added comments, handles startCapture error + better error handling

Author: eyJhb

ios/pcap/ipfinder.go

@@ -1,7 +1,7 @@
 package pcap
 
 import (
-	// "fmt"
+	"fmt"
 	"time"
 
 	"github.com/danielpaulus/go-ios/ios"
@@ -26,24 +26,22 @@ func (n PacketInfo) complete() bool {
 	return (n.IPv6 != "" && n.Mac != "") || (n.IPv4 != "" && n.Mac != "")
 }
 
-// FindIp reads pcap packets until one is found that matches the given MAC
+// FindIPByMac reads pcap packets until one is found that matches the given MAC
 // and contains an IP address. This won't work if the iOS device "automatic Wifi address" privacy
 // feature is enabled. The MAC needs to be static.
 func FindIPByMac(device ios.DeviceEntry) (NetworkInfo, error) {
 	mac, err := ios.GetWifiMac(device)
-	_ = mac
 	if err != nil {
-		return NetworkInfo{}, err
+		return NetworkInfo{}, fmt.Errorf("FindIPMyMac: unable to get WiFi MAC Address: %w", err)
 	}
 
 	// channel to receive PacketInfo
 	c := make(chan PacketInfo)
 	done := make(chan bool)
+	captureError := make(chan error)
 
 	go func() {
-		if err := startCapture(device, c, done); err != nil {
-			log.Error(err)
-		}
+		captureError <- startCapture(device, c, done)
 	}()
 
 	// captureDuration := time.Duration(10 * time.Second)
@@ -55,27 +53,27 @@ func FindIPByMac(device ios.DeviceEntry) (NetworkInfo, error) {
 		}
 	}
 
-	return NetworkInfo{}, nil
+	captureErrorResult := <-captureError
+	if captureErrorResult != nil {
+		return NetworkInfo{}, fmt.Errorf("FindIPByMac: failed to startCapture got err: %w", captureErrorResult)
+	}
+
+	return NetworkInfo{}, fmt.Errorf("failed to get any IP matching the MAC: %s", mac)
 }
 
-// FindIp reads pcap packets until one is found that matches the given MAC
-// and contains an IP address. This won't work if the iOS device "automatic Wifi address" privacy
-// feature is enabled. The MAC needs to be static.
+// FindIPByLazy reads pcap packets for a specified duration, whereafter it will
+// try to find the IP address that occurs the most times, and assume that is the IP of the device.
+// This is of course based on, that the device contacts mulitple IPs, and that there is some traffic.
+// If the device only contains a single IP, then it would be 50/50 which IP will be returned.
+// This is best effort! It's important to generate some traffic, when this function runs to get better results.
 func FindIPByLazy(device ios.DeviceEntry, capture_duration time.Duration) (NetworkInfo, error) {
-	mac, err := ios.GetWifiMac(device)
-	_ = mac
-	if err != nil {
-		return NetworkInfo{}, err
-	}
-
 	// channel to receive PacketInfo
 	c := make(chan PacketInfo)
 	done := make(chan bool)
+	captureError := make(chan error)
 
 	go func() {
-		if err := startCapture(device, c, done); err != nil {
-			log.Error(err)
-		}
+		captureError <- startCapture(device, c, done)
 	}()
 
 	// captureDuration := time.Duration(10 * time.Second)
@@ -96,6 +94,11 @@ func FindIPByLazy(device ios.DeviceEntry, capture_duration time.Duration) (Netwo
 		}
 	}
 
+	captureErrorResult := <-captureError
+	if captureErrorResult != nil {
+		return NetworkInfo{}, fmt.Errorf("FindIPByLazy: failed to startCapture got err: %w", captureErrorResult)
+	}
+
 	highestIPv4Hits, highestIPv4Addr := 0, ""
 	for ipv4, hits := range ipv4Hits {
 		if hits > highestIPv4Hits {
@@ -118,8 +121,9 @@ func FindIPByLazy(device ios.DeviceEntry, capture_duration time.Duration) (Netwo
 func startCapture(device ios.DeviceEntry, c chan PacketInfo, done chan bool) error {
 	intf, err := ios.ConnectToService(device, "com.apple.pcapd")
 	if err != nil {
-		return err
+		return fmt.Errorf("startCapture: failed connecting to com.apple.pcapd with err: %w", err)
 	}
+
 	plistCodec := ios.NewPlistCodec()
 	for {
 		// if the channel is signalling to stop
@@ -131,22 +135,18 @@ func startCapture(device ios.DeviceEntry, c chan PacketInfo, done chan bool) err
 
 		b, err := plistCodec.Decode(intf.Reader())
 		if err != nil {
-			return err
+			return fmt.Errorf("startCapture: failed decoding plistCodec err: %w", err)
 		}
 		decodedBytes, err := fromBytes(b)
 		if err != nil {
-			return err
+			return fmt.Errorf("startCapture: failed decoding fromBytes err: %w", err)
 		}
 		_, packet, err := getPacket(decodedBytes)
 		if err != nil {
-			return err
+			return fmt.Errorf("startCapture: failed getPacket err: %w", err)
 		}
 		if len(packet) > 0 {
-			pInfo, err := parsePacket(packet)
-			if err != nil {
-				return err
-			}
-
+			pInfo := parsePacket(packet)
 			if !pInfo.complete() {
 				continue
 			}
@@ -158,7 +158,7 @@ func startCapture(device ios.DeviceEntry, c chan PacketInfo, done chan bool) err
 	return nil
 }
 
-func parsePacket(p []byte) (PacketInfo, error) {
+func parsePacket(p []byte) PacketInfo {
 	packet := gopacket.NewPacket(p, layers.LayerTypeEthernet, gopacket.Default)
 	res := PacketInfo{}
 
@@ -183,5 +183,5 @@ func parsePacket(p []byte) (PacketInfo, error) {
 		}
 	}
 
-	return res, nil
+	return res
 }