bug 507578 - disable dns prefetch in presence of active proxy r=jduell

modules/libpref/src/init/all.js

@@ -1121,6 +1121,9 @@ pref("network.dns.disableIPv6", false);
 // Default to 30 days. (basically forever)
 pref("network.dnsCacheExpirationGracePeriod", 2592000);
 
+// This preference can be used to turn off DNS prefetch.
+pref("network.dns.disablePrefetch", false);
+
 // This preference controls whether or not URLs with UTF-8 characters are
 // escaped.  Set this preference to TRUE for strict RFC2396 conformance.
 pref("network.standard-url.escape-utf8", true);

netwerk/base/src/nsProtocolProxyService.cpp

@@ -18,6 +18,7 @@
 #include "nsIProtocolProxyCallback.h"
 #include "nsICancelable.h"
 #include "nsIDNSService.h"
+#include "nsPIDNSService.h"
 #include "nsIPrefService.h"
 #include "nsIPrefBranch.h"
 #include "nsReadableUtils.h"
@@ -200,6 +201,8 @@ private:
                 mProxyInfo = nullptr;
 
             LOG(("pac thread callback %s\n", mPACString.get()));
+            if (NS_SUCCEEDED(mStatus))
+                mPPS->MaybeDisableDNSPrefetch(mProxyInfo);
             mCallback->OnProxyAvailable(this, mURI, mProxyInfo, mStatus);
         }
         else if (NS_SUCCEEDED(mStatus) && !mPACURL.IsEmpty()) {
@@ -222,6 +225,8 @@ private:
         }
         else {
             LOG(("pac thread callback did not provide information %X\n", mStatus));
+            if (NS_SUCCEEDED(mStatus))
+                mPPS->MaybeDisableDNSPrefetch(mProxyInfo);
             mCallback->OnProxyAvailable(this, mURI, mProxyInfo, mStatus);
         }
 
@@ -1604,6 +1609,30 @@ nsProtocolProxyService::Resolve_Internal(nsIURI *uri,
     return NS_OK;
 }
 
+void
+nsProtocolProxyService::MaybeDisableDNSPrefetch(nsIProxyInfo *aProxy)
+{
+    // Disable Prefetch in the DNS service if a proxy is in use.
+    if (!aProxy)
+        return;
+
+    nsCOMPtr<nsProxyInfo> pi = do_QueryInterface(aProxy);
+    if (!pi ||
+        !pi->mType ||
+        pi->mType == kProxyType_DIRECT)
+        return;
+
+    nsCOMPtr<nsIDNSService> dns = do_GetService(NS_DNSSERVICE_CONTRACTID);
+    if (!dns)
+        return;
+    nsCOMPtr<nsPIDNSService> pdns = do_QueryInterface(dns);
+    if (!pdns)
+        return;
+
+    // We lose the prefetch optimization for the life of the dns service.
+    pdns->SetPrefetchEnabled(false);
+}
+
 void
 nsProtocolProxyService::ApplyFilters(nsIURI *uri, const nsProtocolInfo &info,
                                      nsIProxyInfo **list)

netwerk/base/src/nsProtocolProxyService.h

@@ -271,6 +271,14 @@ protected:
      */
     NS_HIDDEN_(bool) CanUseProxy(nsIURI *uri, int32_t defaultPort);
 
+    /**
+     * Disable Prefetch in the DNS service if a proxy is in use.
+     *
+     * @param aProxy
+     *        The proxy information
+     */
+    NS_HIDDEN_(void) MaybeDisableDNSPrefetch(nsIProxyInfo *aProxy);
+
 private:
     nsresult SetupPACThread();
     nsresult ResetPACThread();

netwerk/dns/nsDNSService2.cpp

@@ -496,6 +496,20 @@ nsDNSService::SetOffline(bool offline)
     return NS_OK;
 }
 
+NS_IMETHODIMP
+nsDNSService::GetPrefetchEnabled(bool *outVal)
+{
+    *outVal = !mDisablePrefetch;
+    return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDNSService::SetPrefetchEnabled(bool inVal)
+{
+    mDisablePrefetch = !inVal;
+    return NS_OK;
+}
+
 namespace {
 
 class DNSListenerProxy MOZ_FINAL : public nsIDNSListener

netwerk/dns/nsPIDNSService.idl

@@ -10,7 +10,7 @@
  * This is a private interface used by the internals of the networking library.
  * It will never be frozen.  Do not use it in external code.
  */
-[scriptable, uuid(26bd9b9e-90c3-11e1-981c-001fbc092072)]
+[scriptable, uuid(6b16fb1f-5709-4c94-a89f-a22be873c54d)]
 interface nsPIDNSService : nsIDNSService
 {
     /**
@@ -27,6 +27,11 @@ interface nsPIDNSService : nsIDNSService
      */
     void shutdown();
 
+    /**
+     * Whether or not DNS prefetching (aka RESOLVE_SPECULATE) is enabled
+     */
+    attribute boolean prefetchEnabled;
+
     /**
      * @return whether the DNS service is offline.
      */