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// Copyright 2019-2025 The Wait4X Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package mx provides the MX checker for the Wait4X application.
package mx
import (
"context"
"fmt"
"net"
"regexp"
"wait4x.dev/v3/checker"
)
// Option configures an DNS MX records
type Option func(d *MX)
// MX is a DNS MX checker
type MX struct {
nameserver string
address string
expectedDomains []string
resolver *net.Resolver
}
// New creates a new DNS MX checker
func New(address string, opts ...Option) checker.Checker {
d := &MX{
address: address,
resolver: net.DefaultResolver,
}
// apply the list of options to MX
for _, opt := range opts {
opt(d)
}
// Nameserver settings.
if d.nameserver != "" {
d.resolver = &net.Resolver{
Dial: func(ctx context.Context, network, _ string) (net.Conn, error) {
dialer := net.Dialer{}
return dialer.DialContext(ctx, network, d.nameserver)
},
}
}
return d
}
// WithNameServer overrides the default nameserver for the DNS MX checker
func WithNameServer(nameserver string) Option {
return func(d *MX) {
d.nameserver = nameserver
}
}
// WithExpectedDomains sets expected domains for the DNS MX checker
func WithExpectedDomains(domains []string) Option {
return func(d *MX) {
d.expectedDomains = domains
}
}
// Identity returns the identity of the DNS MX checker
func (d *MX) Identity() (string, error) {
return fmt.Sprintf("MX %s %s", d.address, d.expectedDomains), nil
}
// Check checks the DNS MX records
func (d *MX) Check(ctx context.Context) (err error) {
values, err := d.resolver.LookupMX(ctx, d.address)
if err != nil {
return err
}
for _, mx := range values {
if len(d.expectedDomains) == 0 {
return nil
}
for _, expectedDomain := range d.expectedDomains {
matched, _ := regexp.MatchString(expectedDomain, mx.Host)
if matched {
return nil
}
}
}
return checker.NewExpectedError(
"the MX record value doesn't expect", nil,
"actual", values, "expect", d.expectedDomains,
)
}
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