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ftpdatasocket.go
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ftpdatasocket.go
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package graval
import (
"errors"
"math/rand"
"net"
"strconv"
"time"
)
// A data socket is used to send non-control data between the client and
// server.
type ftpDataSocket interface {
Host() string
Port() int
// the standard io.Reader interface
Read(p []byte) (n int, err error)
// the standard io.Writer interface
Write(p []byte) (n int, err error)
// the standard io.Closer interface
Close() error
}
type ftpActiveSocket struct {
conn *net.TCPConn
host string
port int
logger *ftpLogger
}
func newActiveSocket(host string, port int, logger *ftpLogger) (*ftpActiveSocket, error) {
connectTo := buildTcpString(host, port)
logger.Print("Opening active data connection to " + connectTo)
raddr, err := net.ResolveTCPAddr("tcp", connectTo)
if err != nil {
logger.Print(err)
return nil, err
}
tcpConn, err := net.DialTCP("tcp", nil, raddr)
if err != nil {
logger.Print(err)
return nil, err
}
socket := new(ftpActiveSocket)
socket.conn = tcpConn
socket.host = host
socket.port = port
socket.logger = logger
return socket, nil
}
func (socket *ftpActiveSocket) Host() string {
return socket.host
}
func (socket *ftpActiveSocket) Port() int {
return socket.port
}
func (socket *ftpActiveSocket) Read(p []byte) (n int, err error) {
return socket.conn.Read(p)
}
func (socket *ftpActiveSocket) Write(p []byte) (n int, err error) {
return socket.conn.Write(p)
}
func (socket *ftpActiveSocket) Close() error {
return socket.conn.Close()
}
type ftpPassiveSocket struct {
conn *net.TCPConn
port int
listenIP string
logger *ftpLogger
}
func newPassiveSocket(listenIP string, minPort int, maxPort int, logger *ftpLogger) (*ftpPassiveSocket, error) {
socket := new(ftpPassiveSocket)
socket.logger = logger
socket.listenIP = listenIP
go socket.ListenAndServe(minPort, maxPort)
for {
if socket.Port() > 0 {
break
}
time.Sleep(100 * time.Millisecond)
}
return socket, nil
}
func (socket *ftpPassiveSocket) Host() string {
return socket.listenIP
}
func (socket *ftpPassiveSocket) Port() int {
return socket.port
}
func (socket *ftpPassiveSocket) Read(p []byte) (n int, err error) {
if socket.waitForOpenSocket() == false {
return 0, errors.New("data socket unavailable")
}
return socket.conn.Read(p)
}
func (socket *ftpPassiveSocket) Write(p []byte) (n int, err error) {
if socket.waitForOpenSocket() == false {
return 0, errors.New("data socket unavailable")
}
return socket.conn.Write(p)
}
func (socket *ftpPassiveSocket) Close() error {
socket.logger.Print("closing passive data socket")
if socket.conn != nil {
return socket.conn.Close()
}
return nil
}
func (socket *ftpPassiveSocket) ListenAndServe(minPort int, maxPort int) {
listener, err := socket.netListenerInRange(minPort, maxPort)
if err != nil {
socket.logger.Print(err)
return
}
defer listener.Close()
add := listener.Addr().(*net.TCPAddr)
socket.port = add.Port
tcpConn, err := listener.AcceptTCP()
if err != nil {
socket.logger.Print(err)
return
}
socket.conn = tcpConn
}
func (socket *ftpPassiveSocket) waitForOpenSocket() bool {
retries := 0
for {
if socket.conn != nil {
break
}
if retries > 3 {
return false
}
socket.logger.Print("sleeping, socket isn't open")
sleepMs := time.Duration(500 * (retries + 1))
time.Sleep(sleepMs * time.Millisecond)
retries += 1
}
return true
}
func (socket *ftpPassiveSocket) netListenerInRange(min, max int) (*net.TCPListener, error) {
for retries := 1; retries < 100; retries++ {
port := randomPort(min, max)
l, err := net.Listen("tcp", net.JoinHostPort(socket.Host(), strconv.Itoa(port)))
if err == nil {
return l.(*net.TCPListener), nil
}
}
return nil, errors.New("Unable to find available port to listen on")
}
func randomPort(min, max int) int {
if min == 0 && max == 0 {
return 0
} else {
return min + rand.Intn(max-min-1)
}
}