added LPRT command (#48)

cmd.go

@@ -5,6 +5,7 @@
 package server
 
 import (
+	"encoding/binary"
 	"fmt"
 	"log"
 	"strconv"
@@ -36,6 +37,7 @@ var (
 		"EPSV": commandEpsv{},
 		"FEAT": commandFeat{},
 		"LIST": commandList{},
+		"LPRT": commandLprt{},
 		"NLST": commandNlst{},
 		"MDTM": commandMdtm{},
 		"MIC":  commandMic{},
@@ -294,6 +296,69 @@ func (cmd commandEprt) Execute(conn *Conn, param string) {
 	conn.writeMessage(200, "Connection established ("+strconv.Itoa(port)+")")
 }
 
+// commandLprt responds to the LPRT FTP command. It allows the client to
+// request an active data socket with more options than the original PORT
+// command.  FTP Operation Over Big Address Records.
+type commandLprt struct{}
+
+func (cmd commandLprt) IsExtend() bool {
+	return true
+}
+
+func (cmd commandLprt) RequireParam() bool {
+	return true
+}
+
+func (cmd commandLprt) RequireAuth() bool {
+	return true
+}
+
+func (cmd commandLprt) Execute(conn *Conn, param string) {
+	// No tests for this code yet
+
+	parts := strings.Split(param, ",")
+
+	addressFamily, err := strconv.Atoi(parts[0])
+	if addressFamily != 4 {
+		conn.writeMessage(522, "Network protocol not supported, use 4")
+		return
+	}
+
+	addressLength, err := strconv.Atoi(parts[1])
+	if addressLength != 4 {
+		conn.writeMessage(522, "Network IP length not supported, use 4")
+		return
+	}
+
+	host := strings.Join(parts[2:2+addressLength], ".")
+
+	portLength, err := strconv.Atoi(parts[2+addressLength])
+	portAddress := parts[3+addressLength : 3+addressLength+portLength]
+
+	// Convert string[] to byte[]
+	portBytes := make([]byte, portLength)
+	for i := range portAddress {
+		p, _ := strconv.Atoi(portAddress[i])
+		portBytes[i] = byte(p)
+	}
+
+	// convert the bytes to an int
+	port := int(binary.BigEndian.Uint16(portBytes))
+
+	// if the existing connection is on the same host/port don't reconnect
+	if conn.dataConn.Host() == host && conn.dataConn.Port() == port {
+		return
+	}
+
+	socket, err := newActiveSocket(host, port, conn.logger, conn.sessionID)
+	if err != nil {
+		conn.writeMessage(425, "Data connection failed")
+		return
+	}
+	conn.dataConn = socket
+	conn.writeMessage(200, "Connection established ("+strconv.Itoa(port)+")")
+}
+
 // commandEpsv responds to the EPSV FTP command. It allows the client to
 // request a passive data socket with more options than the original PASV
 // command. It mainly adds ipv6 support, although we don't support that yet.