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server.go
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server.go
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// Copyright 2017 VMware, Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package telnet
import (
"fmt"
"io"
"net"
log "github.com/Sirupsen/logrus"
)
// DataHandlerFunc is the callback function in the event of receiving data from the telnet client
type DataHandlerFunc func(w io.Writer, data []byte, tc *Conn)
// CmdHandlerFunc is the callback function in the event of receiving a command from the telnet client
type CmdHandlerFunc func(w io.Writer, cmd []byte, tc *Conn)
// CloseHandlerFunc is the callback function in the event of receiving EOF from the telnet client
type CloseHandlerFunc func(tc *Conn)
var defaultDataHandlerFunc = func(w io.Writer, data []byte, tc *Conn) {}
var defaultCmdHandlerFunc = func(w io.Writer, cmd []byte, tc *Conn) {}
var defaultCloseHandlerFunc = func(tc *Conn) {}
type Handlers struct {
DataHandler DataHandlerFunc
CmdHandler CmdHandlerFunc
CloseHandler CloseHandlerFunc
}
// ServerOpts is the telnet server constructor options
type ServerOpts struct {
Addr string
ServerOpts []byte
ClientOpts []byte
Handlers
}
// Server is the struct representing the telnet server
type Server struct {
ServerOptions map[byte]bool
ClientOptions map[byte]bool
Handlers
ln net.Listener
}
// NewServer is the constructor of the telnet server
func NewServer(opts ServerOpts) *Server {
ts := new(Server)
ts.ClientOptions = make(map[byte]bool)
ts.ServerOptions = make(map[byte]bool)
for _, v := range opts.ServerOpts {
ts.ServerOptions[v] = true
}
for _, v := range opts.ClientOpts {
ts.ClientOptions[v] = true
}
ts.DataHandler = defaultDataHandlerFunc
if opts.DataHandler != nil {
ts.DataHandler = opts.DataHandler
}
ts.CmdHandler = defaultCmdHandlerFunc
if opts.CmdHandler != nil {
ts.CmdHandler = opts.CmdHandler
}
ts.CloseHandler = defaultCloseHandlerFunc
if opts.CloseHandler != nil {
ts.CloseHandler = opts.CloseHandler
}
ln, err := net.Listen("tcp", opts.Addr)
if err != nil {
panic(fmt.Sprintf("cannot start telnet server: %v", err))
}
ts.ln = ln
return ts
}
// Accept accepts a connection and returns the Telnet connection
func (ts *Server) Accept() (*Conn, error) {
// #nosec: Errors unhandled.
conn, _ := ts.ln.Accept()
log.Info("connection received")
opts := connOpts{
conn: conn,
Handlers: ts.Handlers,
clientOpts: ts.ClientOptions,
fsm: newFSM(),
}
tc := newConn(&opts)
go tc.writeLoop()
go tc.dataHandlerWrapper(tc.handlerWriter, tc.dataRW)
go tc.fsm.start()
go tc.startNegotiation()
return tc, nil
}