cover dns resolution failure case

README.md

@@ -27,6 +27,9 @@ syn-flood can be customized with several command line arguments:
 --floodDurationSeconds  int64       Provide the duration of the attack in seconds, -1 for no limit, defaults to -1
 ```
 
+> To be able to run **syn-flood** with unlimited time range, you should also increase your operating system open file
+> limits, you can refer [here](https://www.tecmint.com/increase-set-open-file-limits-in-linux/) about how to do that.
+
 ## Download
 ### Binary
 Binary can be downloaded from [Releases](https://github.com/bilalcaliskan/syn-flood/releases) page.

internal/raw/raw.go

@@ -25,9 +25,12 @@ func StartFlooding(destinationHost string, destinationPort, payloadLength int, f
 		err        error
 	)
 
-	destinationHost = resolveHost(destinationHost)
+	destinationHost, err = resolveHost(destinationHost)
+	if err != nil {
+		return err
+	}
 
-	description := fmt.Sprintf("Flood is in progress, target=%s:%d, floodType=%s, payloadLength=%d\n",
+	description := fmt.Sprintf("Flood is in progress, target=%s:%d, floodType=%s, payloadLength=%d",
 		destinationHost, destinationPort, floodType, payloadLength)
 	bar := progressbar.DefaultBytes(-1, description)
 

internal/raw/utils.go

@@ -82,17 +82,20 @@ func isIP(host string) bool {
 }
 
 // resolveHost function gets a string and returns the ip address while deciding it is an ip address already or DNS record
-func resolveHost(host string) string {
+func resolveHost(host string) (string, error) {
 	if !isIP(host) && isDNS(host) {
 		log.Printf("%s is a DNS record, making DNS lookup\n", host)
 		ipRecords, err := net.DefaultResolver.LookupIP(context.Background(), "ip4", host)
 		if err != nil {
-			log.Fatalf("an error occured on dns lookup: %s", err.Error())
+			log.Printf("an error occured on dns lookup: %s\n", err.Error())
+			return "", err
 		}
 
 		log.Printf("dns lookup succeeded, found %s for %s\n", ipRecords[0].String(), host)
 		host = ipRecords[0].String()
+	} else {
+		log.Printf("%s is already an IP address, skipping DNS resolution\n", host)
 	}
 
-	return host
+	return host, nil
 }

internal/raw/utils_test.go

@@ -12,16 +12,22 @@ func TestResolveHost(t *testing.T) {
 	}{
 		{"case1", "example.com"},
 		{"case2", "93.184.216.34"},
+		{"case3", "nonexisteddns.com"},
 	}
 
 	for _, tc := range cases {
 		t.Run(tc.caseName, func(t *testing.T) {
-			res := resolveHost(tc.host)
-			assert.NotNil(t, res)
+			_, err := resolveHost(tc.host)
+			assert.NotNil(t, err)
 		})
 	}
 }
 
+func TestResolvHostFailure(t *testing.T) {
+	_, err := resolveHost("nonexisteddns.com")
+	assert.NotNil(t, err)
+}
+
 func TestIsDNS(t *testing.T) {
 	cases := []struct {
 		caseName string