Initial commit of code

README.md

@@ -1,4 +1,20 @@
 fldigiattach
 ============
 
-Use fldigi as a modem for Linux's AX.25-stack
+```text
+// fldigiattach is a tool to allow use of fldigi as a modem for Linux's AX.25-stack.
+//
+// This program creates a pty and uses kissattach(8) to attach the KISS
+// interface of fldigi to an axport. After attachment, this program will
+// act as a proxy between the AX.25-stack and fldigi to allow AX.25 over fldigi.
+//
+// Because kissattach daemonizes, you must kill it (as normal) after execution.
+//
+// fldigi 3.22 or later is required (KISS interface), as is kissattach (ax25-tools).
+//
+//   Usage of fldigiattach:
+//     -mtu=0: Sets the mtu of the interface [default is paclen parameter in axports].
+//     -port="": Name of a port given in the axports file
+//     -rx-addr="127.0.0.1:7343": fldigi's rx address
+//     -tx-addr="127.0.0.1:7342": fldigi's tx address
+```

forward.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"io"
+	"log"
+	"net"
+	"os"
+)
+
+func startForwarding(txAddr string, rxAddr string, pty *os.File) {
+	go func() {
+		if _, err := txFrom(txAddr, pty); err != nil {
+			log.Fatal(err)
+		}
+	}()
+	go func() {
+		if _, err := rxTo(rxAddr, pty); err != nil {
+			log.Fatal(err)
+		}
+	}()
+}
+
+func txFrom(txAddr string, pty *os.File) (int64, error) {
+	conn, err := net.Dial("udp", txAddr)
+	if err != nil {
+		return 0, err
+	}
+	defer conn.Close()
+	return io.Copy(conn, pty)
+}
+
+func rxTo(rxAddr string, pty *os.File) (int64, error) {
+	addr, err := net.ResolveUDPAddr("udp", rxAddr)
+	if err != nil {
+		return 0, err
+	}
+	conn, err := net.ListenUDP("udp", addr)
+	if err != nil {
+		return 0, err
+	}
+	defer conn.Close()
+	return io.Copy(pty, conn)
+}

kissattach.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"fmt"
+	krpty "github.com/kr/pty"
+	"os"
+	"os/exec"
+	"time"
+)
+
+func KissAttach(port string, mtu int) (pty *os.File, err error) {
+	pty, tty, err := krpty.Open()
+	if err != nil {
+		return nil, err
+	}
+
+	time.Sleep(100 * time.Millisecond)
+
+	args := []string{tty.Name(), port, "-l"}
+	if mtu > 0 {
+		args = append(args, fmt.Sprintf("-m %d", mtu))
+	}
+
+	c := exec.Command("kissattach", args...)
+	c.Stdout = os.Stdout
+	c.Stderr = os.Stderr
+
+	err = c.Start()
+	if err != nil {
+		pty.Close()
+		return nil, err
+	}
+
+	// Wait for kissattach to open tty
+	time.Sleep(2 * time.Second)
+
+	err = tty.Close()
+	return pty, err
+}

main.go

@@ -0,0 +1,91 @@
+// Copyright 2014 Martin Hebnes Pedersen, LA5NTA. All rights reserved.
+
+// fldigiattach is a tool to allow use of fldigi as a modem for Linux's AX.25-stack.
+//
+// This program creates a pty and uses kissattach(8) to attach the KISS
+// interface of fldigi to an axport. After attachment, this program will
+// act as a proxy between the AX.25-stack and fldigi to allow AX.25 over fldigi.
+//
+// Because kissattach daemonizes, you must kill it (as normal) after execution.
+//
+// fldigi 3.22 or later is required (KISS interface), as is kissattach (ax25-tools).
+//
+//   Usage of fldigiattach:
+//     -mtu=0: Sets the mtu of the interface [default is paclen parameter in axports].
+//     -port="": Name of a port given in the axports file
+//     -rx-addr="127.0.0.1:7343": fldigi's rx address
+//     -tx-addr="127.0.0.1:7342": fldigi's tx address
+//
+package main
+
+import (
+	"flag"
+	"log"
+	"os"
+	"os/signal"
+	"os/user"
+)
+
+const DefTxAddr = "127.0.0.1:7342"
+const DefRxAddr = "127.0.0.1:7343"
+
+var (
+	argMtu  int
+	argPort string
+
+	argTxAddr string
+	argRxAddr string
+)
+
+func init() {
+	flag.StringVar(&argTxAddr, "tx-addr", DefTxAddr, "fldigi's tx address")
+	flag.StringVar(&argRxAddr, "rx-addr", DefRxAddr, "fldigi's rx address")
+	flag.StringVar(&argPort, "port", "", "Name of a port given in the axports file")
+	flag.IntVar(&argMtu, "mtu", 0, "Sets the mtu of the interface [default is paclen parameter in axports].")
+}
+
+func main() {
+	flag.Parse()
+	log.SetFlags(0)
+
+	if argPort == "" {
+		log.Fatal("Argument '-port' is required.")
+	} else if argMtu > 0 && argMtu < 128 {
+		log.Println("Warning: low paclen (mtu) will cause system to hang. This is probably a bug in kissattach.")
+	}
+
+	// Give a hint to the user if not running as root, this is required by kissattach.
+	if !IsRoot() {
+		log.Println("It seems you're not root. You probably should be...")
+	}
+
+	// Attach new pty to AX.25 stack
+	pty, err := KissAttach(argPort, argMtu)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer pty.Close()
+
+	// Forward traffic between pty and fldigi
+	log.Println("Forwarding...")
+	startForwarding(argTxAddr, argRxAddr, pty)
+
+	// Wait for interrupt/kill
+	sig := WaitFor(os.Interrupt, os.Kill)
+	log.Printf("Got %s, exiting. Remember to kill kissattach manually!", sig)
+}
+
+func WaitFor(sig ...os.Signal) os.Signal {
+	c := make(chan os.Signal)
+	signal.Notify(c, sig...)
+	return <-c
+}
+
+func IsRoot() bool {
+	user, err := user.Current()
+	if err != nil {
+		return false
+	} else {
+		return user.Uid == "0"
+	}
+}