From: Kale Blankenship <kale@lemnisys.com>
Date: Sun, 18 Dec 2016 04:40:29 +0000 (-0800)
Subject: net/http: detect Comcast et al DNS and auto-skip DNS tests
X-Git-Tag: go1.9beta1~1800
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=4aa7b142681dba2a1d76e59ecb5dc6923a192eb0;p=gostls13.git

net/http: detect Comcast et al DNS and auto-skip DNS tests

Adds helper function to auto-skip tests when DNS returns
a successful response for a domain known not to exist.

The error from `net.LookupHost` is intentionally ignored
because the DNS tests will fail anyway if there are issues
unrelated to NXDOMAIN responses.

Fixes #17884

Change-Id: I729391bd702218507561818668f791331295299e
Reviewed-on: https://go-review.googlesource.com/34516
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
---

diff --git a/src/net/http/transport_test.go b/src/net/http/transport_test.go
index a58b1839cc..e3de3eb91b 100644
--- a/src/net/http/transport_test.go
+++ b/src/net/http/transport_test.go
@@ -3426,16 +3426,26 @@ func testTransportEventTrace(t *testing.T, h2 bool, noHooks bool) {
 	}
 }
 
-func TestTransportEventTraceRealDNS(t *testing.T) {
-	if testing.Short() && testenv.Builder() == "" {
-		// Skip this test in short mode (the default for
-		// all.bash), in case the user is using a shady/ISP
-		// DNS server hijacking queries.
-		// See issues 16732, 16716.
-		// Our builders use 8.8.8.8, though, which correctly
-		// returns NXDOMAIN, so still run this test there.
-		t.Skip("skipping in short mode")
+var (
+	isDNSHijackedOnce sync.Once
+	isDNSHijacked     bool
+)
+
+func skipIfDNSHijacked(t *testing.T) {
+	// Skip this test if the user is using a shady/ISP
+	// DNS server hijacking queries.
+	// See issues 16732, 16716.
+	isDNSHijackedOnce.Do(func() {
+		addrs, _ := net.LookupHost("dns-should-not-resolve.golang.")
+		isDNSHijacked = len(addrs) != 0
+	})
+	if isDNSHijacked {
+		t.Skip("skipping; test requires non-hijacking DNS server")
 	}
+}
+
+func TestTransportEventTraceRealDNS(t *testing.T) {
+	skipIfDNSHijacked(t)
 	defer afterTest(t)
 	tr := &Transport{}
 	defer tr.CloseIdleConnections()