/
relay.go
282 lines (256 loc) · 6.6 KB
/
relay.go
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package main
import (
"net"
"strconv"
"strings"
"sync"
"time"
"github.com/pkg/errors"
log "github.com/sirupsen/logrus"
)
const MAX_NUMBER_THREADS = 8
type connectionMap struct {
receiver map[string]net.Conn
sender map[string]net.Conn
metadata map[string]string
potentialReceivers map[string]struct{}
sync.RWMutex
}
func (c *connectionMap) IsSenderConnected(key string) (found bool) {
c.RLock()
defer c.RUnlock()
_, found = c.sender[key]
return
}
func (c *connectionMap) IsPotentialReceiverConnected(key string) (found bool) {
c.RLock()
defer c.RUnlock()
_, found = c.potentialReceivers[key]
return
}
type Relay struct {
connections connectionMap
Debug bool
NumberOfConnections int
}
func NewRelay(flags *Flags) *Relay {
r := new(Relay)
r.Debug = flags.Debug
r.NumberOfConnections = MAX_NUMBER_THREADS
log.SetFormatter(&log.TextFormatter{})
if r.Debug {
log.SetLevel(log.DebugLevel)
} else {
log.SetLevel(log.WarnLevel)
}
return r
}
func (r *Relay) Run() {
r.connections = connectionMap{}
r.connections.Lock()
r.connections.receiver = make(map[string]net.Conn)
r.connections.sender = make(map[string]net.Conn)
r.connections.metadata = make(map[string]string)
r.connections.potentialReceivers = make(map[string]struct{})
r.connections.Unlock()
r.runServer()
}
func (r *Relay) runServer() {
logger := log.WithFields(log.Fields{
"function": "main",
})
logger.Debug("Initializing")
var wg sync.WaitGroup
wg.Add(r.NumberOfConnections)
for id := 0; id < r.NumberOfConnections; id++ {
go r.listenerThread(id, &wg)
}
wg.Wait()
}
func (r *Relay) listenerThread(id int, wg *sync.WaitGroup) {
logger := log.WithFields(log.Fields{
"function": "listenerThread:" + strconv.Itoa(27000+id),
})
defer wg.Done()
err := r.listener(id)
if err != nil {
logger.Error(err)
}
}
func (r *Relay) listener(id int) (err error) {
port := strconv.Itoa(27001 + id)
logger := log.WithFields(log.Fields{
"function": "listener" + ":" + port,
})
server, err := net.Listen("tcp", "0.0.0.0:"+port)
if err != nil {
return errors.Wrap(err, "Error listening on "+":"+port)
}
defer server.Close()
logger.Debug("waiting for connections")
//Spawn a new goroutine whenever a client connects
for {
connection, err := server.Accept()
if err != nil {
return errors.Wrap(err, "problem accepting connection")
}
logger.Debugf("Client %s connected", connection.RemoteAddr().String())
go r.clientCommuncation(id, connection)
}
}
func (r *Relay) clientCommuncation(id int, connection net.Conn) {
sendMessage("who?", connection)
m := strings.Split(receiveMessage(connection), ".")
connectionType, codePhrase, metaData := m[0], m[1], m[2]
key := codePhrase + "-" + strconv.Itoa(id)
logger := log.WithFields(log.Fields{
"id": id,
"codePhrase": codePhrase,
})
if connectionType == "s" { // sender connection
if r.connections.IsSenderConnected(key) {
sendMessage("no", connection)
return
}
logger.Debug("got sender")
r.connections.Lock()
r.connections.metadata[key] = metaData
r.connections.sender[key] = connection
r.connections.Unlock()
// wait for receiver
receiversAddress := ""
for {
r.connections.RLock()
if _, ok := r.connections.receiver[key]; ok {
receiversAddress = r.connections.receiver[key].RemoteAddr().String()
logger.Debug("got receiver")
r.connections.RUnlock()
break
}
r.connections.RUnlock()
time.Sleep(100 * time.Millisecond)
}
logger.Debug("telling sender ok")
sendMessage(receiversAddress, connection)
logger.Debug("preparing pipe")
r.connections.Lock()
con1 := r.connections.sender[key]
con2 := r.connections.receiver[key]
r.connections.Unlock()
logger.Debug("piping connections")
Pipe(con1, con2)
logger.Debug("done piping")
r.connections.Lock()
delete(r.connections.sender, key)
delete(r.connections.receiver, key)
delete(r.connections.metadata, key)
delete(r.connections.potentialReceivers, key)
r.connections.Unlock()
logger.Debug("deleted sender and receiver")
} else { //receiver connection "r"
if r.connections.IsPotentialReceiverConnected(key) {
sendMessage("no", connection)
return
}
// add as a potential receiver
r.connections.Lock()
r.connections.potentialReceivers[key] = struct{}{}
r.connections.Unlock()
// wait for sender's metadata
sendersAddress := ""
for {
r.connections.RLock()
if _, ok := r.connections.metadata[key]; ok {
if _, ok2 := r.connections.sender[key]; ok2 {
sendersAddress = r.connections.sender[key].RemoteAddr().String()
logger.Debug("got sender meta data")
r.connections.RUnlock()
break
}
}
r.connections.RUnlock()
if connectionType == "c" {
sendMessage("0-0-0-0.0.0.0", connection)
return
}
time.Sleep(100 * time.Millisecond)
}
// send meta data
r.connections.RLock()
sendMessage(r.connections.metadata[key]+"-"+sendersAddress, connection)
r.connections.RUnlock()
// check for receiver's consent
consent := receiveMessage(connection)
logger.Debugf("consent: %s", consent)
if consent == "ok" {
logger.Debug("got consent")
r.connections.Lock()
r.connections.receiver[key] = connection
r.connections.Unlock()
}
}
return
}
func sendMessage(message string, connection net.Conn) {
message = fillString(message, BUFFERSIZE)
connection.Write([]byte(message))
}
func receiveMessage(connection net.Conn) string {
messageByte := make([]byte, BUFFERSIZE)
connection.Read(messageByte)
return strings.Replace(string(messageByte), ":", "", -1)
}
func fillString(retunString string, toLength int) string {
for {
lengthString := len(retunString)
if lengthString < toLength {
retunString = retunString + ":"
continue
}
break
}
return retunString
}
// chanFromConn creates a channel from a Conn object, and sends everything it
// Read()s from the socket to the channel.
func chanFromConn(conn net.Conn) chan []byte {
c := make(chan []byte)
go func() {
b := make([]byte, BUFFERSIZE)
for {
n, err := conn.Read(b)
if n > 0 {
res := make([]byte, n)
// Copy the buffer so it doesn't get changed while read by the recipient.
copy(res, b[:n])
c <- res
}
if err != nil {
c <- nil
break
}
}
}()
return c
}
// Pipe creates a full-duplex pipe between the two sockets and transfers data from one to the other.
func Pipe(conn1 net.Conn, conn2 net.Conn) {
chan1 := chanFromConn(conn1)
chan2 := chanFromConn(conn2)
for {
select {
case b1 := <-chan1:
if b1 == nil {
return
} else {
conn2.Write(b1)
}
case b2 := <-chan2:
if b2 == nil {
return
} else {
conn1.Write(b2)
}
}
}
}