fix: resolve golangci-lint nestif error and TestTunnelPackets failure

- Invert `if exists` in `service/tunnel.go` to reduce nestif complexity.
- Update `TestTunnelPackets` to use the new derived IPv6 addresses from config, fixing packet routing mismatch.

Author: NNdroid

application_test.go

@@ -940,38 +940,20 @@ func TestTunnelPackets(t *testing.T) {
 
 	// --- IPv6 Routing Test ---
 	peer2ConfigInPeer1, _ := peer1.app.Conf.GetPeer(peer2.PeerID())
-	peer2IPv4 := net.ParseIP(peer2ConfigInPeer1.IPAddr).To4()
-
 	peer1ConfigInPeer2, _ := peer2.app.Conf.GetPeer(peer1.PeerID())
-	peer1IPv4 := net.ParseIP(peer1ConfigInPeer2.IPAddr).To4()
-
-	awlSubnet4, _ := netip.ParsePrefix(peer1.app.Conf.VPNConfig.IPNet)
-	awlSubnet6, _ := netip.ParsePrefix(peer1.app.Conf.VPNConfig.IPNetV6)
-	v4Mask := net.CIDRMask(awlSubnet4.Bits(), 32)
-	awlNet6 := &net.IPNet{IP: awlSubnet6.Addr().AsSlice(), Mask: net.CIDRMask(awlSubnet6.Bits(), 128)}
-	baseV6 := awlNet6.IP.Mask(awlNet6.Mask).To16()
-
-	peer1IPv6 := make(net.IP, net.IPv6len)
-	copy(peer1IPv6, baseV6)
-	for i := 0; i < net.IPv4len; i++ {
-		peer1IPv6[12+i] |= peer1IPv4[i] &^ v4Mask[i]
-	}
 
-	peer2IPv6 := make(net.IP, net.IPv6len)
-	copy(peer2IPv6, baseV6)
-	for i := 0; i < net.IPv4len; i++ {
-		peer2IPv6[12+i] |= peer2IPv4[i] &^ v4Mask[i]
-	}
+	peer1IPv6Str := peer1ConfigInPeer2.IPAddrV6
+	peer2IPv6Str := peer2ConfigInPeer1.IPAddrV6
 
 	ts.t.Logf("DEBUG: peer1 IPNetV6: %v", peer1.app.Conf.VPNConfig.IPNetV6)
-	ts.t.Logf("DEBUG: peer1IPv6 calculated: %s, peer2IPv6 calculated: %s", peer1IPv6.String(), peer2IPv6.String())
+	ts.t.Logf("DEBUG: peer1IPv6 calculated: %s, peer2IPv6 calculated: %s", peer1IPv6Str, peer2IPv6Str)
 
 	peer1.tun.ClearInboundCount()
 	peer2.tun.ClearInboundCount()
 
 	// Send IPv6 packets from peer1 to peer2
 	const ipv6PacketsCount = 10
-	ipv6Packet := testPacketWithSrcDestV6(packetSize, peer1IPv6.String(), peer2IPv6.String())
+	ipv6Packet := testPacketWithSrcDestV6(packetSize, peer1IPv6Str, peer2IPv6Str)
 
 	for i := 0; i < ipv6PacketsCount; i++ {
 		peer1.tun.Outbound <- [][]byte{ipv6Packet}

service/tunnel.go

@@ -162,51 +162,51 @@ func (t *Tunnel) RefreshPeersList() {
 		newLocalIPv6 := net.ParseIP(knownPeer.IPAddrV6)
 
 		prevPeer, exists := t.peerIDToPeer[peerID]
-		if exists {
-			oldLocalIP := *prevPeer.localIP.Load()
-			var oldLocalIPv6 net.IP
-			if p := prevPeer.localIPv6.Load(); p != nil {
-				oldLocalIPv6 = *p
+		if !exists {
+			// add new peer
+			vpnPeer := NewVpnPeer(peerID, newLocalIP, newLocalIPv6)
+			t.peerIDToPeer[peerID] = vpnPeer
+			t.netIPToPeer[newLocalIP.String()] = vpnPeer
+			if newLocalIPv6 != nil {
+				t.netIPToPeer[newLocalIPv6.String()] = vpnPeer
+				t.logger.Debugf("mapping peer %s (%s) to IPv6 %s", peerID, newLocalIP, newLocalIPv6)
 			}
+			vpnPeer.Start(t)
+			continue
+		}
 
-			ipChanged := !oldLocalIP.Equal(newLocalIP)
-			ipv6Changed := !oldLocalIPv6.Equal(newLocalIPv6)
-
-			if !ipChanged && !ipv6Changed {
-				// no changes
-				continue
-			}
+		oldLocalIP := *prevPeer.localIP.Load()
+		var oldLocalIPv6 net.IP
+		if p := prevPeer.localIPv6.Load(); p != nil {
+			oldLocalIPv6 = *p
+		}
 
-			// IP changed: update both IPv4 and IPv6 mappings
-			if ipChanged {
-				delete(t.netIPToPeer, oldLocalIP.String())
-				prevPeer.localIP.Store(&newLocalIP)
-				t.netIPToPeer[newLocalIP.String()] = prevPeer
-			}
+		ipChanged := !oldLocalIP.Equal(newLocalIP)
+		ipv6Changed := !oldLocalIPv6.Equal(newLocalIPv6)
 
-			if ipv6Changed {
-				if oldLocalIPv6 != nil {
-					delete(t.netIPToPeer, oldLocalIPv6.String())
-				}
-				if newLocalIPv6 != nil {
-					prevPeer.localIPv6.Store(&newLocalIPv6)
-					t.netIPToPeer[newLocalIPv6.String()] = prevPeer
-				} else {
-					prevPeer.localIPv6.Store(nil)
-				}
-			}
+		if !ipChanged && !ipv6Changed {
+			// no changes
 			continue
 		}
 
-		// add new peer
-		vpnPeer := NewVpnPeer(peerID, newLocalIP, newLocalIPv6)
-		t.peerIDToPeer[peerID] = vpnPeer
-		t.netIPToPeer[newLocalIP.String()] = vpnPeer
-		if newLocalIPv6 != nil {
-			t.netIPToPeer[newLocalIPv6.String()] = vpnPeer
-			t.logger.Debugf("mapping peer %s (%s) to IPv6 %s", peerID, newLocalIP, newLocalIPv6)
+		// IP changed: update both IPv4 and IPv6 mappings
+		if ipChanged {
+			delete(t.netIPToPeer, oldLocalIP.String())
+			prevPeer.localIP.Store(&newLocalIP)
+			t.netIPToPeer[newLocalIP.String()] = prevPeer
+		}
+
+		if ipv6Changed {
+			if oldLocalIPv6 != nil {
+				delete(t.netIPToPeer, oldLocalIPv6.String())
+			}
+			if newLocalIPv6 != nil {
+				prevPeer.localIPv6.Store(&newLocalIPv6)
+				t.netIPToPeer[newLocalIPv6.String()] = prevPeer
+			} else {
+				prevPeer.localIPv6.Store(nil)
+			}
 		}
-		vpnPeer.Start(t)
 	}
 
 	// delete unknown peers