From 994814b180895f89bad5f3163010a40d0b5a2fa8 Mon Sep 17 00:00:00 2001
From: Callan Bryant <callan.bryant@gmail.com>
Date: Mon, 2 Mar 2020 21:11:45 +0000
Subject: [PATCH] auto external IP detection

---
 init.go  | 17 +++++++++++++++--
 types.go |  2 +-
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/init.go b/init.go
index 4cf6878..f1edabe 100644
--- a/init.go
+++ b/init.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"math/rand"
 	"net"
+	"strings"
 	"time"
 )
 
@@ -14,11 +15,12 @@ func Init() {
 	conf := DsnetConfig{
 		PrivateKey:   privateKey,
 		PresharedKey: presharedKey,
-		Port:         DEFAULT_LISTEN_PORT,
+		ListenPort:   DEFAULT_LISTEN_PORT,
 		Network:      getRandomNetwork(),
 		Peers:        make([]PeerConfig, 0),
 		Domain:       "dsnet",
 		ReportFile:   DEFAULT_REPORT_FILE,
+		ExternalIP:   getExternalIP(),
 	}
 
 	IP := conf.MustAllocateIP()
@@ -27,7 +29,7 @@ func Init() {
 
 	conf.MustSave()
 
-	fmt.Printf("Config written to %s. Please edit.", CONFIG_FILE)
+	fmt.Printf("Config written to %s. Please check/edit.", CONFIG_FILE)
 }
 
 // get a random /22 subnet on 10.0.0.0 (1023 hosts) (or /24?)
@@ -43,3 +45,14 @@ func getRandomNetwork() JSONIPNet {
 		},
 	}
 }
+
+func getExternalIP() net.IP {
+	conn, _ := net.Dial("udp", "8.8.8.8:80")
+	defer conn.Close()
+
+	localAddr := conn.LocalAddr().String()
+	IP := net.ParseIP(strings.Split(localAddr, ":")[0])
+
+	// TODO detect private IP and use icanhazip.com instead
+	return IP
+}
diff --git a/types.go b/types.go
index 538101d..929483b 100644
--- a/types.go
+++ b/types.go
@@ -56,7 +56,7 @@ type DsnetConfig struct {
 	// Network is chosen randomly when not specified
 	Network      JSONIPNet `validate:"required"`
 	ExternalIP   net.IP    `validate:"required,cidr"`
-	ExternalPort int       `validate:"gte=1024,lte=65535"`
+	ListenPort   int       `validate:"gte=1024,lte=65535"`
 	InternalIP   net.IP    `validate:"required,cidr"`
 	InternalDNS  net.IP    `validate:"required,cidr"`
 	// TODO Default subnets to route via VPN