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package dhcpv4
import (
"errors"
"fmt"
"strings"
)
// This option implements the User Class option
// https://tools.ietf.org/html/rfc3004
// OptUserClass represents an option encapsulating User Classes.
type OptUserClass struct {
UserClasses [][]byte
Rfc3004 bool
}
// Code returns the option code
func (op *OptUserClass) Code() OptionCode {
return OptionUserClassInformation
}
// ToBytes serializes the option and returns it as a sequence of bytes
func (op *OptUserClass) ToBytes() []byte {
buf := []byte{byte(op.Code()), byte(op.Length())}
if !op.Rfc3004 && len(op.UserClasses) == 1 {
return append(buf, op.UserClasses[0]...)
}
for _, uc := range op.UserClasses {
buf = append(buf, byte(len(uc)))
buf = append(buf, uc...)
}
return buf
}
// Length returns the option length
func (op *OptUserClass) Length() int {
ret := 0
if !op.Rfc3004 && len(op.UserClasses) == 1 {
return len(op.UserClasses[0])
}
for _, uc := range op.UserClasses {
ret += 1 + len(uc)
}
return ret
}
func (op *OptUserClass) String() string {
ucStrings := make([]string, 0, len(op.UserClasses))
for _, uc := range op.UserClasses {
ucStrings = append(ucStrings, string(uc))
}
return fmt.Sprintf("OptUserClass{userclass=[%s]}", strings.Join(ucStrings, ", "))
}
// ParseOptUserClass returns a new OptUserClass from a byte stream or
// error if any
func ParseOptUserClass(data []byte) (*OptUserClass, error) {
opt := OptUserClass{}
if len(data) < 4 {
return nil, ErrShortByteStream
}
code := OptionCode(data[0])
if code != OptionUserClassInformation {
return nil, fmt.Errorf("expected code %v, got %v", OptionUserClassInformation, code)
}
totalLength := int(data[1])
data = data[2:]
if len(data) < totalLength {
return nil, fmt.Errorf("ParseOptUserClass: short data: length is %d but got %d bytes",
totalLength, len(data))
}
// Check if option is Microsoft style instead of RFC compliant, issue #113
// User-class options are, according to RFC3004, supposed to contain a set
// of strings each with length UC_Len_i. Here we check that this is so,
// by seeing if all the UC_Len_i lengths are consistent with the overall
// option length. If the lengths don't add up, we assume that the option
// is a single string and non RFC3004 compliant
var counting int
for counting < totalLength {
// UC_Len_i does not include itself so add 1
counting += int(data[counting]) + 1
}
if counting != totalLength {
opt.UserClasses = append(opt.UserClasses, data[:totalLength])
return &opt, nil
}
opt.Rfc3004 = true
for i := 0; i < totalLength; {
ucLen := int(data[i])
if ucLen == 0 {
return nil, errors.New("User Class value has invalid length of 0")
}
base := i + 1
if len(data) < base+ucLen {
return nil, fmt.Errorf("ParseOptUserClass: short data: %d bytes; want: %d", len(data), base+ucLen)
}
opt.UserClasses = append(opt.UserClasses, data[base:base+ucLen])
i += base + ucLen
}
if len(opt.UserClasses) < 1 {
return nil, errors.New("ParseOptUserClass: at least one user class is required")
}
return &opt, nil
}
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