Golang: UDP packet forwarding to multiple ports - go

Need help or suggestions in terms of how to do packet forwarding correctly. I received UDP packets from another server and I want to write a function to send the same packets to different processes running on the same machine.
From Server --> Client(Main Process) --> Process 1, Process 2, Process 3
Example Code: For Sending to one service Running on different Ports.
package main
import (
"fmt"
"log"
"net"
)
var message = make([]byte, 1024)
func main() {
s, err := net.ResolveUDPAddr("udp4", "127.0.0.1:6001")
c, err := net.DialUDP("udp4", nil, s)
// c, err := net.ListenUDP("udp4", s)
if err != nil {
fmt.Println(err)
panic(err)
}
defer c.Close()
message := []byte("message")
for {
_, err = c.Write(message)
fmt.Println(">>> Request packet sent to: 127.0.0.1:6001")
if err != nil {
log.Println(err)
}
// for {
// b := make([]byte, 1024)
fmt.Println("waiting for data")
n, addr, err := c.ReadFromUDP(message)
if err != nil {
fmt.Println(err)
}
fmt.Println(addr)
fmt.Println(string(message[:n]))
SendtoAnotherPort(6002, message[:n])
}
}
// SendtoAnotherPort sends a packet to another port
func SendtoAnotherPort(port int, msg []byte) {
s, err := net.ResolveUDPAddr("udp4", "127.0.0.1:6002")
c, err := net.DialUDP("udp4", nil, s)
// c, err := net.ListenUDP("udp4", s)
if err != nil {
fmt.Println(err)
panic(err)
}
_, err = c.WriteTo(message, s)
if err != nil {
log.Println(err)
}
}
Could this be the correct way of doing it? Or Any other suggestions.

Related

Golang socks5 proxy client

I'm trying to make a proxy:
I need to listen to port 1080 (socks 5), and complete a request to a destination using an external ip:port socks 5, I managed to open this connection with the external ip, but I don't know how I could complete the request to the target destination using that external ip.
could someone help me with this?
package main
import (
"bufio"
"errors"
"fmt"
"io"
"log"
"net"
)
const (
ConnectCommand = uint8(1)
BindCommand = uint8(2)
AssociateCommand = uint8(3)
ipv4Address = uint8(1)
fqdnAddress = uint8(3)
ipv6Address = uint8(4)
)
type AddrSpec struct {
FQDN string
IP net.IP
Port int
}
func main() {
l, err := net.Listen("tcp", "127.0.0.1:1080")
if err != nil {
fmt.Print(err)
}
defer l.Close()
for {
conn, err := l.Accept()
if err != nil {
fmt.Print(err)
}
go handle(conn)
}
}
func handle(conn net.Conn) {
defer func() {
_ = conn.Close()
}()
bufConn := bufio.NewReader(conn)
version := []byte{0}
if _, err := bufConn.Read(version); err != nil {
log.Fatalf("cannot read version: %s", err.Error())
}
if version[0] != uint8(5) {
log.Fatalf("unsupported SOCKS version: %v", version)
}
socks5ExternalConn, err := net.Dial("tcp", externalSOCKS5Proxy())
if err != nil {
log.Printf("Connection error: %s", err.Error())
}
dest, err := readAddrSpec(bufConn)
if err != nil {
}
// how i can send request to server with external conn?
}
func externalSOCKS5Proxy() string {
return "externalip:externalport"
}
func readAddrSpec(r io.Reader) (*AddrSpec, error) {
d := &AddrSpec{}
// Get the address type
addrType := []byte{0}
if _, err := r.Read(addrType); err != nil {
return nil, err
}
// Handle on a per type basis
switch addrType[0] {
case ipv4Address:
addr := make([]byte, 4)
if _, err := io.ReadAtLeast(r, addr, len(addr)); err != nil {
return nil, err
}
d.IP = net.IP(addr)
case ipv6Address:
addr := make([]byte, 16)
if _, err := io.ReadAtLeast(r, addr, len(addr)); err != nil {
return nil, err
}
d.IP = net.IP(addr)
case fqdnAddress:
if _, err := r.Read(addrType); err != nil {
return nil, err
}
addrLen := int(addrType[0])
fqdn := make([]byte, addrLen)
if _, err := io.ReadAtLeast(r, fqdn, addrLen); err != nil {
return nil, err
}
d.FQDN = string(fqdn)
default:
return nil, errors.New("unrecognizedAddrType")
}
// Read the port
port := []byte{0, 0}
if _, err := io.ReadAtLeast(r, port, 2); err != nil {
return nil, err
}
d.Port = (int(port[0]) << 8) | int(port[1])
return d, nil
}

go udp requests (packet) loss

i wrote simple server and client for tcp and udp connection
package main
//server.go
import (
"fmt"
"net"
"os"
"os/signal"
"syscall"
)
func main() {
tcp := 0
udp := 0
defer func(o, t *int) {
fmt.Println(*o, *t)
}(&tcp, &udp)
go func() {
l, err := net.ListenTCP("tcp", &net.TCPAddr{
IP: net.ParseIP("0.0.0.0"),
Port: 3000,
})
if err != nil {
panic(err)
}
b := make([]byte, 24)
for {
conn, err := l.Accept()
if err != nil {
continue
}
n, err := conn.Read(b)
if err != nil {
continue
}
r := string(b[:n])
if r == "close" {
conn.Close()
break
} else {
_, err = conn.Write([]byte("pong"))
if err != nil {
continue
}
}
conn.Close()
tcp++
}
l.Close()
}()
go func() {
conn, err := net.ListenUDP("udp", &net.UDPAddr{
IP: net.ParseIP("0.0.0.0"),
Port: 3000,
})
if err != nil {
panic(err)
}
b := make([]byte, 24)
for {
n, addr, err := conn.ReadFromUDP(b)
if err != nil {
continue
}
r := string(b[:n])
if r == "close" {
break
} else {
_, err = conn.WriteToUDP([]byte("pong"), addr)
if err != nil {
continue
}
}
udp++
}
conn.Close()
}()
signals := make(chan os.Signal, 1)
signal.Notify(signals, os.Interrupt, syscall.SIGTERM)
<-signals
}
package main
//client.go
import (
"fmt"
"net"
"os"
"os/signal"
"strconv"
"sync/atomic"
"syscall"
"time"
)
func main() {
t := "tcp"
m := "ping"
c := 1
if len(os.Args) > 1 {
t = os.Args[1]
}
if len(os.Args) > 2 {
m = os.Args[2]
}
if len(os.Args) > 3 {
c, _ = strconv.Atoi(os.Args[3])
}
tcp := int64(0)
udp := int64(0)
defer func(o, t *int64) {
fmt.Println(*o, *t)
}(&tcp, &udp)
if c == 1 {
if t == "tcp" {
addr, err := net.ResolveTCPAddr("tcp", ":3000")
if err != nil {
panic(err)
}
conn, err := net.DialTCP("tcp", nil, addr)
if err != nil {
panic(err)
}
_, err = conn.Write([]byte(m))
if err != nil {
panic(err)
}
tcp++
}
if t == "udp" {
addr, err := net.ResolveUDPAddr("udp", ":3000")
if err != nil {
panic(err)
}
conn, err := net.DialUDP("udp", nil, addr)
if err != nil {
panic(err)
}
_, err = conn.Write([]byte(m))
if err != nil {
panic(err)
}
udp++
}
os.Exit(0)
}
for i := 0; i < c; i++ {
go func() {
a1, err := net.ResolveTCPAddr("tcp", ":3000")
if err != nil {
panic(err)
}
c1, err := net.DialTCP("tcp", nil, a1)
if err != nil {
panic(err)
}
_, err = c1.Write([]byte(m))
if err != nil {
panic(err)
}
buf := make([]byte, 24)
n, err := c1.Read(buf)
if err != nil {
panic(err)
}
if string(buf[:n]) != "pong" {
panic(1)
}
err = c1.Close()
if err != nil {
panic(err)
}
g := atomic.AddInt64(&tcp, 1)
if g % 100 == 0 {
fmt.Println("tcp", g)
time.Sleep(time.Millisecond * 1000)
}
}()
go func() {
a2, err := net.ResolveUDPAddr("udp", ":3000")
if err != nil {
panic(err)
}
c2, err := net.DialUDP("udp", nil, a2)
if err != nil {
panic(err)
}
_, err = c2.Write([]byte(m))
if err != nil {
panic(err)
}
buf := make([]byte, 24)
n, err := c2.Read(buf)
if err != nil {
panic(err)
}
if string(buf[:n]) != "pong" {
panic(1)
}
err = c2.Close()
if err != nil {
panic(err)
}
g := atomic.AddInt64(&udp, 1)
if g % 100 == 0 {
fmt.Println("udp", g)
time.Sleep(time.Millisecond * 1000)
}
}()
}
signals := make(chan os.Signal, 1)
signal.Notify(signals, os.Interrupt, syscall.SIGTERM)
<-signals
}
and get a strange behavior: not all udp requests are sent or handled on many connections.
When i sent 100 or 200 both server and client tells me that all requests worked but from 1000 there is a strange ~5% requests loss on udp for both server and client but no panic.
I know udp allows packet loss but 5% on localhost requests seems like an error.
As we know, the UDP is connectionless, so packet loss may be caused by this nature of UDP. There could be several ways to lower the rate of packet loss.
Slow down the rate of packets sent on the client side
Call SetWriteBuffer to increase the buffer size on the client side and set SetReadBuffer to increase the buffer size on the server side
conn, err := net.DialUDP("udp", nil, addr)
err = conn.SetWriteBuffer(64 * 1024 * 1024)
Check the system network information through netstat -s -udp and get UDP statistics information. You could try to change the default value of rmem_max and rmem_default on the server side. For more details, please refer to 1 and 2

Cannot receive response packets from multicast server in golang

I setup a udp server listening multicast trafic, and create a client to sent test packet. When the server receives the package, it will send a response. Everything is ok, except the client cannot receive the packet from the server. Why?
package main
import (
"log"
"net"
"os"
"time"
"golang.org/x/net/ipv4"
)
func SetupMulticast(ifn, addr string) {
ifi, err := net.InterfaceByName(ifn)
if err != nil {
log.Fatal(err)
}
//server
c, err := net.ListenPacket("udp4", addr)
if err != nil {
log.Fatal(err)
}
log.Printf("listen ad:%s\n", addr)
p := ipv4.NewPacketConn(c)
gAddr, err2 := net.ResolveUDPAddr("udp4", addr)
if err2 != nil {
log.Fatal(err2)
}
if err := p.JoinGroup(ifi, gAddr); err != nil {
log.Fatal(err)
}
if err := p.SetControlMessage(ipv4.FlagDst|ipv4.FlagSrc, true); err != nil {
log.Fatal(err)
}
go func() {
b := make([]byte, 1500)
for {
n, cm, src, err := p.ReadFrom(b)
if err != nil {
break
}
log.Println("receive:", string(b[:n]), cm.Dst.IsMulticast(), cm.Dst)
if n2, err := p.WriteTo([]byte("world!"), nil, src); err != nil {
log.Printf("fail to write back:%v\n", err)
} else {
log.Printf("write back addr: %s length:%d\n", src, n2)
}
}
}()
//client
if conn, err2 := net.DialUDP("udp4", nil /*src*/, gAddr); err2 != nil {
log.Fatal(err)
} else {
go func() {
for {
log.Println("write hello...")
conn.Write([]byte("hello"))
time.Sleep(time.Second * 2)
}
}()
go func() {
b2 := make([]byte, 1500)
for {
n, err := conn.Read(b2)
if err != nil {
log.Panic(err)
}
log.Printf("sender received response:%s\n", string(b2[:n]))
}
}()
}
}
func main() {
If := os.Args[1] //ens33
Addr := os.Args[2] //224.0.0.248:1025
SetupMulticast(If, Addr)
for {
}
}
And the output:
2022/08/17 22:53:53 listen ad:224.0.0.248:1025
2022/08/17 22:53:53 write hello...
2022/08/17 22:53:53 receive: hello true 224.0.0.248
2022/08/17 22:53:53 write back addr: 192.168.19.131:43925 length:6
2022/08/17 22:53:55 write hello...
2022/08/17 22:53:55 receive: hello true 224.0.0.248
2022/08/17 22:53:55 write back addr: 192.168.19.131:43925 length:6
From the logs, there are no any "sender received response" record. I don't know why?

How to close client socket in udp

I have a simple UDP server all that I want is if the IP is equal to 1.1.1.1 for example the client socket will close its like a blacklist system
My code
func main() {
arguments := os.Args
if len(arguments) == 1 {
fmt.Println("Please provide a port number!")
return
}
PORT := ":" + arguments[1]
s, err := net.ResolveUDPAddr("udp4", PORT)
if err != nil {
fmt.Println(err)
return
}
connection, err := net.ListenUDP("udp4", s)
if err != nil {
fmt.Println(err)
return
}
defer connection.Close()
buffer := make([]byte, 1024)
for {
n, addr, err := connection.ReadFromUDP(buffer)
fmt.Print("-> ", string(buffer[0:n-1]))
data := []byte(strconv.Itoa(random(1, 1001)))
fmt.Printf("data: %s\n", string(data))
_, err = connection.WriteToUDP(data, addr)
if err != nil {
fmt.Println(err)
return
}
}
}

Simple server client communication not working

This seemingly simple example is not working as expected and I feel bad for asking but here goes:
There's a client that retries connecting to the server, sends a message, and then waits for a response:
func client() {
var conn net.Conn
var err error
// retry server until it is up
for {
conn, err = net.Dial("tcp", ":8081")
if err == nil {
break
}
log.Println(err)
time.Sleep(time.Second)
}
// write to server
_, err = conn.Write([]byte("request"))
if err != nil {
log.Println(err)
return
}
// block & read from server
var buf []byte
n, err := conn.Read(buf)
if err != nil {
log.Println(err)
return
}
log.Printf("From server: %s\n", buf[:n])
}
It connects to a server which for each connection, reads and interprets the sent data, and sends a response if needed:
func server() {
ln, _ := net.Listen("tcp", ":8081")
for {
conn, _ := ln.Accept()
go handleConn(conn)
}
}
func handleConn(conn net.Conn) {
var buf []byte
n, err := conn.Read(buf)
if err != nil {
return
}
log.Printf("Server got: %s\n", buf)
if string(buf[:n]) == "request" {
_, _ = conn.Write([]byte("response"))
}
}
All driven by the main function:
func main() {
go client()
server()
}
Error handling is omitted for brevity. The expected behavior is that the client will connect to the server and send the message "request" and then block on the read. The server receives "request" and sends the message "response" back to the same connection. The client unblock, prints the received message and exits. Instead, when the program is run, the following is printed:
2019/09/01 22:24:02 From server:
2019/09/01 22:24:02 Server got:
Suggesting that no data was exchanged, and that the client did not block.
The looping in client is strange!
The looping not make sense if read/write is out.
But the error is only this:
//var buf []byte <--- this read 0 bytes
buf := make([]byte, 1024)
n, err := conn.Read(buf)
A proposal for you:
package main
import (
"log"
"net"
"time"
)
func client() {
var conn net.Conn
var err error
// retry server until it is up
for {
log.Printf("Connecting...")
conn, err = net.Dial("tcp", ":8082")
if err != nil {
log.Println(err)
break
}
time.Sleep(time.Second)
// write to server
log.Printf("Writing...")
_, err = conn.Write([]byte("request"))
if err != nil {
log.Println(err)
return
}
// block & read from server
log.Printf("Reading...")
var buf []byte
n, err := conn.Read(buf)
if err != nil {
log.Println(err)
return
}
log.Printf("From server: %s\n", buf[:n])
}
}
func server() {
ln, _ := net.Listen("tcp", ":8082")
for {
conn, _ := ln.Accept()
go handleConn(conn)
}
}
func handleConn(conn net.Conn) {
buf := make([]byte, 1024)
n, err := conn.Read(buf)
if err != nil {
return
}
log.Printf("Server got: [%d bytes] %s\n", n, buf)
if string(buf[:n]) == "request" {
_, _ = conn.Write([]byte("response"))
}
conn.Close()
}
func main() {
go client()
server()
}

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