gecko-dev/netwerk/base/nsDNSPrefetch.cpp

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsDNSPrefetch.h"
#include "nsCOMPtr.h"
#include "nsString.h"
#include "nsThreadUtils.h"

#include "nsIDNSListener.h"
#include "nsIDNSService.h"
#include "nsICancelable.h"
#include "nsIURI.h"
#include "mozilla/Preferences.h"

static nsIDNSService *sDNSService = nullptr;
static bool sESNIEnabled = false;

nsresult
nsDNSPrefetch::Initialize(nsIDNSService *aDNSService)
{
    NS_IF_RELEASE(sDNSService);
    sDNSService =  aDNSService;
    NS_IF_ADDREF(sDNSService);
    mozilla::Preferences::AddBoolVarCache(&sESNIEnabled, "network.security.esni.enabled");
    return NS_OK;
}

nsresult
nsDNSPrefetch::Shutdown()
{
    NS_IF_RELEASE(sDNSService);
    return NS_OK;
}

nsDNSPrefetch::nsDNSPrefetch(nsIURI *aURI,
                             mozilla::OriginAttributes& aOriginAttributes,
                             nsIDNSListener *aListener,
                             bool storeTiming)
    : mOriginAttributes(aOriginAttributes)
    , mStoreTiming(storeTiming)
    , mListener(do_GetWeakReference(aListener))
{
    aURI->GetAsciiHost(mHostname);
    mIsHttps = false;
    aURI->SchemeIs("https", &mIsHttps);
}

nsresult
nsDNSPrefetch::Prefetch(uint16_t flags)
{
    // This can work properly only if this call is on the main thread.
    // Curenlty we use nsDNSPrefetch only in nsHttpChannel which will call
    // PrefetchHigh() from the main thread. Let's add assertion to catch
    // if things change.
    MOZ_ASSERT(NS_IsMainThread(), "Expecting DNS callback on main thread.");

    if (mHostname.IsEmpty())
        return NS_ERROR_NOT_AVAILABLE;

    if (!sDNSService)
        return NS_ERROR_NOT_AVAILABLE;

    nsCOMPtr<nsICancelable> tmpOutstanding;

    if (mStoreTiming)
        mStartTimestamp = mozilla::TimeStamp::Now();
    // If AsyncResolve fails, for example because prefetching is disabled,
    // then our timing will be useless. However, in such a case,
    // mEndTimestamp will be a null timestamp and callers should check
    // TimingsValid() before using the timing.
    nsCOMPtr<nsIEventTarget> main = mozilla::GetMainThreadEventTarget();

    nsresult rv = sDNSService->AsyncResolveNative(mHostname,
                                                  flags | nsIDNSService::RESOLVE_SPECULATE,
                                                  this, main, mOriginAttributes,
                                                  getter_AddRefs(tmpOutstanding));
    if (NS_FAILED(rv)) {
        return rv;
    }

    // Fetch esni keys if needed.
    if (sESNIEnabled && mIsHttps) {
        nsAutoCString esniHost;
        esniHost.Append("_esni.");
        esniHost.Append(mHostname);
        sDNSService->AsyncResolveByTypeNative(esniHost, nsIDNSService::RESOLVE_TYPE_TXT,
                                              flags | nsIDNSService::RESOLVE_SPECULATE,
                                              this, main, mOriginAttributes,
                                              getter_AddRefs(tmpOutstanding));
    }
    return NS_OK;
}

nsresult
nsDNSPrefetch::PrefetchLow(bool refreshDNS)
{
    return Prefetch(nsIDNSService::RESOLVE_PRIORITY_LOW |
      (refreshDNS ? nsIDNSService::RESOLVE_BYPASS_CACHE : 0));
}

nsresult
nsDNSPrefetch::PrefetchMedium(bool refreshDNS)
{
    return Prefetch(nsIDNSService::RESOLVE_PRIORITY_MEDIUM |
      (refreshDNS ? nsIDNSService::RESOLVE_BYPASS_CACHE : 0));
}

nsresult
nsDNSPrefetch::PrefetchHigh(bool refreshDNS)
{
    return Prefetch(refreshDNS ?
                    nsIDNSService::RESOLVE_BYPASS_CACHE : 0);
}

NS_IMPL_ISUPPORTS(nsDNSPrefetch, nsIDNSListener)

NS_IMETHODIMP
nsDNSPrefetch::OnLookupComplete(nsICancelable *request,
                                nsIDNSRecord  *rec,
                                nsresult       status)
{
    MOZ_ASSERT(NS_IsMainThread(), "Expecting DNS callback on main thread.");

    if (mStoreTiming) {
        mEndTimestamp = mozilla::TimeStamp::Now();
    }
    nsCOMPtr<nsIDNSListener> listener = do_QueryReferent(mListener);
    if (listener) {
        listener->OnLookupComplete(request, rec, status);
    }
    return NS_OK;
}

NS_IMETHODIMP
nsDNSPrefetch::OnLookupByTypeComplete(nsICancelable *request,
                                      nsIDNSByTypeRecord *res,
                                      nsresult       status)
{
    MOZ_ASSERT(NS_IsMainThread(), "Expecting DNS callback on main thread.");

    if (mStoreTiming) {
        mEndTimestamp = mozilla::TimeStamp::Now();
    }
    nsCOMPtr<nsIDNSListener> listener = do_QueryReferent(mListener);
    if (listener) {
        listener->OnLookupByTypeComplete(request, res, status);
    }
    return NS_OK;
}