Isolates generic DnsClient from AsyncHostResolver.

net/dns/dns_query.cc

 // 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_query.h"
 
 #include <limits>
 
+#include "net/base/big_endian.h"
 #include "net/base/dns_util.h"
 #include "net/base/io_buffer.h"
+#include "net/base/sys_byteorder.h"
+#include "net/dns/dns_protocol.h"
 
 namespace net {
 
-namespace {
-
-void PackUint16BE(char buf[2], uint16 v) {
-  buf[0] = v >> 8;
-  buf[1] = v & 0xff;
-}
-
-uint16 UnpackUint16BE(char buf[2]) {
-  return static_cast<uint8>(buf[0]) << 8 | static_cast<uint8>(buf[1]);
-}
-
-}  // namespace
-
 // DNS query consists of a 12-byte header followed by a question section.
 // For details, see RFC 1035 section 4.1.1.  This header template sets RD
 // bit, which directs the name server to pursue query recursively, and sets
-// the QDCOUNT to 1, meaning the question section has a single entry.  The
-// first two bytes of the header form a 16-bit random query ID to be copied
-// in the corresponding reply by the name server -- randomized during
-// DnsQuery construction.
-static const char kHeader[] = {0x00, 0x00, 0x01, 0x00, 0x00, 0x01,
-                               0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
-static const size_t kHeaderSize = arraysize(kHeader);
+// the QDCOUNT to 1, meaning the question section has a single entry.
+DnsQuery::DnsQuery(uint16 id, const base::StringPiece& qname, uint16 qtype)
+    : qname_size_(qname.size()) {
+  DCHECK(!DNSDomainToString(qname).empty());
+  // QNAME + QTYPE + QCLASS
+  size_t question_size = qname_size_ + sizeof(uint16) + sizeof(uint16);
+  io_buffer_ = new IOBufferWithSize(sizeof(dns_protocol::Header)
+                                    + question_size);

[mmenke, 2011/12/06 18:08:39]

nit:  Move '+' onto previous line.

[szym, 2011/12/06 19:05:51]

Done.

+  dns_protocol::Header* header =
+      reinterpret_cast<dns_protocol::Header*>(io_buffer_->data());
+  memset(header, 0, sizeof(dns_protocol::Header));
+  header->id = htons(id);
+  header->flags[0] = 0x1;  // RD bit
+  header->qdcount = htons(1);
 
-DnsQuery::DnsQuery(const std::string& qname,
-                   uint16 qtype,
-                   const RandIntCallback& rand_int_cb)
-    : qname_size_(qname.size()),
-      rand_int_cb_(rand_int_cb) {
-  DCHECK(DnsResponseBuffer(reinterpret_cast<const uint8*>(qname.c_str()),
-                           qname.size()).DNSName(NULL));
-  DCHECK(qtype == kDNS_A || qtype == kDNS_AAAA);
-
-  io_buffer_ = new IOBufferWithSize(kHeaderSize + question_size());
-
-  int byte_offset = 0;
-  char* buffer_head = io_buffer_->data();
-  memcpy(&buffer_head[byte_offset], kHeader, kHeaderSize);
-  byte_offset += kHeaderSize;
-  memcpy(&buffer_head[byte_offset], &qname[0], qname_size_);
-  byte_offset += qname_size_;
-  PackUint16BE(&buffer_head[byte_offset], qtype);
-  byte_offset += sizeof(qtype);
-  PackUint16BE(&buffer_head[byte_offset], kClassIN);
-  RandomizeId();
+  // Write question section after the header.
+  BigEndianWriter writer(reinterpret_cast<char*>(header + 1), question_size);
+  writer.WriteBytes(qname.data(), qname.size());
+  writer.WriteU16(qtype);
+  writer.WriteU16(dns_protocol::kClassIN);
 }
 
 DnsQuery::~DnsQuery() {
 }
 
+DnsQuery* DnsQuery::CloneWithNewId(uint16 id) const {
+  return new DnsQuery(*this, id);
+}
+
 uint16 DnsQuery::id() const {
-  return UnpackUint16BE(&io_buffer_->data()[0]);
+  const dns_protocol::Header* h =
+      reinterpret_cast<const dns_protocol::Header*>(io_buffer_->data());
+  return ntohs(h->id);
+}
+
+base::StringPiece DnsQuery::qname() const {
+  return base::StringPiece(io_buffer_->data() + sizeof(dns_protocol::Header),
+                           qname_size_);
 }
 
 uint16 DnsQuery::qtype() const {
-  return UnpackUint16BE(&io_buffer_->data()[kHeaderSize + qname_size_]);
+  uint16 type;
+  ReadBigEndian<uint16>(io_buffer_->data() +
+                        sizeof(dns_protocol::Header) +
+                        qname_size_, &type);
+  return type;
 }
 
-DnsQuery* DnsQuery::CloneWithNewId() const {
-  return new DnsQuery(qname(), qtype(), rand_int_cb_);
+base::StringPiece DnsQuery::question() const {
+  return base::StringPiece(io_buffer_->data() + sizeof(dns_protocol::Header),
+                           qname_size_ + sizeof(uint16) + sizeof(uint16));
 }
 
-size_t DnsQuery::question_size() const {
-  return qname_size_          // QNAME
-    + sizeof(uint16)          // QTYPE
-    + sizeof(uint16);         // QCLASS
-}
-
-const char* DnsQuery::question_data() const {
-  return &io_buffer_->data()[kHeaderSize];
-}
-
-const std::string DnsQuery::qname() const {
-  return std::string(question_data(), qname_size_);
-}
-
-void DnsQuery::RandomizeId() {
-  PackUint16BE(&io_buffer_->data()[0], rand_int_cb_.Run(
-      std::numeric_limits<uint16>::min(),
-      std::numeric_limits<uint16>::max()));
+DnsQuery::DnsQuery(const DnsQuery& orig, uint16 id) {
+  qname_size_ = orig.qname_size_;
+  io_buffer_ = new IOBufferWithSize(orig.io_buffer()->size());
+  memcpy(io_buffer_.get()->data(), orig.io_buffer()->data(),
+         io_buffer_.get()->size());
+  dns_protocol::Header* header =
+      reinterpret_cast<dns_protocol::Header*>(io_buffer_->data());
+  header->id = htons(id);
 }
 
 }  // namespace net