From 8b49d09725d77c886a2f88596040d0c9ea471fd6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Torjus=20H=C3=A5kestad?= <torjus@usit.uio.no>
Date: Tue, 22 Feb 2022 20:22:36 +0100
Subject: [PATCH] Initial commit

---
 README.md | 20 ++++++++++++++++++
 go.mod    |  3 +++
 main.go   | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 84 insertions(+)
 create mode 100644 README.md
 create mode 100644 go.mod
 create mode 100644 main.go

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..ffe9519
--- /dev/null
+++ b/README.md
@@ -0,0 +1,20 @@
+# udprelay
+
+Minimal example to show how to relay UDP packets.
+
+
+
+## Build
+
+```text
+go build -o udprelay main.go
+```
+
+
+## Usage
+```text
+./udprelay -addr "127.0.0.1:9998" -dest "192.168.1.10:9999"
+2022/02/21 15:41:50 Listening to 127.0.0.1:9998 - Relaying to 192.168.1.10:9999
+...
+2022/02/21 15:42:03 3 bytes relayed from 127.0.0.1:64078 to destination.
+```
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..4fea550
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module git.t-juice.club/torjus/udprelay
+
+go 1.17
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..51d1430
--- /dev/null
+++ b/main.go
@@ -0,0 +1,61 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"net"
+)
+
+func main() {
+	var addr, dest string
+	flag.StringVar(&addr, "addr", ":9999", "listen address")
+	flag.StringVar(&dest, "dest", "", "destination")
+
+	flag.Parse()
+
+	if dest == "" {
+		fmt.Println("Error: missing -dest")
+		fmt.Println("run with -h to see options.")
+
+		return
+	}
+
+	log.Printf("Listening to %s - Relaying to %s", addr, dest)
+	raddr, err := net.ResolveUDPAddr("udp", dest)
+	if err != nil {
+		panic(err)
+	}
+	udpConn, err := net.DialUDP("udp", nil, raddr)
+	if err != nil {
+		panic(err)
+	}
+	defer udpConn.Close()
+
+	laddr, err := net.ResolveUDPAddr("udp", addr)
+	if err != nil {
+		panic(err)
+	}
+
+	l, err := net.ListenUDP("udp", laddr)
+	if err != nil {
+		panic(err)
+	}
+	defer l.Close()
+
+	for {
+		buf := make([]byte, 1024)
+		n, raddr, err := l.ReadFrom(buf)
+		log.Printf("received packet %d\n", n)
+
+		if err != nil {
+			panic(err)
+		}
+
+		if _, err := udpConn.Write(buf[0:n]); err != nil {
+			log.Printf("error relaying data: %s\n", err)
+		}
+
+		log.Printf("%d bytes relayed from %s to destination.\n", n, raddr.String())
+	}
+}