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package dhcpv4
import (
"errors"
"fmt"
"strings"
"github.com/u-root/u-root/pkg/uio"
)
// 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 := uio.NewBigEndianBuffer(nil)
if !op.Rfc3004 {
buf.WriteBytes(op.UserClasses[0])
} else {
for _, uc := range op.UserClasses {
buf.Write8(uint8(len(uc)))
buf.WriteBytes(uc)
}
}
return buf.Data()
}
func (op *OptUserClass) String() string {
ucStrings := make([]string, 0, len(op.UserClasses))
if !op.Rfc3004 {
ucStrings = append(ucStrings, string(op.UserClasses[0]))
} else {
for _, uc := range op.UserClasses {
ucStrings = append(ucStrings, string(uc))
}
}
return fmt.Sprintf("User Class Information -> %v", strings.Join(ucStrings, ", "))
}
// ParseOptUserClass returns a new OptUserClass from a byte stream or
// error if any
func ParseOptUserClass(data []byte) (*OptUserClass, error) {
opt := OptUserClass{}
buf := uio.NewBigEndianBuffer(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 < buf.Len() {
// UC_Len_i does not include itself so add 1
counting += int(data[counting]) + 1
}
if counting != buf.Len() {
opt.UserClasses = append(opt.UserClasses, data)
return &opt, nil
}
opt.Rfc3004 = true
for buf.Has(1) {
ucLen := buf.Read8()
if ucLen == 0 {
return nil, fmt.Errorf("DHCP user class must have length greater than 0")
}
opt.UserClasses = append(opt.UserClasses, buf.CopyN(int(ucLen)))
}
if len(opt.UserClasses) == 0 {
return nil, errors.New("ParseOptUserClass: at least one user class is required")
}
return &opt, buf.FinError()
}
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