Add an eviction mechanism for SDCH dictionaries.

net/base/sdch_manager.h

Index: net/base/sdch_manager.h
diff --git a/net/base/sdch_manager.h b/net/base/sdch_manager.h
index 0948b4c71782764569ee988726320a371752a263..d51fda8c5c3e7182aba69f7c9537d3b90b06f207 100644
--- a/net/base/sdch_manager.h
+++ b/net/base/sdch_manager.h
@@ -59,11 +59,6 @@ class NET_EXPORT SdchManager {
   typedef std::map<std::string, scoped_refptr<base::RefCountedData<Dictionary>>>
       DictionaryMap;
 
-  // Use the following static limits to block DOS attacks until we implement
-  // a cached dictionary evicition strategy.
-  static const size_t kMaxDictionarySize;
-  static const size_t kMaxDictionaryCount;
-
   class NET_EXPORT_PRIVATE Dictionary {
    public:
     // Construct a vc-diff usable dictionary from the dictionary_text starting
@@ -72,6 +67,7 @@ class NET_EXPORT SdchManager {
     Dictionary(const std::string& dictionary_text,
                size_t offset,
                const std::string& client_hash,
+               const std::string& server_hash,
                const GURL& url,
                const std::string& domain,
                const std::string& path,
@@ -85,6 +81,7 @@ class NET_EXPORT SdchManager {
 
     const GURL& url() const { return url_; }
     const std::string& client_hash() const { return client_hash_; }
+    const std::string& server_hash() const { return server_hash_; }
     const std::string& domain() const { return domain_; }
     const std::string& path() const { return path_; }
     const base::Time& expiration() const { return expiration_; }
@@ -128,6 +125,10 @@ class NET_EXPORT SdchManager {
     // it has a specific dictionary pre-cached.
     std::string client_hash_;
 
+    // Part of the hash of text_ that the server uses to identify the
+    // dictionary it wants used for decoding.
+    std::string server_hash_;
+
     // The GURL that arrived with the text_ in a URL request to specify where
     // this dictionary may be used.
     const GURL url_;
@@ -233,6 +234,10 @@ class NET_EXPORT SdchManager {
   SdchProblemCode OnGetDictionary(const GURL& request_url,
                                   const GURL& dictionary_url);
 
+  // Send out appropriate events notifying observers that a dictionary
+  // was successfully used to decode a request.
+  void OnDictionaryUsed(const std::string& server_hash);
+
   // Get a handle to the available dictionaries that might be used
   // for encoding responses for the given URL. The return set will not
   // include expired dictionaries. If no dictionaries
@@ -270,10 +275,16 @@ class NET_EXPORT SdchManager {
   // dictionaries. This addition will fail if addition is illegal
   // (data in the dictionary is not acceptable from the
   // dictionary_url; dictionary already added, etc.).
+  // If |server_hash| is non-null, returns the server has that may be

[Bence, 2015/01/08 14:37:17]

s/server has/server hash/

[Randy Smith (Not in Mondays), 2015/01/08 15:48:23]

Done.

+  // used as an argument to GetDictionarySetByHash.
   // Returns SDCH_OK if the addition was successfull, and corresponding error
   // code otherwise.
   SdchProblemCode AddSdchDictionary(const std::string& dictionary_text,
-                                    const GURL& dictionary_url);
+                                    const GURL& dictionary_url,
+                                    std::string* server_hash_p);
+
+  // Remove an SDCH dictionary
+  SdchProblemCode RemoveSdchDictionary(const std::string& server_hash);
 
   // Registration for events generated by the SDCH subsystem.
   void AddObserver(SdchObserver* observer);