From a0269ec5652696de792ec2459263876a83d8c410 Mon Sep 17 00:00:00 2001 From: Martin Hebnes Pedersen Date: Mon, 27 Oct 2014 20:28:14 +0100 Subject: [PATCH] Initial commit of code --- README.md | 18 +++++++++- forward.go | 43 ++++++++++++++++++++++++ kissattach.go | 39 ++++++++++++++++++++++ main.go | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 190 insertions(+), 1 deletion(-) create mode 100644 forward.go create mode 100644 kissattach.go create mode 100644 main.go diff --git a/README.md b/README.md index 35028f3..9484923 100644 --- a/README.md +++ b/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 +``` diff --git a/forward.go b/forward.go new file mode 100644 index 0000000..6de4cee --- /dev/null +++ b/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) +} diff --git a/kissattach.go b/kissattach.go new file mode 100644 index 0000000..93bd52d --- /dev/null +++ b/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 +} diff --git a/main.go b/main.go new file mode 100644 index 0000000..bae4aa2 --- /dev/null +++ b/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" + } +}