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resolve.go
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resolve.go
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package main
import (
"time"
log "github.com/Sirupsen/logrus"
"github.com/miekg/dns"
"strings"
)
func ResolveTryAll(req *dns.Msg, resolvers []string) (resp *dns.Msg, err error) {
for _, resolver := range resolvers {
log.WithFields(log.Fields{"fqdn": req.Question[0].Name, "resolver": resolver}).Debug("Recursing")
resp, err = Resolve(req, resolver)
if err == nil {
break
}
}
return
}
// Proxy a request to an external server
func Resolve(req *dns.Msg, resolver string) (resp *dns.Msg, err error) {
resp, err = resolveTransport(req, "udp", resolver)
if err != nil {
if resp != nil && resp.Truncated {
log.Debug("Response truncated, retrying with TCP")
resp, err = resolveTransport(req, "tcp", resolver)
} else {
log.WithFields(log.Fields{"fqdn": req.Question[0].Name, "resolver": resolver}).Warn("Recurser error: ", err)
}
}
return
}
func resolveTransport(req *dns.Msg, transport, resolver string) (resp *dns.Msg, err error) {
// Default to port 53
if !strings.Contains(resolver, ":") {
resolver = resolver + ":53"
}
t := time.Duration(*recurserTimeout) * time.Second
c := &dns.Client{
Net: transport,
DialTimeout: t,
ReadTimeout: t,
WriteTimeout: t,
}
resp, _, err = c.Exchange(req, resolver)
return
}