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|
package tracer
import (
"encoding/json"
"fmt"
"net"
"os"
"time"
"github.com/sirupsen/logrus"
)
type TracerCommand struct {
Cmd TracerCmd `json:"tracerCmd"`
ForwardingPorts []int `json:"forwardingPorts,omitempty"`
DestinationAddress []string `json:"destinationAddress,omitempty"`
}
type TracerCmd int
const (
Ok TracerCmd = iota
RegisterForwardPorts
ConnectToAddress
)
func Main() error {
r := os.Stdin
w := os.Stdout
dec := json.NewDecoder(r)
for {
var cmd TracerCommand
err := dec.Decode(&cmd)
if err != nil {
logrus.WithError(err).Errorf("failed to decode")
break
}
logrus.Infof("decoded = %v", cmd)
switch cmd.Cmd {
case RegisterForwardPorts:
for _, p := range cmd.ForwardingPorts {
readyChan := make(chan bool)
go func(port int, c chan bool) {
err := listenLoop(port, c)
if err != nil {
logrus.WithError(err).Errorf("failed to listen on port %d", port)
}
}(p, readyChan)
<-readyChan
}
cmd = TracerCommand{
Cmd: Ok,
}
case ConnectToAddress:
addrs := []string{}
for i := range cmd.DestinationAddress {
addr := cmd.DestinationAddress[i]
err = tryToConnect(addr)
if err != nil {
logrus.WithError(err).Warnf("failed to connect to %s", addr)
continue
}
addrs = append(addrs, addr)
}
cmd = TracerCommand{
Cmd: Ok,
DestinationAddress: addrs,
}
}
m, err := json.Marshal(cmd)
if err != nil {
logrus.WithError(err).Errorf("failed to encode")
}
_, err = w.Write(m)
if err != nil {
logrus.WithError(err).Errorf("failed to write")
}
}
logrus.Infof("Exit.")
return nil
}
func listenLoop(port int, readyChan chan bool) error {
l, err := net.Listen("tcp", fmt.Sprintf(":%d", port))
if err != nil {
return err
}
defer l.Close()
readyChan <- true
logrus.Infof("started to listen on port %d", port)
for {
conn, err := l.Accept()
if err != nil {
return err
}
conn.Close()
}
}
func tryToConnect(addr string) error {
conn, err := net.DialTimeout("tcp", addr, 10*time.Millisecond)
if err != nil {
return err
}
defer conn.Close()
logrus.Infof("successfully connected to %s", addr)
return nil
}
|
