Track how often we successfully resolve non-'compliant' domain names.

net/dns/host_resolver_proc.cc

 // Copyright (c) 2012 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/host_resolver_proc.h"
 
 #include "build/build_config.h"
 
 #include "base/logging.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/sys_byteorder.h"
 #include "net/base/address_list.h"
 #include "net/base/net_errors.h"
 #include "net/base/sys_addrinfo.h"
 #include "net/dns/dns_reloader.h"
 #include "net/dns/dns_util.h"
 
 #if defined(OS_OPENBSD)
 #define AI_ADDRCONFIG 0
 #endif
@@ skipping 98 matching lines @@
 // static
 HostResolverProc* HostResolverProc::GetDefault() {
   return default_proc_;
 }
 
 int SystemHostResolverCall(const std::string& host,
                            AddressFamily address_family,
                            HostResolverFlags host_resolver_flags,
                            AddressList* addrlist,
                            int* os_error) {
-  // Make sure |host| is properly formed.
+  // Make sure |host| is properly formed. Save the validity check result so that
+  // we can count how often invalid names (see |net::IsValidHostLabelCharacter|)
+  // successfully resolve, if ever. TODO(crbug.com/695474): Remove this when we
+  // no longer need the UMA metrics.

[Ryan Sleevi, 2017/06/02 13:39:55]

https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/NH-S6KCkr2M

// Make sure |host| is properly formed. Record whether or not the name was valid
(see
// net::IsValidHostLabelCharacter), so that it's possible to measure how often
invalid
// names successfully resolve.
// TODO(https://crbug.com/695474): Remove this once invalid names are
consistently
// rejected.

+  bool valid_hostname = false;
   {
     std::string out_ignored;
-    if (!DNSDomainFromDot(host, &out_ignored))
+    if (!DNSDomainFromDotWithValidityCheck(host, &out_ignored, &valid_hostname))
       return ERR_NAME_NOT_RESOLVED;
   }
 
   if (os_error)
     *os_error = 0;
 
   struct addrinfo* ai = NULL;
   struct addrinfo hints = {0};
 
   switch (address_family) {
@@ skipping 104 matching lines @@
 
 #if defined(OS_ANDROID)
   // Workaround for Android's getaddrinfo leaving ai==NULL without an error.
   // http://crbug.com/134142
   if (ai == NULL)
     return ERR_NAME_NOT_RESOLVED;
 #endif
 
   *addrlist = AddressList::CreateFromAddrinfo(ai);
   freeaddrinfo(ai);
+  UMA_HISTOGRAM_BOOLEAN("Net.SuccessfulResolutionWithValidDNSName",
+                        valid_hostname);
   return OK;
 }
 
 SystemHostResolverProc::SystemHostResolverProc() : HostResolverProc(NULL) {}
 
 int SystemHostResolverProc::Resolve(const std::string& hostname,
                                     AddressFamily address_family,
                                     HostResolverFlags host_resolver_flags,
                                     AddressList* addr_list,
                                     int* os_error) {
   return SystemHostResolverCall(hostname,
                                 address_family,
                                 host_resolver_flags,
                                 addr_list,
                                 os_error);
 }
 
 SystemHostResolverProc::~SystemHostResolverProc() {}
 
 }  // namespace net