localhost interface

config/config.go

@@ -1,9 +1,36 @@
 package config
 
-import "github.com/go-playground/validator/v10"
+import (
+	"github.com/go-playground/validator/v10"
+	"log"
+	"net"
+)
 
 var v = validator.New()
 
+func init() {
+	if err := v.RegisterValidation("iface", func(fl validator.FieldLevel) bool {
+		name, ok := fl.Field().Interface().(string)
+		if ok {
+			ifaces, err := net.Interfaces()
+			if err != nil {
+				log.Printf("error getting interfaces: %v", err)
+				return false
+			}
+
+			for _, i := range ifaces {
+				if i.Name == name {
+					return true
+				}
+			}
+		}
+
+		return false
+	}); err != nil {
+
+	}
+}
+
 type Configuration struct {
 	Host  Host
 	Peers []Peer `validate:"dive"`
@@ -19,7 +46,7 @@ type Host struct {
 type Peer struct {
 	Method string `validate:"oneof=TCP UDP"`
 
-	LocalHost string `validate:"omitempty,ip"`
+	LocalHost string `validate:"omitempty,ip|iface"`
 	LocalPort uint   `validate:"max=65535"`
 
 	RemoteHost string `validate:"required_with=RemotePort,omitempty,fqdn|ip"`
@@ -32,6 +59,30 @@ type Peer struct {
 	RetryWait uint
 }
 
+func (p Peer) GetLocalHost() string {
+	if err := v.Var(p.LocalHost, "ip"); err == nil {
+		return p.LocalHost
+	}
+
+	iface, err := net.InterfaceByName(p.LocalHost)
+	if err != nil {
+		panic(err)
+	}
+
+	if iface != nil {
+		addrs, err := iface.Addrs()
+		if err != nil {
+			panic(err)
+		}
+
+		if len(addrs) > 0 {
+			return addrs[0].String()
+		}
+	}
+
+	return "invalid"
+}
+
 func (c Configuration) Validate() error {
 	return v.Struct(c)
 }