From e8ae07c3cec83f0d03e553526bbd58863d2594ff Mon Sep 17 00:00:00 2001
From: Lifei Chen <hustclf@gmail.com>
Date: Fri, 18 Sep 2020 20:04:29 +0800
Subject: [PATCH] Return an error when addr is empty

---
 ping.go      | 4 ++++
 ping_test.go | 5 +++++
 2 files changed, 9 insertions(+)

diff --git a/ping.go b/ping.go
index f402439..f226933 100644
--- a/ping.go
+++ b/ping.go
@@ -46,6 +46,7 @@ package ping
 import (
 	"bytes"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"math"
 	"math/rand"
@@ -230,6 +231,9 @@ func (p *Pinger) IPAddr() *net.IPAddr {
 
 // Resolve does the DNS lookup for the Pinger address and sets IP protocol.
 func (p *Pinger) Resolve() error {
+	if len(p.addr) == 0 {
+		return errors.New("addr cannot be empty")
+	}
 	ipaddr, err := net.ResolveIPAddr(p.network, p.addr)
 	if err != nil {
 		return err
diff --git a/ping_test.go b/ping_test.go
index 18973b4..a27b5e3 100644
--- a/ping_test.go
+++ b/ping_test.go
@@ -358,6 +358,11 @@ func TestSetIPAddr(t *testing.T) {
 	AssertEqualStrings(t, googleaddr.String(), p.Addr())
 }
 
+func TestEmptyIPAddr(t *testing.T) {
+	_, err := NewPinger("")
+	AssertError(t, err, "empty pinger did not return an error")
+}
+
 func TestStatisticsSunny(t *testing.T) {
 	// Create a localhost ipv4 pinger
 	p := New("localhost")