Limit number of service instances passed to onServiceList listeners.

chrome/browser/extensions/api/mdns/mdns_api.cc

 // Copyright 2013 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 "chrome/browser/extensions/api/mdns/mdns_api.h"
 
 #include <vector>
 
 #include "base/lazy_instance.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/common/extensions/api/mdns.h"
 #include "extensions/browser/extension_registry.h"
 
 namespace extensions {
 
 namespace mdns = api::mdns;
 
 namespace {
 
 // Whitelisted mDNS service types.
 const char kCastServiceType[] = "_googlecast._tcp.local";
 const char kPrivetServiceType[] = "_privet._tcp.local";
 const char kTestServiceType[] = "_testing._tcp.local";
 
+// Maximum number of services that may be included in an onServiceList event
+// as arguments.
+const uint8 kMaxServicesPerOnServiceListEvent = 64;
+
 bool IsServiceTypeWhitelisted(const std::string& service_type) {
   return service_type == kCastServiceType ||
          service_type == kPrivetServiceType ||
          service_type == kTestServiceType;
 }
 
 }  // namespace
 
 MDnsAPI::MDnsAPI(content::BrowserContext* context) : browser_context_(context) {
   DCHECK(browser_context_);
@@ skipping 98 matching lines @@
   service_types_ = new_service_types;
 }
 
 void MDnsAPI::OnDnsSdEvent(const std::string& service_type,
                            const DnsSdRegistry::DnsSdServiceList& services) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   std::vector<linked_ptr<mdns::MDnsService> > args;
   for (DnsSdRegistry::DnsSdServiceList::const_iterator it = services.begin();
        it != services.end(); ++it) {
+    if (args.size() == kMaxServicesPerOnServiceListEvent) {
+      VLOG(logging::LOG_WARNING)
+          << "Truncating service instances reported in onServiceList event to "
+          << "max: "
+          << kMaxServicesPerOnServiceListEvent;
+      break;
+    }
     linked_ptr<mdns::MDnsService> mdns_service =
         make_linked_ptr(new mdns::MDnsService);
     mdns_service->service_name = (*it).service_name;
     mdns_service->service_host_port = (*it).service_host_port;
     mdns_service->ip_address = (*it).ip_address;
     mdns_service->service_data = (*it).service_data;
     args.push_back(mdns_service);
   }
 
   scoped_ptr<base::ListValue> results = mdns::OnServiceList::Create(args);
   scoped_ptr<Event> event(
       new Event(mdns::OnServiceList::kEventName, results.Pass()));
   event->restrict_to_browser_context = browser_context_;
   event->filter_info.SetServiceType(service_type);
 
   // TODO(justinlin): To avoid having listeners without filters getting all
   // events, modify API to have this event require filters.
   // TODO(reddaly): If event isn't on whitelist, ensure it does not get
   // broadcast to extensions.
   extensions::EventRouter::Get(browser_context_)->BroadcastEvent(event.Pass());
 }
 
+ExtensionFunction::ResponseAction
+MdnsGetMaxServiceInstancesPerEventFunction::Run() {
+  return RespondNow(OneArgument(new base::FundamentalValue(
+      kMaxServicesPerOnServiceListEvent)));
+}
+
 }  // namespace extensions