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rdatamx.go
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/
rdatamx.go
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// Copyright 2018, Shulhan <ms@kilabit.info>. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package dns
import (
"fmt"
"strings"
libnet "github.com/shuLhan/share/lib/net"
)
const (
defMXPreference int16 = 10
)
// RDataMX MX records cause type A additional section processing for the host
// specified by EXCHANGE. The use of MX RRs is explained in detail in
// [RFC-974].
type RDataMX struct {
// A 16 bit integer which specifies the preference given to this RR
// among others at the same owner. Lower values are preferred.
Preference int16
// A <domain-name> which specifies a host willing to act as a mail
// exchange for the owner name.
Exchange string
}
//
// String return readable representation of MX record.
//
func (mx *RDataMX) String() string {
var b strings.Builder
fmt.Fprintf(&b, "{Preference:%d Exchange:%s}", mx.Preference,
mx.Exchange)
return b.String()
}
//
// initAndValidate initialize and validate the MX fields.
//
func (mx *RDataMX) initAndValidate() error {
if mx.Preference <= 0 {
mx.Preference = defMXPreference
}
if !libnet.IsHostnameValid([]byte(mx.Exchange), true) {
return fmt.Errorf("invalid or empty MX Exchange %q",
string(mx.Exchange))
}
return nil
}