123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869 |
- // Copyright 2018 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.
- #ifndef NET_HTTP_PROXY_FALLBACK_H_
- #define NET_HTTP_PROXY_FALLBACK_H_
- // ------------------------------------------------------------
- // Proxy Fallback Overview
- // ------------------------------------------------------------
- //
- // Proxy fallback is a feature that is split between the proxy resolution layer
- // and the HTTP layers.
- //
- // The proxy resolution layer is responsible for:
- // * Obtaining a list of proxies to use
- // (ProxyResolutionService::ResolveProxy). Proxy lists are (usually) the
- // result of having evaluated a PAC script, such as:
- // return "PROXY foobar1:8080; HTTPS foobar2:8080; DIRECT";
- //
- // * Re-ordering the proxy list such that proxies that have recently failed
- // are given lower priority (ProxyInfo::DeprioritizeBadProxies)
- //
- // * Maintaining the expiring cache of proxies that have recently failed.
- //
- //
- // The HTTP layer is responsible for:
- // * Attempting to issue the URLRequest through each of the
- // proxies, in the order specified by the list.
- //
- // * Deciding whether this attempt was successful, whether it was a failure
- // but should keep trying other proxies, or whether it was a failure and
- // should stop trying other proxies.
- //
- // * Upon successful completion of an attempt though a proxy, calling
- // ProxyResolutionService::ReportSuccess to inform it of all the failed
- // attempts that were made. (A proxy is only considered to be "bad"
- // if the request was able to be completed through some other proxy).
- //
- //
- // Exactly how to interpret the proxy lists returned by PAC is not specified by
- // a standard. The justifications for what errors are considered for fallback
- // are given beside the implementation.
- #include "net/base/net_export.h"
- namespace net {
- class ProxyServer;
- // Returns true if a failed request issued through a proxy server should be
- // re-tried using the next proxy in the fallback list.
- //
- // The proxy fallback logic is a compromise between compatibility and
- // increasing odds of success, and may choose not to retry a request on the
- // next proxy option, even though that could work.
- //
- // - |proxy| is the proxy server that failed the request.
- // - |error| is the error for the request when it was sent through |proxy|.
- // - |final_error| is an out parameter that is set with the "final" error to
- // report to the caller. The error is only re-written in cases where
- // CanFalloverToNextProxy() returns false.
- NET_EXPORT bool CanFalloverToNextProxy(const ProxyServer& proxy,
- int error,
- int* final_error);
- } // namespace net
- #endif // NET_HTTP_PROXY_FALLBACK_H_
|