Remove edns0 from DnsConfig

This does not appear to be used by anything. When it was added in 2011,
there was some musing about using it but it seems it never was
(https://codereview.chromium.org/7518028/diff/12006/net/dns/dns_config_service_posix.cc#newcode52).

Bug: 831665
Change-Id: I1181594cb9f84ba406228075834c4fbfed42a21a
Reviewed-on: https://chromium-review.googlesource.com/1007664Reviewed-by: Matt Menke <mmenke@chromium.org>
Commit-Queue: Rob Percival <robpercival@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550571}

net/dns/dns_config_service.cc

@@ -24,7 +24,6 @@ DnsConfig::DnsConfig()
       timeout(base::TimeDelta::FromMilliseconds(kDnsDefaultTimeoutMs)),
       attempts(2),
       rotate(false),
-      edns0(false),
       use_local_ipv6(false) {}
 
 DnsConfig::DnsConfig(const DnsConfig& other) = default;
@@ -44,7 +43,6 @@ bool DnsConfig::EqualsIgnoreHosts(const DnsConfig& d) const {
          (timeout == d.timeout) &&
          (attempts == d.attempts) &&
          (rotate == d.rotate) &&
-         (edns0 == d.edns0) &&
          (use_local_ipv6 == d.use_local_ipv6);
 }
 
@@ -57,7 +55,6 @@ void DnsConfig::CopyIgnoreHosts(const DnsConfig& d) {
   timeout = d.timeout;
   attempts = d.attempts;
   rotate = d.rotate;
-  edns0 = d.edns0;
   use_local_ipv6 = d.use_local_ipv6;
 }
 
@@ -80,7 +77,6 @@ std::unique_ptr<base::Value> DnsConfig::ToValue() const {
   dict->SetDouble("timeout", timeout.InSecondsF());
   dict->SetInteger("attempts", attempts);
   dict->SetBoolean("rotate", rotate);
-  dict->SetBoolean("edns0", edns0);
   dict->SetBoolean("use_local_ipv6", use_local_ipv6);
   dict->SetInteger("num_hosts", hosts.size());
   list = std::make_unique<base::ListValue>();

net/dns/dns_config_service.h

@@ -88,8 +88,6 @@ struct NET_EXPORT_PRIVATE DnsConfig {
   int attempts;
   // Round robin entries in |nameservers| for subsequent requests.
   bool rotate;
-  // Enable EDNS0 extensions.
-  bool edns0;
 
   // Indicates system configuration uses local IPv6 connectivity, e.g.,
   // DirectAccess. This is exposed for HostResolver to skip IPv6 probes,

net/dns/dns_config_service_posix.cc

@@ -562,9 +562,6 @@ ConfigParsePosixResult ConvertResStateToDnsConfig(const struct __res_state& res,
 #if defined(RES_ROTATE)
   dns_config->rotate = res.options & RES_ROTATE;
 #endif
-#if defined(RES_USE_EDNS0)
-  dns_config->edns0 = res.options & RES_USE_EDNS0;
-#endif
 #if !defined(RES_USE_DNSSEC)
   // Some versions of libresolv don't have support for the DO bit. In this
   // case, we proceed without it.

net/dns/dns_config_service_posix_unittest.cc

@@ -115,7 +115,6 @@ void InitializeExpectedConfig(DnsConfig* config) {
   config->timeout = base::TimeDelta::FromSeconds(4);
   config->attempts = 7;
   config->rotate = true;
-  config->edns0 = false;
   config->append_to_multi_label_name = true;
   config->search.clear();
   config->search.push_back("chromium.org");

net/dns/fuzzed_host_resolver.cc

@@ -214,9 +214,6 @@ void FuzzedHostResolver::SetDnsClientEnabled(bool enabled) {
 
   config.rotate = data_provider_->ConsumeBool();
 
-  // Doesn't currently seem to do anything.
-  config.edns0 = false;
-
   config.use_local_ipv6 = data_provider_->ConsumeBool();
 
   std::unique_ptr<DnsClient> dns_client = DnsClient::CreateClientForTesting(

net/tools/gdig/gdig.cc

@@ -87,8 +87,6 @@ std::string DnsConfigToString(const DnsConfig& dns_config) {
   base::StringAppendF(&output, "options attempts:%d\n", dns_config.attempts);
   if (dns_config.rotate)
     output.append("options rotate\n");
-  if (dns_config.edns0)
-    output.append("options edns0\n");
   return output;
 }