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cursed gso
This commit is contained in:
JackDoan
191
cmd/gso/gso.go
Normal file
191
cmd/gso/gso.go
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@@ -0,0 +1,191 @@
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package main
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import (
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"encoding/binary"
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"errors"
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"flag"
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"fmt"
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"log"
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"net"
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"net/netip"
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"time"
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"unsafe"
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"golang.org/x/sys/unix"
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)
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const (
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// UDP_SEGMENT enables GSO segmentation
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UDP_SEGMENT = 103
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// Maximum GSO segment size (typical MTU - headers)
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maxGSOSize = 1400
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)
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func main() {
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destAddr := flag.String("dest", "10.4.0.16:4202", "Destination address")
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gsoSize := flag.Int("gso", 1400, "GSO segment size")
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totalSize := flag.Int("size", 14000, "Total payload size to send")
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count := flag.Int("count", 1, "Number of packets to send")
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flag.Parse()
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if *gsoSize > maxGSOSize {
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log.Fatalf("GSO size %d exceeds maximum %d", *gsoSize, maxGSOSize)
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}
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// Resolve destination address
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_, err := net.ResolveUDPAddr("udp", *destAddr)
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if err != nil {
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log.Fatalf("Failed to resolve address: %v", err)
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}
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// Create a raw UDP socket with GSO support
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fd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_UDP)
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if err != nil {
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log.Fatalf("Failed to create socket: %v", err)
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}
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defer unix.Close(fd)
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// Bind to a local address
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localAddr := &unix.SockaddrInet4{
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Port: 0, // Let the system choose a port
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}
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if err := unix.Bind(fd, localAddr); err != nil {
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log.Fatalf("Failed to bind socket: %v", err)
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}
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fmt.Printf("Sending UDP packets with GSO enabled\n")
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fmt.Printf("Destination: %s\n", *destAddr)
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fmt.Printf("GSO segment size: %d bytes\n", *gsoSize)
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fmt.Printf("Total payload size: %d bytes\n", *totalSize)
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fmt.Printf("Number of packets: %d\n\n", *count)
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// Create payload
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payload := make([]byte, *totalSize)
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for i := range payload {
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payload[i] = byte(i % 256)
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}
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dest := netip.MustParseAddrPort(*destAddr)
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//if err := unix.SetsockoptInt(fd, unix.SOL_UDP, unix.UDP_SEGMENT, 1400); err != nil {
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// panic(err)
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//}
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for i := 0; i < *count; i++ {
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err := WriteBatch(fd, payload, dest, uint16(*gsoSize), true)
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if err != nil {
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log.Printf("Send error on packet %d: %v", i, err)
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continue
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}
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if (i+1)%100 == 0 || i == *count-1 {
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fmt.Printf("Sent %d packets\n", i+1)
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}
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}
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fmt.Printf("now, let's send without the correct ctrl header\n")
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time.Sleep(time.Second)
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for i := 0; i < *count; i++ {
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err := WriteBatch(fd, payload, dest, uint16(*gsoSize), false)
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if err != nil {
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log.Printf("Send error on packet %d: %v", i, err)
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continue
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}
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if (i+1)%100 == 0 || i == *count-1 {
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fmt.Printf("Sent %d packets\n", i+1)
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}
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}
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}
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func WriteBatch(fd int, payload []byte, addr netip.AddrPort, segSize uint16, withHeader bool) error {
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msgs := make([]rawMessage, 0, 1)
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iovs := make([]iovec, 0, 1)
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names := make([][unix.SizeofSockaddrInet6]byte, 0, 1)
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sent := 0
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pkts := []BatchPacket{
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{
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Payload: payload,
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Addr: addr,
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},
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}
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for _, pkt := range pkts {
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if len(pkt.Payload) == 0 {
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sent++
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continue
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}
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msgs = append(msgs, rawMessage{})
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iovs = append(iovs, iovec{})
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names = append(names, [unix.SizeofSockaddrInet6]byte{})
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idx := len(msgs) - 1
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msg := &msgs[idx]
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iov := &iovs[idx]
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name := &names[idx]
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setIovecSlice(iov, pkt.Payload)
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msg.Hdr.Iov = iov
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msg.Hdr.Iovlen = 1
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if withHeader {
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setRawMessageControl(msg, buildGSOControlMessage(segSize)) //
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} else {
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setRawMessageControl(msg, nil) //
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}
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msg.Hdr.Flags = 0
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nameLen, err := encodeSockaddr(name[:], pkt.Addr)
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if err != nil {
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return err
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}
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msg.Hdr.Name = &name[0]
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msg.Hdr.Namelen = nameLen
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}
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if len(msgs) == 0 {
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return errors.New("nothing to write")
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}
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offset := 0
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for offset < len(msgs) {
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n, _, errno := unix.Syscall6(
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unix.SYS_SENDMMSG,
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uintptr(fd),
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uintptr(unsafe.Pointer(&msgs[offset])),
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uintptr(len(msgs)-offset),
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0,
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0,
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0,
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)
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if errno != 0 {
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if errno == unix.EINTR {
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continue
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}
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return &net.OpError{Op: "sendmmsg", Err: errno}
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}
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if n == 0 {
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break
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}
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offset += int(n)
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}
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return nil
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}
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func buildGSOControlMessage(segSize uint16) []byte {
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control := make([]byte, unix.CmsgSpace(2))
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hdr := (*unix.Cmsghdr)(unsafe.Pointer(&control[0]))
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hdr.Level = unix.SOL_UDP
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hdr.Type = unix.UDP_SEGMENT
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setCmsgLen(hdr, unix.CmsgLen(2))
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binary.NativeEndian.PutUint16(control[unix.CmsgLen(0):unix.CmsgLen(0)+2], uint16(segSize))
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return control
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}
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85
cmd/gso/helper.go
Normal file
85
cmd/gso/helper.go
Normal file
@@ -0,0 +1,85 @@
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package main
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import (
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"encoding/binary"
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"fmt"
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"net/netip"
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"unsafe"
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"golang.org/x/sys/unix"
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)
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type iovec struct {
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Base *byte
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Len uint64
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}
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type msghdr struct {
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Name *byte
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Namelen uint32
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Pad0 [4]byte
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Iov *iovec
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Iovlen uint64
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Control *byte
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Controllen uint64
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Flags int32
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Pad1 [4]byte
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}
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type rawMessage struct {
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Hdr msghdr
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Len uint32
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Pad0 [4]byte
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}
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type BatchPacket struct {
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Payload []byte
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Addr netip.AddrPort
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}
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func encodeSockaddr(dst []byte, addr netip.AddrPort) (uint32, error) {
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if addr.Addr().Is4() {
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if !addr.Addr().Is4() {
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return 0, fmt.Errorf("Listener is IPv4, but writing to IPv6 remote")
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}
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var sa unix.RawSockaddrInet4
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sa.Family = unix.AF_INET
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sa.Addr = addr.Addr().As4()
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binary.BigEndian.PutUint16((*[2]byte)(unsafe.Pointer(&sa.Port))[:], addr.Port())
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size := unix.SizeofSockaddrInet4
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copy(dst[:size], (*(*[unix.SizeofSockaddrInet4]byte)(unsafe.Pointer(&sa)))[:])
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return uint32(size), nil
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}
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var sa unix.RawSockaddrInet6
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sa.Family = unix.AF_INET6
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sa.Addr = addr.Addr().As16()
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binary.BigEndian.PutUint16((*[2]byte)(unsafe.Pointer(&sa.Port))[:], addr.Port())
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size := unix.SizeofSockaddrInet6
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copy(dst[:size], (*(*[unix.SizeofSockaddrInet6]byte)(unsafe.Pointer(&sa)))[:])
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return uint32(size), nil
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}
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func setRawMessageControl(msg *rawMessage, buf []byte) {
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if len(buf) == 0 {
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msg.Hdr.Control = nil
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msg.Hdr.Controllen = 0
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return
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}
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msg.Hdr.Control = &buf[0]
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msg.Hdr.Controllen = uint64(len(buf))
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}
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func setCmsgLen(h *unix.Cmsghdr, l int) {
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h.Len = uint64(l)
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}
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func setIovecSlice(iov *iovec, b []byte) {
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if len(b) == 0 {
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iov.Base = nil
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iov.Len = 0
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return
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}
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iov.Base = &b[0]
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iov.Len = uint64(len(b))
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}
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