Added docs and some minor improvements to code

README.md

@@ -0,0 +1,39 @@
+# Tun-Tana-Tun (टन-टना-टन)
+
+This project is a simple TCP Proxy allows bring remote ports listening on localhost.
+
+This main reason why this project exists is to be used with [gokrazy](https://gokrazy.org)
+on Raspberry Pi.
+
+# Usage
+
+```
+Usage of tuntanatun:
+  -debug
+        Enable Logs
+  -local string
+        Local Address (default "localhost:9999")
+  -remote string
+        Remote Address (default "localhost:80")
+```
+
+# A simple use case
+
+By using gokrazy there are challenges in creating a network interface and running [Tailscale](https://tailscale.com) on it, so we use userspace networking mode of Tailscale.
+
+There are work-arounds in accessing the peers using HTTP_PROXY variable, like most of the HTTP Requests can use this variable and proxy it through, the problem comes when there is a need to connect to a port with non-HTTP like connecting to a Database.
+
+The simple solution is to use `SOCKS` proxy, which allows all traffic to be proxied, and fortunately `tailscaled` allows setting a `SOCKS5` proxy listener/server through command line arguments.
+
+Now we can try to connect to the desired service/server in VPN, but alas, there's one more problem.
+
+To use this proxy the program should respect the proxy variable like `ALL_PROXY`, we know `HTTP_PROXY` is always used for any `net/http` functions but as this `SOCKS` proxy implementation is not yet in standard library normal packages don't use it.
+
+One option is to change the service code to use this proxy implementation, which is simply a change in `net.Dialer` using `proxy.FromEnvironment()`. Which requires changes in possibly everything and building again.
+
+Another option is to bring that port, from remote server to `localhost`. This is also called tunneling, or port forwarding. We use a local port and connect to remote host:port and proxy it.
+
+Following diagram shows this in action.
+
+![diagram](docs/tuntanatun-light.png)
+

main.go

@@ -2,7 +2,6 @@
 package main
 
 import (
-	"context"
 	"flag"
 	"fmt"
 	"io"
@@ -12,8 +11,11 @@ import (
 	"golang.org/x/net/proxy"
 )
 
-var localAddr *string = flag.String("local", "localhost:9999", "local address")
-var remoteAddr *string = flag.String("remote", "localhost:80", "remote address")
+var (
+	localAddr  = flag.String("local", "127.0.0.1:5432", "Local Address")
+	remoteAddr = flag.String("remote", "100.0.0.1:5432", "Remote Address")
+	debug      = flag.Bool("debug", false, "Enable Logs")
+)
 
 func main() {
 	flag.Parse()
@@ -21,19 +23,21 @@ func main() {
 
 	listener, err := net.Listen("tcp", *localAddr)
 	if err != nil {
-		panic(err)
+		log.Fatal(err)
 	}
 
 	for {
 		conn, err := listener.Accept()
-		log.Println("New connection", conn.RemoteAddr())
+		if *debug {
+			log.Println("New connection", conn.RemoteAddr())
+		}
 		if err != nil {
 			log.Println("error accepting connection", err)
 			continue
 		}
 		go func() {
 			defer conn.Close()
-			conn2, err := proxy.Dial(context.Background(), "tcp", *remoteAddr)
+			conn2, err := proxy.FromEnvironment().Dial("tcp", *remoteAddr)
 			if err != nil {
 				log.Println("error dialing remote addr", err)
 				return
@@ -43,7 +47,9 @@ func main() {
 			go copy(closer, conn2, conn)
 			go copy(closer, conn, conn2)
 			<-closer
-			log.Println("Connection complete", conn.RemoteAddr())
+			if *debug {
+				log.Println("Connection complete", conn.RemoteAddr())
+			}
 		}()
 	}
 }