README
¶
pack.ag/tftp
pack.ag/tftp is a cross-platform, concurrent TFTP client and server implementation for Go.
Standards Implemented
- Binary Transfer (RFC 1350)
- Netascii Transfer (RFC 1350)
- Option Extension (RFC 2347)
- Blocksize Option (RFC 2348)
- Timeout Interval Option (RFC 2349)
- Transfer Size Option (RFC 2349)
- Windowsize Option (RFC 7440)
Unique Features
-
Single Port Mode
TL;DR: It allows TFTP to work through firewalls.
A standard TFTP server implementation receives requests on port 69 and allocates a new high port (over 1024) dedicated to that request. In single port mode, the same port is used for transmit and receive. If the server is started on port 69, all communication will be done on port 69.
The primary use case of this feature is to play nicely with firewalls. Most firewalls will prevent the typical case where the server responds back on a random port because they have no way of knowing that it is in response to a request that went out on port 69. In single port mode, the firewall will see a request go out to a server on port 69 and that server respond back on the same port, which most firewalls will allow.
Of course if the firewall in question is configured to block TFTP connections, this setting won't help you.
Enable single port mode with the
--single-portflag. This is currently marked experimental as is diverges from the TFTP standard.
Installation
go get -u pack.ag/tftp
API
The API was inspired by Go's well-known net/http API. If you can write a net/http handler or middleware, you should have no problem doing the same with pack.ag/tftp.
Configuration Functions
One area that is noticeably different from net/http is the configuration of clients and servers. pack.ag/tftp uses "configuration functions" rather than the direct modification of the Client/Server struct or a configuration struct passed into the factory functions.
A few explanations of this pattern:
- Self-referential functions and the design of options by Rob Pike
- Functional options for friendly APIs by Dave Cheney [video]
If this sounds complicated, don't worry, the public API is quiet simple. The NewClient and NewServer functions take zero or more configuration functions.
Want all defaults? Don't pass anything.
Want a Client configured for blocksize 9000 and windowsize 16? Pass in ClientBlocksize(9000) and ClientWindowsize(16).
// Default Client
tftp.NewClient()
// Client with blocksize 9000, windowsize 16
tftp.NewClient(tftp.ClientBlocksize(9000), tftp.ClientWindowsize(16))
// Configuring with a slice of options
opts := []tftp.ClientOpt{
tftp.ClientMode(tftp.ModeOctet),
tftp.ClientBlocksize(9000),
tftp.ClientWindowsize(16),
tftp.ClientTimeout(1),
tftp.ClientTransferSize(true),
tftp.ClientRetransmit(3),
}
tftp.NewClient(opts...)
Examples
Read File From Server, Print to stdout
client := tftp.NewClient()
resp, err := client.Get("myftp.local/myfile")
if err != nil {
log.Fatalln(err)
}
err := io.Copy(os.Stdout, resp)
if err != nil {
log.Fatalln(err)
}
Write File to Server
file, err := os.Open("myfile")
if err != nil {
log.Fatalln(err)
}
defer file.Close()
// Get the file info se we can send size (not required)
fileInfo, err := file.Stat()
if err != nil {
log.Println("error getting file size:", err)
}
client := tftp.NewClient()
err := client.Put("myftp.local/myfile", file, fileInfo.Size())
if err != nil {
log.Fatalln(err)
}
HTTP Proxy
This rather contrived example proxies an incoming GET request to GitHub's public API. A more realistic use case might be proxying to PXE boot files on an HTTP server.
const baseURL = "https://api.github.com/"
func proxyTFTP(w tftp.ReadRequest) {
// Append the requested path to the baseURL
url := baseURL + w.Name()
// Send the HTTP request
resp, err := http.DefaultClient.Get(url)
if err != nil {
// This could send more specific errors, but here we'read
// choosing to simply send "file not found"" with the error
// message from the HTTP client back to the TFTP client.
w.WriteError(tftp.ErrCodeFileNotFound, err.Error())
return
}
defer resp.Body.Close()
// Copy the body of the response to the TFTP client.
if _, err := io.Copy(w, resp.Body); err != nil {
log.Println(err)
}
}
This function doesn't itself implement the required ReadHandler interface, but we can make it a ReadHandler with the ReadHandlerFunc adapter (much like http.HandlerFunc).
readHandler := tftp.ReadHandlerFunc(proxyTFTP)
server.ReadHandler(readHandler)
server.ListenAndServe()
# trivialt get localhost:6900 repos/golang/go -o - | jq
{
"id": 23096959,
"name": "go",
"full_name": "golang/go",
...
}
Full example in examples/httpproxy/httpproxy.go.
Save Files to Database
Here tftpDB implements the WriteHandler interface directly.
// tftpDB embeds a *sql.DB and implements the tftp.ReadHandler interface.
type tftpDB struct {
*sql.DB
}
func (db *tftpDB) ReceiveTFTP(w tftp.WriteRequest) {
// Read the data from the client into memory
data, err := ioutil.ReadAll(w)
if err != nil {
log.Println(err)
return
}
// Insert the IP address of the client and the data into the database
res, err := db.Exec("INSERT INTO tftplogs (ip, log) VALUES (?, ?)", w.Addr().IP.String(), string(data))
if err != nil {
log.Println(err)
return
}
// Log a message with the details
id, _ := res.LastInsertId()
log.Printf("Inserted %d bytes of data from %s. (ID=%d)", len(data), w.Addr().IP, id)
}
# go run examples/database/database.go
2016/04/30 11:20:27 Inserted 32 bytes of data from 127.0.0.1. (ID=13)
Full example including checking the size before accepting the request in examples/database/database.go.
Documentation
¶
Overview ¶
Package tftp provides TFTP client and server implementations.
Index ¶
- Constants
- Variables
- func ErrorCause(err error) error
- func IsOptionParsingError(err error) bool
- func IsRemoteError(err error) bool
- func IsUnexpectedDatagram(err error) bool
- type Client
- type ClientOpt
- type ErrorCode
- type ReadHandler
- type ReadHandlerFunc
- type ReadRequest
- type ReadWriteHandler
- type Response
- type Server
- type ServerOpt
- type TransferMode
- type WriteHandler
- type WriteHandlerFunc
- type WriteRequest
Constants ¶
const ( // ErrCodeNotDefined - Not defined, see error message (if any). ErrCodeNotDefined ErrorCode = 0x0 // ErrCodeFileNotFound - File not found. ErrCodeFileNotFound ErrorCode = 0x1 // ErrCodeAccessViolation - Access violation. ErrCodeAccessViolation ErrorCode = 0x2 // ErrCodeDiskFull - Disk full or allocation exceeded. ErrCodeDiskFull ErrorCode = 0x3 // ErrCodeIllegalOperation - Illegal TFTP operation. ErrCodeIllegalOperation ErrorCode = 0x4 // ErrCodeUnknownTransferID - Unknown transfer ID. ErrCodeUnknownTransferID ErrorCode = 0x5 // ErrCodeFileAlreadyExists - File already exists. ErrCodeFileAlreadyExists ErrorCode = 0x6 // ErrCodeNoSuchUser - No such user. ErrCodeNoSuchUser ErrorCode = 0x7 // ModeNetASCII is the string for netascii transfer mode ModeNetASCII TransferMode = "netascii" // ModeOctet is the string for octet/binary transfer mode ModeOctet TransferMode = "octet" )
Variables ¶
var ( // ErrInvalidURL indicates that the URL passed to Get or Put is invalid. ErrInvalidURL = errors.New("invalid URL") // ErrInvalidHostIP indicates an empty or invalid host. ErrInvalidHostIP = errors.New("invalid host/IP") // ErrInvalidFile indicates an empty or invalid file. ErrInvalidFile = errors.New("invalid file") // ErrSizeNotReceived indicates tsize was not negotiated. ErrSizeNotReceived = errors.New("size not received") // ErrAddressNotAvailable indicates the server address was requested before // the server had been started. ErrAddressNotAvailable = errors.New("address not available until server has been started") // ErrNoRegisteredHandlers indicates no handlers were registered before starting the server. ErrNoRegisteredHandlers = errors.New("no handlers registered") // ErrInvalidNetwork indicates that a network other than udp, udp4, or udp6 was configured. ErrInvalidNetwork = errors.New("invalid network: must be udp, udp4, or udp6") // ErrInvalidBlocksize indicates that a blocksize outside the range 8 to 65464 was configured. ErrInvalidBlocksize = errors.New("invalid blocksize: must be between 8 and 65464") // ErrInvalidTimeout indicates that a timeout outside the range 1 to 255 was configured. ErrInvalidTimeout = errors.New("invalid timeout: must be between 1 and 255") // ErrInvalidWindowsize indicates that a windowsize outside the range 1 to 65535 was configured. ErrInvalidWindowsize = errors.New("invalid windowsize: must be between 1 and 65535") // ErrInvalidMode indicates that a mode other than ModeNetASCII or ModeOctet was configured. ErrInvalidMode = errors.New("invalid transfer mode: must be ModeNetASCII or ModeOctet") // ErrInvalidRetransmit indicates that the retransmit limit was configured with a negative value. ErrInvalidRetransmit = errors.New("invalid retransmit: cannot be negative") // ErrMaxRetries indicates that the maximum number of retries has been reached. ErrMaxRetries = errors.New("max retries reached") )
Functions ¶
func ErrorCause ¶
ErrorCause extracts the original error from an error wrapped by tftp.
func IsOptionParsingError ¶
IsOptionParsingError allows a consumer to check if an error was induced during option parsing.
func IsRemoteError ¶
IsRemoteError allows a consumer to check if an error was an error by the remote client/server.
func IsUnexpectedDatagram ¶
IsUnexpectedDatagram allows a consumer to check if an error is an unexpected datagram.
Types ¶
type Client ¶
type Client struct {
// contains filtered or unexported fields
}
Client makes requests to a server.
func NewClient ¶
NewClient returns a configured Client.
Any number of ClientOpts can be provided to modify the default client behavior.
type ClientOpt ¶
ClientOpt is a function that configures a Client.
func ClientBlocksize ¶
ClientBlocksize configures the number of data bytes that will be send in each datagram. Valid range is 8 to 65464.
Default: 512.
func ClientMode ¶
func ClientMode(mode TransferMode) ClientOpt
ClientMode configures the mode.
Valid options are ModeNetASCII and ModeOctet. Default is ModeNetASCII.
func ClientRetransmit ¶
ClientRetransmit configures the per-packet retransmission limit for all requests.
Default: 10.
func ClientTimeout ¶
ClientTimeout configures the number of seconds to wait before resending an unacknowledged datagram. Valid range is 1 to 255.
Default: 1.
func ClientTransferSize ¶
ClientTransferSize requests for the server to send the file size before sending.
Default: enabled.
func ClientWindowsize ¶
ClientWindowsize configures the number of datagrams that will be transmitted before needing an acknowledgement.
Default: 1.
type ReadHandler ¶
type ReadHandler interface {
ServeTFTP(ReadRequest)
}
ReadHandler responds to a TFTP read request.
type ReadHandlerFunc ¶
type ReadHandlerFunc func(ReadRequest)
ReadHandlerFunc is an adapter type to allow a function to serve as a ReadHandler.
func (ReadHandlerFunc) ServeTFTP ¶
func (h ReadHandlerFunc) ServeTFTP(w ReadRequest)
ServeTFTP calls the ReadHandlerFunc function.
type ReadRequest ¶
type ReadRequest interface {
// Addr is the network address of the client.
Addr() *net.UDPAddr
// Name is the file name requested by the client.
Name() string
// Write write's data to the client.
Write([]byte) (int, error)
// WriteError sends an error to the client and terminates the
// connection. WriteError can only be called once. Write cannot
// be called after an error has been written.
WriteError(ErrorCode, string)
// WriteSize sets the transfer size (tsize) value to be sent to
// the client. It must be called before any calls to Write.
WriteSize(int64)
// TransferMode returns the TFTP transfer mode requested by the client.
TransferMode() TransferMode
}
ReadRequest is provided to a ReadHandler's ServeTFTP method.
type ReadWriteHandler ¶
type ReadWriteHandler interface {
ReadHandler
WriteHandler
}
ReadWriteHandler combines ReadHandler and WriteHandler.
func FileServer ¶
func FileServer(dir string) ReadWriteHandler
FileServer creates a handler for sending and reciving files on the filesystem.
type Response ¶
type Response struct {
// contains filtered or unexported fields
}
Response is an io.Reader for receiving files from a TFTP server.
type Server ¶
type Server struct {
// contains filtered or unexported fields
}
Server contains the configuration to run a TFTP server.
A ReadHandler, WriteHandler, or both can be registered to the server. If one of the handlers isn't registered, the server will return errors to clients attempting to use them.
func NewServer ¶
NewServer returns a configured Server.
Addr is the network address to listen on and is in the form "host:port". If a no host is given the server will listen on all interfaces.
Any number of ServerOpts can be provided to configure optional values.
func (*Server) Addr ¶
Addr is the network address of the server. It is available after the server has been started.
func (*Server) ListenAndServe ¶
ListenAndServe starts a configured server.
func (*Server) ReadHandler ¶
func (s *Server) ReadHandler(rh ReadHandler)
ReadHandler registers a ReadHandler for the server.
func (*Server) WriteHandler ¶
func (s *Server) WriteHandler(wh WriteHandler)
WriteHandler registers a WriteHandler for the server.
type ServerOpt ¶
ServerOpt is a function that configures a Server.
func ServerNet ¶
ServerNet configures the network a server listens on. Must be one of: udp, udp4, udp6.
Default: udp.
func ServerRetransmit ¶
ServerRetransmit configures the per-packet retransmission limit for all requests.
Default: 10.
func ServerSinglePort ¶
ServerSinglePort enables the server to service all requests via a single port rather than the standard TFTP behavior of each client communicating on a separate port.
This is an experimental feature.
Default is disabled.
type WriteHandler ¶
type WriteHandler interface {
ReceiveTFTP(WriteRequest)
}
WriteHandler responds to a TFTP write request.
type WriteHandlerFunc ¶
type WriteHandlerFunc func(WriteRequest)
WriteHandlerFunc is an adapter type to allow a function to serve as a WriteHandler.
func (WriteHandlerFunc) ReceiveTFTP ¶
func (h WriteHandlerFunc) ReceiveTFTP(w WriteRequest)
ReceiveTFTP calls the WriteHandlerFunc function.
type WriteRequest ¶
type WriteRequest interface {
// Addr is the network address of the client.
Addr() *net.UDPAddr
// Name is the file name provided by the client.
Name() string
// Read reads the request data from the client.
Read([]byte) (int, error)
// Size returns the transfer size (tsize) as provided by the client.
// If the tsize option was not negotiated, an error will be returned.
Size() (int64, error)
// WriteError sends an error to the client and terminates the
// connection. WriteError can only be called once. Read cannot
// be called after an error has been written.
WriteError(ErrorCode, string)
// TransferMode returns the TFTP transfer mode requested by the client.
TransferMode() TransferMode
}
WriteRequest is provided to a WriteHandler's ReceiveTFTP method.
Source Files
Directories