| // 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/dns/dns_response.h" |
| |
| #include "net/base/dns_util.h" |
| #include "net/base/io_buffer.h" |
| #include "net/base/net_errors.h" |
| #include "net/dns/dns_query.h" |
| |
| namespace net { |
| |
| // RFC 1035, section 4.2.1: Messages carried by UDP are restricted to 512 |
| // bytes (not counting the IP nor UDP headers). |
| static const int kMaxResponseSize = 512; |
| |
| DnsResponse::DnsResponse(DnsQuery* query) |
| : query_(query), |
| io_buffer_(new IOBufferWithSize(kMaxResponseSize + 1)) { |
| DCHECK(query_); |
| } |
| |
| DnsResponse::~DnsResponse() { |
| } |
| |
| int DnsResponse::Parse(int nbytes, IPAddressList* ip_addresses) { |
| // Response includes query, it should be at least that size. |
| if (nbytes < query_->io_buffer()->size() || nbytes > kMaxResponseSize) |
| return ERR_DNS_MALFORMED_RESPONSE; |
| |
| DnsResponseBuffer response(reinterpret_cast<uint8*>(io_buffer_->data()), |
| io_buffer_->size()); |
| uint16 id; |
| if (!response.U16(&id) || id != query_->id()) // Make sure IDs match. |
| return ERR_DNS_MALFORMED_RESPONSE; |
| |
| uint8 flags, rcode; |
| if (!response.U8(&flags) || !response.U8(&rcode)) |
| return ERR_DNS_MALFORMED_RESPONSE; |
| |
| if (flags & 2) // TC is set -- server wants TCP, we don't support it (yet?). |
| return ERR_DNS_SERVER_REQUIRES_TCP; |
| |
| rcode &= 0x0f; // 3 means NXDOMAIN, the rest means server failed. |
| if (rcode && (rcode != 3)) |
| return ERR_DNS_SERVER_FAILED; |
| |
| uint16 query_count, answer_count, authority_count, additional_count; |
| if (!response.U16(&query_count) || |
| !response.U16(&answer_count) || |
| !response.U16(&authority_count) || |
| !response.U16(&additional_count)) { |
| return ERR_DNS_MALFORMED_RESPONSE; |
| } |
| |
| if (query_count != 1) // Sent a single question, shouldn't have changed. |
| return ERR_DNS_MALFORMED_RESPONSE; |
| |
| base::StringPiece question; // Make sure question section is echoed back. |
| if (!response.Block(&question, query_->question_size()) || |
| memcmp(question.data(), query_->question_data(), |
| query_->question_size())) { |
| return ERR_DNS_MALFORMED_RESPONSE; |
| } |
| |
| if (answer_count < 1) |
| return ERR_NAME_NOT_RESOLVED; |
| |
| IPAddressList rdatas; |
| while (answer_count--) { |
| uint32 ttl; |
| uint16 rdlength, qtype, qclass; |
| if (!response.DNSName(NULL) || |
| !response.U16(&qtype) || |
| !response.U16(&qclass) || |
| !response.U32(&ttl) || |
| !response.U16(&rdlength)) { |
| return ERR_DNS_MALFORMED_RESPONSE; |
| } |
| if (qtype == query_->qtype() && |
| qclass == kClassIN && |
| (rdlength == kIPv4AddressSize || rdlength == kIPv6AddressSize)) { |
| base::StringPiece rdata; |
| if (!response.Block(&rdata, rdlength)) |
| return ERR_DNS_MALFORMED_RESPONSE; |
| rdatas.push_back(IPAddressNumber(rdata.begin(), rdata.end())); |
| } else if (!response.Skip(rdlength)) |
| return ERR_DNS_MALFORMED_RESPONSE; |
| } |
| |
| if (rdatas.empty()) |
| return ERR_NAME_NOT_RESOLVED; |
| |
| if (ip_addresses) |
| ip_addresses->swap(rdatas); |
| return OK; |
| } |
| |
| } // namespace net |