From e448c779ee6bc416a8678c0f1f35b263b04f64b9 Mon Sep 17 00:00:00 2001
From: "Dr. Adedayo Adetoye" <dayo.dev@gmail.com>
Date: Wed, 6 Mar 2019 09:46:29 +0000
Subject: [PATCH] Fix: some channel closing issues

---
 portscan.go | 47 ++++++++++++++++++++++++++---------------------
 1 file changed, 26 insertions(+), 21 deletions(-)

diff --git a/portscan.go b/portscan.go
index 99b5dc0..ac70dc2 100644
--- a/portscan.go
+++ b/portscan.go
@@ -521,31 +521,36 @@ func listenForACKPackets(handle *pcap.Handle, route routeFinder, config ScanConf
 			go func() {
 				defer close(out)
 				for {
-					packet, err := packetSource.NextPacket()
-					if err == io.EOF {
+					select {
+					case <-stop:
 						return
-					}
-					if err != nil {
-						if err.Error() == pcap.NextErrorTimeoutExpired.Error() {
-							continue
+					default:
+						packet, err := packetSource.NextPacket()
+						if err == io.EOF {
+							return
 						}
-						return
-					}
-					parser.DecodeLayers(packet.Data(), &decodedLayers)
-					for _, lyr := range decodedLayers {
-						//Look for TCP ACK
-						if lyr.Contains(layers.LayerTypeTCP) {
-							ack := PortACK{
-								Host: ip.SrcIP.String(),
-								Port: strings.Split(tcp.SrcPort.String(), "(")[0],
-								SYN:  tcp.SYN,
-								RST:  tcp.RST,
+						if err != nil {
+							if err.Error() == pcap.NextErrorTimeoutExpired.Error() {
+								continue
 							}
-							output <- ack
-							if !config.Quiet && ack.IsOpen() {
-								fmt.Printf("%s:%s (%s) is %s\n", ack.Host, ack.Port, ack.GetServiceName(), ack.Status())
+							return
+						}
+						parser.DecodeLayers(packet.Data(), &decodedLayers)
+						for _, lyr := range decodedLayers {
+							//Look for TCP ACK
+							if lyr.Contains(layers.LayerTypeTCP) {
+								ack := PortACK{
+									Host: ip.SrcIP.String(),
+									Port: strings.Split(tcp.SrcPort.String(), "(")[0],
+									SYN:  tcp.SYN,
+									RST:  tcp.RST,
+								}
+								output <- ack
+								if !config.Quiet && ack.IsOpen() {
+									fmt.Printf("%s:%s (%s) is %s\n", ack.Host, ack.Port, ack.GetServiceName(), ack.Status())
+								}
+								break
 							}
-							break
 						}
 					}
 				}