net: treat EAI_NODATA as errNoSuchHost

man getaddrinfo:
EAI_NODATA
              The specified network host exists, but does not have any
              network addresses defined.

In the go resolver we treat this kind of error as nosuchhost.

Change-Id: I69fab6f8da8e3a86907e65104bca9f055968633a
GitHub-Last-Rev: b4891e2add
GitHub-Pull-Request: golang/go#57507
Reviewed-on: https://go-review.googlesource.com/c/go/+/459955
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Mateusz Poliwczak <mpoliwczak34@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/internal/syscall/unix/net_darwin.go

@@ -17,6 +17,7 @@ const (
 	AI_MASK      = 0x1407
 
 	EAI_AGAIN    = 2
+	EAI_NODATA   = 7
 	EAI_NONAME   = 8
 	EAI_SYSTEM   = 11
 	EAI_OVERFLOW = 14

src/net/cgo_unix.go

@@ -166,7 +166,7 @@ func cgoLookupHostIP(network, name string) (addrs []IPAddr, err error) {
 				// comes up again. golang.org/issue/6232.
 				err = syscall.EMFILE
 			}
-		case _C_EAI_NONAME:
+		case _C_EAI_NONAME, _C_EAI_NODATA:
 			err = errNoSuchHost
 			isErrorNoSuchHost = true
 		default:

src/net/cgo_unix_cgo.go

@@ -7,6 +7,8 @@
 package net
 
 /*
+#define _GNU_SOURCE
+
 #cgo CFLAGS: -fno-stack-protector
 #include <sys/types.h>
 #include <sys/socket.h>
@@ -16,6 +18,10 @@ package net
 #include <string.h>
 #include <stdlib.h>
 
+#ifndef EAI_NODATA
+#define EAI_NODATA -5
+#endif
+
 // If nothing else defined EAI_OVERFLOW, make sure it has a value.
 #ifndef EAI_OVERFLOW
 #define EAI_OVERFLOW -12
@@ -29,6 +35,7 @@ const (
 	_C_AF_INET6     = C.AF_INET6
 	_C_AF_UNSPEC    = C.AF_UNSPEC
 	_C_EAI_AGAIN    = C.EAI_AGAIN
+	_C_EAI_NODATA   = C.EAI_NODATA
 	_C_EAI_NONAME   = C.EAI_NONAME
 	_C_EAI_OVERFLOW = C.EAI_OVERFLOW
 	_C_EAI_SYSTEM   = C.EAI_SYSTEM

src/net/cgo_unix_syscall.go

@@ -19,6 +19,7 @@ const (
 	_C_AF_UNSPEC    = syscall.AF_UNSPEC
 	_C_EAI_AGAIN    = unix.EAI_AGAIN
 	_C_EAI_NONAME   = unix.EAI_NONAME
+	_C_EAI_NODATA   = unix.EAI_NODATA
 	_C_EAI_OVERFLOW = unix.EAI_OVERFLOW
 	_C_EAI_SYSTEM   = unix.EAI_SYSTEM
 	_C_IPPROTO_TCP  = syscall.IPPROTO_TCP

src/net/lookup_test.go

@@ -8,6 +8,7 @@ package net
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"internal/testenv"
 	"net/netip"
@@ -1398,3 +1399,66 @@ func TestDNSTimeout(t *testing.T) {
 	checkErr(err2)
 	cancel()
 }
+
+func TestLookupNoData(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("not supported on plan9")
+	}
+
+	mustHaveExternalNetwork(t)
+
+	testLookupNoData(t, "default resolver")
+
+	func() {
+		defer forceGoDNS()()
+		testLookupNoData(t, "forced go resolver")
+	}()
+
+	func() {
+		defer forceCgoDNS()()
+		testLookupNoData(t, "forced cgo resolver")
+	}()
+}
+
+func testLookupNoData(t *testing.T, prefix string) {
+	attempts := 0
+	for {
+		// Domain that doesn't have any A/AAAA RRs, but has different one (in this case a TXT),
+		// so that it returns an empty response without any error codes (NXDOMAIN).
+		_, err := LookupHost("golang.rsc.io")
+		if err == nil {
+			t.Errorf("%v: unexpected success", prefix)
+			return
+		}
+
+		var dnsErr *DNSError
+		if errors.As(err, &dnsErr) {
+			succeeded := true
+			if !dnsErr.IsNotFound {
+				succeeded = false
+				t.Logf("%v: IsNotFound is set to false", prefix)
+			}
+
+			if dnsErr.Err != errNoSuchHost.Error() {
+				succeeded = false
+				t.Logf("%v: error message is not equal to: %v", prefix, errNoSuchHost.Error())
+			}
+
+			if succeeded {
+				return
+			}
+		}
+
+		testenv.SkipFlakyNet(t)
+		if attempts < len(backoffDuration) {
+			dur := backoffDuration[attempts]
+			t.Logf("%v: backoff %v after failure %v\n", prefix, dur, err)
+			time.Sleep(dur)
+			attempts++
+			continue
+		}
+
+		t.Errorf("%v: unexpected error: %v", prefix, err)
+		return
+	}
+}