2 files changed, 182 insertions, 4 deletions

diff --git a/net/base/network_change_notifier_linux.cc b/net/base/network_change_notifier_linux.cc
index e6eba24..647a2ad 100644
--- a/net/base/network_change_notifier_linux.cc
+++ b/net/base/network_change_notifier_linux.cc
@@ -4,9 +4,156 @@
 
 #include "net/base/network_change_notifier_linux.h"
 
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/rtnetlink.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "base/message_loop.h"
+#include "net/base/net_errors.h"
+
 namespace net {
 
-NetworkChangeNotifierLinux::NetworkChangeNotifierLinux() {}
-NetworkChangeNotifierLinux::~NetworkChangeNotifierLinux() {}
+namespace {
+
+const int kInvalidSocket = -1;
+
+// Return true on success, false on failure.
+// Too small a function to bother putting in a library?
+bool SetNonBlocking(int fd) {
+  int flags = fcntl(fd, F_GETFL, 0);
+  if (-1 == flags)
+    return false;
+  return fcntl(fd, F_SETFL, flags | O_NONBLOCK) == 0 ? true : false;
+}
+
+}  // namespace
+
+NetworkChangeNotifierLinux::NetworkChangeNotifierLinux()
+    : netlink_fd_(kInvalidSocket),
+      loop_(MessageLoopForIO::current()) {
+  netlink_fd_ = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
+  if (netlink_fd_ < 0) {
+    PLOG(ERROR) << "Error creating netlink socket";
+    return;
+  }
+
+  if (!SetNonBlocking(netlink_fd_)) {
+    PLOG(ERROR) << "Failed to set netlink socket to non-blocking mode.";
+    if (close(netlink_fd_) != 0)
+      PLOG(ERROR) << "Failed to close socket";
+    netlink_fd_ = kInvalidSocket;
+    return;
+  }
+
+  memset(&local_addr_, 0, sizeof(local_addr_));
+  local_addr_.nl_family = AF_NETLINK;
+  local_addr_.nl_pid = getpid();
+  local_addr_.nl_groups =
+      RTMGRP_IPV4_IFADDR | RTMGRP_IPV6_IFADDR | RTMGRP_NOTIFY;
+  int ret = bind(netlink_fd_, reinterpret_cast<struct sockaddr*>(&local_addr_),
+                 sizeof(local_addr_));
+  if (ret < 0) {
+    PLOG(ERROR) << "Error binding netlink socket";
+    if (close(netlink_fd_) != 0)
+      PLOG(ERROR) << "Failed to close socket";
+    netlink_fd_ = kInvalidSocket;
+    return;
+  }
+
+  ListenForNotifications();
+}
+
+NetworkChangeNotifierLinux::~NetworkChangeNotifierLinux() {
+  if (netlink_fd_ != kInvalidSocket) {
+    if (close(netlink_fd_) != 0)
+      PLOG(ERROR) << "Failed to close socket";
+    netlink_fd_ = kInvalidSocket;
+    netlink_watcher_.StopWatchingFileDescriptor();
+  }
+}
+
+void NetworkChangeNotifierLinux::OnFileCanReadWithoutBlocking(int fd) {
+  DCHECK_EQ(fd, netlink_fd_);
+
+  ListenForNotifications();
+}
+
+void NetworkChangeNotifierLinux::OnFileCanWriteWithoutBlocking(int /* fd */) {
+  NOTREACHED();
+}
+
+void NetworkChangeNotifierLinux::ListenForNotifications() {
+  char buf[4096];
+  int rv = ReadNotificationMessage(buf, arraysize(buf));
+  while (rv > 0 ) {
+    const struct nlmsghdr* netlink_message_header =
+        reinterpret_cast<struct nlmsghdr*>(buf);
+    HandleNotifications(netlink_message_header, rv);
+    rv = ReadNotificationMessage(buf, arraysize(buf));
+  }
+
+  if (rv == ERR_IO_PENDING) {
+    rv = loop_->WatchFileDescriptor(
+        netlink_fd_, false, MessageLoopForIO::WATCH_READ, &netlink_watcher_,
+        this);
+    LOG_IF(ERROR, !rv) << "Failed to watch netlink socket: " << netlink_fd_;
+  }
+}
+
+int NetworkChangeNotifierLinux::ReadNotificationMessage(char* buf, size_t len) {
+  DCHECK_NE(len, 0u);
+  DCHECK(buf);
+
+  memset(buf, 0, sizeof(buf));
+  int rv = recv(netlink_fd_, buf, len, 0);
+  if (rv > 0) {
+    return rv;
+  } else {
+    DCHECK_NE(rv, 0);
+    if (errno != EAGAIN && errno != EWOULDBLOCK) {
+      PLOG(DFATAL) << "recv";
+      return ERR_FAILED;
+    }
+
+    return ERR_IO_PENDING;
+  }
+}
+
+void NetworkChangeNotifierLinux::HandleNotifications(
+    const struct nlmsghdr* netlink_message_header, size_t len) {
+  DCHECK(netlink_message_header);
+  for (; NLMSG_OK(netlink_message_header, len);
+       netlink_message_header = NLMSG_NEXT(netlink_message_header, len)) {
+    int netlink_message_type = netlink_message_header->nlmsg_type;
+    switch (netlink_message_type) {
+      case NLMSG_DONE:
+        NOTREACHED()
+            << "This is a monitoring netlink socket.  It should never be done.";
+        return;
+      case NLMSG_ERROR:
+        LOG(ERROR) << "Unexpected netlink error.";
+        return;
+      // During IP address changes, we will see all these messages.  Only fire
+      // the notification when we get a new address or remove an address.  We
+      // may still end up notifying observers more than strictly necessary, but
+      // if the primary interface goes down and back up, then this is necessary.
+      case RTM_NEWADDR:
+      case RTM_DELADDR:
+        helper_.OnIPAddressChanged();
+        return;
+      case RTM_NEWLINK:
+      case RTM_DELLINK:
+        return;
+      default:
+        LOG(DFATAL) << "Received unexpected netlink message type: "
+                    << netlink_message_type;
+        return;
+    }
+  }
+}
 
 }  // namespace net
diff --git a/net/base/network_change_notifier_linux.h b/net/base/network_change_notifier_linux.h
index 78111c9..609c9c8 100644
--- a/net/base/network_change_notifier_linux.h
+++ b/net/base/network_change_notifier_linux.h
@@ -5,15 +5,25 @@
 #ifndef NET_BASE_NETWORK_CHANGE_NOTIFIER_LINUX_H_
 #define NET_BASE_NETWORK_CHANGE_NOTIFIER_LINUX_H_
 
+// socket.h is needed to define types for the linux kernel header netlink.h
+// so it needs to come before netlink.h.
+#include <sys/socket.h>
+#include <linux/netlink.h>
 #include "base/basictypes.h"
+#include "base/message_loop.h"
 #include "net/base/network_change_notifier_helper.h"
 
+struct nlmsghdr;
+
 namespace net {
 
-class NetworkChangeNotifierLinux : public NetworkChangeNotifier {
+class NetworkChangeNotifierLinux
+    : public NetworkChangeNotifier, public MessageLoopForIO::Watcher {
  public:
   NetworkChangeNotifierLinux();
 
+  // NetworkChangeNotifier methods:
+
   virtual void AddObserver(Observer* observer) {
     helper_.AddObserver(observer);
   }
@@ -22,13 +32,34 @@ class NetworkChangeNotifierLinux : public NetworkChangeNotifier {
     helper_.RemoveObserver(observer);
   }
 
+  // MessageLoopForIO::Watcher methods:
+
+  virtual void OnFileCanReadWithoutBlocking(int fd);
+  virtual void OnFileCanWriteWithoutBlocking(int /* fd */);
+
  private:
   virtual ~NetworkChangeNotifierLinux();
 
-  void OnIPAddressChanged() { helper_.OnIPAddressChanged(); }
+  // Starts listening for netlink messages.  Also handles the messages if there
+  // are any available on the netlink socket.
+  void ListenForNotifications();
+
+  // Attempts to read from the netlink socket into |buf| of length |len|.
+  // Returns the bytes read on synchronous success and ERR_IO_PENDING if the
+  // recv() would block.  Otherwise, it returns a net error code.
+  int ReadNotificationMessage(char* buf, size_t len);
+
+  // Handles the netlink message and notifies the observers.
+  void HandleNotifications(
+      const struct nlmsghdr* netlink_message_header, size_t len);
 
   internal::NetworkChangeNotifierHelper helper_;
 
+  int netlink_fd_;  // This is the netlink socket descriptor.
+  struct sockaddr_nl local_addr_;
+  MessageLoopForIO* const loop_;
+  MessageLoopForIO::FileDescriptorWatcher netlink_watcher_;
+
   DISALLOW_COPY_AND_ASSIGN(NetworkChangeNotifierLinux);
 };