Measure how often DNS hostnames aren't in preferred name form.

net/dns/dns_util_unittest.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/dns/dns_util.h"
 
 #include "testing/gtest/include/gtest/gtest.h"
 
+namespace {
+
+bool IsValidDNSDomainName(const char* name) {
+  size_t length = strlen(name);
+  for (size_t i = 0; i < length; ++i) {
+    if (name[i] == '.') {
+      if (i == 0 || name[i - 1] == '.') {
+        return false;
+      } else {

[Ryan Sleevi, 2017/03/22 00:16:07]

https://chromium.googlesource.com/chromium/src/+/master/styleguide/c++/c++.md

Discourages else after return

[palmer, 2017/03/22 01:03:34]

Done.

+        continue;
+      }
+    }
+
+    if (!net::IsValidLabelCharacter(name[i], i == 0 || name[i - 1] == '.')) {
+      return false;
+    }
+  }
+  return true;
+}
+
+}  // namespace
+
 namespace net {
 
 class DNSUtilTest : public testing::Test {
 };
 
 // IncludeNUL converts a char* to a std::string and includes the terminating
 // NUL in the result.
 static std::string IncludeNUL(const char* in) {
   return std::string(in, strlen(in) + 1);
 }
@@ skipping 43 matching lines @@
             DNSDomainToString(IncludeNUL("\003foo\003bar\002uk")));
 
   // It should cope with a lack of root label.
   EXPECT_EQ("foo.bar", DNSDomainToString("\003foo\003bar"));
 
   // Invalid inputs should return an empty string.
   EXPECT_EQ("", DNSDomainToString(IncludeNUL("\x80")));
   EXPECT_EQ("", DNSDomainToString("\x06"));
 }
 
+TEST_F(DNSUtilTest, IsValidDNSDomain) {
+  const char* const bad_hostnames[] = {
+      "%20%20noodles.blorg", "noo dles.blorg ",    "noo dles.blorg. ",
+      "^noodles.blorg",      "noodles^.blorg",     "noo&dles.blorg",
+      "noodles.blorg`",      "www.-noodles.blorg",
+  };
+
+  // TODO(palmer): In the future, when we can remove support for invalid names,
+  // change the calls to from |IsValidDNSDomainName| to |IsValidDNSDomain|, and
+  // remove |IsValidDNSDomainName| (defined above).
+
+  for (size_t i = 0; i < arraysize(bad_hostnames); ++i) {
+    EXPECT_FALSE(IsValidDNSDomainName(bad_hostnames[i]));
+  }
+
+  const char* const good_hostnames[] = {
+      "www.noodles.blorg",   "1www.noodles.blorg", "www.2noodles.blorg",
+      "www.n--oodles.blorg", "www.noodl_es.blorg", "www.no-_odles.blorg",
+      "www_.noodles.blorg",  "www.noodles.blorg.", "_privet._tcp.local",
+  };
+
+  for (size_t i = 0; i < arraysize(good_hostnames); ++i) {
+    EXPECT_TRUE(IsValidDNSDomainName(good_hostnames[i]));
+  }
+}
+
 }  // namespace net