doggo/pkg/resolvers/classic.go

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package resolvers
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import (
"github.com/miekg/dns"
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"github.com/sirupsen/logrus"
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)
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// ClassicResolver represents the config options for setting up a Resolver.
type ClassicResolver struct {
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client *dns.Client
server string
resolverOptions Options
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}
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// ClassicResolverOpts holds options for setting up a Classic resolver.
type ClassicResolverOpts struct {
IPv4Only bool
IPv6Only bool
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UseTLS bool
UseTCP bool
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}
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// NewClassicResolver accepts a list of nameservers and configures a DNS resolver.
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func NewClassicResolver(server string, classicOpts ClassicResolverOpts, resolverOpts Options) (Resolver, error) {
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net := "udp"
client := &dns.Client{
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Timeout: resolverOpts.Timeout,
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Net: "udp",
}
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if classicOpts.UseTCP {
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net = "tcp"
}
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if classicOpts.IPv4Only {
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net = net + "4"
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}
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if classicOpts.IPv6Only {
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net = net + "6"
}
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if classicOpts.UseTLS {
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net = net + "-tls"
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}
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client.Net = net
return &ClassicResolver{
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client: client,
server: server,
resolverOptions: resolverOpts,
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}, nil
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}
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// Lookup takes a dns.Question and sends them to DNS Server.
// It parses the Response from the server in a custom output format.
func (r *ClassicResolver) Lookup(question dns.Question) (Response, error) {
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var (
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rsp Response
messages = prepareMessages(question, r.resolverOptions.Ndots, r.resolverOptions.SearchList)
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)
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for _, msg := range messages {
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r.resolverOptions.Logger.WithFields(logrus.Fields{
"domain": msg.Question[0].Name,
"ndots": r.resolverOptions.Ndots,
"nameserver": r.server,
}).Debug("Attempting to resolve")
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in, rtt, err := r.client.Exchange(&msg, r.server)
if err != nil {
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return rsp, err
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}
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// pack questions in output.
for _, q := range msg.Question {
ques := Question{
Name: q.Name,
Class: dns.ClassToString[q.Qclass],
Type: dns.TypeToString[q.Qtype],
}
rsp.Questions = append(rsp.Questions, ques)
}
// get the authorities and answers.
output := parseMessage(in, rtt, r.server)
rsp.Authorities = output.Authorities
rsp.Answers = output.Answers
if len(output.Answers) > 0 {
// stop iterating the searchlist.
break
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}
}
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return rsp, nil
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}