Added more documentation and prepared some structural changes

dyndns/nswrapper/ip.go

@@ -0,0 +1,109 @@
+package nswrapper
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"net"
+	"net/http"
+	"strings"
+
+	"github.com/benjaminbear/docker-ddns-server/dyndns/ipparser"
+)
+
+// GetIPType finds out if the IP is IPv4 or IPv6
+func GetIPType(ipAddr string) string {
+	if ipparser.ValidIP4(ipAddr) {
+		return "A"
+	} else if ipparser.ValidIP6(ipAddr) {
+		return "AAAA"
+	} else {
+		return ""
+	}
+}
+
+// GetCallerIP searches for the "real" IP senders has actually.
+// If its a private address we won't use it.
+func GetCallerIP(r *http.Request) (string, error) {
+	fmt.Println("request", r.Header)
+	for _, h := range []string{"X-Real-Ip", "X-Forwarded-For"} {
+		addresses := strings.Split(r.Header.Get(h), ",")
+		// march from right to left until we get a public address
+		// that will be the address right before our proxy.
+		for i := len(addresses) - 1; i >= 0; i-- {
+			ip := strings.TrimSpace(addresses[i])
+			// header can contain spaces too, strip those out.
+			realIP := net.ParseIP(ip)
+			if !realIP.IsGlobalUnicast() || isPrivateSubnet(realIP) {
+				// bad address, go to next
+				continue
+			}
+			return ip, nil
+		}
+	}
+	return "", errors.New("no match")
+}
+
+// ShrinkUserAgent simply cuts the user agent information if its too long to display.
+func ShrinkUserAgent(agent string) string {
+	agentParts := strings.Split(agent, " ")
+
+	return agentParts[0]
+}
+
+// ipRange - a structure that holds the start and end of a range of ip addresses
+type ipRange struct {
+	start net.IP
+	end   net.IP
+}
+
+// inRange - check to see if a given ip address is within a range given
+func inRange(r ipRange, ipAddress net.IP) bool {
+	// strcmp type byte comparison
+	if bytes.Compare(ipAddress, r.start) >= 0 && bytes.Compare(ipAddress, r.end) < 0 {
+		return true
+	}
+	return false
+}
+
+var privateRanges = []ipRange{
+	ipRange{
+		start: net.ParseIP("10.0.0.0"),
+		end:   net.ParseIP("10.255.255.255"),
+	},
+	ipRange{
+		start: net.ParseIP("100.64.0.0"),
+		end:   net.ParseIP("100.127.255.255"),
+	},
+	ipRange{
+		start: net.ParseIP("172.16.0.0"),
+		end:   net.ParseIP("172.31.255.255"),
+	},
+	ipRange{
+		start: net.ParseIP("192.0.0.0"),
+		end:   net.ParseIP("192.0.0.255"),
+	},
+	ipRange{
+		start: net.ParseIP("192.168.0.0"),
+		end:   net.ParseIP("192.168.255.255"),
+	},
+	ipRange{
+		start: net.ParseIP("198.18.0.0"),
+		end:   net.ParseIP("198.19.255.255"),
+	},
+}
+
+// isPrivateSubnet - check to see if this ip is in a private subnet
+func isPrivateSubnet(ipAddress net.IP) bool {
+	// my use case is only concerned with ipv4 atm
+	if ipCheck := ipAddress.To4(); ipCheck != nil {
+		// iterate over all our ranges
+		for _, r := range privateRanges {
+			// check if this ip is in a private range
+			if inRange(r, ipAddress) {
+				return true
+			}
+		}
+	}
+	return false
+}

dyndns/nswrapper/update.go

@@ -0,0 +1,85 @@
+package nswrapper
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"os/exec"
+)
+
+// UpdateRecord builds a nsupdate file and updates a record by executing it with nsupdate.
+func UpdateRecord(hostname string, ipAddr string, addrType string, zone string, ttl int) error {
+	fmt.Printf("%s record update request: %s -> %s\n", addrType, hostname, ipAddr)
+
+	f, err := ioutil.TempFile(os.TempDir(), "dyndns")
+	if err != nil {
+		return err
+	}
+
+	defer os.Remove(f.Name())
+	w := bufio.NewWriter(f)
+
+	w.WriteString(fmt.Sprintf("server %s\n", "localhost"))
+	w.WriteString(fmt.Sprintf("zone %s\n", zone))
+	w.WriteString(fmt.Sprintf("update delete %s.%s %s\n", hostname, zone, addrType))
+	w.WriteString(fmt.Sprintf("update add %s.%s %v %s %s\n", hostname, zone, ttl, addrType, ipAddr))
+	w.WriteString("send\n")
+
+	w.Flush()
+	f.Close()
+
+	cmd := exec.Command("/usr/bin/nsupdate", f.Name())
+	var out bytes.Buffer
+	var stderr bytes.Buffer
+	cmd.Stdout = &out
+	cmd.Stderr = &stderr
+	err = cmd.Run()
+	if err != nil {
+		return fmt.Errorf("%v: %v", err, stderr.String())
+	}
+
+	if out.String() != "" {
+		return fmt.Errorf(out.String())
+	}
+
+	return nil
+}
+
+// DeleteRecord builds a nsupdate file and deletes a record by executing it with nsupdate.
+func DeleteRecord(hostname string, zone string) error {
+	fmt.Printf("record delete request: %s\n", hostname)
+
+	f, err := ioutil.TempFile(os.TempDir(), "dyndns")
+	if err != nil {
+		return err
+	}
+
+	defer os.Remove(f.Name())
+	w := bufio.NewWriter(f)
+
+	w.WriteString(fmt.Sprintf("server %s\n", "localhost"))
+	w.WriteString(fmt.Sprintf("zone %s\n", zone))
+	w.WriteString(fmt.Sprintf("update delete %s.%s\n", hostname, zone))
+	w.WriteString("send\n")
+
+	w.Flush()
+	f.Close()
+
+	cmd := exec.Command("/usr/bin/nsupdate", f.Name())
+	var out bytes.Buffer
+	var stderr bytes.Buffer
+	cmd.Stdout = &out
+	cmd.Stderr = &stderr
+	err = cmd.Run()
+	if err != nil {
+		return fmt.Errorf("%v: %v", err, stderr.String())
+	}
+
+	if out.String() != "" {
+		return fmt.Errorf(out.String())
+	}
+
+	return nil
+}