netfilter: conntrack: add nf_ct_iter_data object for nf_ct_iterate_cleanup*()

This patch adds a structure to collect all the context data that is
passed to the cleanup iterator.

struct nf_ct_iter_data {
struct net *net;
void *data;
u32 portid;
int report;
};

There is a netns field that allows to clean up conntrack entries
specifically owned by the specified netns.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nf_nat_masquerade: add netns refcount tracker to masq_dev_work

If compiled with CONFIG_NET_NS_REFCNT_TRACKER=y,
using put_net_track() in iterate_cleanup_work()
and netns_tracker_alloc() in nf_nat_masq_schedule()
might help us finding netns refcount imbalances.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nf_nat_masquerade: defer conntrack walk to work queue

The ipv4 and device notifiers are called with RTNL mutex held.
The table walk can take some time, better not block other RTNL users.

'ip a' has been reported to block for up to 20 seconds when conntrack table
has many entries and device down events are frequent (e.g., PPP).

Reported-and-tested-by: Martin Zaharinov <micron10@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nf_nat_masquerade: make async masq_inet6_event handling generic

masq_inet6_event is called asynchronously from system work queue,
because the inet6 notifier is atomic and nf_iterate_cleanup can sleep.

The ipv4 and device notifiers call nf_iterate_cleanup directly.

This is legal, but these notifiers are called with RTNL mutex held.
A large conntrack table with many devices coming and going will have severe
impact on the system usability, with 'ip a' blocking for several seconds.

This change places the defer code into a helper and makes it more
generic so ipv4 and ifdown notifiers can be converted to defer the
cleanup walk as well in a follow patch.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nf_nat_masquerade: unify ipv4/6 notifier registration

Only reason for having two different register functions was because of
ipt_MASQUERADE and ip6t_MASQUERADE being two different modules.

Previous patch merged those into xt_MASQUERADE, so we can merge this too.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nf_nat: merge ip/ip6 masquerade headers

Both are now implemented by nf_nat_masquerade.c, so no need to keep
different headers.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nat: don't register device notifier twice

Otherwise, we get notifier list corruption.

This is the most simple fix: remove the device notifier call chain
from the ipv6 masquerade register function and handle it only
in the ipv4 version.

The better fix is merge
nf_nat_masquerade_ipv4/6_(un)register_notifier
into a single
nf_nat_masquerade_(un)register_notifiers

but to do this its needed to first merge the two masquerade modules
into a single xt_MASQUERADE.

Furthermore, we need to use different refcounts for ipv4/ipv6
until we can merge MASQUERADE.

Fixes: d1aca8ab3104a ("netfilter: nat: merge ipv4 and ipv6 masquerade functionality")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nat: merge ipv4 and ipv6 masquerade functionality

Before:
text data bss dec hex filename
13916 1412 4128 19456 4c00 nf_nat.ko
4510 968 4 5482 156a nf_nat_ipv4.ko
5146 944 8 6098 17d2 nf_nat_ipv6.ko

After:
text data bss dec hex filename
16566 1576 4136 22278 5706 nf_nat.ko
3187 844 0 4031 fbf nf_nat_ipv4.ko
3598 844 0 4442 115a nf_nat_ipv6.ko

... so no drastic changes in combined size.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>