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pcap_linux.go
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pcap_linux.go
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//go:build pcap
// +build pcap
package phantomtcp
import (
"net"
"syscall"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
)
func SendPacket(packet gopacket.Packet) error {
switch link := packet.LinkLayer().(type) {
case *layers.Ethernet:
err := pcapHandle.WritePacketData(packet.Data())
return err
default:
payload := link.LayerPayload()
var sa syscall.Sockaddr
var lsa syscall.Sockaddr
var domain int
switch ip := packet.NetworkLayer().(type) {
case *layers.IPv4:
var addr [4]byte
copy(addr[:4], ip.DstIP.To4()[:4])
sa = &syscall.SockaddrInet4{Addr: addr, Port: 0}
var laddr [4]byte
copy(laddr[:4], ip.SrcIP.To4()[:4])
lsa = &syscall.SockaddrInet4{Addr: laddr, Port: 0}
domain = syscall.AF_INET
if payload[8] == 32 {
return nil
}
payload[8] = 32
case *layers.IPv6:
var addr [16]byte
copy(addr[:16], ip.DstIP[:16])
sa = &syscall.SockaddrInet6{Addr: addr, Port: 0}
var laddr [16]byte
copy(laddr[:16], ip.SrcIP[:16])
lsa = &syscall.SockaddrInet6{Addr: laddr, Port: 0}
domain = syscall.AF_INET6
if payload[7] == 32 {
return nil
}
payload[7] = 32
}
raw_fd, err := syscall.Socket(domain, syscall.SOCK_RAW, syscall.IPPROTO_RAW)
if err != nil {
syscall.Close(raw_fd)
return err
}
err = syscall.Bind(raw_fd, lsa)
if err != nil {
syscall.Close(raw_fd)
return err
}
err = syscall.Sendto(raw_fd, payload, 0, sa)
if err != nil {
syscall.Close(raw_fd)
return err
}
syscall.Close(raw_fd)
}
return nil
}
func ModifyAndSendPacket(connInfo *ConnectionInfo, payload []byte, hint uint32, ttl uint8, count int) error {
linkLayer := connInfo.Link
ipLayer := connInfo.IP
var tcpLayer *layers.TCP
if hint&HINT_TFO != 0 {
tcpLayer = &connInfo.TCP
tcpLayer.Seq -= uint32(len(payload))
var cookie []byte = nil
switch ip := ipLayer.(type) {
case *layers.IPv4:
result, ok := TFOCookies.Load(ip.DstIP.String())
if ok {
cookie = result.([]byte)
} else {
payload = nil
}
case *layers.IPv6:
result, ok := TFOCookies.Load(ip.DstIP.String())
if ok {
cookie = result.([]byte)
} else {
payload = nil
}
}
tcpLayer.Options = append(connInfo.TCP.Options,
layers.TCPOption{34, uint8(len(cookie)), cookie},
)
} else {
tcpLayer = &layers.TCP{
SrcPort: connInfo.TCP.SrcPort,
DstPort: connInfo.TCP.DstPort,
Seq: connInfo.TCP.Seq,
Ack: connInfo.TCP.Ack,
DataOffset: 5,
ACK: true,
PSH: true,
Window: connInfo.TCP.Window,
}
if hint&HINT_WMD5 != 0 {
tcpLayer.Options = []layers.TCPOption{
layers.TCPOption{19, 16, []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
}
} else if hint&HINT_WTIME != 0 {
tcpLayer.Options = []layers.TCPOption{
layers.TCPOption{8, 8, []byte{0, 0, 0, 0, 0, 0, 0, 0}},
}
}
}
if hint&HINT_NACK != 0 {
tcpLayer.ACK = false
tcpLayer.Ack = 0
} else if hint&HINT_WACK != 0 {
tcpLayer.Ack += uint32(tcpLayer.Window)
}
// And create the packet with the layers
buffer := gopacket.NewSerializeBuffer()
var options gopacket.SerializeOptions
options.FixLengths = true
if hint&HINT_WCSUM == 0 {
options.ComputeChecksums = true
}
if hint&HINT_WSEQ != 0 {
tcpLayer.Seq--
fakepayload := make([]byte, len(payload)+1)
fakepayload[0] = 0xFF
copy(fakepayload[1:], payload)
payload = fakepayload
}
tcpLayer.SetNetworkLayerForChecksum(ipLayer)
if linkLayer != nil {
link := linkLayer.(*layers.Ethernet)
switch ip := ipLayer.(type) {
case *layers.IPv4:
if hint&HINT_TTL != 0 {
ip.TTL = ttl
}
gopacket.SerializeLayers(buffer, options,
link, ip, tcpLayer, gopacket.Payload(payload),
)
case *layers.IPv6:
if hint&HINT_TTL != 0 {
ip.HopLimit = ttl
}
gopacket.SerializeLayers(buffer, options,
link, ip, tcpLayer, gopacket.Payload(payload),
)
}
outgoingPacket := buffer.Bytes()
for i := 0; i < count; i++ {
err := pcapHandle.WritePacketData(outgoingPacket)
if err != nil {
return err
}
}
} else {
var network string
var laddr net.IPAddr
var raddr net.IPAddr
switch ip := ipLayer.(type) {
case *layers.IPv4:
laddr = net.IPAddr{ip.SrcIP, ""}
raddr = net.IPAddr{ip.DstIP, ""}
network = "ip4:tcp"
case *layers.IPv6:
laddr = net.IPAddr{ip.SrcIP, ""}
raddr = net.IPAddr{ip.DstIP, ""}
network = "ip6:tcp"
}
conn, err := net.DialIP(network, &laddr, &raddr)
if err != nil {
return err
}
defer conn.Close()
if hint&HINT_TTL != 0 {
f, err := conn.File()
if err != nil {
return err
}
defer f.Close()
fd := int(f.Fd())
err = syscall.SetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_TTL, int(ttl))
if err != nil {
return err
}
}
tcpLayer.SetNetworkLayerForChecksum(ipLayer)
gopacket.SerializeLayers(buffer, options,
tcpLayer, gopacket.Payload(payload),
)
outgoingPacket := buffer.Bytes()
for i := 0; i < count; i++ {
_, err = conn.Write(outgoingPacket)
if err != nil {
return err
}
}
}
return nil
}