| // Copyright 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/port_suggester.h" |
| |
| #include "base/logging.h" |
| #include "net/base/host_port_pair.h" |
| |
| namespace net { |
| |
| PortSuggester::PortSuggester(const HostPortPair& server, uint64 seed) |
| : call_count_(0), |
| previous_suggestion_(-1) { |
| unsigned char hash_bytes[base::kSHA1Length]; |
| base::SHA1HashBytes( |
| reinterpret_cast<const unsigned char*>(server.host().data()), |
| server.host().length(), hash_bytes); |
| COMPILE_ASSERT(sizeof(seed_) < sizeof(hash_bytes), seed_larger_than_hash); |
| memcpy(&seed_, hash_bytes, sizeof(seed_)); |
| seed_ ^= seed ^ server.port(); |
| } |
| |
| int PortSuggester::SuggestPort(int min, int max) { |
| // Sometimes our suggestion can't be used, so we ensure that if additional |
| // calls are made, then each call (probably) provides a new suggestion. |
| if (++call_count_ > 1) { |
| // Evolve the seed. |
| unsigned char hash_bytes[base::kSHA1Length]; |
| base::SHA1HashBytes(reinterpret_cast<const unsigned char *>(&seed_), |
| sizeof(seed_), hash_bytes); |
| memcpy(&seed_, hash_bytes, sizeof(seed_)); |
| } |
| DCHECK_LE(min, max); |
| DCHECK_GT(min, 0); |
| int range = max - min + 1; |
| // Ports (and hence the extent of the |range|) are generally under 2^16, so |
| // the tiny non-uniformity in the pseudo-random distribution is not |
| // significant. |
| previous_suggestion_ = static_cast<int>(seed_ % range) + min; |
| return previous_suggestion_; |
| } |
| |
| int PortSuggester::previous_suggestion() const { |
| DCHECK_LT(0u, call_count_); |
| return previous_suggestion_; |
| } |
| |
| } // namespace net |