[release-branch.go1.7] net: don't avoid resolving .local addresses

.local addresses are used by things like Kubernetes and Weave DNS; Go
should not avoid resolving them.

This is a partial revert of https://golang.org/cl/21328 which was too
strict of an interpretation of RFC 6762.

Fixes #16739

Change-Id: I349415b4eab5d61240dd18217bd95dc7d2105cd5
Reviewed-on: https://go-review.googlesource.com/27250
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-on: https://go-review.googlesource.com/28632

diff --git a/src/net/dnsclient_unix.go b/src/net/dnsclient_unix.go
index 8f2dff46751b0e31778a1fc1e92d030d630c5f19..d12944c208f87063b2bba5ccfce22f47d9745c0a 100644 (file)
--- a/src/net/dnsclient_unix.go
+++ b/src/net/dnsclient_unix.go
@@ -338,8 +338,9 @@ func lookup(ctx context.Context, name string, qtype uint16) (cname string, rrs [
 }
 
 // avoidDNS reports whether this is a hostname for which we should not
-// use DNS. Currently this includes only .onion and .local names,
-// per RFC 7686 and RFC 6762, respectively. See golang.org/issue/13705.
+// use DNS. Currently this includes only .onion, per RFC 7686. See
+// golang.org/issue/13705. Does not cover .local names (RFC 6762),
+// see golang.org/issue/16739.
 func avoidDNS(name string) bool {
        if name == "" {
                return true
@@ -347,7 +348,7 @@ func avoidDNS(name string) bool {
        if name[len(name)-1] == '.' {
                name = name[:len(name)-1]
        }
-       return stringsHasSuffixFold(name, ".onion") || stringsHasSuffixFold(name, ".local")
+       return stringsHasSuffixFold(name, ".onion")
 }
 
 // nameList returns a list of names for sequential DNS queries.

diff --git a/src/net/dnsclient_unix_test.go b/src/net/dnsclient_unix_test.go
index 09bbd488660673284de1408fa9feb1f2bf6314f6..c953c1efaf6688483ae7ac838a94619013865af4 100644 (file)
--- a/src/net/dnsclient_unix_test.go
+++ b/src/net/dnsclient_unix_test.go
@@ -112,10 +112,11 @@ func TestAvoidDNSName(t *testing.T) {
                {"foo.ONION", true},
                {"foo.ONION.", true},
 
-               {"foo.local.", true},
-               {"foo.local", true},
-               {"foo.LOCAL", true},
-               {"foo.LOCAL.", true},
+               // But do resolve *.local address; Issue 16739
+               {"foo.local.", false},
+               {"foo.local", false},
+               {"foo.LOCAL", false},
+               {"foo.LOCAL.", false},
 
                {"", true}, // will be rejected earlier too