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package packet
import (
"fmt"
"math/rand"
"net"
"time"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/google/gopacket/pcap"
)
func Ack(targetIP string, targetPort int) error {
random := rand.New(rand.NewSource(time.Now().UnixNano()))
srcIP := net.ParseIP("0.0.0.0").To4()
srcPort := random.Intn(65535)
dstIP := net.ParseIP(targetIP).To4()
dstPort := targetPort
// Open up a packet handle for packet writes.
handle, err := pcap.OpenLive("bridge100", 1024, false, pcap.BlockForever)
if err != nil {
return fmt.Errorf("Failed to open device: %v", err)
}
defer handle.Close()
// Ethernet layer
eth := &layers.Ethernet{
SrcMAC: net.HardwareAddr{0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF},
DstMAC: net.HardwareAddr{0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF},
EthernetType: layers.EthernetTypeIPv4,
}
// IP layer
ip := &layers.IPv4{
SrcIP: srcIP,
DstIP: dstIP,
Version: 4,
TTL: 64,
Protocol: layers.IPProtocolTCP,
}
// TCP layer
tcp := &layers.TCP{
SrcPort: layers.TCPPort(srcPort),
DstPort: layers.TCPPort(dstPort),
ACK: true,
Seq: uint32(rand.Int31()),
Ack: uint32(rand.Int31()),
Window: 14600,
}
tcp.SetNetworkLayerForChecksum(ip)
// Serialize the packet
buf := gopacket.NewSerializeBuffer()
opts := gopacket.SerializeOptions{
ComputeChecksums: true,
FixLengths: true,
}
err = gopacket.SerializeLayers(buf, opts, eth, ip, tcp)
if err != nil {
return fmt.Errorf("Failed to serialize packet: %v", err)
}
// Send the packet
err = handle.WritePacketData(buf.Bytes())
if err != nil {
return fmt.Errorf("Failed to write packet: %v", err)
}
return nil
}
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