return crc
+}
+
+/*
+
+ */