Avoids the "re-encode HPACK as SPDY3" step.

net/quic/spdy_utils.cc

 // Copyright (c) 2013 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/quic/spdy_utils.h"
 
 #include <memory>
 #include <vector>
 
 #include "base/stl_util.h"
@@ skipping 102 matching lines @@
 bool SpdyUtils::CopyAndValidateHeaders(const QuicHeaderList& header_list,
                                        int64_t* content_length,
                                        SpdyHeaderBlock* headers) {
   for (const auto& p : header_list) {
     const string& name = p.first;
     if (name.empty()) {
       DVLOG(1) << "Header name must not be empty.";
       return false;
     }
 
-    if (std::any_of(name.begin(), name.end(), base::IsAsciiUpper<char>)) {
-      DLOG(ERROR) << "Malformed header: Header name " << name
-                  << " contains upper-case characters.";
-      return false;
-    }
-
     auto iter = headers->find(name);
     if (iter == headers->end()) {
       (*headers)[name] = p.second;
     } else if (name == "cookie") {
       // Obeys section 8.1.2.5 in RFC 7540 for cookie reconstruction.
       headers->ReplaceOrAppendHeader(
           name, base::StringPrintf("%s; %s", iter->second.as_string().c_str(),
                                    p.second.c_str()));
     } else {
       // This header had multiple values, so it must be reconstructed.
       string value = base::StringPrintf(
           "%s%c%s", iter->second.as_string().c_str(), '\0', p.second.c_str());

[dahollings, 2016/05/23 21:15:17]

birenroy@ pointed out that this could be one possible source of the bug: If more
than two headers with the same key are reconstructed, all but the first and last
may get lost due to the interaction between nullchar delimiting, null terminated
strings, and stringprintf. The current change will cause this code to get hit
from quic_chromium_client_stream, whereas before it only appears to be used in
quic_simple_server_stream and quic_spdy_client_stream.

[Ryan Hamilton, 2016/05/24 16:08:29]

Ah, interesting. That sounds potentially problematic.

       headers->ReplaceOrAppendHeader(name, value);
     }
   }
 
   if (ContainsKey(*headers, "content-length")) {
     // Check whether multiple values are consistent.
     StringPiece content_length_header = (*headers)["content-length"];
     vector<string> values =
         base::SplitString(content_length_header, base::StringPiece("\0", 1),
                           base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
@@ skipping 97 matching lines @@
   return GURL(GetUrlFromHeaderBlock(headers)).host();
 }
 
 // static
 bool SpdyUtils::UrlIsValid(const SpdyHeaderBlock& headers) {
   string url(GetUrlFromHeaderBlock(headers));
   return url != "" && GURL(url).is_valid();
 }
 
 }  // namespace net