doggo/pkg/resolvers/dnscrypt.go

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package resolvers
import (
"time"
"github.com/ameshkov/dnscrypt/v2"
"github.com/miekg/dns"
"github.com/mr-karan/logf"
)
// DNSCryptResolver represents the config options for setting up a Resolver.
type DNSCryptResolver struct {
client *dnscrypt.Client
server string
resolverInfo *dnscrypt.ResolverInfo
resolverOptions Options
}
// DNSCryptResolverOpts holds options for setting up a DNSCrypt resolver.
type DNSCryptResolverOpts struct {
UseTCP bool
}
// NewDNSCryptResolver accepts a list of nameservers and configures a DNS resolver.
func NewDNSCryptResolver(server string, dnscryptOpts DNSCryptResolverOpts, resolverOpts Options) (Resolver, error) {
net := "udp"
if dnscryptOpts.UseTCP {
net = "tcp"
}
client := &dnscrypt.Client{Net: net, Timeout: resolverOpts.Timeout, UDPSize: 4096}
resolverInfo, err := client.Dial(server)
if err != nil {
return nil, err
}
return &DNSCryptResolver{
client: client,
resolverInfo: resolverInfo,
server: resolverInfo.ServerAddress,
resolverOptions: resolverOpts,
}, nil
}
// 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 *DNSCryptResolver) Lookup(question dns.Question) (Response, error) {
var (
rsp Response
messages = prepareMessages(question, r.resolverOptions.Ndots, r.resolverOptions.SearchList)
)
for _, msg := range messages {
r.resolverOptions.Logger.WithFields(logf.Fields{
"domain": msg.Question[0].Name,
"ndots": r.resolverOptions.Ndots,
"nameserver": r.server,
}).Debug("Attempting to resolve")
now := time.Now()
in, err := r.client.Exchange(&msg, r.resolverInfo)
if err != nil {
return rsp, err
}
rtt := time.Since(now)
// 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
}
}
return rsp, nil
}