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

net/dns/dns_util.cc

Index: net/dns/dns_util.cc
diff --git a/net/dns/dns_util.cc b/net/dns/dns_util.cc
index 217aedc50010252bde6c50459220751e0163f4c6..3b6ad0d9c048c3ae4482064ddbc2de51c957be9b 100644
--- a/net/dns/dns_util.cc
+++ b/net/dns/dns_util.cc
@@ -29,12 +29,26 @@
 #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];
@@ -60,6 +74,8 @@ bool DNSDomainFromDot(const base::StringPiece& dotted, std::string* out) {
     }
     if (labellen >= sizeof label)
       return false;
+    if (!IsValidLabelCharacter(ch, labellen == 0))
+      return false;
     label[labellen++] = ch;
   }