net: add IsNotFound field to DNSError
This adds the ability to determine if a lookup error was
due to a non-existent hostname. Previously users needed
to do string matching on the DNSError.Err value.
Fixes #28635
Change-Id: If4bd3ad32cbc2db5614f2c6b72e0a9161d813efa
Reviewed-on: https://go-review.googlesource.com/c/go/+/168597
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/net/cgo_unix.go b/src/net/cgo_unix.go
index 6420fd0..2baab5f 100644
--- a/src/net/cgo_unix.go
+++ b/src/net/cgo_unix.go
@@ -158,6 +158,7 @@
var res *C.struct_addrinfo
gerrno, err := C.getaddrinfo((*C.char)(unsafe.Pointer(&h[0])), nil, &hints, &res)
if gerrno != 0 {
+ isErrorNoSuchHost := false
switch gerrno {
case C.EAI_SYSTEM:
if err == nil {
@@ -172,10 +173,12 @@
}
case C.EAI_NONAME:
err = errNoSuchHost
+ isErrorNoSuchHost = true
default:
err = addrinfoErrno(gerrno)
}
- return nil, "", &DNSError{Err: err.Error(), Name: name}
+
+ return nil, "", &DNSError{Err: err.Error(), Name: name, IsNotFound: isErrorNoSuchHost}
}
defer C.freeaddrinfo(res)
diff --git a/src/net/dnsclient_unix.go b/src/net/dnsclient_unix.go
index 7ed4ea8..478ee51 100644
--- a/src/net/dnsclient_unix.go
+++ b/src/net/dnsclient_unix.go
@@ -284,10 +284,8 @@
if err == errNoSuchHost {
// The name does not exist, so trying
// another server won't help.
- //
- // TODO: indicate this in a more
- // obvious way, such as a field on
- // DNSError?
+
+ dnsErr.IsNotFound = true
return p, server, dnsErr
}
lastErr = dnsErr
@@ -306,9 +304,8 @@
if err == errNoSuchHost {
// The name does not exist, so trying another
// server won't help.
- //
- // TODO: indicate this in a more obvious way,
- // such as a field on DNSError?
+
+ lastErr.(*DNSError).IsNotFound = true
return p, server, lastErr
}
}
@@ -398,7 +395,7 @@
// Other lookups might allow broader name syntax
// (for example Multicast DNS allows UTF-8; see RFC 6762).
// For consistency with libc resolvers, report no such host.
- return dnsmessage.Parser{}, "", &DNSError{Err: errNoSuchHost.Error(), Name: name}
+ return dnsmessage.Parser{}, "", &DNSError{Err: errNoSuchHost.Error(), Name: name, IsNotFound: true}
}
resolvConf.tryUpdate("/etc/resolv.conf")
resolvConf.mu.RLock()
@@ -575,7 +572,7 @@
}
if !isDomainName(name) {
// See comment in func lookup above about use of errNoSuchHost.
- return nil, dnsmessage.Name{}, &DNSError{Err: errNoSuchHost.Error(), Name: name}
+ return nil, dnsmessage.Name{}, &DNSError{Err: errNoSuchHost.Error(), Name: name, IsNotFound: true}
}
resolvConf.tryUpdate("/etc/resolv.conf")
resolvConf.mu.RLock()
diff --git a/src/net/dnsclient_unix_test.go b/src/net/dnsclient_unix_test.go
index f1ed58c..1b67494 100644
--- a/src/net/dnsclient_unix_test.go
+++ b/src/net/dnsclient_unix_test.go
@@ -666,7 +666,7 @@
wantErr *DNSError
}{
{true, &DNSError{Name: fqdn, Err: "server misbehaving", IsTemporary: true}},
- {false, &DNSError{Name: fqdn, Err: errNoSuchHost.Error()}},
+ {false, &DNSError{Name: fqdn, Err: errNoSuchHost.Error(), IsNotFound: true}},
}
for _, tt := range cases {
r := Resolver{PreferGo: true, StrictErrors: tt.strictErrors, Dial: fake.DialContext}
@@ -1138,9 +1138,10 @@
}
makeNxDomain := func() error {
return &DNSError{
- Err: errNoSuchHost.Error(),
- Name: name,
- Server: server,
+ Err: errNoSuchHost.Error(),
+ Name: name,
+ Server: server,
+ IsNotFound: true,
}
}
@@ -1472,6 +1473,32 @@
}
}
+func TestIssueNoSuchHostExists(t *testing.T) {
+ 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.RCodeNameError,
+ },
+ Questions: q.Questions,
+ }, nil
+ },
+ }, "golang.org.", dnsmessage.TypeALL)
+ if err == nil {
+ t.Fatal("expected an error")
+ }
+ if _, ok := err.(Error); !ok {
+ t.Fatalf("err = %#v; wanted something supporting net.Error", err)
+ }
+ if de, ok := err.(*DNSError); !ok {
+ t.Fatalf("err = %#v; wanted a *net.DNSError", err)
+ } else if !de.IsNotFound {
+ t.Fatalf("IsNotFound = false for err = %#v; want IsNotFound == true", err)
+ }
+}
+
// TestNoSuchHost verifies that tryOneName works correctly when the domain does
// not exist.
//
@@ -1541,6 +1568,9 @@
if de.Err != errNoSuchHost.Error() {
t.Fatalf("Err = %#v; wanted %q", de.Err, errNoSuchHost.Error())
}
+ if !de.IsNotFound {
+ t.Fatalf("IsNotFound = %v wanted true", de.IsNotFound)
+ }
})
}
}
diff --git a/src/net/lookup.go b/src/net/lookup.go
index 0af1e2c..24d0d25 100644
--- a/src/net/lookup.go
+++ b/src/net/lookup.go
@@ -177,7 +177,7 @@
// Make sure that no matter what we do later, host=="" is rejected.
// parseIP, for example, does accept empty strings.
if host == "" {
- return nil, &DNSError{Err: errNoSuchHost.Error(), Name: host}
+ return nil, &DNSError{Err: errNoSuchHost.Error(), Name: host, IsNotFound: true}
}
if ip, _ := parseIPZone(host); ip != nil {
return []string{host}, nil
@@ -238,7 +238,7 @@
// Make sure that no matter what we do later, host=="" is rejected.
// parseIP, for example, does accept empty strings.
if host == "" {
- return nil, &DNSError{Err: errNoSuchHost.Error(), Name: host}
+ return nil, &DNSError{Err: errNoSuchHost.Error(), Name: host, IsNotFound: true}
}
if ip, zone := parseIPZone(host); ip != nil {
return []IPAddr{{IP: ip, Zone: zone}}, nil
diff --git a/src/net/lookup_test.go b/src/net/lookup_test.go
index 28a895e..ed477a7 100644
--- a/src/net/lookup_test.go
+++ b/src/net/lookup_test.go
@@ -877,6 +877,9 @@
if !strings.HasSuffix(err.Error(), errNoSuchHost.Error()) {
t.Fatalf("lookup error = %v, want %v", err, errNoSuchHost)
}
+ if !err.(*DNSError).IsNotFound {
+ t.Fatalf("lookup error = %v, want true", err.(*DNSError).IsNotFound)
+ }
}
func TestLookupContextCancel(t *testing.T) {
diff --git a/src/net/lookup_windows.go b/src/net/lookup_windows.go
index 8a68d18..cd071c5 100644
--- a/src/net/lookup_windows.go
+++ b/src/net/lookup_windows.go
@@ -56,7 +56,12 @@
if proto, err := lookupProtocolMap(name); err == nil {
return proto, nil
}
- r.err = &DNSError{Err: r.err.Error(), Name: name}
+
+ dnsError := &DNSError{Err: r.err.Error(), Name: name}
+ if r.err == errNoSuchHost {
+ dnsError.IsNotFound = true
+ }
+ r.err = dnsError
}
return r.proto, r.err
case <-ctx.Done():
@@ -98,7 +103,12 @@
var result *syscall.AddrinfoW
e := syscall.GetAddrInfoW(syscall.StringToUTF16Ptr(name), nil, &hints, &result)
if e != nil {
- return nil, &DNSError{Err: winError("getaddrinfow", e).Error(), Name: name}
+ err := winError("getaddrinfow", e)
+ dnsError := &DNSError{Err: err.Error(), Name: name}
+ if err == errNoSuchHost {
+ dnsError.IsNotFound = true
+ }
+ return nil, dnsError
}
defer syscall.FreeAddrInfoW(result)
addrs := make([]IPAddr, 0, 5)
@@ -176,7 +186,12 @@
if port, err := lookupPortMap(network, service); err == nil {
return port, nil
}
- return 0, &DNSError{Err: winError("getaddrinfow", e).Error(), Name: network + "/" + service}
+ err := winError("getaddrinfow", e)
+ dnsError := &DNSError{Err: err.Error(), Name: network + "/" + service}
+ if err == errNoSuchHost {
+ dnsError.IsNotFound = true
+ }
+ return 0, dnsError
}
defer syscall.FreeAddrInfoW(result)
if result == nil {
diff --git a/src/net/net.go b/src/net/net.go
index b44ecb6..0e07862 100644
--- a/src/net/net.go
+++ b/src/net/net.go
@@ -579,6 +579,7 @@
Server string // server used
IsTimeout bool // if true, timed out; not all timeouts set this
IsTemporary bool // if true, error is temporary; not all errors set this
+ IsNotFound bool // if true, host could not be found
}
func (e *DNSError) Error() string {
