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netxlite: call getaddrinfo and handle platform-specific oddities (#764)

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This commit changes our system resolver to call getaddrinfo directly when CGO is enabled. This change allows us to:

1. obtain the CNAME easily

2. obtain the real getaddrinfo retval

3. handle platform specific oddities such as `EAI_NODATA`
returned on Android devices

See https://github.com/ooni/probe/issues/2029 and https://github.com/ooni/probe/issues/2029#issuecomment-1140258729 in particular.

See https://github.com/ooni/probe/issues/2033 for documentation regarding the desire to see `getaddrinfo`'s retval.

See https://github.com/ooni/probe/issues/2118 for possible follow-up changes.
This commit is contained in:
Simone Basso 2022-05-28 15:10:30 +02:00 • committed by GitHub
commit cf6dbe48e0
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36 changed files with 1259 additions and 59 deletions
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25
internal/netxlite/classify.go
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@ -249,18 +249,34 @@ const (
// DNSOverHTTPSTransport and DNSOverUDPTransport). Their suffix matches the equivalent
// unexported errors used by the Go standard library.
var (
ErrOODNSNoSuchHost = fmt.Errorf("ooniresolver: %s", DNSNoSuchHostSuffix)
// ErrOODNSNoSuchHost means NXDOMAIN.
ErrOODNSNoSuchHost = fmt.Errorf("ooniresolver: %s", DNSNoSuchHostSuffix)
// ErrOODNSMisbehaving is the error typically returned by the `netgo`resolver
// when it cannot really make sense of the error.
ErrOODNSMisbehaving = fmt.Errorf("ooniresolver: %s", DNSServerMisbehavingSuffix)
ErrOODNSNoAnswer = fmt.Errorf("ooniresolver: %s", DNSNoAnswerSuffix)
// ErrOODNSNoAnswer means that we've got a valid DNS response that
// did not contain any answer for the original query. This could happen
// when we query for AAAA and the domain only has A records.
ErrOODNSNoAnswer = fmt.Errorf("ooniresolver: %s", DNSNoAnswerSuffix)
)
// These errors are not part of the Go standard library but we can
// return them in our custom resolvers.
var (
ErrOODNSRefused = errors.New("ooniresolver: refused")
// ErrOODNSRefused indicates that the response's Rcode was "refused"
ErrOODNSRefused = errors.New("ooniresolver: refused")
// ErrOODNSServfail indicates that the response's Rcode was "servfail"
ErrOODNSServfail = errors.New("ooniresolver: servfail")
)
// ErrAndroidDNSCacheNoData is the kind of error returned by our getaddrinfo
// code on Android when we see EAI_NODATA, an error condition that could mean
// anything as explained in getaddrinfo_linux.go.
var ErrAndroidDNSCacheNoData = errors.New(FailureAndroidDNSCacheNoData)
// classifyResolverError maps DNS resolution errors to
// OONI failure strings.
//
@ -291,6 +307,9 @@ func classifyResolverError(err error) string {
if errors.Is(err, ErrDNSReplyWithWrongQueryID) {
return FailureDNSReplyWithWrongQueryID
}
if errors.Is(err, ErrAndroidDNSCacheNoData) {
return FailureAndroidDNSCacheNoData
}
return classifyGenericError(err)
}