payload.go

//
// Helpers for parsing and encoding a unified DHCP message,
// including the header and the options
//
package main

import (
	"bytes"
	"fmt"
	"log"
)

type DHCPMessage struct {
	Header  *MessageHeader
	Options *Options
}

func NewDhcpMessage() *DHCPMessage {
	return &DHCPMessage{
		Options: NewOptions(),
		Header:  &MessageHeader{},
	}
}

func (m *DHCPMessage) Encode(buf *bytes.Buffer) error {
	err := m.Header.Encode(buf)
	if err != nil {
		return fmt.Errorf("Writing dhcp header to our payload: %v", err)
	}

	err = m.Options.Encode(buf)
	if err != nil {
		return fmt.Errorf("Writing dhcp options to our payload: %v", err)
	}

	return nil
}

func ParseDhcpMessage(buf []byte) (*DHCPMessage, error) {
	reader := bytes.NewReader(buf)

	header, err := ParseMessageHeader(reader)
	if err != nil {
		return nil, err
	}

	// Parse arbitrary options
	options := ParseOptions(reader)

	// ClientAddr overriden by option?
	// FIXME: verify if this logic is actually needed
	if option, ok := options.Get(OPTION_REQUESTED_IP); ok {
		if option.Header.Length == 4 {
			ip, err := BytesToFixedV4(option.Data)
			if err == nil {
				header.ClientAddr = ip
			} else {
				log.Printf("Failed converting byte stream to fixed v4")
			}
		}
	}

	return &DHCPMessage{
		Options: options,
		Header:  header,
	}, nil
}