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Unified Diff: net/filter/sdch_policy_delegate.cc

Issue 1662763002: [ON HOLD] Implement pull-based design for content decoding (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: rebased Created 4 years, 4 months ago
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Index: net/filter/sdch_policy_delegate.cc
diff --git a/net/filter/sdch_policy_delegate.cc b/net/filter/sdch_policy_delegate.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5bb2b2565629979a8367187075888540950d01fd
--- /dev/null
+++ b/net/filter/sdch_policy_delegate.cc
@@ -0,0 +1,174 @@
+// Copyright 2016 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 "net/filter/sdch_policy_delegate.h"
+
+#include "base/metrics/histogram_macros.h"
+#include "base/values.h"
+#include "net/base/sdch_net_log_params.h"
+#include "net/filter/sdch_source_stream.h"
+
+namespace net {
+
+namespace {
+
+const char kRefreshHtml[] =
+ "<head><META HTTP-EQUIV=\"Refresh\" CONTENT=\"0\"></head>";
+
+} // namespace
+
+SdchPolicyDelegate::SdchPolicyDelegate(std::unique_ptr<Context> context)
+ : dictionary_requested_(false), context_(std::move(context)) {}
+
+SdchPolicyDelegate::~SdchPolicyDelegate() {}
+
+// Dictionary errors are often the first indication that the SDCH stream has
+// become corrupt. There are many possible causes: non-200 response codes, a
+// cached non-SDCH-ified reply, the server opting not to use SDCH, a cached
+// SDCH-ified reply for which the SdchManager did not have the dictionary, a
+// corrupted response, or a response that claims to be SDCH but isn't actually.
+// These are handled here by issuing a meta-refresh or swapping to passthrough
+// mode if appropriate, or failing the request if the error is unrecoverable.
+bool SdchPolicyDelegate::OnDictionaryError(SdchSourceStream* source) {
+ // HTTP 404 might be an unencoded error page, so if decoding failed, pass it
+ // through.
+ // TODO(xunjieli): Figure out whether this special case can be removed.
+ // crbug.com/516773.
+ if (context_->GetResponseCode() == 404) {
+ source->StopDecoding();
+ LogSdchProblem(SDCH_PASS_THROUGH_404_CODE);
+ return true;
+ }
+
+ // HTTP !200 gets a meta-refresh for HTML and a hard failure otherwise.
+ if (context_->GetResponseCode() != 200)
+ return IssueMetaRefreshIfPossible(source);
+
+ // If this is a cached result and the source hasn't requested a dictionary, it
+ // probably never had a dictionary to begin and is an unencoded response from
+ // earlier. If the source has requested a dictionary, but there was still a
+ // dictionary error, then the SdchManager does not have it so this method
+ // needs to issue a meta-refresh to get it.
+ if (context_->IsCachedContent() && !dictionary_requested_) {
+ source->StopDecoding();
+ LogSdchProblem(SDCH_PASS_THROUGH_OLD_CACHED);
+ return true;
+ }
+
+ // Ow. The original request didn't advertise any dictionaries, but the
+ // response claimed to be SDCH, but did not have a plausible dictionary hash.
+ // There is no way to repair this situation: the original request already
+ // didn't advertise any dictionaries, and retrying it would likely have the
+ // same result. Blacklist the domain and try passing through.
+ if (!context_->SdchDictionariesAdvertised() && !dictionary_requested_) {
+ GURL url;
+ if (!context_->GetURL(&url))
+ return false;
+ source->StopDecoding();
+ context_->GetSdchManager()->BlacklistDomain(url,
+ SDCH_PASSING_THROUGH_NON_SDCH);
+ return true;
+ }
+
+ return IssueMetaRefreshIfPossible(source);
+}
+
+bool SdchPolicyDelegate::OnDecodingError(SdchSourceStream* source) {
+ // A decoding error, as opposed to a dictionary error, indicates a
+ // decompression failure partway through the payload of the SDCH stream,
+ // which means that the filter already witnessed a valid dictionary ID and
+ // successfully retrieved a dictionary for it. Decoding errors are not
+ // recoverable and it is not appropriate to stop decoding, so there are
+ // relatively few error cases here.
+ //
+ // In particular, a decoding error for an HTML payload is recoverable by
+ // issuing a meta-refresh, but to avoid having that happen too often, this
+ // class also temporarily blacklists the domain. A decoding error for a
+ // non-HTML payload is unrecoverable, so such an error gets a permanent
+ // blacklist entry. If the content was cached, no blacklisting is needed.
+ return IssueMetaRefreshIfPossible(source);
+}
+
+bool SdchPolicyDelegate::OnGetDictionary(const std::string& server_id,
+ const std::string** text) {
+ dictionary_requested_ = true;
+ SdchManager::DictionarySet* set = context_->SdchDictionariesAdvertised();
+ if (set) {
+ *text = set->GetDictionaryText(server_id);
+ if (*text)
+ return true;
+ }
+ GURL url;
+ if (!context_->GetURL(&url))
+ return false;
+ // This is a hack. Naively, the dictionaries available for
+ // decoding should be only the ones advertised. However, there are
+ // cases, specifically resources encoded with old dictionaries living
+ // in the cache, that mean the full set of dictionaries should be made
+ // available for decoding. It's not known how often this happens;
+ // if it happens rarely enough, this code can be removed.
+ //
+ // TODO(rdsmith): Long-term, a better solution is necessary, since
+ // an entry in the cache being encoded with the dictionary doesn't
+ // guarantee that the dictionary is present. That solution probably
+ // involves storing unencoded resources in the cache, but might
+ // involve evicting encoded resources on dictionary removal.
+ // See http://crbug.com/383405.
+ SdchProblemCode rv = SDCH_OK;
+ unexpected_dictionary_set_ =
+ context_->GetSdchManager()->GetDictionarySetByHash(url, server_id, &rv);
+ if (unexpected_dictionary_set_) {
+ *text = unexpected_dictionary_set_->GetDictionaryText(server_id);
+ LogSdchProblem(context_->IsCachedContent()
+ ? SDCH_UNADVERTISED_DICTIONARY_USED_CACHED
+ : SDCH_UNADVERTISED_DICTIONARY_USED);
+ if (*text)
+ return true;
+ } else {
+ LogSdchProblem(SDCH_DICTIONARY_HASH_NOT_FOUND);
+ }
+ return false;
+}
+
+bool SdchPolicyDelegate::IssueMetaRefreshIfPossible(SdchSourceStream* source) {
+ std::string mime_type;
+ GURL url;
+ if (!context_->GetMimeType(&mime_type) || !context_->GetURL(&url))
+ return false;
+ SdchManager* manager = context_->GetSdchManager();
+
+ // Errors for non-HTML payloads are unrecoverable and get the domain
+ // blacklisted indefinitely.
+ if (mime_type.npos == mime_type.find("text/html")) {
+ SdchProblemCode problem =
+ (context_->IsCachedContent() ? SDCH_CACHED_META_REFRESH_UNSUPPORTED
+ : SDCH_META_REFRESH_UNSUPPORTED);
+ manager->BlacklistDomainForever(url, problem);
+ LogSdchProblem(problem);
+ return false;
+ }
+
+ if (context_->IsCachedContent()) {
+ // Cached content is a probably startup tab, so just get the fresh content
+ // and try again, without disabling SDCH.
+ LogSdchProblem(SDCH_META_REFRESH_CACHED_RECOVERY);
+ } else {
+ // Since it wasn't in the cache, blacklist for some period to get the
+ // correct content.
+ manager->BlacklistDomain(url, SDCH_META_REFRESH_RECOVERY);
+ LogSdchProblem(SDCH_META_REFRESH_RECOVERY);
+ }
+
+ source->ReplaceOutput(kRefreshHtml, strlen(kRefreshHtml));
+ return true;
+}
+
+void SdchPolicyDelegate::LogSdchProblem(SdchProblemCode problem) {
+ SdchManager::SdchErrorRecovery(problem);
+ context_->GetNetLog().AddEvent(
+ NetLog::TYPE_SDCH_DECODING_ERROR,
+ base::Bind(&NetLogSdchResourceProblemCallback, problem));
+}
+
+} // namespace net
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