Linux: Monitor resolv.conf for changes and use that to reload resolver.

net/base/host_resolver_impl.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/base/host_resolver_impl.h"
 
 #if defined(OS_WIN)
 #include <Winsock2.h>
 #elif defined(OS_POSIX)
 #include <netdb.h>
@@ skipping 12 matching lines @@
 #include "base/metrics/histogram.h"
 #include "base/stl_util-inl.h"
 #include "base/string_util.h"
 #include "base/task.h"
 #include "base/threading/worker_pool.h"
 #include "base/time.h"
 #include "base/utf_string_conversions.h"
 #include "base/values.h"
 #include "net/base/address_list.h"
 #include "net/base/address_list_net_log_param.h"
+#include "net/base/dns_reloader.h"
 #include "net/base/host_port_pair.h"
 #include "net/base/host_resolver_proc.h"
 #include "net/base/net_errors.h"
 #include "net/base/net_log.h"
 #include "net/base/net_util.h"
 
 #if defined(OS_WIN)
 #include "net/base/winsock_init.h"
 #endif
 
@@ skipping 1061 matching lines @@
   job_pools_[POOL_NORMAL] = new JobPool(max_jobs, 100u * max_jobs);
 
 #if defined(OS_WIN)
   EnsureWinsockInit();
 #endif
 #if defined(OS_POSIX) && !defined(OS_MACOSX)
   if (HaveOnlyLoopbackAddresses())
     additional_resolver_flags_ |= HOST_RESOLVER_LOOPBACK_ONLY;
 #endif
   NetworkChangeNotifier::AddIPAddressObserver(this);
+#if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_OPENBSD)
+  DnsReloaderInit();
+  NetworkChangeNotifier::AddDNSObserver(this);
+#endif
 }
 
 HostResolverImpl::~HostResolverImpl() {
   // Cancel the outstanding jobs. Those jobs may contain several attached
   // requests, which will also be cancelled.
   DiscardIPv6ProbeJob();
 
   CancelAllJobs();
 
   // In case we are being deleted during the processing of a callback.
   if (cur_completing_job_)
     cur_completing_job_->Cancel();
 
   NetworkChangeNotifier::RemoveIPAddressObserver(this);
+#if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_OPENBSD)
+  NetworkChangeNotifier::RemoveDNSObserver(this);
+#endif
 
   // Delete the job pools.
   for (size_t i = 0u; i < arraysize(job_pools_); ++i)
     delete job_pools_[i];
 }
 
 void HostResolverImpl::ProbeIPv6Support() {
   DCHECK(CalledOnValidThread());
   DCHECK(!ipv6_probe_monitoring_);
   ipv6_probe_monitoring_ = true;
@@ skipping 488 matching lines @@
   if (HaveOnlyLoopbackAddresses()) {
     additional_resolver_flags_ |= HOST_RESOLVER_LOOPBACK_ONLY;
   } else {
     additional_resolver_flags_ &= ~HOST_RESOLVER_LOOPBACK_ONLY;
   }
 #endif
   AbortAllInProgressJobs();
   // |this| may be deleted inside AbortAllInProgressJobs().
 }
 
+void HostResolverImpl::OnDNSChanged() {
+  // If the DNS server has changed, existing cached info could be wrong so we
+  // have to drop our internal cache :( Note that OS level DNS caches, such
+  // as NSCD's cache should be dropped automatically by the OS when
+  // resolv.conf changes so we don't need to do anything to clear that cache.
+  if (cache_.get())
+    cache_->clear();
+  // Existing jobs will have been sent to the original server so they need to
+  // be aborted. TODO(Craig): Should these jobs be restarted?
+  AbortAllInProgressJobs();
+  // |this| may be deleted inside AbortAllInProgressJobs().
+}
+
 }  // namespace net