option_custom.cc

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// Copyright (C) 2012-2023 Internet Systems Consortium, Inc. ("ISC")
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
#include <config.h>
#include <dhcp/libdhcp++.h>
#include <dhcp/option_data_types.h>
#include <dhcp/option_custom.h>
#include <exceptions/isc_assert.h>
#include <util/encode/hex.h>
 
using namespace isc::asiolink;
 
namespace isc {
namespace dhcp {
 
OptionCustom::OptionCustom(const OptionDefinition& def,
                           Universe u)
    : Option(u, def.getCode(), OptionBuffer()),
      definition_(def) {
    setEncapsulatedSpace(def.getEncapsulatedSpace());
    createBuffers();
}
 
OptionCustom::OptionCustom(const OptionDefinition& def,
                           Universe u,
                           const OptionBuffer& data)
    : Option(u, def.getCode(), data.begin(), data.end()),
      definition_(def) {
    setEncapsulatedSpace(def.getEncapsulatedSpace());
    createBuffers(getData());
}
 
OptionCustom::OptionCustom(const OptionDefinition& def,
                           Universe u,
                           OptionBufferConstIter first,
                           OptionBufferConstIter last)
    : Option(u, def.getCode(), first, last),
      definition_(def) {
    setEncapsulatedSpace(def.getEncapsulatedSpace());
    createBuffers(getData());
}
 
OptionPtr
OptionCustom::clone() const {
    return (cloneInternal<OptionCustom>());
}
 
void
OptionCustom::addArrayDataField(const IOAddress& address) {
    checkArrayType();
 
    if ((address.isV4() && definition_.getType() != OPT_IPV4_ADDRESS_TYPE) ||
        (address.isV6() && definition_.getType() != OPT_IPV6_ADDRESS_TYPE)) {
        isc_throw(BadDataTypeCast, "invalid address specified "
                  << address << ". Expected a valid IPv"
                  << (definition_.getType() == OPT_IPV4_ADDRESS_TYPE ?
                      "4" : "6") << " address.");
    }
 
    OptionBuffer buf;
    OptionDataTypeUtil::writeAddress(address, buf);
    buffers_.push_back(buf);
}
 
void
OptionCustom::addArrayDataField(const std::string& value) {
    checkArrayType();
 
    OpaqueDataTuple::LengthFieldType lft = OptionDataTypeUtil::getTupleLenFieldType(getUniverse());
    OptionBuffer buf;
    OptionDataTypeUtil::writeTuple(value, lft, buf);
    buffers_.push_back(buf);
}
 
void
OptionCustom::addArrayDataField(const OpaqueDataTuple& value) {
    checkArrayType();
 
    OptionBuffer buf;
    OptionDataTypeUtil::writeTuple(value, buf);
    buffers_.push_back(buf);
}
 
void
OptionCustom::addArrayDataField(const bool value) {
    checkArrayType();
 
    OptionBuffer buf;
    OptionDataTypeUtil::writeBool(value, buf);
    buffers_.push_back(buf);
}
 
void
OptionCustom::addArrayDataField(const PrefixLen& prefix_len,
                                const asiolink::IOAddress& prefix) {
    checkArrayType();
 
    if (definition_.getType() != OPT_IPV6_PREFIX_TYPE) {
        isc_throw(BadDataTypeCast, "IPv6 prefix can be specified only for"
                  " an option comprising an array of IPv6 prefix values");
    }
 
    OptionBuffer buf;
    OptionDataTypeUtil::writePrefix(prefix_len, prefix, buf);
    buffers_.push_back(buf);
}
 
void
OptionCustom::addArrayDataField(const PSIDLen& psid_len, const PSID& psid) {
    checkArrayType();
 
    if (definition_.getType() != OPT_PSID_TYPE) {
        isc_throw(BadDataTypeCast, "PSID value can be specified onlu for"
                  " an option comprising an array of PSID length / value"
                  " tuples");
    }
 
    OptionBuffer buf;
    OptionDataTypeUtil::writePsid(psid_len, psid, buf);
    buffers_.push_back(buf);
}
 
void
OptionCustom::checkIndex(const uint32_t index) const {
    if (index >= buffers_.size()) {
        isc_throw(isc::OutOfRange, "specified data field index " << index
                  << " is out of range.");
    }
}
 
void
OptionCustom::createBuffer(OptionBuffer& buffer,
                           const OptionDataType data_type) const {
    // For data types that have a fixed size we can use the
    // utility function to get the buffer's size.
    size_t data_size = OptionDataTypeUtil::getDataTypeLen(data_type);
 
    // For variable data sizes the utility function returns zero.
    // It is ok for string values because the default string
    // is 'empty'. However for FQDN the empty value is not valid
    // so we initialize it to '.'. For prefix there is a prefix
    // length fixed field.
    if (data_size == 0) {
        if (data_type == OPT_FQDN_TYPE) {
            OptionDataTypeUtil::writeFqdn(".", buffer);
 
        } else if (data_type == OPT_IPV6_PREFIX_TYPE) {
            OptionDataTypeUtil::writePrefix(PrefixLen(0),
                                            IOAddress::IPV6_ZERO_ADDRESS(),
                                            buffer);
        }
    } else {
        // At this point we can resize the buffer. Note that
        // for string values we are setting the empty buffer
        // here.
        buffer.resize(data_size);
    }
}
 
void
OptionCustom::createBuffers() {
    definition_.validate();
 
    std::vector<OptionBuffer> buffers;
 
    OptionDataType data_type = definition_.getType();
    // This function is called when an empty data buffer has been
    // passed to the constructor. In such cases values for particular
    // data fields will be set using modifier functions but for now
    // we need to initialize a set of buffers that are specified
    // for an option by its definition. Since there is no data yet,
    // we are going to fill these buffers with default values.
    if (data_type == OPT_RECORD_TYPE) {
        // For record types we need to iterate over all data fields
        // specified in option definition and create corresponding
        // buffers for each of them.
        const OptionDefinition::RecordFieldsCollection fields =
            definition_.getRecordFields();
 
        for (OptionDefinition::RecordFieldsConstIter field = fields.begin();
             field != fields.end(); ++field) {
            OptionBuffer buf;
            createBuffer(buf, *field);
            // We have the buffer with default value prepared so we
            // add it to the set of buffers.
            buffers.push_back(buf);
        }
    } else if (!definition_.getArrayType() &&
               data_type != OPT_EMPTY_TYPE) {
        // For either 'empty' options we don't have to create any buffers
        // for obvious reason. For arrays we also don't create any buffers
        // yet because the set of fields that belong to the array is open
        // ended so we can't allocate required buffers until we know how
        // many of them are needed.
        // For non-arrays we have a single value being held by the option
        // so we have to allocate exactly one buffer.
        OptionBuffer buf;
        createBuffer(buf, data_type);
        // Add a buffer that we have created and leave.
        buffers.push_back(buf);
    }
    // The 'swap' is used here because we want to make sure that we
    // don't touch buffers_ until we successfully allocate all
    // buffers to be stored there.
    std::swap(buffers, buffers_);
}
 
size_t
OptionCustom::bufferLength(const OptionDataType data_type, bool in_array,
                           OptionBuffer::const_iterator begin,
                           OptionBuffer::const_iterator end) const {
    // For fixed-size data type such as boolean, integer, even
    // IP address we can use the utility function to get the required
    // buffer size.
    size_t data_size = OptionDataTypeUtil::getDataTypeLen(data_type);
 
    // For variable size types (e.g. string) the function above will
    // return 0 so we need to do a runtime check of the length.
    if (data_size == 0) {
        // FQDN is a special data type as it stores variable length data
        // but the data length is encoded in the buffer. The easiest way
        // to obtain the length of the data is to read the FQDN. The
        // utility function will return the size of the buffer on success.
        if (data_type == OPT_FQDN_TYPE) {
            std::string fqdn =
                OptionDataTypeUtil::readFqdn(OptionBuffer(begin, end));
            // The size of the buffer holding an FQDN is always
            // 1 byte larger than the size of the string
            // representation of this FQDN.
            data_size = fqdn.size() + 1;
        } else if (!definition_.getArrayType() &&
                   ((data_type == OPT_BINARY_TYPE) ||
                    (data_type == OPT_STRING_TYPE))) {
            // In other case we are dealing with string or binary value
            // which size can't be determined. Thus we consume the
            // remaining part of the buffer for it. Note that variable
            // size data can be laid at the end of the option only and
            // that the validate() function in OptionDefinition object
            // should have checked wheter it is a case for this option.
            data_size = std::distance(begin, end);
        } else if (data_type == OPT_IPV6_PREFIX_TYPE) {
            // The size of the IPV6 prefix type is determined as
            // one byte (which is the size of the prefix in bits)
            // followed by the prefix bits (right-padded with
            // zeros to the nearest octet boundary)
            if ((begin == end) && !in_array)
                return 0;
            PrefixTuple prefix =
                OptionDataTypeUtil::readPrefix(OptionBuffer(begin, end));
            // Data size comprises 1 byte holding a prefix length and the
            // prefix length (in bytes) rounded to the nearest byte boundary.
            data_size = sizeof(uint8_t) + (prefix.first.asUint8() + 7) / 8;
        } else if (data_type == OPT_TUPLE_TYPE) {
            OpaqueDataTuple::LengthFieldType lft =
                OptionDataTypeUtil::getTupleLenFieldType(getUniverse());
            std::string value =
                OptionDataTypeUtil::readTuple(OptionBuffer(begin, end), lft);
            data_size = value.size();
            // The size of the buffer holding a tuple is always
            // 1 or 2 byte larger than the size of the string
            data_size += getUniverse() == Option::V4 ? 1 : 2;
        } else {
            // If we reached the end of buffer we assume that this option is
            // truncated because there is no remaining data to initialize
            // an option field.
            isc_throw(OutOfRange, "option buffer truncated");
        }
    }
 
    return data_size;
}
 
void
OptionCustom::createBuffers(const OptionBuffer& data_buf) {
    // Check that the option definition is correct as we are going
    // to use it to split the data_ buffer into set of sub buffers.
    definition_.validate();
 
    std::vector<OptionBuffer> buffers;
    OptionBuffer::const_iterator data = data_buf.begin();
 
    OptionDataType data_type = definition_.getType();
    if (data_type == OPT_RECORD_TYPE) {
        // An option comprises a record of data fields. We need to
        // get types of these data fields to allocate enough space
        // for each buffer.
        const OptionDefinition::RecordFieldsCollection& fields =
            definition_.getRecordFields();
 
        // Go over all data fields within a record.
        for (OptionDefinition::RecordFieldsConstIter field = fields.begin();
             field != fields.end(); ++field) {
            size_t data_size = bufferLength(*field, false,
                                            data, data_buf.end());
 
            // Our data field requires that there is a certain chunk of
            // data left in the buffer. If not, option is truncated.
            if (std::distance(data, data_buf.end()) < data_size) {
                isc_throw(OutOfRange, "option buffer truncated");
            }
 
            // Store the created buffer.
            buffers.push_back(OptionBuffer(data, data + data_size));
            // Proceed to the next data field.
            data += data_size;
        }
 
        // Get extra buffers when the last field is an array.
        if (definition_.getArrayType()) {
            while (data != data_buf.end()) {
                // Code copied from the standard array case
                size_t data_size = bufferLength(fields.back(), true,
                                                data, data_buf.end());
                isc_throw_assert(data_size > 0);
                if (std::distance(data, data_buf.end()) < data_size) {
                    break;
                }
                buffers.push_back(OptionBuffer(data, data + data_size));
                data += data_size;
            }
        }
 
        // Unpack suboptions if any.
        else if (data != data_buf.end() && !getEncapsulatedSpace().empty()) {
            unpackOptions(OptionBuffer(data, data_buf.end()));
        }
 
    } else if (data_type != OPT_EMPTY_TYPE) {
        // If data_type value is other than OPT_RECORD_TYPE, our option is
        // empty (have no data at all) or it comprises one or more
        // data fields of the same type. The type of those fields
        // is held in the data_type variable so let's use it to determine
        // a size of buffers.
        size_t data_size = OptionDataTypeUtil::getDataTypeLen(data_type);
        // The check below will fail if the input buffer is too short
        // for the data size being held by this option.
        // Note that data_size returned by getDataTypeLen may be zero
        // if variable length data is being held by the option but
        // this will not cause this check to throw exception.
        if (std::distance(data, data_buf.end()) < data_size) {
            isc_throw(OutOfRange, "option buffer truncated");
        }
        // For an array of values we are taking different path because
        // we have to handle multiple buffers.
        if (definition_.getArrayType()) {
            while (data != data_buf.end()) {
                data_size = bufferLength(data_type, true, data, data_buf.end());
                // We don't perform other checks for data types that can't be
                // used together with array indicator such as strings, empty field
                // etc. This is because OptionDefinition::validate function should
                // have checked this already. Thus data_size must be greater than
                // zero.
                isc_throw_assert(data_size > 0);
                // Get chunks of data and store as a collection of buffers.
                // Truncate any remaining part which length is not divisible by
                // data_size. Note that it is ok to truncate the data if and only
                // if the data buffer is long enough to keep at least one value.
                // This has been checked above already.
                if (std::distance(data, data_buf.end()) < data_size) {
                    break;
                }
                buffers.push_back(OptionBuffer(data, data + data_size));
                data += data_size;
            }
        } else {
            // For non-arrays the data_size can be zero because
            // getDataTypeLen returns zero for variable size data types
            // such as strings. Simply take whole buffer.
            data_size = bufferLength(data_type, false, data, data_buf.end());
            if ((data_size > 0) && (std::distance(data, data_buf.end()) >= data_size)) {
                buffers.push_back(OptionBuffer(data, data + data_size));
                data += data_size;
            } else {
                isc_throw(OutOfRange, "option buffer truncated");
            }
 
            // Unpack suboptions if any.
            if (data != data_buf.end() && !getEncapsulatedSpace().empty()) {
                unpackOptions(OptionBuffer(data, data_buf.end()));
            }
        }
    } else {
        // Unpack suboptions if any.
        if (data != data_buf.end() && !getEncapsulatedSpace().empty()) {
            unpackOptions(OptionBuffer(data, data_buf.end()));
        }
    }
    // If everything went ok we can replace old buffer set with new ones.
    std::swap(buffers_, buffers);
}
 
std::string
OptionCustom::dataFieldToText(const OptionDataType data_type,
                              const uint32_t index) const {
    std::ostringstream text;
 
    // Get the value of the data field.
    switch (data_type) {
    case OPT_BINARY_TYPE:
        text << util::encode::encodeHex(readBinary(index));
        break;
    case OPT_BOOLEAN_TYPE:
        text << (readBoolean(index) ? "true" : "false");
        break;
    case OPT_INT8_TYPE:
        text << static_cast<int>(readInteger<int8_t>(index));
        break;
    case OPT_INT16_TYPE:
        text << readInteger<int16_t>(index);
        break;
    case OPT_INT32_TYPE:
        text << readInteger<int32_t>(index);
        break;
    case OPT_UINT8_TYPE:
        text << static_cast<unsigned>(readInteger<uint8_t>(index));
        break;
    case OPT_UINT16_TYPE:
        text << readInteger<uint16_t>(index);
        break;
    case OPT_UINT32_TYPE:
        text << readInteger<uint32_t>(index);
        break;
    case OPT_IPV4_ADDRESS_TYPE:
    case OPT_IPV6_ADDRESS_TYPE:
        text << readAddress(index);
        break;
    case OPT_FQDN_TYPE:
        text << "\"" << readFqdn(index) << "\"";
        break;
    case OPT_TUPLE_TYPE:
        text << "\"" << readTuple(index) << "\"";
        break;
    case OPT_STRING_TYPE:
        text << "\"" << readString(index) << "\"";
        break;
    case OPT_PSID_TYPE:
    {
        PSIDTuple t = readPsid(index);
        text << "len=" << t.first.asUnsigned() << ",psid=" << t.second.asUint16();
    }
    default:
        ;
    }
 
    // Append data field type in brackets.
    text << " (" << OptionDataTypeUtil::getDataTypeName(data_type) << ")";
 
    return (text.str());
}
 
void
OptionCustom::pack(isc::util::OutputBuffer& buf, bool check) const {
 
    // Pack DHCP header (V4 or V6).
    packHeader(buf, check);
 
    // Write data from buffers.
    for (std::vector<OptionBuffer>::const_iterator it = buffers_.begin();
         it != buffers_.end(); ++it) {
        // In theory the createBuffers function should have taken
        // care that there are no empty buffers added to the
        // collection but it is almost always good to make sure.
        if (!it->empty()) {
            buf.writeData(&(*it)[0], it->size());
        }
    }
 
    // Write suboptions.
    packOptions(buf, check);
}
 
 
IOAddress
OptionCustom::readAddress(const uint32_t index) const {
    checkIndex(index);
 
    // The address being read can be either IPv4 or IPv6. The decision
    // is made based on the buffer length. If it holds 4 bytes it is IPv4
    // address, if it holds 16 bytes it is IPv6.
    if (buffers_[index].size() == asiolink::V4ADDRESS_LEN) {
        return (OptionDataTypeUtil::readAddress(buffers_[index], AF_INET));
    } else if (buffers_[index].size() == asiolink::V6ADDRESS_LEN) {
        return (OptionDataTypeUtil::readAddress(buffers_[index], AF_INET6));
    } else {
        isc_throw(BadDataTypeCast, "unable to read data from the buffer as"
                  << " IP address. Invalid buffer length "
                  << buffers_[index].size() << ".");
    }
}
 
void
OptionCustom::writeAddress(const IOAddress& address,
                           const uint32_t index) {
    checkIndex(index);
 
    if ((address.isV4() && buffers_[index].size() != V4ADDRESS_LEN) ||
        (address.isV6() && buffers_[index].size() != V6ADDRESS_LEN)) {
        isc_throw(BadDataTypeCast, "invalid address specified "
                  << address << ". Expected a valid IPv"
                  << (buffers_[index].size() == V4ADDRESS_LEN ? "4" : "6")
                  << " address.");
    }
 
    OptionBuffer buf;
    OptionDataTypeUtil::writeAddress(address, buf);
    std::swap(buf, buffers_[index]);
}
 
const OptionBuffer&
OptionCustom::readBinary(const uint32_t index) const {
    checkIndex(index);
    return (buffers_[index]);
}
 
void
OptionCustom::writeBinary(const OptionBuffer& buf,
                          const uint32_t index) {
    checkIndex(index);
    buffers_[index] = buf;
}
 
std::string
OptionCustom::readTuple(const uint32_t index) const {
    checkIndex(index);
    OpaqueDataTuple::LengthFieldType lft = OptionDataTypeUtil::getTupleLenFieldType(getUniverse());
    return (OptionDataTypeUtil::readTuple(buffers_[index], lft));
}
 
void
OptionCustom::readTuple(OpaqueDataTuple& tuple,
                        const uint32_t index) const {
    checkIndex(index);
    OptionDataTypeUtil::readTuple(buffers_[index], tuple);
}
 
void
OptionCustom::writeTuple(const std::string& value, const uint32_t index) {
    checkIndex(index);
 
    buffers_[index].clear();
    OpaqueDataTuple::LengthFieldType lft = OptionDataTypeUtil::getTupleLenFieldType(getUniverse());
    OptionDataTypeUtil::writeTuple(value, lft, buffers_[index]);
}
 
void
OptionCustom::writeTuple(const OpaqueDataTuple& value, const uint32_t index) {
    checkIndex(index);
 
    buffers_[index].clear();
    OptionDataTypeUtil::writeTuple(value, buffers_[index]);
}
 
bool
OptionCustom::readBoolean(const uint32_t index) const {
    checkIndex(index);
    return (OptionDataTypeUtil::readBool(buffers_[index]));
}
 
void
OptionCustom::writeBoolean(const bool value, const uint32_t index) {
    checkIndex(index);
 
    buffers_[index].clear();
    OptionDataTypeUtil::writeBool(value, buffers_[index]);
}
 
std::string
OptionCustom::readFqdn(const uint32_t index) const {
    checkIndex(index);
    return (OptionDataTypeUtil::readFqdn(buffers_[index]));
}
 
void
OptionCustom::writeFqdn(const std::string& fqdn, const uint32_t index) {
    checkIndex(index);
 
    // Create a temporary buffer where the FQDN will be written.
    OptionBuffer buf;
    // Try to write to the temporary buffer rather than to the
    // buffers_ member directly guarantees that we don't modify
    // (clear) buffers_ until we are sure that the provided FQDN
    // is valid.
    OptionDataTypeUtil::writeFqdn(fqdn, buf);
    // If we got to this point it means that the FQDN is valid.
    // We can move the contents of the temporary buffer to the
    // target buffer.
    std::swap(buffers_[index], buf);
}
 
PrefixTuple
OptionCustom::readPrefix(const uint32_t index) const {
    checkIndex(index);
    return (OptionDataTypeUtil::readPrefix(buffers_[index]));
}
 
void
OptionCustom::writePrefix(const PrefixLen& prefix_len,
                          const IOAddress& prefix,
                          const uint32_t index) {
    checkIndex(index);
 
    OptionBuffer buf;
    OptionDataTypeUtil::writePrefix(prefix_len, prefix, buf);
    // If there are no errors while writing PSID to a buffer, we can
    // replace the current buffer with a new buffer.
    std::swap(buffers_[index], buf);
}
 
 
PSIDTuple
OptionCustom::readPsid(const uint32_t index) const {
    checkIndex(index);
    return (OptionDataTypeUtil::readPsid(buffers_[index]));
}
 
void
OptionCustom::writePsid(const PSIDLen& psid_len, const PSID& psid,
                        const uint32_t index) {
    checkIndex(index);
 
    OptionBuffer buf;
    OptionDataTypeUtil::writePsid(psid_len, psid, buf);
    // If there are no errors while writing PSID to a buffer, we can
    // replace the current buffer with a new buffer.
    std::swap(buffers_[index], buf);
}
 
 
std::string
OptionCustom::readString(const uint32_t index) const {
    checkIndex(index);
    return (OptionDataTypeUtil::readString(buffers_[index]));
}
 
void
OptionCustom::writeString(const std::string& text, const uint32_t index) {
    checkIndex(index);
 
    // Let's clear a buffer as we want to replace the value of the
    // whole buffer. If we fail to clear the buffer the data will
    // be appended.
    buffers_[index].clear();
    // If the text value is empty we can leave because the buffer
    // is already empty.
    if (!text.empty()) {
        OptionDataTypeUtil::writeString(text, buffers_[index]);
    }
}
 
void
OptionCustom::unpack(OptionBufferConstIter begin,
                     OptionBufferConstIter end) {
    initialize(begin, end);
}
 
uint16_t
OptionCustom::len() const {
    // The length of the option is a sum of option header ...
    size_t length = getHeaderLen();
 
    // ... lengths of all buffers that hold option data ...
    for (std::vector<OptionBuffer>::const_iterator buf = buffers_.begin();
         buf != buffers_.end(); ++buf) {
        length += buf->size();
    }
 
    // ... and lengths of all suboptions
    for (OptionCollection::const_iterator it = options_.begin();
         it != options_.end();
         ++it) {
        length += (*it).second->len();
    }
 
    return (static_cast<uint16_t>(length));
}
 
void OptionCustom::initialize(const OptionBufferConstIter first,
                              const OptionBufferConstIter last) {
    setData(first, last);
 
    // Chop the data_ buffer into set of buffers that represent
    // option fields data.
    createBuffers(getData());
}
 
std::string OptionCustom::toText(int indent) const {
    std::stringstream output;
 
    output << headerToText(indent) << ":";
 
    OptionDataType data_type = definition_.getType();
    if (data_type == OPT_RECORD_TYPE) {
        const OptionDefinition::RecordFieldsCollection& fields =
            definition_.getRecordFields();
 
        // For record types we iterate over fields defined in
        // option definition and match the appropriate buffer
        // with them.
        for (OptionDefinition::RecordFieldsConstIter field = fields.begin();
             field != fields.end(); ++field) {
            output << " " << dataFieldToText(*field, std::distance(fields.begin(),
                                                                   field));
        }
 
        // If the last record field is an array iterate on extra buffers
        if (definition_.getArrayType()) {
            for (unsigned int i = fields.size(); i < getDataFieldsNum(); ++i) {
                output << " " << dataFieldToText(fields.back(), i);
            }
        }
    } else {
        // For non-record types we iterate over all buffers
        // and print the data type set globally for an option
        // definition. We take the same code path for arrays
        // and non-arrays as they only differ in such a way that
        // non-arrays have just single data field.
        for (unsigned int i = 0; i < getDataFieldsNum(); ++i) {
            output << " " << dataFieldToText(definition_.getType(), i);
        }
    }
 
    // Append suboptions.
    output << suboptionsToText(indent + 2);
 
    return (output.str());
}
 
} // end of isc::dhcp namespace
} // end of isc namespace