| // Copyright 2017 The Fuchsia Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| package tftp |
| |
| import ( |
| "bytes" |
| "errors" |
| "fmt" |
| "strconv" |
| "strings" |
| "time" |
| ) |
| |
| const ( |
| ServerPort = 33340 // tftp server port |
| ClientPort = 33341 // tftp client port |
| ) |
| |
| const ( |
| // Ethernet MTU, less the TFTP, UDP and IP header lengths (RFC 2348). |
| defaultBlockSize = 1428 // default block size |
| // Arbitrary. |
| timeout = 1 * time.Second // default udp client timeout |
| // Arbitrary. |
| retries = 8 // default number of timeout retries |
| // Point at where window size gains begin to tail off (RFC 7440) |
| // A higher window size begins to cause increased NACKs over |
| // lossy connections. |
| defaultWindowSize = 16 // default window size |
| ) |
| |
| const ( |
| opRrq = uint8(1) // read request (RRQ) |
| opWrq = uint8(2) // write request (WRQ) |
| opData = uint8(3) // data |
| opAck = uint8(4) // acknowledgement |
| opError = uint8(5) // error |
| opOack = uint8(6) // option acknowledgment |
| ) |
| |
| const ( |
| errorUndefined = uint16(0) // Not defined, see error message (if any) |
| errorFileNotFound = uint16(1) // File not found |
| errorAccessViolation = uint16(2) // Access violation |
| errorDiskFull = uint16(3) // Disk full or allocation exceeded |
| errorIllegalOperation = uint16(4) // Illegal TFTP operation |
| errorUnknownID = uint16(5) // Unknown transfer ID |
| errorFileExists = uint16(6) // File already exists |
| errorNoSuchUser = uint16(7) // No such user |
| errorBadOptions = uint16(8) // Bad options |
| |
| // ErrorBusy is a Fuchsia-specific extension to the set of TFTP error |
| // codes, meant to indicate that the server cannot currently handle a |
| // request, but may be able to at some future time. |
| errorBusy = uint16(0x143) // 'B' + 'U' + 'S' + 'Y' |
| ) |
| |
| const ( |
| opCodeOffset = 1 // op code offset in packet |
| blockNumberOffset = 2 // block number offset in packet |
| dataOffset = 4 // data start in packet |
| ) |
| |
| // ErrShouldWait indicates that the target is busy. |
| var ErrShouldWait = fmt.Errorf("target is busy") |
| |
| type options struct { |
| blockSize uint16 |
| timeout time.Duration |
| transferSize uint64 |
| windowSize uint16 |
| } |
| |
| func writeOption(b *bytes.Buffer, name string, value int64) { |
| writeString(b, name) |
| writeString(b, strconv.FormatInt(value, 10)) |
| } |
| |
| func writeString(b *bytes.Buffer, s string) { |
| b.WriteString(s) |
| b.WriteByte(0) |
| } |
| |
| func parseOACK(bs []byte) (*options, error) { |
| var o options |
| |
| for len(bs) > 0 { |
| opt, rest, err := netasciiString(bs) |
| if err != nil { |
| return nil, fmt.Errorf("reading option name: %s", err) |
| } |
| bs = rest |
| val, rest, err := netasciiString(bs) |
| if err != nil { |
| return nil, fmt.Errorf("reading option %q value: %s", opt, err) |
| } |
| bs = rest |
| switch strings.ToLower(opt) { |
| case "blksize": |
| size, err := strconv.ParseUint(val, 10, 16) |
| if err != nil { |
| return nil, fmt.Errorf("unsupported block size %q", val) |
| } |
| o.blockSize = uint16(size) |
| case "timeout": |
| seconds, err := strconv.ParseUint(val, 10, 8) |
| if err != nil { |
| return nil, fmt.Errorf("unsupported timeout %q", val) |
| } |
| o.timeout = time.Second * time.Duration(seconds) |
| case "tsize": |
| size, err := strconv.ParseUint(val, 10, 64) |
| if err != nil { |
| return nil, fmt.Errorf("unsupported transfer size %q", val) |
| } |
| o.transferSize = uint64(size) |
| case "windowsize": |
| size, err := strconv.ParseUint(val, 10, 16) |
| if err != nil { |
| return nil, fmt.Errorf("unsupported window size %q", val) |
| } |
| o.windowSize = uint16(size) |
| } |
| } |
| |
| return &o, nil |
| } |
| |
| func netasciiString(bs []byte) (string, []byte, error) { |
| for i, b := range bs { |
| if b == 0 { |
| return string(bs[:i]), bs[i+1:], nil |
| } else if b < 0x20 || b > 0x7e { |
| return "", nil, fmt.Errorf("invalid netascii byte %q at offset %d", b, i) |
| } |
| } |
| return "", nil, errors.New("no null terminated string found") |
| } |