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package dhcpv4
import (
"fmt"
"net"
)
// This option implements the domain name server option
// https://tools.ietf.org/html/rfc2132
// OptDomainNameServer represents an option encapsulating the domain name
// servers.
type OptDomainNameServer struct {
NameServers []net.IP
}
// ParseOptDomainNameServer returns a new OptDomainNameServer from a byte
// stream, or error if any.
func ParseOptDomainNameServer(data []byte) (*OptDomainNameServer, error) {
if len(data) < 2 {
return nil, ErrShortByteStream
}
code := OptionCode(data[0])
if code != OptionDomainNameServer {
return nil, fmt.Errorf("expected code %v, got %v", OptionDomainNameServer, 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
}
nameservers := make([]net.IP, 0, length%4)
for idx := 0; idx < length; idx += 4 {
b := data[2+idx : 2+idx+4]
nameservers = append(nameservers, net.IPv4(b[0], b[1], b[2], b[3]))
}
return &OptDomainNameServer{NameServers: nameservers}, nil
}
// Code returns the option code.
func (o *OptDomainNameServer) Code() OptionCode {
return OptionDomainNameServer
}
// ToBytes returns a serialized stream of bytes for this option.
func (o *OptDomainNameServer) ToBytes() []byte {
ret := []byte{byte(o.Code()), byte(o.Length())}
for _, ns := range o.NameServers {
ret = append(ret, ns.To4()...)
}
return ret
}
// String returns a human-readable string.
func (o *OptDomainNameServer) String() string {
var servers string
for idx, ns := range o.NameServers {
servers += ns.String()
if idx < len(o.NameServers)-1 {
servers += ", "
}
}
return fmt.Sprintf("Domain Name Servers -> %v", servers)
}
// Length returns the length of the data portion (excluding option code an byte
// length).
func (o *OptDomainNameServer) Length() int {
return len(o.NameServers) * 4
}
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