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fix(netxlite/dns): more stricly mirror stdlib error strings (#513)

Browse source 
This diff attempts to modify the errors reported by our custom
resolver by matching more strings from the stdlib.

Part of https://github.com/ooni/probe/issues/1733 and diff has been
extracted from https://github.com/ooni/probe-cli/pull/506.
This commit is contained in:
Simone Basso 2021-09-27 16:48:46 +02:00 • committed by GitHub
commit 24b230fd38
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17 changed files with 177 additions and 52 deletions
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28
internal/netxlite/errorsx/classify.go
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@ -84,12 +84,18 @@ func classifyWithStringSuffix(err error) string {
if strings.HasSuffix(s, "TLS handshake timeout") {
return FailureGenericTimeoutError
}
if strings.HasSuffix(s, "no such host") {
if strings.HasSuffix(s, DNSNoSuchHostSuffix) {
// This is dns_lookup_error in MK but such error is used as a
// generic "hey, the lookup failed" error. Instead, this error
// that we return here is significantly more specific.
return FailureDNSNXDOMAINError
}
if strings.HasSuffix(s, DNSServerMisbehavingSuffix) {
return FailureDNSServerMisbehaving
}
if strings.HasSuffix(s, DNSNoAnswerSuffix) {
return FailureDNSNoAnswer
}
if strings.HasSuffix(s, "use of closed network connection") {
return FailureConnectionAlreadyClosed
}
@ -223,6 +229,21 @@ func quicIsCertificateError(alert uint8) bool {
// filters for DNS bogons MUST use this error.
var ErrDNSBogon = errors.New("dns: detected bogon address")
// These strings are same as the standard library.
const (
DNSNoSuchHostSuffix = "no such host"
DNSServerMisbehavingSuffix = "server misbehaving"
DNSNoAnswerSuffix = "no answer from DNS server"
)
// These errors are returned by the decoder and/or the serial resolver.
var (
ErrOODNSNoSuchHost = fmt.Errorf("ooniresolver: %s", DNSNoSuchHostSuffix)
ErrOODNSRefused = errors.New("ooniresolver: refused")
ErrOODNSMisbehaving = fmt.Errorf("ooniresolver: %s", DNSServerMisbehavingSuffix)
ErrOODNSNoAnswer = fmt.Errorf("ooniresolver: %s", DNSNoAnswerSuffix)
)
// ClassifyResolverError maps an error occurred during a domain name
// resolution to the corresponding OONI failure string.
//
@ -239,6 +260,11 @@ func ClassifyResolverError(err error) string {
if errors.Is(err, ErrDNSBogon) {
return FailureDNSBogonError // not in MK
}
// Implementation note: we match errors that share the same
// string of the stdlib in the generic classifier.
if errors.Is(err, ErrOODNSRefused) {
return FailureDNSRefusedError // not in MK
}
return ClassifyGenericError(err)
}