[net] HostResolverImpl + DnsTransaction + DnsConfigService = Asynchronous DNS ready for experiments.

net/dns/dns_response.cc

Index: net/dns/dns_response.cc
diff --git a/net/dns/dns_response.cc b/net/dns/dns_response.cc
index 760bd5b68064dbc60c6a0f5b14b63e3e9d9b6f71..0df83c4b88eafad6bfef2e119e5fac050da0f045 100644
--- a/net/dns/dns_response.cc
+++ b/net/dns/dns_response.cc
@@ -5,6 +5,7 @@
 #include "net/dns/dns_response.h"
 
 #include "base/sys_byteorder.h"
+#include "net/base/address_list.h"
 #include "net/base/big_endian.h"
 #include "net/base/dns_util.h"
 #include "net/base/io_buffer.h"
@@ -220,4 +221,51 @@ const dns_protocol::Header* DnsResponse::header() const {
   return reinterpret_cast<const dns_protocol::Header*>(io_buffer_->data());
 }
 
+bool DnsResponseToAddressList(const DnsResponse* response,
+                              AddressList* addr_list,
+                              base::TimeDelta* ttl) {
+  DCHECK(response->IsValid());
+  // DnsTransaction already verified that |response| matches the issued query
+  // in terms of query header. We still need to determine if there is a valid
+  // chain of CNAMEs from the query name to the RR owner name.
+
+  // Expected owner of record.
+  std::string expected_name = response->GetDottedName();
+
+  // getcanonname in eglibc returns the first owner name of an A or AAAA RR.
+  std::string canon_name;
+
+  uint32 ttl_sec = kuint32max;
+  IPAddressList ip_addresses;
+  DnsRecordParser parser = response->Parser();
+  DnsResourceRecord record;
+  while (parser.ParseRecord(&record)) {
+    if (record.name != expected_name) {
+      // We ignore records owned by unexpected name.
+      continue;
+    }
+    if (record.type == dns_protocol::kTypeCNAME) {
+      // New |hostname|, following the CNAME chain.
+      if (!parser.ParseName(record.rdata.begin(), &expected_name)) {
+        return false;
+      }
+    } else if (record.type == response->qtype() &&
+        (record.rdata.size() == kIPv4AddressSize ||
+         record.rdata.size() == kIPv6AddressSize)) {
+      ip_addresses.push_back(IPAddressNumber(record.rdata.begin(),
+                                             record.rdata.end()));
+      ttl_sec = std::min(ttl_sec, record.ttl);
+      if (canon_name.empty())
+        canon_name = record.name;
+    }
+  }
+  if (ip_addresses.empty())
+    return false;
+
+  *addr_list = AddressList::CreateFromIPAddressList(ip_addresses,
+                                                    canon_name);
+  *ttl = base::TimeDelta::FromSeconds(ttl_sec);
+  return true;
+}
+
 }  // namespace net