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package dhcpv4
import (
"fmt"
"net"
)
// This option implements the network time protocol servers option
// https://tools.ietf.org/html/rfc2132
// OptNTPServers represents an option encapsulating the NTP servers.
type OptNTPServers struct {
NTPServers []net.IP
}
// ParseOptNTPServers returns a new OptNTPServers from a byte stream, or error if any.
func ParseOptNTPServers(data []byte) (*OptNTPServers, error) {
if len(data) < 2 {
return nil, ErrShortByteStream
}
code := OptionCode(data[0])
if code != OptionNTPServers {
return nil, fmt.Errorf("expected code %v, got %v", OptionNTPServers, code)
}
length := int(data[1])
if length == 0 || length%4 != 0 {
return nil, fmt.Errorf("Invalid length: expected multiple of 4 larger than 4, got %v", length)
}
if len(data) < 2+length {
return nil, ErrShortByteStream
}
ntpServers := make([]net.IP, 0, length%4)
for idx := 0; idx < length; idx += 4 {
b := data[2+idx : 2+idx+4]
ntpServers = append(ntpServers, net.IPv4(b[0], b[1], b[2], b[3]))
}
return &OptNTPServers{NTPServers: ntpServers}, nil
}
// Code returns the option code.
func (o *OptNTPServers) Code() OptionCode {
return OptionNTPServers
}
// ToBytes returns a serialized stream of bytes for this option.
func (o *OptNTPServers) ToBytes() []byte {
ret := []byte{byte(o.Code()), byte(o.Length())}
for _, ntp := range o.NTPServers {
ret = append(ret, ntp.To4()...)
}
return ret
}
// String returns a human-readable string.
func (o *OptNTPServers) String() string {
var ntpServers string
for idx, ntp := range o.NTPServers {
ntpServers += ntp.String()
if idx < len(o.NTPServers)-1 {
ntpServers += ", "
}
}
return fmt.Sprintf("NTP Servers -> %v", ntpServers)
}
// Length returns the length of the data portion (excluding option code an byte
// length).
func (o *OptNTPServers) Length() int {
return len(o.NTPServers) * 4
}
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