It's a terrible thing to hold dev in iptables target. When the dev is
being removed, unregister_netdevice has to wait for the dev to become
free. dmesg will keep logging the err:
kernel:unregister_netdevice: waiting for veth0_in to become free. \
Usage count = 1
until iptables rules with this target are removed manually.
The worse thing is when deleting a netns, a virtual nic will be deleted
instead of reset to init_net in default_device_ops exit/exit_batch. As
it is earlier than to flush the iptables rules in iptable_filter_net_ops
exit, unregister_netdevice will block to wait for the nic to become free.
As unregister_netdevice is actually waiting for iptables rules flushing
while iptables rules have to be flushed after unregister_netdevice. This
'dead lock' will cause unregister_netdevice to block there forever. As
the netns is not available to operate at that moment, iptables rules can
not even be flushed manually either.
The reproducer can be:
# ip netns add test
# ip link add veth0_in type veth peer name veth0_out
# ip link set veth0_in netns test
# ip netns exec test ip link set lo up
# ip netns exec test ip link set veth0_in up
# ip netns exec test iptables -I INPUT -d 1.2.3.4 -i veth0_in -j \
CLUSTERIP --new --clustermac 89:d4:47:eb:9a:fa --total-nodes 3 \
--local-node 1 --hashmode sourceip-sourceport
# ip netns del test
This issue can be triggered by all virtual nics with ipt_CLUSTERIP.
This patch is to fix it by not holding dev in ipt_CLUSTERIP, but saving
the dev->ifindex instead of the dev.
As Pablo Neira Ayuso's suggestion, it will refresh c->ifindex and dev's
mc by registering a netdevice notifier, just as what xt_TEE does. So it
removes the old codes updating dev's mc, and also no need to initialize
c->ifindex with dev->ifindex.
But as one config can be shared by more than one targets, and the netdev
notifier is per config, not per target. It couldn't get e->ip.iniface
in the notifier handler. So e->ip.iniface has to be saved into config.
Note that for backwards compatibility, this patch doesn't remove the
codes checking if the dev exists before creating a config.
v1->v2:
- As Pablo Neira Ayuso's suggestion, register a netdevice notifier to
manage c->ifindex and dev's mc.
Reported-by: Jianlin Shi <jishi@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
202f59afd4