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// Copyright (C) MongoDB, Inc. 2022-present.
//
// 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
package examples
import (
"context"
"log"
"net"
"sync"
"testing"
"time"
"github.com/miekg/dns"
"go.mongodb.org/mongo-driver/bson"
"go.mongodb.org/mongo-driver/mongo"
"go.mongodb.org/mongo-driver/mongo/options"
)
func resolve(ctx context.Context, cache *dnsCache, in *dns.Conn, out *dns.Conn) {
for ctx.Err() == nil {
q, err := in.ReadMsg()
if err != nil {
// TODO: Handle error.
log.Fatalf("Unhandled error in ReadMsg: %v", err)
}
if len(q.Question) != 1 {
// Multiple questions in a single query is not actually used in real life.
continue
}
a, err := func() (*dns.Msg, error) {
cache.lock.Lock()
defer cache.lock.Unlock()
now := time.Now()
if rr, ok := cache.records[q.Question[0]]; ok && rr.exp.After(now) {
a := new(dns.Msg)
a.SetReply(q)
a.Compress = false
a.Answer = append(a.Answer, rr.record)
return a, nil
}
err := out.WriteMsg(q)
if err != nil {
return nil, err
}
m, err := out.ReadMsg()
if err != nil {
return nil, err
}
l := len(m.Answer)
for i, q := range m.Question {
if i >= l {
break
}
a := m.Answer[i]
cache.records[q] = &RR{
a,
now.Add(time.Second * time.Duration(a.Header().Ttl)),
}
}
return m, nil
}()
if err != nil {
// TODO: Handle error.
log.Fatalf("Unhandled error in record retrieval: %v", err)
}
if err := in.WriteMsg(a); err != nil {
// TODO: Handle error.
log.Fatalf("Unhandled error in WriteMsg: %v", err)
}
}
}
type RR struct {
record dns.RR
exp time.Time
}
type dnsCache struct {
records map[dns.Question]*RR
lock sync.Mutex
}
type dialer struct {
*net.Dialer
cache *dnsCache
}
func NewDialer() dialer {
cache := &dnsCache{
records: make(map[dns.Question]*RR),
lock: sync.Mutex{},
}
return dialer{
Dialer: &net.Dialer{
Resolver: &net.Resolver{
PreferGo: true,
Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
var d net.Dialer
outConn, err := d.DialContext(ctx, network, address)
conn, inConn := net.Pipe()
if err == nil {
go resolve(ctx, cache, &dns.Conn{Conn: inConn}, &dns.Conn{Conn: outConn})
}
return conn, err
},
},
},
cache: cache,
}
}
func TestCustomDialer(t *testing.T) {
client, err := mongo.NewClient(options.Client().ApplyURI("mongodb://testurl:27017").SetDialer(NewDialer()))
if err != nil {
t.Fatalf("error creating client: %v", err)
}
ctx := context.Background()
err = client.Connect(ctx)
if err != nil {
t.Fatalf("error connecting: %v", err)
}
defer client.Disconnect(context.Background())
coll := client.Database("test").Collection("test")
_, err = coll.InsertOne(context.Background(), bson.D{{"text", "text"}})
if err != nil {
t.Fatalf("error inserting: %v", err)
}
}
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