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Jan Klaban committed Feb 1, 2025
1 parent 587a30d commit f146c41
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Showing 2 changed files with 48 additions and 62 deletions.
2 changes: 2 additions & 0 deletions base/serial.go
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,8 @@ const (
SerialNoFlowControl = 1
SerialSWFlowControl = 2
SerialHWFlowControl = 3
SerialDCDFlowControl = 17
SerialDSRFlowControl = 19
)

type SerialStream interface {
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108 changes: 46 additions & 62 deletions rfc2217/rfc2217.go
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Original file line number Diff line number Diff line change
Expand Up @@ -83,40 +83,47 @@ func (r *rfc2217Serial) Open() error {

// set basic telnet options like binary, echo and go ahead ability (seen from other source)
r.logf("negotiating telnet options")
if err := r.writeOption(BINARY_OPTION, WILL); err != nil {
return err
}
if err := r.writeOption(SGA_OPTION, WILL); err != nil {
return err
}
if err := r.writeOption(COM_PORT_OPTION, WILL); err != nil {
return err
}
r.writebuffer = r.writeOption(r.writebuffer[:0], BINARY_OPTION, WILL)
r.writebuffer = r.writeOption(r.writebuffer, SGA_OPTION, WILL)
r.writebuffer = r.writeOption(r.writebuffer, COM_PORT_OPTION, WILL)
// do purge here?
if err := r.sendSubnegotiation(12, []byte{0x03}); err != nil { // purge data
return err
}
r.writebuffer = r.writeSubnegotiation(r.writebuffer, 12, []byte{0x03}) // purge data
// is there really at least some answer? or handle negotiation during reading itself?
// but according to RFC855, binary is by default false, so at least some answer should be here, same for SGA, dont know how com port option... this is a bit weird
// also send some artifical signature
r.writebuffer = r.writeSignature(r.writebuffer)

// request current settings (baud rate, control, parity, data bits, stop bits)
cmd := []byte{0, 0, 0, 0}
r.writebuffer = r.writeSubnegotiation(r.writebuffer, 1, cmd[:]) // request baud rate
r.writebuffer = r.writeSubnegotiation(r.writebuffer, 2, cmd[:1]) // data size
r.writebuffer = r.writeSubnegotiation(r.writebuffer, 3, cmd[:1]) // parity
r.writebuffer = r.writeSubnegotiation(r.writebuffer, 4, cmd[:1]) // stop bits
r.writebuffer = r.writeSubnegotiation(r.writebuffer, 5, cmd[:1]) // control

r.isopen = true
return r.writeSignature()
return r.transport.Write(r.writebuffer)
}

func (r *rfc2217Serial) writeOption(option byte, intent byte) error {
return r.transport.Write([]byte{IAC, intent, option})
func (r *rfc2217Serial) writeOption(src []byte, option byte, intent byte) []byte {
return append(src, IAC, intent, option)
}

func (r *rfc2217Serial) writeSignature() error {
var buffer [6 + len(Signature)]byte // signature doesnt containt IAC
buffer[0] = IAC
buffer[1] = SB
buffer[2] = COM_PORT_OPTION
buffer[3] = 0 // suboption signature, cant find it written damn it, if there is no text then the fuck no zero and directly IAC,SE ?
copy(buffer[4:], Signature)
buffer[4+len(Signature)] = IAC
buffer[5+len(Signature)] = SE
return r.transport.Write(buffer[:])
func (r *rfc2217Serial) writeSignature(src []byte) []byte {
src = append(src, IAC, SB, COM_PORT_OPTION, 0)
src = append(src, Signature...)
return append(src, IAC, SE)
}

func (r *rfc2217Serial) writeSubnegotiation(src []byte, cmd byte, value []byte) []byte {
src = append(src, IAC, SB, COM_PORT_OPTION, cmd)
for _, b := range value { // maybe a bit too much
if b == IAC {
src = append(src, IAC)
}
src = append(src, b)
}
return append(src, IAC, SE)
}

func (r *rfc2217Serial) getCode() (byte, error) {
Expand Down Expand Up @@ -163,7 +170,7 @@ func (r *rfc2217Serial) processCommand(cmd byte) (err error) {
case BINARY_OPTION, SGA_OPTION, COM_PORT_OPTION:
default:
r.logf("other party has intent to do %v", code)
return r.writeOption(code, WONT)
return r.transport.Write([]byte{IAC, WONT, code}) // immediate response
}
case DONT:
code, err = r.getCode()
Expand All @@ -176,7 +183,7 @@ func (r *rfc2217Serial) processCommand(cmd byte) (err error) {
return fmt.Errorf("unsupported mandatory option")
default:
r.logf("other party has intent not to do %v", code)
return r.writeOption(code, WONT)
return r.transport.Write([]byte{IAC, WONT, code})
}
case SB:
return r.handleSubnegotiation()
Expand Down Expand Up @@ -233,7 +240,8 @@ func (r *rfc2217Serial) processSubnegotiation(sub []byte) error {
switch sub[0] {
case 0: // signature
if len(sub) == 1 { // wanted signature?
return r.writeSignature()
r.writebuffer = r.writeSignature(r.writebuffer[:0])
return r.transport.Write(r.writebuffer)
}
r.logf("signature: \"%s\"", strings.Trim(string(sub[1:]), "\x00 \n\r\t"))
case 101: // set baud rate
Expand Down Expand Up @@ -280,7 +288,7 @@ func (r *rfc2217Serial) processSubnegotiation(sub []byte) error {
return fmt.Errorf("invalid subnegotiation length")
}
switch sub[1] {
case base.SerialNoFlowControl, base.SerialSWFlowControl, base.SerialHWFlowControl:
case base.SerialNoFlowControl, base.SerialSWFlowControl, base.SerialHWFlowControl, base.SerialDCDFlowControl, base.SerialDSRFlowControl:
r.control = int(sub[1])
r.logf("reported control: %d", r.control)
default:
Expand Down Expand Up @@ -371,32 +379,20 @@ func (r *rfc2217Serial) SetMaxReceivedBytes(m int64) {
r.transport.SetMaxReceivedBytes(m)
}

func (r *rfc2217Serial) sendSubnegotiation(cmd byte, value []byte) error {
r.writebuffer = r.writebuffer[:0]
r.writebuffer = append(r.writebuffer, IAC, SB, COM_PORT_OPTION, cmd)
for _, b := range value { // maybe a bit too much
if b == IAC {
r.writebuffer = append(r.writebuffer, IAC)
}
r.writebuffer = append(r.writebuffer, b)
}
r.writebuffer = append(r.writebuffer, IAC, SE)
return r.transport.Write(r.writebuffer)
}

// SetFlowControl implements SerialStream.
func (r *rfc2217Serial) SetFlowControl(flowControl int) error {
if !r.isopen {
return base.ErrNotOpened
}

switch flowControl {
case base.SerialNoFlowControl, base.SerialSWFlowControl, base.SerialHWFlowControl:
case base.SerialNoFlowControl, base.SerialSWFlowControl, base.SerialHWFlowControl, base.SerialDCDFlowControl, base.SerialDSRFlowControl:
default:
return fmt.Errorf("unsupported flow control %d", flowControl)
}

return r.sendSubnegotiation(5, []byte{byte(flowControl)})
r.writebuffer = r.writeSubnegotiation(r.writebuffer[:0], 5, []byte{byte(flowControl)})
return r.transport.Write(r.writebuffer)
}

// SetSpeed implements SerialStream.
Expand Down Expand Up @@ -428,26 +424,14 @@ func (r *rfc2217Serial) SetSpeed(baudRate int, dataBits int, parity int, stopBit
}

binary.BigEndian.PutUint32(cmd[:], uint32(baudRate))
err := r.sendSubnegotiation(1, cmd[:])
if err != nil {
return fmt.Errorf("unable to set baudrate: %w", err)
}
r.writebuffer = r.writeSubnegotiation(r.writebuffer[:0], 1, cmd[:])
cmd[0] = byte(dataBits)
err = r.sendSubnegotiation(2, cmd[:1])
if err != nil {
return fmt.Errorf("unable to set data bits: %w", err)
}
r.writebuffer = r.writeSubnegotiation(r.writebuffer, 2, cmd[:1])
cmd[0] = byte(parity)
err = r.sendSubnegotiation(3, cmd[:1])
if err != nil {
return fmt.Errorf("unable to set parity: %w", err)
}
r.writebuffer = r.writeSubnegotiation(r.writebuffer, 3, cmd[:1])
cmd[0] = byte(stopBits)
err = r.sendSubnegotiation(4, cmd[:1])
if err != nil {
return fmt.Errorf("unable to set stop bits: %w", err)
}
return nil
r.writebuffer = r.writeSubnegotiation(r.writebuffer, 4, cmd[:1])
return r.transport.Write(r.writebuffer)
}

// Write implements SerialStream.
Expand All @@ -458,7 +442,7 @@ func (r *rfc2217Serial) Write(src []byte) error {
if len(src) == 0 {
return nil
}
// escape IAC bytes
// escape IAC bytes, llimit size and chunk that thing, even not optimally due to lower MTU?
r.writebuffer = r.writebuffer[:0]
for _, b := range src {
if b == IAC {
Expand Down

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