ebpf: experiments.

ebpf/snoop/main.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+
+	"golang.zx2c4.com/wireguard/tun"
+)
+
+func main() {
+	if err := run(); err != nil {
+		log.Fatal(err)
+		os.Exit(1)
+	}
+}
+
+const ifaceName = "hack0"
+
+func run() error {
+	dev, err := tun.CreateTUN(ifaceName, 1280)
+	if err != nil {
+		return fmt.Errorf("creating tun: %v", err)
+	}
+	defer dev.Close()
+
+	if err := exec.Command("ip", "link", "set", ifaceName, "addrgenmode", "none").Run(); err != nil {
+		return fmt.Errorf("bringing up iface: %v", err)
+	}
+	if err := exec.Command("ip", "link", "set", ifaceName, "up").Run(); err != nil {
+		return fmt.Errorf("bringing up iface: %v", err)
+	}
+
+	for {
+		var b [1284]byte
+		n, err := dev.Read(b[:], 4)
+		if err != nil {
+			return fmt.Errorf("reading from tun: %v", err)
+		}
+
+		bs := b[4 : 4+n]
+
+		fmt.Printf("received packet of %d bytes\n", len(bs))
+		hexdump(bs)
+	}
+}
+
+func hexdump(bs []byte) {
+	for i := range bs {
+		switch {
+		case i == 0:
+		case i%16 == 0:
+			fmt.Println("")
+		case i%8 == 0:
+			fmt.Printf("  ")
+		}
+		fmt.Printf("%02x ", bs[i])
+	}
+	fmt.Printf("\n\n")
+}