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

net/dns/dns_util.cc

 // Copyright (c) 2011 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 <errno.h>
 #include <limits.h>
 
 #include <cstring>
 
 #include "base/metrics/field_trial.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "build/build_config.h"
 #include "net/base/address_list.h"
 
+#if defined(OS_POSIX)
+#include <netinet/in.h>
+#if !defined(OS_NACL)
+#include <net/if.h>
+#if !defined(OS_ANDROID)
+#include <ifaddrs.h>
+#endif  // !defined(OS_ANDROID)
+#endif  // !defined(OS_NACL)
+#endif  // defined(OS_POSIX)
+
+#if defined(OS_ANDROID)
+#include "net/android/network_library.h"
+#endif
+
 namespace net {
 
 // Based on DJB's public domain code.
 bool DNSDomainFromDot(const base::StringPiece& dotted, std::string* out) {
   const char* buf = dotted.data();
-  unsigned n = dotted.size();
+  size_t n = dotted.size();
   char label[63];
   size_t labellen = 0; /* <= sizeof label */
   char name[255];
   size_t namelen = 0; /* <= sizeof name */
   char ch;
+  bool valid_name = true;
 
   for (;;) {
     if (!n)
       break;
     ch = *buf++;
     --n;
     if (ch == '.') {
       // Don't allow empty labels per http://crbug.com/456391.
       if (!labellen)
         return false;
       if (namelen + labellen + 1 > sizeof name)
         return false;
       name[namelen++] = static_cast<char>(labellen);
       memcpy(name + namelen, label, labellen);
       namelen += labellen;
       labellen = 0;
       continue;
     }
     if (labellen >= sizeof label)
       return false;
+    if (!IsValidLabelCharacter(ch, labellen == 0)) {
+      // TODO(palmer): In the future, when we can remove support for invalid
+      // names, return false here instead (and remove the UMA counter).
+      valid_name = false;
+    }
     label[labellen++] = ch;
   }
 
+  UMA_HISTOGRAM_BOOLEAN("Net.ValidDNSName", valid_name);

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

Do you want to record this after line 85/87?

[palmer, 2017/03/22 01:03:33]

Oops, yes. Done.

+
   // Allow empty label at end of name to disable suffix search.
   if (labellen) {
     if (namelen + labellen + 1 > sizeof name)
       return false;
     name[namelen++] = static_cast<char>(labellen);
     memcpy(name + namelen, label, labellen);
     namelen += labellen;
     labellen = 0;
   }
 
   if (namelen + 1 > sizeof name)
     return false;
   if (namelen == 0) // Empty names e.g. "", "." are not valid.
     return false;
   name[namelen++] = 0;  // This is the root label (of length 0).
 
   *out = std::string(name, namelen);
   return true;
 }
 
 bool IsValidDNSDomain(const base::StringPiece& dotted) {
   std::string dns_formatted;
   return DNSDomainFromDot(dotted, &dns_formatted);
 }
 
+bool IsValidLabelCharacter(char c, bool is_first_char) {
+  return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
+         (c >= '0' && c <= '9') || (!is_first_char && c == '-') || c == '_';
+}
+
 std::string DNSDomainToString(const base::StringPiece& domain) {
   std::string ret;
 
   for (unsigned i = 0; i < domain.size() && domain[i]; i += domain[i] + 1) {
 #if CHAR_MIN < 0
     if (domain[i] < 0)
       return std::string();
 #endif
     if (domain[i] > 63)
       return std::string();
@@ skipping 71 matching lines @@
     return DELTA_IDENTICAL;
   else if (same_size && !any_missing)
     return DELTA_REORDERED;
   else if (any_match)
     return DELTA_OVERLAP;
   else
     return DELTA_DISJOINT;
 }
 
 }  // namespace net