Init commit: open file and print link type

src/analyzer.go

@@ -0,0 +1,20 @@
+package main
+
+import (
+	"github.com/google/gopacket"
+	"github.com/google/gopacket/layers"
+	"log"
+)
+
+// Analyzes the given packet source
+func analyzePCAP(source *gopacket.PacketSource, linkType layers.LinkType) error {
+	log.Printf("PCAP capture link type is %s (ID %d)", getNameOfLinkType(linkType), linkType)
+	// TODO: maybe, just maybe, we wanna print more here than just the link type :)
+	_, _ = source, linkType
+	return nil
+}
+
+// Returns the name of the LinkType constant handed over
+func getNameOfLinkType(lt layers.LinkType) string {
+	return lt.String()
+}

src/file.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"flag"
+	"github.com/google/gopacket"
+	"github.com/google/gopacket/layers"
+	"github.com/google/gopacket/pcap"
+)
+
+var (
+	filenameFlag *string
+)
+
+// Registers the flag --file
+func registerFileFlags() {
+	filenameFlag = flag.String("file", "", "PCAP file to base analysis on")
+}
+
+// Opens the PCAP, returns its packets and the link type or an error
+func openPCAP() (*gopacket.PacketSource, layers.LinkType, error) {
+	// Open specified file
+	handle, openErr := pcap.OpenOffline(*filenameFlag)
+	if openErr != nil {
+		// There were some problems opening the file
+		return nil, 0, openErr
+	}
+
+	// Open given handle as packet source and return it
+	packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
+	return packetSource, handle.LinkType(), nil
+}

src/main.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+)
+
+func main() {
+	// important things first
+	printMOTD()
+
+	// register flags
+	registerFileFlags()
+	flag.Parse()
+
+	// Open the given PCAP
+	packetSource, linkType, fileErr := openPCAP()
+	if fileErr != nil {
+		// Encountered problems with the PCAP - permission and/or existance error
+		log.Fatalf("Error occured while opeining specified file: %s", fileErr.Error())
+	}
+
+	// Start analyzing
+	analyzeErr := analyzePCAP(packetSource, linkType)
+	if analyzeErr != nil {
+		// Mh, encountered some problems while analyzingfil
+		log.Fatalf("Error occurred while analyzing: %s", analyzeErr.Error())
+	}
+}
+
+// Prints a simple figlet-style ASCII art
+func printMOTD() {
+	fmt.Println(" _ __   __ _ _ __   ___ __ _ _ __")
+	fmt.Println("| '_ \\ / _` | '_ \\ / __/ _` | '_ \\")
+	fmt.Println("| |_) | (_| | | | | (_| (_| | |_) |")
+	fmt.Println("| .__/ \\__,_|_| |_|\\___\\__,_| .__/")
+	fmt.Println("|_|                         |_|")
+	fmt.Println("PanCAP: Analyzer for capture files\n")
+}