get.go - omci-lib-go - Gitiles

 /*
  * Copyright (c) 2018 - present.  Boling Consulting Solutions (bcsw.net)
  * Copyright 2020-present Open Networking Foundation

  * 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 omci

 import (
 	"encoding/binary"
 	"errors"
 	"fmt"
 	"github.com/google/gopacket"
 	me "github.com/opencord/omci-lib-go/generated"
 )

 type GetRequest struct {
 	MeBasePacket
 	AttributeMask uint16
 }

 func (omci *GetRequest) String() string {
 	return fmt.Sprintf("%v, Mask: %#x",
 		omci.MeBasePacket.String(), omci.AttributeMask)
 }

 // LayerType returns LayerTypeGetRequest
 func (omci *GetRequest) LayerType() gopacket.LayerType {
 	return LayerTypeGetRequest
 }

 // CanDecode returns the set of layer types that this DecodingLayer can decode
 func (omci *GetRequest) CanDecode() gopacket.LayerClass {
 	return LayerTypeGetRequest
 }

 // NextLayerType returns the layer type contained by this DecodingLayer.
 func (omci *GetRequest) NextLayerType() gopacket.LayerType {
 	return gopacket.LayerTypePayload
 }

 // DecodeFromBytes decodes the given bytes of a Get Request into this layer
 func (omci *GetRequest) DecodeFromBytes(data []byte, p gopacket.PacketBuilder) error {
 	// Common ClassID/EntityID decode in msgBase
 	var hdrSize int
 	if omci.Extended {
 		hdrSize = 6 + 2
 	} else {
 		hdrSize = 4 + 2
 	}
 	err := omci.MeBasePacket.DecodeFromBytes(data, p, hdrSize)
 	if err != nil {
 		return err
 	}
 	meDefinition, omciErr := me.LoadManagedEntityDefinition(omci.EntityClass,
 		me.ParamData{EntityID: omci.EntityInstance})
 	if omciErr.StatusCode() != me.Success {
 		return omciErr.GetError()
 	}
 	// ME needs to support Get
 	if !me.SupportsMsgType(meDefinition, me.Get) {
 		return me.NewProcessingError("managed entity does not support Get Message-Type")
 	}
 	if omci.Extended {
 		if len(data) < 8 {
 			p.SetTruncated()
 			return errors.New("frame too small")
 		}
 		omci.AttributeMask = binary.BigEndian.Uint16(data[6:])
 	} else {
 		omci.AttributeMask = binary.BigEndian.Uint16(data[4:])
 	}
 	return nil
 }

 func decodeGetRequest(data []byte, p gopacket.PacketBuilder) error {
 	omci := &GetRequest{}
 	omci.MsgLayerType = LayerTypeGetRequest
 	return decodingLayerDecoder(omci, data, p)
 }

 func decodeGetRequestExtended(data []byte, p gopacket.PacketBuilder) error {
 	omci := &GetRequest{}
 	omci.MsgLayerType = LayerTypeGetRequest
 	omci.Extended = true
 	return decodingLayerDecoder(omci, data, p)
 }

 // SerializeTo provides serialization of an Get Request message
 func (omci *GetRequest) SerializeTo(b gopacket.SerializeBuffer, _ gopacket.SerializeOptions) error {
 	// Basic (common) OMCI Header is 8 octets, 10
 	err := omci.MeBasePacket.SerializeTo(b)
 	if err != nil {
 		return err
 	}
 	meDefinition, omciErr := me.LoadManagedEntityDefinition(omci.EntityClass,
 		me.ParamData{EntityID: omci.EntityInstance})
 	if omciErr.StatusCode() != me.Success {
 		return omciErr.GetError()
 	}
 	// ME needs to support Set
 	if !me.SupportsMsgType(meDefinition, me.Get) {
 		return me.NewProcessingError("managed entity does not support Get Message-Type")
 	}
 	maskOffset := 0
 	if omci.Extended {
 		maskOffset = 2
 	}
 	bytes, err := b.AppendBytes(2 + maskOffset)
 	if err != nil {
 		return err
 	}
 	if omci.Extended {
 		binary.BigEndian.PutUint16(bytes, uint16(2))
 	}
 	binary.BigEndian.PutUint16(bytes[maskOffset:], omci.AttributeMask)
 	return nil
 }

 type GetResponse struct {
 	MeBasePacket
 	Result                   me.Results
 	AttributeMask            uint16
 	Attributes               me.AttributeValueMap
 	UnsupportedAttributeMask uint16
 	FailedAttributeMask      uint16
 }

 func (omci *GetResponse) String() string {
 	return fmt.Sprintf("%v, Result: %d (%v), Mask: %#x, Unsupported: %#x, Failed: %#x, attributes: %v",
 		omci.MeBasePacket.String(), omci.Result, omci.Result, omci.AttributeMask,
 		omci.UnsupportedAttributeMask, omci.FailedAttributeMask, omci.Attributes)
 }

 // LayerType returns LayerTypeGetResponse
 func (omci *GetResponse) LayerType() gopacket.LayerType {
 	return LayerTypeGetResponse
 }

 // CanDecode returns the set of layer types that this DecodingLayer can decode
 func (omci *GetResponse) CanDecode() gopacket.LayerClass {
 	return LayerTypeGetResponse
 }

 // NextLayerType returns the layer type contained by this DecodingLayer.
 func (omci *GetResponse) NextLayerType() gopacket.LayerType {
 	return gopacket.LayerTypePayload
 }

 // DecodeFromBytes decodes the given bytes of a Get Response into this layer
 func (omci *GetResponse) DecodeFromBytes(data []byte, p gopacket.PacketBuilder) error {
 	// Common ClassID/EntityID decode in msgBase
 	err := omci.MeBasePacket.DecodeFromBytes(data, p, 4+3)
 	if err != nil {
 		return err
 	}
 	meDefinition, omciErr := me.LoadManagedEntityDefinition(omci.EntityClass,
 		me.ParamData{EntityID: omci.EntityInstance})
 	if omciErr.StatusCode() != me.Success {
 		return omciErr.GetError()
 	}
 	// ME needs to support Get
 	if !me.SupportsMsgType(meDefinition, me.Get) {
 		return me.NewProcessingError("managed entity does not support Get Message-Type")
 	}
 	if omci.Extended {
 		if len(data) < 13 {
 			p.SetTruncated()
 			return errors.New("frame too small")
 		}
 		omci.Result = me.Results(data[6])
 		omci.AttributeMask = binary.BigEndian.Uint16(data[7:])

 		// If Attribute failed or Unknown, decode optional attribute mask
 		if omci.Result == me.AttributeFailure {
 			omci.UnsupportedAttributeMask = binary.BigEndian.Uint16(data[9:])
 			omci.FailedAttributeMask = binary.BigEndian.Uint16(data[11:])
 		}
 	} else {
 		omci.Result = me.Results(data[4])
 		omci.AttributeMask = binary.BigEndian.Uint16(data[5:])

 		// If Attribute failed or Unknown, decode optional attribute mask
 		if omci.Result == me.AttributeFailure {
 			omci.UnsupportedAttributeMask = binary.BigEndian.Uint16(data[32:34])
 			omci.FailedAttributeMask = binary.BigEndian.Uint16(data[34:36])
 		}
 	}
 	// Attribute decode. Note that the ITU-T G.988 specification states that the
 	//                   Unsupported and Failed attribute masks are always present
 	//                   but only valid if the status code== 9.  However some XGS
 	//                   ONUs (T&W and Alpha, perhaps more) will use these last 4
 	//                   octets for data if the status code == 0.  So accommodate
 	//                   this behaviour in favor of greater interoperability.
 	firstOctet := 7
 	lastOctet := 36
 	if omci.Extended {
 		firstOctet = 13
 		lastOctet = len(data)
 	}

 	switch omci.Result {
 	case me.ProcessingError, me.NotSupported, me.UnknownEntity, me.UnknownInstance, me.DeviceBusy:
 		return nil // Done (do not try and decode attributes)

 	case me.AttributeFailure:
 		if !omci.Extended {
 			lastOctet = 32
 		}
 	}
 	omci.Attributes, err = meDefinition.DecodeAttributes(omci.AttributeMask,
 		data[firstOctet:lastOctet], p, byte(GetResponseType))
 	if err != nil {
 		return err
 	}
 	// Validate all attributes support read
 	for attrName := range omci.Attributes {
 		attr, err := me.GetAttributeDefinitionByName(meDefinition.GetAttributeDefinitions(), attrName)
 		if err != nil {
 			return err
 		}
 		if attr.Index != 0 && !me.SupportsAttributeAccess(*attr, me.Read) {
 			msg := fmt.Sprintf("attribute '%v' does not support read access", attrName)
 			return me.NewProcessingError(msg)
 		}
 	}
 	if eidDef, eidDefOK := meDefinition.GetAttributeDefinitions()[0]; eidDefOK {
 		omci.Attributes[eidDef.GetName()] = omci.EntityInstance
 		return nil
 	}
 	return errors.New("all Managed Entities have an EntityID attribute")
 }

 func decodeGetResponse(data []byte, p gopacket.PacketBuilder) error {
 	omci := &GetResponse{}
 	omci.MsgLayerType = LayerTypeGetResponse
 	return decodingLayerDecoder(omci, data, p)
 }

 func decodeGetResponseExtended(data []byte, p gopacket.PacketBuilder) error {
 	omci := &GetResponse{}
 	omci.MsgLayerType = LayerTypeGetResponse
 	omci.Extended = true
 	return decodingLayerDecoder(omci, data, p)
 }

 // SerializeTo provides serialization of an Get Response message
 func (omci *GetResponse) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
 	// Basic (common) OMCI Header is 8 octets, 10
 	if err := omci.MeBasePacket.SerializeTo(b); err != nil {
 		return err
 	}
 	meDefinition, omciErr := me.LoadManagedEntityDefinition(omci.EntityClass,
 		me.ParamData{EntityID: omci.EntityInstance})

 	if omciErr.StatusCode() != me.Success {
 		return omciErr.GetError()
 	}
 	// ME needs to support Get
 	if !me.SupportsMsgType(meDefinition, me.Get) {
 		return me.NewProcessingError("managed entity does not support the Get Message-Type")
 	}
 	resultOffset := 0
 	attributeErrExtra := 0

 	if omci.Extended {
 		resultOffset = 2
 		attributeErrExtra = 4 // Attribute mask + attribute error masks
 	}
 	// Space for result + mask (both types) + (len & error masks if extended)
 	buffer, err := b.AppendBytes(3 + resultOffset + attributeErrExtra)
 	if err != nil {
 		return err
 	}
 	// Save result and initial mask. Other header fields updated after
 	// attribute copy
 	buffer[resultOffset] = byte(omci.Result)
 	binary.BigEndian.PutUint16(buffer[resultOffset+1:], omci.AttributeMask)

 	// Validate all attributes requested support read
 	for attrName := range omci.Attributes {
 		var attr *me.AttributeDefinition
 		attr, err = me.GetAttributeDefinitionByName(meDefinition.GetAttributeDefinitions(), attrName)
 		if err != nil {
 			return err
 		}
 		if attr.Index != 0 && (attr.Mask&omci.AttributeMask != 0) && !me.SupportsAttributeAccess(*attr, me.Read) {
 			msg := fmt.Sprintf("attribute '%v' does not support read access", attrName)
 			return me.NewProcessingError(msg)
 		}
 	}
 	// Attribute serialization
 	switch omci.Result {
 	default:
 		if omci.Extended {
 			// Minimum length is 7 for extended an need to write error masks
 			binary.BigEndian.PutUint16(buffer, uint16(7))
 			binary.BigEndian.PutUint32(buffer[resultOffset+3:], 0)
 		}
 		break

 	case me.Success, me.AttributeFailure:
 		// TODO: Baseline only supported at this time)
 		var available int
 		if omci.Extended {
 			available = MaxExtendedLength - 18 - 4 // Less: header, mic
 		} else {
 			available = MaxBaselineLength - 11 - 4 - 8 // Less: header, failed attributes, length, mic
 		}
 		// Serialize to temporary buffer if we may need to reset values due to
 		// recoverable truncation errors
 		attributeBuffer := gopacket.NewSerializeBuffer()
 		var failedMask uint16
 		err, failedMask = meDefinition.SerializeAttributes(omci.Attributes, omci.AttributeMask,
 			attributeBuffer, byte(GetResponseType), available, opts.FixLengths)

 		if err != nil {
 			return err
 		}
 		if failedMask != 0 {
 			// Not all attributes would fit
 			omci.FailedAttributeMask |= failedMask
 			omci.AttributeMask &= ^failedMask
 			omci.Result = me.AttributeFailure

 			// Adjust already recorded values
 			buffer[resultOffset] = byte(omci.Result)
 			binary.BigEndian.PutUint16(buffer[resultOffset+1:], omci.AttributeMask)
 		}
 		if omci.Extended {
 			// Set length and any failure masks
 			binary.BigEndian.PutUint16(buffer, uint16(len(attributeBuffer.Bytes())+7))

 			if omci.Result == me.AttributeFailure {
 				binary.BigEndian.PutUint16(buffer[resultOffset+3:], omci.UnsupportedAttributeMask)
 				binary.BigEndian.PutUint16(buffer[resultOffset+5:], omci.FailedAttributeMask)
 			} else {
 				binary.BigEndian.PutUint32(buffer[resultOffset+3:], 0)
 			}
 		}
 		// Copy over attributes to the original serialization buffer
 		var newSpace []byte

 		newSpace, err = b.AppendBytes(len(attributeBuffer.Bytes()))
 		if err != nil {
 			return err
 		}
 		copy(newSpace, attributeBuffer.Bytes())

 		if !omci.Extended {
 			// Calculate space left. Max  - msgType header - OMCI trailer - spacedUsedSoFar
 			bytesLeft := MaxBaselineLength - 4 - 8 - len(b.Bytes())

 			var remainingBytes []byte
 			remainingBytes, err = b.AppendBytes(bytesLeft + 4)

 			if err != nil {
 				return me.NewMessageTruncatedError(err.Error())
 			}
 			copy(remainingBytes, lotsOfZeros[:])

 			if omci.Result == me.AttributeFailure {
 				binary.BigEndian.PutUint16(remainingBytes[bytesLeft-4:bytesLeft-2], omci.UnsupportedAttributeMask)
 				binary.BigEndian.PutUint16(remainingBytes[bytesLeft-2:bytesLeft], omci.FailedAttributeMask)
 			}
 		}
 	}
 	return nil
 }
	/*
	* Copyright (c) 2018 - present. Boling Consulting Solutions (bcsw.net)
	* Copyright 2020-present Open Networking Foundation

	* 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 omci

	import (
	"encoding/binary"
	"errors"
	"fmt"
	"github.com/google/gopacket"
	me "github.com/opencord/omci-lib-go/generated"
	)

	type GetRequest struct {
	MeBasePacket
	AttributeMask uint16
	}

	func (omci *GetRequest) String() string {
	return fmt.Sprintf("%v, Mask: %#x",
	omci.MeBasePacket.String(), omci.AttributeMask)
	}

	// LayerType returns LayerTypeGetRequest
	func (omci *GetRequest) LayerType() gopacket.LayerType {
	return LayerTypeGetRequest
	}

	// CanDecode returns the set of layer types that this DecodingLayer can decode
	func (omci *GetRequest) CanDecode() gopacket.LayerClass {
	return LayerTypeGetRequest
	}

	// NextLayerType returns the layer type contained by this DecodingLayer.
	func (omci *GetRequest) NextLayerType() gopacket.LayerType {
	return gopacket.LayerTypePayload
	}

	// DecodeFromBytes decodes the given bytes of a Get Request into this layer
	func (omci *GetRequest) DecodeFromBytes(data []byte, p gopacket.PacketBuilder) error {
	// Common ClassID/EntityID decode in msgBase
	var hdrSize int
	if omci.Extended {
	hdrSize = 6 + 2
	} else {
	hdrSize = 4 + 2
	}
	err := omci.MeBasePacket.DecodeFromBytes(data, p, hdrSize)
	if err != nil {
	return err
	}
	meDefinition, omciErr := me.LoadManagedEntityDefinition(omci.EntityClass,
	me.ParamData{EntityID: omci.EntityInstance})
	if omciErr.StatusCode() != me.Success {
	return omciErr.GetError()
	}
	// ME needs to support Get
	if !me.SupportsMsgType(meDefinition, me.Get) {
	return me.NewProcessingError("managed entity does not support Get Message-Type")
	}
	if omci.Extended {
	if len(data) < 8 {
	p.SetTruncated()
	return errors.New("frame too small")
	}
	omci.AttributeMask = binary.BigEndian.Uint16(data[6:])
	} else {
	omci.AttributeMask = binary.BigEndian.Uint16(data[4:])
	}
	return nil
	}

	func decodeGetRequest(data []byte, p gopacket.PacketBuilder) error {
	omci := &GetRequest{}
	omci.MsgLayerType = LayerTypeGetRequest
	return decodingLayerDecoder(omci, data, p)
	}

	func decodeGetRequestExtended(data []byte, p gopacket.PacketBuilder) error {
	omci := &GetRequest{}
	omci.MsgLayerType = LayerTypeGetRequest
	omci.Extended = true
	return decodingLayerDecoder(omci, data, p)
	}

	// SerializeTo provides serialization of an Get Request message
	func (omci *GetRequest) SerializeTo(b gopacket.SerializeBuffer, _ gopacket.SerializeOptions) error {
	// Basic (common) OMCI Header is 8 octets, 10
	err := omci.MeBasePacket.SerializeTo(b)
	if err != nil {
	return err
	}
	meDefinition, omciErr := me.LoadManagedEntityDefinition(omci.EntityClass,
	me.ParamData{EntityID: omci.EntityInstance})
	if omciErr.StatusCode() != me.Success {
	return omciErr.GetError()
	}
	// ME needs to support Set
	if !me.SupportsMsgType(meDefinition, me.Get) {
	return me.NewProcessingError("managed entity does not support Get Message-Type")
	}
	maskOffset := 0
	if omci.Extended {
	maskOffset = 2
	}
	bytes, err := b.AppendBytes(2 + maskOffset)
	if err != nil {
	return err
	}
	if omci.Extended {
	binary.BigEndian.PutUint16(bytes, uint16(2))
	}
	binary.BigEndian.PutUint16(bytes[maskOffset:], omci.AttributeMask)
	return nil
	}

	type GetResponse struct {
	MeBasePacket
	Result me.Results
	AttributeMask uint16
	Attributes me.AttributeValueMap
	UnsupportedAttributeMask uint16
	FailedAttributeMask uint16
	}

	func (omci *GetResponse) String() string {
	return fmt.Sprintf("%v, Result: %d (%v), Mask: %#x, Unsupported: %#x, Failed: %#x, attributes: %v",
	omci.MeBasePacket.String(), omci.Result, omci.Result, omci.AttributeMask,
	omci.UnsupportedAttributeMask, omci.FailedAttributeMask, omci.Attributes)
	}

	// LayerType returns LayerTypeGetResponse
	func (omci *GetResponse) LayerType() gopacket.LayerType {
	return LayerTypeGetResponse
	}

	// CanDecode returns the set of layer types that this DecodingLayer can decode
	func (omci *GetResponse) CanDecode() gopacket.LayerClass {
	return LayerTypeGetResponse
	}

	// NextLayerType returns the layer type contained by this DecodingLayer.
	func (omci *GetResponse) NextLayerType() gopacket.LayerType {
	return gopacket.LayerTypePayload
	}

	// DecodeFromBytes decodes the given bytes of a Get Response into this layer
	func (omci *GetResponse) DecodeFromBytes(data []byte, p gopacket.PacketBuilder) error {
	// Common ClassID/EntityID decode in msgBase
	err := omci.MeBasePacket.DecodeFromBytes(data, p, 4+3)
	if err != nil {
	return err
	}
	meDefinition, omciErr := me.LoadManagedEntityDefinition(omci.EntityClass,
	me.ParamData{EntityID: omci.EntityInstance})
	if omciErr.StatusCode() != me.Success {
	return omciErr.GetError()
	}
	// ME needs to support Get
	if !me.SupportsMsgType(meDefinition, me.Get) {
	return me.NewProcessingError("managed entity does not support Get Message-Type")
	}
	if omci.Extended {
	if len(data) < 13 {
	p.SetTruncated()
	return errors.New("frame too small")
	}
	omci.Result = me.Results(data[6])
	omci.AttributeMask = binary.BigEndian.Uint16(data[7:])

	// If Attribute failed or Unknown, decode optional attribute mask
	if omci.Result == me.AttributeFailure {
	omci.UnsupportedAttributeMask = binary.BigEndian.Uint16(data[9:])
	omci.FailedAttributeMask = binary.BigEndian.Uint16(data[11:])
	}
	} else {
	omci.Result = me.Results(data[4])
	omci.AttributeMask = binary.BigEndian.Uint16(data[5:])

	// If Attribute failed or Unknown, decode optional attribute mask
	if omci.Result == me.AttributeFailure {
	omci.UnsupportedAttributeMask = binary.BigEndian.Uint16(data[32:34])
	omci.FailedAttributeMask = binary.BigEndian.Uint16(data[34:36])
	}
	}
	// Attribute decode. Note that the ITU-T G.988 specification states that the
	// Unsupported and Failed attribute masks are always present
	// but only valid if the status code== 9. However some XGS
	// ONUs (T&W and Alpha, perhaps more) will use these last 4
	// octets for data if the status code == 0. So accommodate
	// this behaviour in favor of greater interoperability.
	firstOctet := 7
	lastOctet := 36
	if omci.Extended {
	firstOctet = 13
	lastOctet = len(data)
	}

	switch omci.Result {
	case me.ProcessingError, me.NotSupported, me.UnknownEntity, me.UnknownInstance, me.DeviceBusy:
	return nil // Done (do not try and decode attributes)

	case me.AttributeFailure:
	if !omci.Extended {
	lastOctet = 32
	}
	}
	omci.Attributes, err = meDefinition.DecodeAttributes(omci.AttributeMask,
	data[firstOctet:lastOctet], p, byte(GetResponseType))
	if err != nil {
	return err
	}
	// Validate all attributes support read
	for attrName := range omci.Attributes {
	attr, err := me.GetAttributeDefinitionByName(meDefinition.GetAttributeDefinitions(), attrName)
	if err != nil {
	return err
	}
	if attr.Index != 0 && !me.SupportsAttributeAccess(*attr, me.Read) {
	msg := fmt.Sprintf("attribute '%v' does not support read access", attrName)
	return me.NewProcessingError(msg)
	}
	}
	if eidDef, eidDefOK := meDefinition.GetAttributeDefinitions()[0]; eidDefOK {
	omci.Attributes[eidDef.GetName()] = omci.EntityInstance
	return nil
	}
	return errors.New("all Managed Entities have an EntityID attribute")
	}

	func decodeGetResponse(data []byte, p gopacket.PacketBuilder) error {
	omci := &GetResponse{}
	omci.MsgLayerType = LayerTypeGetResponse
	return decodingLayerDecoder(omci, data, p)
	}

	func decodeGetResponseExtended(data []byte, p gopacket.PacketBuilder) error {
	omci := &GetResponse{}
	omci.MsgLayerType = LayerTypeGetResponse
	omci.Extended = true
	return decodingLayerDecoder(omci, data, p)
	}

	// SerializeTo provides serialization of an Get Response message
	func (omci *GetResponse) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
	// Basic (common) OMCI Header is 8 octets, 10
	if err := omci.MeBasePacket.SerializeTo(b); err != nil {
	return err
	}
	meDefinition, omciErr := me.LoadManagedEntityDefinition(omci.EntityClass,
	me.ParamData{EntityID: omci.EntityInstance})

	if omciErr.StatusCode() != me.Success {
	return omciErr.GetError()
	}
	// ME needs to support Get
	if !me.SupportsMsgType(meDefinition, me.Get) {
	return me.NewProcessingError("managed entity does not support the Get Message-Type")
	}
	resultOffset := 0
	attributeErrExtra := 0

	if omci.Extended {
	resultOffset = 2
	attributeErrExtra = 4 // Attribute mask + attribute error masks
	}
	// Space for result + mask (both types) + (len & error masks if extended)
	buffer, err := b.AppendBytes(3 + resultOffset + attributeErrExtra)
	if err != nil {
	return err
	}
	// Save result and initial mask. Other header fields updated after
	// attribute copy
	buffer[resultOffset] = byte(omci.Result)
	binary.BigEndian.PutUint16(buffer[resultOffset+1:], omci.AttributeMask)

	// Validate all attributes requested support read
	for attrName := range omci.Attributes {
	var attr *me.AttributeDefinition
	attr, err = me.GetAttributeDefinitionByName(meDefinition.GetAttributeDefinitions(), attrName)
	if err != nil {
	return err
	}
	if attr.Index != 0 && (attr.Mask&omci.AttributeMask != 0) && !me.SupportsAttributeAccess(*attr, me.Read) {
	msg := fmt.Sprintf("attribute '%v' does not support read access", attrName)
	return me.NewProcessingError(msg)
	}
	}
	// Attribute serialization
	switch omci.Result {
	default:
	if omci.Extended {
	// Minimum length is 7 for extended an need to write error masks
	binary.BigEndian.PutUint16(buffer, uint16(7))
	binary.BigEndian.PutUint32(buffer[resultOffset+3:], 0)
	}
	break

	case me.Success, me.AttributeFailure:
	// TODO: Baseline only supported at this time)
	var available int
	if omci.Extended {
	available = MaxExtendedLength - 18 - 4 // Less: header, mic
	} else {
	available = MaxBaselineLength - 11 - 4 - 8 // Less: header, failed attributes, length, mic
	}
	// Serialize to temporary buffer if we may need to reset values due to
	// recoverable truncation errors
	attributeBuffer := gopacket.NewSerializeBuffer()
	var failedMask uint16
	err, failedMask = meDefinition.SerializeAttributes(omci.Attributes, omci.AttributeMask,
	attributeBuffer, byte(GetResponseType), available, opts.FixLengths)

	if err != nil {
	return err
	}
	if failedMask != 0 {
	// Not all attributes would fit
	omci.FailedAttributeMask \|= failedMask
	omci.AttributeMask &= ^failedMask
	omci.Result = me.AttributeFailure

	// Adjust already recorded values
	buffer[resultOffset] = byte(omci.Result)
	binary.BigEndian.PutUint16(buffer[resultOffset+1:], omci.AttributeMask)
	}
	if omci.Extended {
	// Set length and any failure masks
	binary.BigEndian.PutUint16(buffer, uint16(len(attributeBuffer.Bytes())+7))

	if omci.Result == me.AttributeFailure {
	binary.BigEndian.PutUint16(buffer[resultOffset+3:], omci.UnsupportedAttributeMask)
	binary.BigEndian.PutUint16(buffer[resultOffset+5:], omci.FailedAttributeMask)
	} else {
	binary.BigEndian.PutUint32(buffer[resultOffset+3:], 0)
	}
	}
	// Copy over attributes to the original serialization buffer
	var newSpace []byte

	newSpace, err = b.AppendBytes(len(attributeBuffer.Bytes()))
	if err != nil {
	return err
	}
	copy(newSpace, attributeBuffer.Bytes())

	if !omci.Extended {
	// Calculate space left. Max - msgType header - OMCI trailer - spacedUsedSoFar
	bytesLeft := MaxBaselineLength - 4 - 8 - len(b.Bytes())

	var remainingBytes []byte
	remainingBytes, err = b.AppendBytes(bytesLeft + 4)

	if err != nil {
	return me.NewMessageTruncatedError(err.Error())
	}
	copy(remainingBytes, lotsOfZeros[:])

	if omci.Result == me.AttributeFailure {
	binary.BigEndian.PutUint16(remainingBytes[bytesLeft-4:bytesLeft-2], omci.UnsupportedAttributeMask)
	binary.BigEndian.PutUint16(remainingBytes[bytesLeft-2:bytesLeft], omci.FailedAttributeMask)
	}
	}
	}
	return nil
	}