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// 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/dns_response.h"
#include "net/base/dns_util.h"
#include "net/base/net_errors.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
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