[net] Adds AddressTrackerLinux which keeps track of interface addresses using rtnetlink.

net/base/network_change_notifier_netlink_linux.cc

-// Copyright (c) 2010 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/network_change_notifier_netlink_linux.h"
-
-#include <fcntl.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 <linux/rtnetlink.h>
-#include <string.h>
-#include <unistd.h>
-
-#include "base/logging.h"
-
-namespace {
-
-// 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;
-}
-
-bool IsIPv6Update(const struct nlmsghdr* netlink_message_header) {
-  const struct ifaddrmsg* address_message =
-      reinterpret_cast<struct ifaddrmsg*>(NLMSG_DATA(netlink_message_header));
-  return address_message->ifa_family == AF_INET6;
-}
-
-bool IsDuplicateIPv6AddressUpdate(
-    const struct nlmsghdr* netlink_message_header) {
-  const struct ifaddrmsg* address_message =
-      reinterpret_cast<struct ifaddrmsg*>(NLMSG_DATA(netlink_message_header));
-  int address_message_length = IFA_PAYLOAD(netlink_message_header);
-  const struct rtattr* route_attribute =
-      reinterpret_cast<struct rtattr*>(IFA_RTA(address_message));
-  DCHECK_EQ(address_message->ifa_family, AF_INET6);
-
-  // Look for a cacheinfo attribute, and ignore new address broadcasts
-  // where the updated time stamp is newer than the created time stamp.
-  while (RTA_OK(route_attribute, address_message_length)) {
-    if (route_attribute->rta_type == IFA_CACHEINFO) {
-      struct ifa_cacheinfo* cache_info =
-          reinterpret_cast<struct ifa_cacheinfo*>(RTA_DATA(route_attribute));
-      if (cache_info->cstamp != cache_info->tstamp)
-        return true;
-    }
-    route_attribute = RTA_NEXT(route_attribute, address_message_length);
-  }
-  return false;
-}
-
-}  // namespace
-
-int InitializeNetlinkSocket() {
-  int sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
-  if (sock < 0) {
-    PLOG(ERROR) << "Error creating netlink socket";
-    return -1;
-  }
-
-  if (!SetNonBlocking(sock)) {
-    PLOG(ERROR) << "Failed to set netlink socket to non-blocking mode.";
-    if (close(sock) != 0)
-      PLOG(ERROR) << "Failed to close socket";
-    return -1;
-  }
-
-  struct sockaddr_nl local_addr;
-  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(sock, reinterpret_cast<struct sockaddr*>(&local_addr),
-                 sizeof(local_addr));
-  if (ret < 0) {
-    PLOG(ERROR) << "Error binding netlink socket";
-    if (close(sock) != 0)
-      PLOG(ERROR) << "Failed to close socket";
-    return -1;
-  }
-
-  return sock;
-}
-
-bool HandleNetlinkMessage(char* buf, size_t len) {
-  const struct nlmsghdr* netlink_message_header =
-      reinterpret_cast<struct nlmsghdr*>(buf);
-  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 false;
-      case NLMSG_ERROR:
-        LOG(ERROR) << "Unexpected netlink error.";
-        return false;
-      // 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:
-        if (IsIPv6Update(netlink_message_header) &&
-            IsDuplicateIPv6AddressUpdate(netlink_message_header))
-          return false;
-        return true;
-      case RTM_DELADDR:
-        return true;
-      case RTM_NEWLINK:
-      case RTM_DELLINK:
-        return false;
-      default:
-        LOG(DFATAL) << "Received unexpected netlink message type: "
-                    << netlink_message_type;
-        return false;
-    }
-  }
-
-  return false;
-}