Revert 113282 - Isolates generic DnsClient from AsyncHostResolver.

net/dns/dns_query.cc

Index: net/dns/dns_query.cc
===================================================================
--- net/dns/dns_query.cc	(revision 113383)
+++ net/dns/dns_query.cc	(working copy)
@@ -6,78 +6,91 @@
 
 #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.
-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);
-  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);
+// 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);
 
-  // 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(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();
 }
 
 DnsQuery::~DnsQuery() {
 }
 
-DnsQuery* DnsQuery::CloneWithNewId(uint16 id) const {
-  return new DnsQuery(*this, id);
+uint16 DnsQuery::id() const {
+  return UnpackUint16BE(&io_buffer_->data()[0]);
 }
 
-uint16 DnsQuery::id() const {
-  const dns_protocol::Header* header =
-      reinterpret_cast<const dns_protocol::Header*>(io_buffer_->data());
-  return ntohs(header->id);
+uint16 DnsQuery::qtype() const {
+  return UnpackUint16BE(&io_buffer_->data()[kHeaderSize + qname_size_]);
 }
 
-base::StringPiece DnsQuery::qname() const {
-  return base::StringPiece(io_buffer_->data() + sizeof(dns_protocol::Header),
-                           qname_size_);
+DnsQuery* DnsQuery::CloneWithNewId() const {
+  return new DnsQuery(qname(), qtype(), rand_int_cb_);
 }
 
-uint16 DnsQuery::qtype() const {
-  uint16 type;
-  ReadBigEndian<uint16>(io_buffer_->data() +
-                        sizeof(dns_protocol::Header) +
-                        qname_size_, &type);
-  return type;
+size_t DnsQuery::question_size() const {
+  return qname_size_          // QNAME
+    + sizeof(uint16)          // QTYPE
+    + sizeof(uint16);         // QCLASS
 }
 
-base::StringPiece DnsQuery::question() const {
-  return base::StringPiece(io_buffer_->data() + sizeof(dns_protocol::Header),
-                           qname_size_ + sizeof(uint16) + sizeof(uint16));
+const char* DnsQuery::question_data() const {
+  return &io_buffer_->data()[kHeaderSize];
 }
 
-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);
+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()));
+}
+
 }  // namespace net