From 8fb9008c9564899fdbd3a621437eea17b79b9f52 Mon Sep 17 00:00:00 2001
From: Jean-Louis Huynen <huynenjl@gmail.com>
Date: Mon, 1 Apr 2019 15:01:01 +0200
Subject: [PATCH] Fix #4

---
 .gitignore          |  4 +---
 d4-goclient.go      | 35 ++++++++++++++++++++++-------------
 d4-goclient_test.go | 35 +++++++++++++++++++++++++++++++++++
 3 files changed, 58 insertions(+), 16 deletions(-)
 create mode 100644 d4-goclient_test.go

diff --git a/.gitignore b/.gitignore
index 9b5e95c..ebe06e1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,9 +5,7 @@
 *.so
 *.dylib
 *.vscode
-
-# Test binary, build with `go test -c`
-*.test
+*.idea
 
 # Output of the go coverage tool, specifically when used with LiteIDE
 *.out
diff --git a/d4-goclient.go b/d4-goclient.go
index f0291a9..7155287 100644
--- a/d4-goclient.go
+++ b/d4-goclient.go
@@ -16,6 +16,7 @@ import (
 	"net"
 	"os"
 	"os/signal"
+	"regexp"
 	"strconv"
 	"strings"
 	"time"
@@ -46,7 +47,6 @@ const (
 )
 
 type (
-
 	// A d4 writer implements the io.Writer Interface by implementing Write() and Close()
 	// it accepts an io.Writer as sink
 	d4Writer struct {
@@ -362,7 +362,6 @@ func setReaderWriters(d4 *d4S) bool {
 	isn, dstnet := isNet((*d4).conf.destination)
 	if isn {
 		dial := net.Dialer{
-			DualStack:     true,
 			Timeout:       (*d4).ct,
 			KeepAlive:     (*d4).cka,
 			FallbackDelay: 0,
@@ -410,32 +409,42 @@ func setReaderWriters(d4 *d4S) bool {
 }
 
 func isNet(host string) (bool, string) {
+	// DNS regex
+	validDNS := regexp.MustCompile(`^(([a-zA-Z]{1})|([a-zA-Z]{1}[a-zA-Z]{1})|([a-zA-Z]{1}[0-9]{1})|([0-9]{1}[a-zA-Z]{1})|([a-zA-Z0-9][a-zA-Z0-9-_]{1,61}[a-zA-Z0-9]))\.([a-zA-Z]{2,6}|[a-zA-Z0-9-]{2,30}\.[a-zA-Z
+ ]{2,3})$`)
 	// Check ipv6
 	if strings.HasPrefix(host, "[") {
 		// Parse an IP-Literal in RFC 3986 and RFC 6874.
-		// E.g., "[fe80::1]", "[fe80::1%25en0]", "[fe80::1]:80".
+		// E.g., "[fe80::1]:80".
 		i := strings.LastIndex(host, "]")
 		if i < 0 {
-			panic("Unmatched [ in destination config")
+			infof("Unmatched [ in destination config")
+			return false, ""
 		}
 		if !validPort(host[i+1:]) {
-			panic("No valid port specified")
+			infof("No valid port specified")
+			return false, ""
 		}
 		// trim brackets
-
 		if net.ParseIP(strings.Trim(host[:i+1], "[]")) != nil {
 			infof(fmt.Sprintf("Server IP: %s, Server Port: %s\n", host[:i+1], host[i+1:]))
 			return true, host
 		}
 	} else {
-		// Ipv4
+		// Ipv4 or DNS name
 		ss := strings.Split(string(host), ":")
-		if !validPort(":" + ss[1]) {
-			panic("No valid port specified")
-		}
-		if net.ParseIP(ss[0]) != nil {
-			infof(fmt.Sprintf("Server IP: %s, Server Port: %s\n", ss[0], ss[1]))
-			return true, host
+		if len(ss) > 1 {
+			if !validPort(":" + ss[1]) {
+				infof("No valid port specified")
+				return false, ""
+			}
+			if net.ParseIP(ss[0]) != nil {
+				infof(fmt.Sprintf("Server IP: %s, Server Port: %s\n", ss[0], ss[1]))
+				return true, host
+			} else if validDNS.MatchString(ss[0]) {
+				infof(fmt.Sprintf("DNS: %s, Server Port: %s\n", ss[0], ss[1]))
+				return true, host
+			}
 		}
 	}
 	return false, host
diff --git a/d4-goclient_test.go b/d4-goclient_test.go
new file mode 100644
index 0000000..0bc2b28
--- /dev/null
+++ b/d4-goclient_test.go
@@ -0,0 +1,35 @@
+package main
+
+import (
+	"testing"
+)
+
+var testCases = []struct {
+	name     string
+	str      string
+	expected bool
+}{
+	{"Well-formed IPv4 with port", "127.0.0.1:4443", true},
+	{"Well-formed IPv4 without port", "127.0.0.1", false},
+	{"Malformed IPv4 with port", "127..0.1:4443", false},
+	{"Malformed IPv4 without port", "127..0.1", false},
+	{"Well-formed IPv6 with port - 2", "[::1]:4443", true},
+	{"Well-formed IPv6 without port", "[fe80::1%25en0]", false},
+	{"Malformed IPv6 with port", "[::::1]:4443", false},
+	{"Malformed IPv6 without port", "[::::::::1]", false},
+	{"Malformed IPv6 : missing square brackets", "::::::::1:4443", false},
+	{"Well-formed DNS name with port", "toto.circl.lu:4443", true},
+	{"Well-formed DNS name without port", "toto.circl.lu", false},
+	{"Malformed DNS name with port", ".:4443", false},
+}
+
+func TestIsNet(t *testing.T) {
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			b, _ := isNet(tc.str)
+			if b != tc.expected {
+				t.Fail()
+			}
+		})
+	}
+}