[Linux] Listen to and correctly handle IPv6 address change announcements.

net/base/network_change_notifier_netlink_linux.cc

Index: net/base/network_change_notifier_netlink_linux.cc
diff --git a/net/base/network_change_notifier_netlink_linux.cc b/net/base/network_change_notifier_netlink_linux.cc
index 5f71f45a96d217562ad99383b5578cf1eba9b196..493e17ae2c8eb8ac8d7a1d101eedbbe4d9b1f65e 100644
--- a/net/base/network_change_notifier_netlink_linux.cc
+++ b/net/base/network_change_notifier_netlink_linux.cc
@@ -26,6 +26,35 @@ bool SetNonBlocking(int fd) {
   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() {
@@ -46,7 +75,8 @@ int InitializeNetlinkSocket() {
   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_NOTIFY;
+  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) {
@@ -79,6 +109,10 @@ bool HandleNetlinkMessage(char* buf, size_t len) {
       // 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: