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batman-adv: Add inconsistent hardif netlink dump detection

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The netlink dump functionality transfers a large number of entries from the
kernel to userspace. It is rather likely that the transfer has to
interrupted and later continued. During that time, it can happen that
either new entries are added or removed. The userspace could than either
receive some entries multiple times or miss entries.

Commit 670dc2833d ("netlink: advertise incomplete dumps") introduced a
mechanism to inform userspace about this problem. Userspace can then decide
whether it is necessary or not to retry dumping the information again.

The netlink dump functions have to be switched to exclusive locks to avoid
changes while the current message is prepared. And an external generation
sequence counter is introduced which tracks all modifications of the list.

Reported-by: Matthias Schiffer <mschiffer@universe-factory.net>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
This commit is contained in:
Sven Eckelmann
2018-10-30 22:01:24 +01:00
committed by Simon Wunderlich
parent 9264c85c8b
commit fb69be6979
4 changed files with 19 additions and 10 deletions
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3
net/batman-adv/hard-interface.c
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@@ -951,6 +951,7 @@ batadv_hardif_add_interface(struct net_device *net_dev)
batadv_check_known_mac_addr(hard_iface->net_dev);
kref_get(&hard_iface->refcount);
list_add_tail_rcu(&hard_iface->list, &batadv_hardif_list);
batadv_hardif_generation++;
return hard_iface;
@@ -993,6 +994,7 @@ void batadv_hardif_remove_interfaces(void)
list_for_each_entry_safe(hard_iface, hard_iface_tmp,
&batadv_hardif_list, list) {
list_del_rcu(&hard_iface->list);
batadv_hardif_generation++;
batadv_hardif_remove_interface(hard_iface);
}
rtnl_unlock();
@@ -1054,6 +1056,7 @@ static int batadv_hard_if_event(struct notifier_block *this,
case NETDEV_UNREGISTER:
case NETDEV_PRE_TYPE_CHANGE:
list_del_rcu(&hard_iface->list);
batadv_hardif_generation++;
batadv_hardif_remove_interface(hard_iface);
break;