On Sat, May 20, 2017 at 05:08:06PM +0800, Xin Long wrote:
> 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 only
> save dev->ifindex instead of dev. When removing the mc from the dev,
> it will get dev by c->ifindex through dev_get_by_index.
>
> Note that it doesn't save dev->name but dev->ifindex, as a dev->name
> can be changed, it will confuse ipt_CLUSTERIP.
>
> Reported-by: Jianlin Shi <jishi@xxxxxxxxxx>
> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
OK. Let's fix this finally... One comment below.
> net/ipv4/netfilter/ipt_CLUSTERIP.c | 31 ++++++++++++++++++-------------
> 1 file changed, 18 insertions(+), 13 deletions(-)
>
> diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c
> index 038f293..d1adb2f 100644
> --- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
> +++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
> @@ -47,7 +47,7 @@ struct clusterip_config {
>
> __be32 clusterip; /* the IP address */
> u_int8_t clustermac[ETH_ALEN]; /* the MAC address */
> - struct net_device *dev; /* device */
> + int ifindex; /* device ifindex */
> u_int16_t num_total_nodes; /* total number of nodes */
> unsigned long local_nodes; /* node number array */
>
> @@ -98,19 +98,23 @@ clusterip_config_put(struct clusterip_config *c)
> * entry(rule) is removed, remove the config from lists, but don't free it
> * yet, since proc-files could still be holding references */
> static inline void
> -clusterip_config_entry_put(struct clusterip_config *c)
> +clusterip_config_entry_put(struct net *net, struct clusterip_config *c)
> {
> - struct net *net = dev_net(c->dev);
> struct clusterip_net *cn = net_generic(net, clusterip_net_id);
>
> local_bh_disable();
> if (refcount_dec_and_lock(&c->entries, &cn->lock)) {
> + struct net_device *dev;
> +
> list_del_rcu(&c->list);
> spin_unlock(&cn->lock);
> local_bh_enable();
>
> - dev_mc_del(c->dev, c->clustermac);
> - dev_put(c->dev);
> + dev = dev_get_by_index(net, c->ifindex);
> + if (dev) {
> + dev_mc_del(dev, c->clustermac);
> + dev_put(dev);
> + }
>
> /* In case anyone still accesses the file, the open/close
> * functions are also incrementing the refcount on their own,
> @@ -182,7 +186,7 @@ clusterip_config_init(const struct ipt_clusterip_tgt_info *i, __be32 ip,
> if (!c)
> return ERR_PTR(-ENOMEM);
>
> - c->dev = dev;
> + c->ifindex = dev->ifindex;
> c->clusterip = ip;
> memcpy(&c->clustermac, &i->clustermac, ETH_ALEN);
> c->num_total_nodes = i->num_total_nodes;
> @@ -427,12 +431,14 @@ static int clusterip_tg_check(const struct xt_tgchk_param *par)
> }
>
> config = clusterip_config_init(cipinfo,
> - e->ip.dst.s_addr, dev);
> + e->ip.dst.s_addr, dev);
> if (IS_ERR(config)) {
> dev_put(dev);
> return PTR_ERR(config);
> }
> - dev_mc_add(config->dev, config->clustermac);
> +
> + dev_mc_add(dev, config->clustermac);
> + dev_put(dev);
> }
> }
> cipinfo->config = config;
> @@ -458,7 +464,7 @@ static void clusterip_tg_destroy(const struct xt_tgdtor_param *par)
>
> /* if no more entries are referencing the config, remove it
> * from the list and destroy the proc entry */
> - clusterip_config_entry_put(cipinfo->config);
> + clusterip_config_entry_put(par->net, cipinfo->config);
>
> clusterip_config_put(cipinfo->config);
>
> @@ -558,10 +564,9 @@ arp_mangle(void *priv,
> * addresses on different interfacs. However, in the CLUSTERIP case
> * this wouldn't work, since we didn't subscribe the mcast group on
> * other interfaces */
> - if (c->dev != state->out) {
> - pr_debug("not mangling arp reply on different "
> - "interface: cip'%s'-skb'%s'\n",
> - c->dev->name, state->out->name);
> + if (c->ifindex != state->out->ifindex) {
I'm missing the code to register_netdevice_notifier() so we can
refresh c->ifindex.
Just like we do in net/netfilter/xt_TEE.c
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