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 f80eaee9c54a80fbd6a96ea13dc4d78167c629ad..90a31427b6835281367a00a549d86505f158ce15 100644
--- a/net/dns/dns_util.cc
+++ b/net/dns/dns_util.cc
@@ -10,22 +10,38 @@
 #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)
@@ -46,6 +62,11 @@ bool DNSDomainFromDot(const base::StringPiece& dotted, std::string* out) {
     }
     if (labellen >= sizeof label)
       return false;
+    if (!IsValidHostLabelCharacter(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;
   }
 
@@ -59,6 +80,8 @@ bool DNSDomainFromDot(const base::StringPiece& dotted, std::string* out) {
     labellen = 0;
   }
 
+  UMA_HISTOGRAM_BOOLEAN("Net.ValidDNSName", valid_name);

[Ryan Sleevi, 2017/03/22 01:10:46]

Did you mean to move this down further? That is, to after line 90 :)

I just wasn't sure because of the short-circuits below

+
   if (namelen + 1 > sizeof name)
     return false;
   if (namelen == 0) // Empty names e.g. "", "." are not valid.
@@ -74,6 +97,11 @@ bool IsValidDNSDomain(const base::StringPiece& dotted) {
   return DNSDomainFromDot(dotted, &dns_formatted);
 }
 
+bool IsValidHostLabelCharacter(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;