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>
@@ skipping 11 matching lines @@
 #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 {
+
+bool IsValidLabelCharacter(char c, bool is_first_char) {
+  if (!isalnum(c) && c != '_') {

[eroman, 2017/03/14 16:07:49]

Drive-by comment: isalnum() depends on the user's locale, which is not actually
what we want here.

In general the C string functions as full of traps and not usually appropriate
for use in the //net protocol code.

+    if (is_first_char) {
+      return false;
+    }
+    return c == '-';
+  }
+  return true;
+}
+
+}  // namespace
+
 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;
 
   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))
+      return false;
     label[labellen++] = ch;
   }
 
   // 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;
@@ skipping 150 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