support for getting an IP from an interface, and skip DNS record update if IP address is the same with last one

config_sample.json

@@ -19,6 +19,7 @@
     }
   ],
   "ip_url": "http://members.3322.org/dyndns/getip",
+  "ip_interface": "eth0",
   "socks5_proxy": "",
   "notify": {
     "enabled": false,

handler/cloudflare_handler.go

@@ -74,6 +74,7 @@ func (handler *CloudflareHandler) DomainLoop(domain *godns.Domain, panicChan cha
 		}
 	}()
 
+	var lastIP string
 	for {
 		currentIP, err := godns.GetCurrentIP(handler.Configuration)
 		if err != nil {
@@ -81,7 +82,11 @@ func (handler *CloudflareHandler) DomainLoop(domain *godns.Domain, panicChan cha
 			continue
 		}
 		log.Println("Current IP is:", currentIP)
-		// TODO: check against locally cached IP, if no change, skip update
+		//check against locally cached IP, if no change, skip update
+		if (currentIP == lastIP){
+			log.Printf("IP is the same as cached one. Skip update.\n")
+		} else {
+			lastIP = currentIP
 
 			log.Println("Checking IP for domain", domain.DomainName)
 			zoneID := handler.getZone(domain.DomainName)
@@ -104,7 +109,7 @@ func (handler *CloudflareHandler) DomainLoop(domain *godns.Domain, panicChan cha
 			} else {
 				log.Println("Failed to find zone for domain:", domain.DomainName)
 			}
-
+		}
 		// Interval is 5 minutes
 		log.Printf("Going to sleep, will start next checking in %d minutes...\r\n", godns.INTERVAL)
 		time.Sleep(time.Minute * godns.INTERVAL)

handler/dnspod_handler.go

@@ -36,6 +36,7 @@ func (handler *DNSPodHandler) DomainLoop(domain *godns.Domain, panicChan chan<-
 		}
 	}()
 
+	var lastIP string
 	for {
 		log.Printf("Checking IP for domain %s \r\n", domain.DomainName)
 		domainID := handler.GetDomain(domain.DomainName)
@@ -52,6 +53,12 @@ func (handler *DNSPodHandler) DomainLoop(domain *godns.Domain, panicChan chan<-
 		}
 		log.Println("currentIP is:", currentIP)
 
+		//check against locally cached IP, if no change, skip update
+		if (currentIP == lastIP){
+			log.Printf("IP is the same as cached one. Skip update.\n")
+		}else{
+			lastIP = currentIP
+			
 			for _, subDomain := range domain.SubDomains {
 
 				subDomainID, ip := handler.GetSubDomain(domainID, subDomain)
@@ -76,7 +83,7 @@ func (handler *DNSPodHandler) DomainLoop(domain *godns.Domain, panicChan chan<-
 					log.Printf("%s.%s Current IP is same as domain IP, no need to update...\n", subDomain, domain.DomainName)
 				}
 			}
-
+		} 
 		// Interval is 5 minutes
 		log.Printf("Going to sleep, will start next checking in %d minutes...\r\n", godns.INTERVAL)
 		time.Sleep(time.Minute * godns.INTERVAL)

handler/he_handler.go

@@ -39,6 +39,7 @@ func (handler *HEHandler) DomainLoop(domain *godns.Domain, panicChan chan<- godn
 		}
 	}()
 
+	var lastIP string
 	for {
 		currentIP, err := godns.GetCurrentIP(handler.Configuration)
 
@@ -48,6 +49,12 @@ func (handler *HEHandler) DomainLoop(domain *godns.Domain, panicChan chan<- godn
 		}
 		log.Println("currentIP is:", currentIP)
 
+		//check against locally cached IP, if no change, skip update
+		if (currentIP == lastIP){
+			log.Printf("IP is the same as cached one. Skip update.\n")
+		} else {
+			lastIP = currentIP
+			
 			for _, subDomain := range domain.SubDomains {
 				log.Printf("%s.%s Start to update record IP...\n", subDomain, domain.DomainName)
 				handler.UpdateIP(domain.DomainName, subDomain, currentIP)
@@ -58,11 +65,12 @@ func (handler *HEHandler) DomainLoop(domain *godns.Domain, panicChan chan<- godn
 					godns.SendNotify(handler.Configuration, fmt.Sprintf("%s.%s", subDomain, domain.DomainName), currentIP)
 				}
 			}
-
+		}
 		// Interval is 5 minutes
 		log.Printf("Going to sleep, will start next checking in %d minutes...\r\n", godns.INTERVAL)
 		time.Sleep(time.Minute * godns.INTERVAL)
 	}
+
 }
 
 // UpdateIP update subdomain with current IP

settings.go

@@ -33,6 +33,9 @@ type Settings struct {
 	LogPath     string   `json:"log_path"`
 	Socks5Proxy string   `json:"socks5_proxy"`
 	Notify      Notify   `json:"notify"`
+	IPInterface string   `json:"ip_interface"`
+	//the code is not ready to update AAAA record
+	//IPType      string   `json:"ip_type"`
 }
 
 // LoadSettings -- Load settings from config file

utils.go

@@ -8,6 +8,7 @@ import (
 	"log"
 	"net/http"
 	"strings"
+    "net"
 
 	"golang.org/x/net/proxy"
 	"gopkg.in/gomail.v2"
@@ -43,8 +44,87 @@ const (
 	CLOUDFLARE = "Cloudflare"
 )
 
-// GetCurrentIP gets public IP from internet
+//GetIPFromInterface gets IP address from the specific interface
+func GetIPFromInterface(configuration *Settings) (string,error) {
+ 	ifaces, err := net.InterfaceByName(configuration.IPInterface)
+	if err != nil {
+		log.Println("can't get network device "+configuration.IPInterface+":", err)
+		return "", err
+	}
+
+	addrs, err  :=ifaces.Addrs();
+	if err != nil {
+		log.Println("can't get address from "+configuration.IPInterface+":", err)
+		return "", err
+	}
+
+	for _, addr := range addrs {
+		var ip net.IP
+		switch v := addr.(type) {
+		case *net.IPNet:
+			ip = v.IP
+		case *net.IPAddr:
+			ip = v.IP
+		}
+		if (ip == nil){
+			continue;
+		}
+
+		if (!(ip.IsGlobalUnicast() &&!(ip.IsUnspecified()||ip.IsMulticast()||ip.IsLoopback()||ip.IsLinkLocalUnicast()||ip.IsLinkLocalMulticast()||ip.IsInterfaceLocalMulticast()))){
+			continue;
+		} 
+
+		//the code is not ready for updating an AAAA record
+		/*
+		if (isIPv4(ip.String())){
+			if (configuration.IPType=="IPv6"){
+				continue;
+			}
+		}else{
+			if (configuration.IPType!="IPv6"){
+				continue;
+			}
+		} */
+		if (!isIPv4(ip.String())){
+			continue;
+		}
+
+		return ip.String(),nil
+		 
+	}
+	return "", errors.New("can't get a vaild address from "+configuration.IPInterface)
+}
+
+func isIPv4(ip string) bool{
+	return strings.Count(ip, ":") < 2
+}
+
+//GetCurrentIP gets an IP from either internet or specific interface, depending on configuration
 func GetCurrentIP(configuration *Settings) (string, error) {
+	var err error
+
+	if (configuration.IPUrl != ""){ 
+		ip, err := GetIPOnline(configuration)
+		if (err != nil){
+			log.Println("get ip online failed. Fallback to get ip from interface if possible.")
+		}else{
+			return ip,nil
+		}
+	}
+
+	if (configuration.IPInterface != ""){
+		ip, err := GetIPFromInterface(configuration)
+		if (err != nil){ 
+			log.Println("get ip from interface failed. There is no more ways to try.")
+		}else{
+			return ip,nil
+		}
+	}
+
+	return "", err
+}
+// GetIPOnline gets public IP from internet
+func GetIPOnline(configuration *Settings) (string, error) {
 	client := &http.Client{}
 
 	if configuration.Socks5Proxy != "" {