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net: fail fast for DNS rcode success with no answers of requested type

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DNS responses which do not contain answers of the requested type return
errNoSuchHost, the same error as rcode name error. Prior to
golang.org/cl/37879, both cases resulted in no additional name servers
being consulted for the question. That CL changed the behavior for both
cases. Issue #25336 was filed about the rcode name error case and
golang.org/cl/113815 fixed it. This CL fixes the no answers of requested
type case as well.

Fixes #27525

Change-Id: I52fadedcd195f16adf62646b76bea2ab3b15d117
Reviewed-on: https://go-review.googlesource.com/133675
Run-TryBot: Ian Gudger <igudger@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Ian Gudger 2018-09-05 23:53:36 -07:00 • committed by Brad Fitzpatrick
parent da0d1a44ba
commit 94f48ddb96
2 changed files with 158 additions and 100 deletions
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143
src/net/dnsclient_unix_test.go
View file

@ -1427,28 +1427,35 @@ func TestDNSGoroutineRace(t *testing.T) {
}
}
func lookupWithFake(fake fakeDNSServer, name string, typ dnsmessage.Type) error {
r := Resolver{PreferGo: true, Dial: fake.DialContext}
resolvConf.mu.RLock()
conf := resolvConf.dnsConfig
resolvConf.mu.RUnlock()
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
_, _, err := r.tryOneName(ctx, conf, name, typ)
return err
}
// Issue 8434: verify that Temporary returns true on an error when rcode
// is SERVFAIL
func TestIssue8434(t *testing.T) {
msg := dnsmessage.Message{
Header: dnsmessage.Header{
RCode: dnsmessage.RCodeServerFailure,
err := lookupWithFake(fakeDNSServer{
rh: func(n, _ string, q dnsmessage.Message, _ time.Time) (dnsmessage.Message, error) {
return dnsmessage.Message{
Header: dnsmessage.Header{
ID: q.ID,
Response: true,
RCode: dnsmessage.RCodeServerFailure,
},
Questions: q.Questions,
}, nil
},
}
b, err := msg.Pack()
if err != nil {
t.Fatal("Pack failed:", err)
}
var p dnsmessage.Parser
h, err := p.Start(b)
if err != nil {
t.Fatal("Start failed:", err)
}
if err := p.SkipAllQuestions(); err != nil {
t.Fatal("SkipAllQuestions failed:", err)
}
err = checkHeader(&p, h, "golang.org", "foo:53")
}, "golang.org.", dnsmessage.TypeALL)
if err == nil {
t.Fatal("expected an error")
}
@ -1464,50 +1471,76 @@ func TestIssue8434(t *testing.T) {
}
}
// Issue 12778: verify that NXDOMAIN without RA bit errors as
// "no such host" and not "server misbehaving"
// TestNoSuchHost verifies that tryOneName works correctly when the domain does
// not exist.
//
// Issue 12778: verify that NXDOMAIN without RA bit errors as "no such host"
// and not "server misbehaving"
//
// Issue 25336: verify that NXDOMAIN errors fail fast.
func TestIssue12778(t *testing.T) {
lookups := 0
fake := fakeDNSServer{
rh: func(n, _ string, q dnsmessage.Message, _ time.Time) (dnsmessage.Message, error) {
lookups++
return dnsmessage.Message{
Header: dnsmessage.Header{
ID: q.ID,
Response: true,
RCode: dnsmessage.RCodeNameError,
RecursionAvailable: false,
},
Questions: q.Questions,
}, nil
//
// Issue 27525: verify that empty answers fail fast.
func TestNoSuchHost(t *testing.T) {
tests := []struct {
name string
f func(string, string, dnsmessage.Message, time.Time) (dnsmessage.Message, error)
}{
{
"NXDOMAIN",
func(n, _ string, q dnsmessage.Message, _ time.Time) (dnsmessage.Message, error) {
return dnsmessage.Message{
Header: dnsmessage.Header{
ID: q.ID,
Response: true,
RCode: dnsmessage.RCodeNameError,
RecursionAvailable: false,
},
Questions: q.Questions,
}, nil
},
},
{
"no answers",
func(n, _ string, q dnsmessage.Message, _ time.Time) (dnsmessage.Message, error) {
return dnsmessage.Message{
Header: dnsmessage.Header{
ID: q.ID,
Response: true,
RCode: dnsmessage.RCodeSuccess,
RecursionAvailable: false,
Authoritative: true,
},
Questions: q.Questions,
}, nil
},
},
}
r := Resolver{PreferGo: true, Dial: fake.DialContext}
resolvConf.mu.RLock()
conf := resolvConf.dnsConfig
resolvConf.mu.RUnlock()
for _, test := range tests {
t.Run(test.name, func(t *testing.T) {
lookups := 0
err := lookupWithFake(fakeDNSServer{
rh: func(n, s string, q dnsmessage.Message, d time.Time) (dnsmessage.Message, error) {
lookups++
return test.f(n, s, q, d)
},
}, ".", dnsmessage.TypeALL)
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
if lookups != 1 {
t.Errorf("got %d lookups, wanted 1", lookups)
}
_, _, err := r.tryOneName(ctx, conf, ".", dnsmessage.TypeALL)
if lookups != 1 {
t.Errorf("got %d lookups, wanted 1", lookups)
}
if err == nil {
t.Fatal("expected an error")
}
de, ok := err.(*DNSError)
if !ok {
t.Fatalf("err = %#v; wanted a *net.DNSError", err)
}
if de.Err != errNoSuchHost.Error() {
t.Fatalf("Err = %#v; wanted %q", de.Err, errNoSuchHost.Error())
if err == nil {
t.Fatal("expected an error")
}
de, ok := err.(*DNSError)
if !ok {
t.Fatalf("err = %#v; wanted a *net.DNSError", err)
}
if de.Err != errNoSuchHost.Error() {
t.Fatalf("Err = %#v; wanted %q", de.Err, errNoSuchHost.Error())
}
})
}
}