| // Copyright (c) 2011 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/base/sdch_filter.h" |
| |
| #include <limits.h> |
| #include <ctype.h> |
| #include <algorithm> |
| |
| #include "base/file_util.h" |
| #include "base/logging.h" |
| #include "base/metrics/histogram.h" |
| #include "net/base/sdch_manager.h" |
| |
| #include "sdch/open-vcdiff/src/google/vcdecoder.h" |
| |
| namespace net { |
| |
| SdchFilter::SdchFilter(const FilterContext& filter_context) |
| : filter_context_(filter_context), |
| decoding_status_(DECODING_UNINITIALIZED), |
| vcdiff_streaming_decoder_(NULL), |
| dictionary_hash_(), |
| dictionary_hash_is_plausible_(false), |
| dictionary_(NULL), |
| dest_buffer_excess_(), |
| dest_buffer_excess_index_(0), |
| source_bytes_(0), |
| output_bytes_(0), |
| possible_pass_through_(false) { |
| bool success = filter_context.GetMimeType(&mime_type_); |
| DCHECK(success); |
| success = filter_context.GetURL(&url_); |
| DCHECK(success); |
| } |
| |
| SdchFilter::~SdchFilter() { |
| // All code here is for gathering stats, and can be removed when SDCH is |
| // considered stable. |
| |
| static int filter_use_count = 0; |
| ++filter_use_count; |
| if (META_REFRESH_RECOVERY == decoding_status_) { |
| UMA_HISTOGRAM_COUNTS("Sdch3.FilterUseBeforeDisabling", filter_use_count); |
| } |
| |
| if (vcdiff_streaming_decoder_.get()) { |
| if (!vcdiff_streaming_decoder_->FinishDecoding()) { |
| decoding_status_ = DECODING_ERROR; |
| SdchManager::SdchErrorRecovery(SdchManager::INCOMPLETE_SDCH_CONTENT); |
| // Make it possible for the user to hit reload, and get non-sdch content. |
| // Note this will "wear off" quickly enough, and is just meant to assure |
| // in some rare case that the user is not stuck. |
| SdchManager::BlacklistDomain(url_); |
| UMA_HISTOGRAM_COUNTS("Sdch3.PartialBytesIn", |
| static_cast<int>(filter_context_.GetByteReadCount())); |
| UMA_HISTOGRAM_COUNTS("Sdch3.PartialVcdiffIn", source_bytes_); |
| UMA_HISTOGRAM_COUNTS("Sdch3.PartialVcdiffOut", output_bytes_); |
| } |
| } |
| |
| if (!dest_buffer_excess_.empty()) { |
| // Filter chaining error, or premature teardown. |
| SdchManager::SdchErrorRecovery(SdchManager::UNFLUSHED_CONTENT); |
| UMA_HISTOGRAM_COUNTS("Sdch3.UnflushedBytesIn", |
| static_cast<int>(filter_context_.GetByteReadCount())); |
| UMA_HISTOGRAM_COUNTS("Sdch3.UnflushedBufferSize", |
| dest_buffer_excess_.size()); |
| UMA_HISTOGRAM_COUNTS("Sdch3.UnflushedVcdiffIn", source_bytes_); |
| UMA_HISTOGRAM_COUNTS("Sdch3.UnflushedVcdiffOut", output_bytes_); |
| } |
| |
| if (filter_context_.IsCachedContent()) { |
| // Not a real error, but it is useful to have this tally. |
| // TODO(jar): Remove this stat after SDCH stability is validated. |
| SdchManager::SdchErrorRecovery(SdchManager::CACHE_DECODED); |
| return; // We don't need timing stats, and we aready got ratios. |
| } |
| |
| switch (decoding_status_) { |
| case DECODING_IN_PROGRESS: { |
| if (output_bytes_) |
| UMA_HISTOGRAM_PERCENTAGE("Sdch3.Network_Decode_Ratio_a", |
| static_cast<int>( |
| (filter_context_.GetByteReadCount() * 100) / output_bytes_)); |
| UMA_HISTOGRAM_COUNTS("Sdch3.Network_Decode_Bytes_VcdiffOut_a", |
| output_bytes_); |
| filter_context_.RecordPacketStats(FilterContext::SDCH_DECODE); |
| |
| // Allow latency experiments to proceed. |
| SdchManager::Global()->SetAllowLatencyExperiment(url_, true); |
| return; |
| } |
| case PASS_THROUGH: { |
| filter_context_.RecordPacketStats(FilterContext::SDCH_PASSTHROUGH); |
| return; |
| } |
| case DECODING_UNINITIALIZED: { |
| SdchManager::SdchErrorRecovery(SdchManager::UNINITIALIZED); |
| return; |
| } |
| case WAITING_FOR_DICTIONARY_SELECTION: { |
| SdchManager::SdchErrorRecovery(SdchManager::PRIOR_TO_DICTIONARY); |
| return; |
| } |
| case DECODING_ERROR: { |
| SdchManager::SdchErrorRecovery(SdchManager::DECODE_ERROR); |
| return; |
| } |
| case META_REFRESH_RECOVERY: { |
| // Already accounted for when set. |
| return; |
| } |
| } // end of switch. |
| } |
| |
| bool SdchFilter::InitDecoding(Filter::FilterType filter_type) { |
| if (decoding_status_ != DECODING_UNINITIALIZED) |
| return false; |
| |
| // Handle case where sdch filter is guessed, but not required. |
| if (FILTER_TYPE_SDCH_POSSIBLE == filter_type) |
| possible_pass_through_ = true; |
| |
| // Initialize decoder only after we have a dictionary in hand. |
| decoding_status_ = WAITING_FOR_DICTIONARY_SELECTION; |
| return true; |
| } |
| |
| #ifndef NDEBUG |
| static const char* kDecompressionErrorHtml = |
| "<head><META HTTP-EQUIV=\"Refresh\" CONTENT=\"0\"></head>" |
| "<div style=\"position:fixed;top:0;left:0;width:100%;border-width:thin;" |
| "border-color:black;border-style:solid;text-align:left;font-family:arial;" |
| "font-size:10pt;foreground-color:black;background-color:white\">" |
| "An error occurred. This page will be reloaded shortly. " |
| "Or press the \"reload\" button now to reload it immediately." |
| "</div>"; |
| #else |
| static const char* kDecompressionErrorHtml = |
| "<head><META HTTP-EQUIV=\"Refresh\" CONTENT=\"0\"></head>"; |
| #endif |
| |
| Filter::FilterStatus SdchFilter::ReadFilteredData(char* dest_buffer, |
| int* dest_len) { |
| int available_space = *dest_len; |
| *dest_len = 0; // Nothing output yet. |
| |
| if (!dest_buffer || available_space <= 0) |
| return FILTER_ERROR; |
| |
| if (WAITING_FOR_DICTIONARY_SELECTION == decoding_status_) { |
| FilterStatus status = InitializeDictionary(); |
| if (FILTER_NEED_MORE_DATA == status) |
| return FILTER_NEED_MORE_DATA; |
| if (FILTER_ERROR == status) { |
| DCHECK_EQ(DECODING_ERROR, decoding_status_); |
| DCHECK_EQ(0u, dest_buffer_excess_index_); |
| DCHECK(dest_buffer_excess_.empty()); |
| // This is where we try very hard to do error recovery, and make this |
| // protocol robust in the face of proxies that do many different things. |
| // If we decide that things are looking very bad (too hard to recover), |
| // we may even issue a "meta-refresh" to reload the page without an SDCH |
| // advertisement (so that we are sure we're not hurting anything). |
| // |
| // Watch out for an error page inserted by the proxy as part of a 40x |
| // error response. When we see such content molestation, we certainly |
| // need to fall into the meta-refresh case. |
| if (filter_context_.GetResponseCode() == 404) { |
| // We could be more generous, but for now, only a "NOT FOUND" code will |
| // cause a pass through. All other bad codes will fall into a |
| // meta-refresh. |
| SdchManager::SdchErrorRecovery(SdchManager::PASS_THROUGH_404_CODE); |
| decoding_status_ = PASS_THROUGH; |
| } else if (filter_context_.GetResponseCode() != 200) { |
| // We need to meta-refresh, with SDCH disabled. |
| } else if (filter_context_.IsCachedContent() |
| && !dictionary_hash_is_plausible_) { |
| // We must have hit the back button, and gotten content that was fetched |
| // before we *really* advertised SDCH and a dictionary. |
| SdchManager::SdchErrorRecovery(SdchManager::PASS_THROUGH_OLD_CACHED); |
| decoding_status_ = PASS_THROUGH; |
| } else if (possible_pass_through_) { |
| // This is the potentially most graceful response. There really was no |
| // error. We were just overly cautious when we added a TENTATIVE_SDCH. |
| // We added the sdch coding tag, and it should not have been added. |
| // This can happen in server experiments, where the server decides |
| // not to use sdch, even though there is a dictionary. To be |
| // conservative, we locally added the tentative sdch (fearing that a |
| // proxy stripped it!) and we must now recant (pass through). |
| SdchManager::SdchErrorRecovery(SdchManager::DISCARD_TENTATIVE_SDCH); |
| // However.... just to be sure we don't get burned by proxies that |
| // re-compress with gzip or other system, we can sniff to see if this |
| // is compressed data etc. For now, we do nothing, which gets us into |
| // the meta-refresh result. |
| // TODO(jar): Improve robustness by sniffing for valid text that we can |
| // actual use re: decoding_status_ = PASS_THROUGH; |
| } else if (dictionary_hash_is_plausible_) { |
| // We need a meta-refresh since we don't have the dictionary. |
| // The common cause is a restart of the browser, where we try to render |
| // cached content that was saved when we had a dictionary. |
| } else if (filter_context_.IsSdchResponse()) { |
| // This is a very corrupt SDCH request response. We can't decode it. |
| // We'll use a meta-refresh, and get content without asking for SDCH. |
| // This will also progressively disable SDCH for this domain. |
| } else { |
| // One of the first 9 bytes precluded consideration as a hash. |
| // This can't be an SDCH payload, even though the server said it was. |
| // This is a major error, as the server or proxy tagged this SDCH even |
| // though it is not! |
| // Meta-refresh won't help, as we didn't advertise an SDCH dictionary!! |
| // Worse yet, meta-refresh could lead to an infinite refresh loop. |
| SdchManager::SdchErrorRecovery(SdchManager::PASSING_THROUGH_NON_SDCH); |
| decoding_status_ = PASS_THROUGH; |
| // ... but further back-off on advertising SDCH support. |
| SdchManager::BlacklistDomain(url_); |
| } |
| |
| if (decoding_status_ == PASS_THROUGH) { |
| dest_buffer_excess_ = dictionary_hash_; // Send what we scanned. |
| } else { |
| // This is where we try to do the expensive meta-refresh. |
| if (std::string::npos == mime_type_.find("text/html")) { |
| // Since we can't do a meta-refresh (along with an exponential |
| // backoff), we'll just make sure this NEVER happens again. |
| SdchManager::BlacklistDomainForever(url_); |
| if (filter_context_.IsCachedContent()) |
| SdchManager::SdchErrorRecovery( |
| SdchManager::CACHED_META_REFRESH_UNSUPPORTED); |
| else |
| SdchManager::SdchErrorRecovery( |
| SdchManager::META_REFRESH_UNSUPPORTED); |
| return FILTER_ERROR; |
| } |
| // HTML content means we can issue a meta-refresh, and get the content |
| // again, perhaps without SDCH (to be safe). |
| if (filter_context_.IsCachedContent()) { |
| // Cached content is probably a startup tab, so we'll just get fresh |
| // content and try again, without disabling sdch. |
| SdchManager::SdchErrorRecovery( |
| SdchManager::META_REFRESH_CACHED_RECOVERY); |
| } else { |
| // Since it wasn't in the cache, we definately need at least some |
| // period of blacklisting to get the correct content. |
| SdchManager::BlacklistDomain(url_); |
| SdchManager::SdchErrorRecovery(SdchManager::META_REFRESH_RECOVERY); |
| } |
| decoding_status_ = META_REFRESH_RECOVERY; |
| // Issue a meta redirect with SDCH disabled. |
| dest_buffer_excess_ = kDecompressionErrorHtml; |
| } |
| } else { |
| DCHECK_EQ(DECODING_IN_PROGRESS, decoding_status_); |
| } |
| } |
| |
| int amount = OutputBufferExcess(dest_buffer, available_space); |
| *dest_len += amount; |
| dest_buffer += amount; |
| available_space -= amount; |
| DCHECK_GE(available_space, 0); |
| |
| if (available_space <= 0) |
| return FILTER_OK; |
| DCHECK(dest_buffer_excess_.empty()); |
| DCHECK_EQ(0u, dest_buffer_excess_index_); |
| |
| if (decoding_status_ != DECODING_IN_PROGRESS) { |
| if (META_REFRESH_RECOVERY == decoding_status_) { |
| // Absorb all input data. We've already output page reload HTML. |
| next_stream_data_ = NULL; |
| stream_data_len_ = 0; |
| return FILTER_NEED_MORE_DATA; |
| } |
| if (PASS_THROUGH == decoding_status_) { |
| // We must pass in available_space, but it will be changed to bytes_used. |
| FilterStatus result = CopyOut(dest_buffer, &available_space); |
| // Accumulate the returned count of bytes_used (a.k.a., available_space). |
| *dest_len += available_space; |
| return result; |
| } |
| DCHECK(false); |
| decoding_status_ = DECODING_ERROR; |
| return FILTER_ERROR; |
| } |
| |
| if (!next_stream_data_ || stream_data_len_ <= 0) |
| return FILTER_NEED_MORE_DATA; |
| |
| bool ret = vcdiff_streaming_decoder_->DecodeChunk( |
| next_stream_data_, stream_data_len_, &dest_buffer_excess_); |
| // Assume all data was used in decoding. |
| next_stream_data_ = NULL; |
| source_bytes_ += stream_data_len_; |
| stream_data_len_ = 0; |
| output_bytes_ += dest_buffer_excess_.size(); |
| if (!ret) { |
| vcdiff_streaming_decoder_.reset(NULL); // Don't call it again. |
| decoding_status_ = DECODING_ERROR; |
| SdchManager::SdchErrorRecovery(SdchManager::DECODE_BODY_ERROR); |
| return FILTER_ERROR; |
| } |
| |
| amount = OutputBufferExcess(dest_buffer, available_space); |
| *dest_len += amount; |
| dest_buffer += amount; |
| available_space -= amount; |
| if (0 == available_space && !dest_buffer_excess_.empty()) |
| return FILTER_OK; |
| return FILTER_NEED_MORE_DATA; |
| } |
| |
| Filter::FilterStatus SdchFilter::InitializeDictionary() { |
| const size_t kServerIdLength = 9; // Dictionary hash plus null from server. |
| size_t bytes_needed = kServerIdLength - dictionary_hash_.size(); |
| DCHECK_GT(bytes_needed, 0u); |
| if (!next_stream_data_) |
| return FILTER_NEED_MORE_DATA; |
| if (static_cast<size_t>(stream_data_len_) < bytes_needed) { |
| dictionary_hash_.append(next_stream_data_, stream_data_len_); |
| next_stream_data_ = NULL; |
| stream_data_len_ = 0; |
| return FILTER_NEED_MORE_DATA; |
| } |
| dictionary_hash_.append(next_stream_data_, bytes_needed); |
| DCHECK(kServerIdLength == dictionary_hash_.size()); |
| stream_data_len_ -= bytes_needed; |
| DCHECK_LE(0, stream_data_len_); |
| if (stream_data_len_ > 0) |
| next_stream_data_ += bytes_needed; |
| else |
| next_stream_data_ = NULL; |
| |
| DCHECK(!dictionary_.get()); |
| dictionary_hash_is_plausible_ = true; // Assume plausible, but check. |
| |
| SdchManager::Dictionary* dictionary = NULL; |
| if ('\0' == dictionary_hash_[kServerIdLength - 1]) |
| SdchManager::Global()->GetVcdiffDictionary(std::string(dictionary_hash_, 0, |
| kServerIdLength - 1), |
| url_, &dictionary); |
| else |
| dictionary_hash_is_plausible_ = false; |
| |
| if (!dictionary) { |
| DCHECK(dictionary_hash_.size() == kServerIdLength); |
| // Since dictionary was not found, check to see if hash was even plausible. |
| for (size_t i = 0; i < kServerIdLength - 1; ++i) { |
| char base64_char = dictionary_hash_[i]; |
| if (!isalnum(base64_char) && '-' != base64_char && '_' != base64_char) { |
| dictionary_hash_is_plausible_ = false; |
| break; |
| } |
| } |
| if (dictionary_hash_is_plausible_) |
| SdchManager::SdchErrorRecovery(SdchManager::DICTIONARY_HASH_NOT_FOUND); |
| else |
| SdchManager::SdchErrorRecovery(SdchManager::DICTIONARY_HASH_MALFORMED); |
| decoding_status_ = DECODING_ERROR; |
| return FILTER_ERROR; |
| } |
| dictionary_ = dictionary; |
| vcdiff_streaming_decoder_.reset(new open_vcdiff::VCDiffStreamingDecoder); |
| vcdiff_streaming_decoder_->SetAllowVcdTarget(false); |
| vcdiff_streaming_decoder_->StartDecoding(dictionary_->text().data(), |
| dictionary_->text().size()); |
| decoding_status_ = DECODING_IN_PROGRESS; |
| return FILTER_OK; |
| } |
| |
| int SdchFilter::OutputBufferExcess(char* const dest_buffer, |
| size_t available_space) { |
| if (dest_buffer_excess_.empty()) |
| return 0; |
| DCHECK(dest_buffer_excess_.size() > dest_buffer_excess_index_); |
| size_t amount = std::min(available_space, |
| dest_buffer_excess_.size() - dest_buffer_excess_index_); |
| memcpy(dest_buffer, dest_buffer_excess_.data() + dest_buffer_excess_index_, |
| amount); |
| dest_buffer_excess_index_ += amount; |
| if (dest_buffer_excess_.size() <= dest_buffer_excess_index_) { |
| DCHECK(dest_buffer_excess_.size() == dest_buffer_excess_index_); |
| dest_buffer_excess_.clear(); |
| dest_buffer_excess_index_ = 0; |
| } |
| return amount; |
| } |
| |
| } // namespace net |
