Add simple non-response-based question parsing for mDNS passive listening

net/dns/dns_response.h

Index: net/dns/dns_response.h
diff --git a/net/dns/dns_response.h b/net/dns/dns_response.h
index 78fb73571028ad6fa3e47d2f81eaf1516e373372..e918b4568a6048dc26cc5079521c18826329964f 100644
--- a/net/dns/dns_response.h
+++ b/net/dns/dns_response.h
@@ -115,6 +115,10 @@ class NET_EXPORT_PRIVATE DnsResponse {
   // packet matches the |query| id and question.
   bool InitParse(int nbytes, const DnsQuery& query);
 
+  // Assuming the internal buffer holds |nbytes| bytes, initialize the parser
+  // without matching it against an existing query.
+  bool InitParse(int nbytes);

[szym, 2013/04/17 22:11:12]

I suggest keeping it distinct, e.g., InitParseWithoutQuery(...) since the
semantics are substantially different from InitParse.

The comment should also indicate that the parser is still positioned after the
question section.

[szym, 2013/04/17 23:30:27]

After some more thinking, I suggest InitParseIgnoreQuery.
I'd also be OK if you used InitParse here and InitParseMatchQuery for the other
method.

[Noam Samuel, 2013/04/18 19:03:17]

Done.

+
   // Returns true if response is valid, that is, after successful InitParse.
   bool IsValid() const;
 
@@ -132,6 +136,9 @@ class NET_EXPORT_PRIVATE DnsResponse {
   // Returns qname in dotted format.
   std::string GetDottedName() const;
 
+  // Returns the offset of the response.
+  size_t GetResponseOffset() const;

[szym, 2013/04/17 22:11:12]

"Response" is confusing. (This is DnsResponse.) I suggest "answer" in reference
to "answer section".

That said, I don't think this is needed, see comments in .cc

[Noam Samuel, 2013/04/18 19:03:17]

Made irrelevant.

On 2013/04/17 22:11:12, szym wrote:

+
   // Returns an iterator to the resource records in the answer section.
   // The iterator is valid only in the scope of the DnsResponse.
   // This operation is idempotent.