conntrack nf_confirm logic cannot handle cloned skbs referencing
the same nf_conn entry, which will happen for multicast (broadcast)
frames on bridges.
Example:
macvlan0
|
br0
/ \
ethX ethY
ethX (or Y) receives a L2 multicast or broadcast packet containing
an IP packet, flow is not yet in conntrack table.
1. skb passes through bridge and fake-ip (br_netfilter)Prerouting.
-> skb->_nfct now references a unconfirmed entry
2. skb is broad/mcast packet. bridge now passes clones out on each bridge
interface.
3. skb gets passed up the stack.
4. In macvlan case, macvlan driver retains clone(s) of the mcast skb
and schedules a work queue to send them out on the lower devices.
The clone skb->_nfct is not a copy, it is the same entry as the
original skb. The macvlan rx handler then returns RX_HANDLER_PASS.
5. Normal conntrack hooks (in NF_INET_LOCAL_IN) confirm the orig skb.
The Macvlan broadcast worker and normal confirm path will race.
This race will not happen if step 2 already confirmed a clone. In that
case later steps perform skb_clone() with skb->_nfct already confirmed (in
hash table). This works fine.
But such confirmation won't happen when eb/ip/nftables rules dropped the
packets before they reached the nf_confirm step in postrouting.
Pablo points out that nf_conntrack_bridge doesn't allow use of stateful
nat, so we can safely discard the nf_conn entry and let inet call
conntrack again.
This doesn't work for bridge netfilter: skb could have a nat
transformation. Also bridge nf prevents re-invocation of inet prerouting
via 'sabotage_in' hook.
Work around this problem by explicit confirmation of the entry at LOCAL_IN
time, before upper layer has a chance to clone the unconfirmed entry.
The downside is that this disables NAT and conntrack helpers.
Alternative fix would be to add locking to all code parts that deal with
unconfirmed packets, but even if that could be done in a sane way this
opens up other problems, for example:
-m physdev --physdev-out eth0 -j SNAT --snat-to 1.2.3.4
-m physdev --physdev-out eth1 -j SNAT --snat-to 1.2.3.5
For multicast case, only one of such conflicting mappings will be
created, conntrack only handles 1:1 NAT mappings.
Users should set create a setup that explicitly marks such traffic
NOTRACK (conntrack bypass) to avoid this, but we cannot auto-bypass
them, ruleset might have accept rules for untracked traffic already,
so user-visible behaviour would change.
Suggested-by: Pablo Neira Ayuso <pablo@netfilter.org>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217777
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
When unoffloading a device, it is important to ensure that all
relevant deferred events are delivered to it before it disassociates
itself from the bridge.
Before this change, this was true for the normal case when a device
maps 1:1 to a net_bridge_port, i.e.
br0
/
swp0
When swp0 leaves br0, the call to switchdev_deferred_process() in
del_nbp() makes sure to process any outstanding events while the
device is still associated with the bridge.
In the case when the association is indirect though, i.e. when the
device is attached to the bridge via an intermediate device, like a
LAG...
br0
/
lag0
/
swp0
...then detaching swp0 from lag0 does not cause any net_bridge_port to
be deleted, so there was no guarantee that all events had been
processed before the device disassociated itself from the bridge.
Fix this by always synchronously processing all deferred events before
signaling completion of unoffloading back to the driver.
Fixes: 4e51bf44a03a ("net: bridge: move the switchdev object replay helpers to "push" mode")
Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Before this change, generation of the list of MDB events to replay
would race against the creation of new group memberships, either from
the IGMP/MLD snooping logic or from user configuration.
While new memberships are immediately visible to walkers of
br->mdb_list, the notification of their existence to switchdev event
subscribers is deferred until a later point in time. So if a replay
list was generated during a time that overlapped with such a window,
it would also contain a replay of the not-yet-delivered event.
The driver would thus receive two copies of what the bridge internally
considered to be one single event. On destruction of the bridge, only
a single membership deletion event was therefore sent. As a
consequence of this, drivers which reference count memberships (at
least DSA), would be left with orphan groups in their hardware
database when the bridge was destroyed.
This is only an issue when replaying additions. While deletion events
may still be pending on the deferred queue, they will already have
been removed from br->mdb_list, so no duplicates can be generated in
that scenario.
To a user this meant that old group memberships, from a bridge in
which a port was previously attached, could be reanimated (in
hardware) when the port joined a new bridge, without the new bridge's
knowledge.
For example, on an mv88e6xxx system, create a snooping bridge and
immediately add a port to it:
root@infix-06-0b-00:~$ ip link add dev br0 up type bridge mcast_snooping 1 && \
> ip link set dev x3 up master br0
And then destroy the bridge:
root@infix-06-0b-00:~$ ip link del dev br0
root@infix-06-0b-00:~$ mvls atu
ADDRESS FID STATE Q F 0 1 2 3 4 5 6 7 8 9 a
DEV:0 Marvell 88E6393X
33:33:00:00:00:6a 1 static - - 0 . . . . . . . . . .
33:33:ff:87:e4:3f 1 static - - 0 . . . . . . . . . .
ff:ff:ff:ff:ff:ff 1 static - - 0 1 2 3 4 5 6 7 8 9 a
root@infix-06-0b-00:~$
The two IPv6 groups remain in the hardware database because the
port (x3) is notified of the host's membership twice: once via the
original event and once via a replay. Since only a single delete
notification is sent, the count remains at 1 when the bridge is
destroyed.
Then add the same port (or another port belonging to the same hardware
domain) to a new bridge, this time with snooping disabled:
root@infix-06-0b-00:~$ ip link add dev br1 up type bridge mcast_snooping 0 && \
> ip link set dev x3 up master br1
All multicast, including the two IPv6 groups from br0, should now be
flooded, according to the policy of br1. But instead the old
memberships are still active in the hardware database, causing the
switch to only forward traffic to those groups towards the CPU (port
0).
Eliminate the race in two steps:
1. Grab the write-side lock of the MDB while generating the replay
list.
This prevents new memberships from showing up while we are generating
the replay list. But it leaves the scenario in which a deferred event
was already generated, but not delivered, before we grabbed the
lock. Therefore:
2. Make sure that no deferred version of a replay event is already
enqueued to the switchdev deferred queue, before adding it to the
replay list, when replaying additions.
Fixes: 4f2673b3a2b6 ("net: bridge: add helper to replay port and host-joined mdb entries")
Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The original idea of the delay_time check was to not apply multicast
snooping too early when an MLD querier appears. And to instead wait at
least for MLD reports to arrive before switching from flooding to group
based, MLD snooped forwarding, to avoid temporary packet loss.
However in a batman-adv mesh network it was noticed that after 248 days of
uptime 32bit MIPS based devices would start to signal that they had
stopped applying multicast snooping due to missing queriers - even though
they were the elected querier and still sending MLD queries themselves.
While time_is_before_jiffies() generally is safe against jiffies
wrap-arounds, like the code comments in jiffies.h explain, it won't
be able to track a difference larger than ULONG_MAX/2. With a 32bit
large jiffies and one jiffies tick every 10ms (CONFIG_HZ=100) on these MIPS
devices running OpenWrt this would result in a difference larger than
ULONG_MAX/2 after 248 (= 2^32/100/60/60/24/2) days and
time_is_before_jiffies() would then start to return false instead of
true. Leading to multicast snooping not being applied to multicast
packets anymore.
Fix this issue by using a proper timer_list object which won't have this
ULONG_MAX/2 difference limitation.
Fixes: b00589af3b04 ("bridge: disable snooping if there is no querier")
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://lore.kernel.org/r/20240127175033.9640-1-linus.luessing@c0d3.blue
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
An skb can be added to a neigh->arp_queue while waiting for an arp
reply. Where original skb's skb->dev can be different to neigh's
neigh->dev. For instance in case of bridging dnated skb from one veth to
another, the skb would be added to a neigh->arp_queue of the bridge.
As skb->dev can be reset back to nf_bridge->physindev and used, and as
there is no explicit mechanism that prevents this physindev from been
freed under us (for instance neigh_flush_dev doesn't cleanup skbs from
different device's neigh queue) we can crash on e.g. this stack:
arp_process
neigh_update
skb = __skb_dequeue(&neigh->arp_queue)
neigh_resolve_output(..., skb)
...
br_nf_dev_xmit
br_nf_pre_routing_finish_bridge_slow
skb->dev = nf_bridge->physindev
br_handle_frame_finish
Let's use plain ifindex instead of net_device link. To peek into the
original net_device we will use dev_get_by_index_rcu(). Thus either we
get device and are safe to use it or we don't get it and drop skb.
Fixes: c4e70a87d975 ("netfilter: bridge: rename br_netfilter.c to br_netfilter_hooks.c")
Suggested-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
It appears that there is a typo in the code where the nlattr array is
being parsed with policy br_cfm_cc_ccm_tx_policy, but the instance is
being accessed via IFLA_BRIDGE_CFM_CC_RDI_INSTANCE, which is associated
with the policy br_cfm_cc_rdi_policy.
This problem was introduced by commit 2be665c3940d ("bridge: cfm: Netlink
SET configuration Interface.").
Though it seems like a harmless typo since these two enum owns the exact
same value (1 here), it is quite misleading hence fix it by using the
correct enum IFLA_BRIDGE_CFM_CC_CCM_TX_INSTANCE here.
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Reviewed-by: Simon Horman <horms@kernel.org>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Implement MDB bulk deletion support in the bridge driver, allowing MDB entries to be deleted in bulk according to provided parameters. Signed-off-by: Ido Schimmel <idosch@nvidia.com> Reviewed-by: Petr Machata <petrm@nvidia.com> Acked-by: Nikolay Aleksandrov <razor@blackwall.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Add kAPI/uAPI field for bridge doc. Update struct net_bridge_vlan comments to fix doc build warning. Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com> Signed-off-by: Hangbin Liu <liuhangbin@gmail.com> Acked-by: Nikolay Aleksandrov <razor@blackwall.org> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
K2CI reported a problem:
consume_skb(skb);
return err;
[nf_br_ip_fragment() error] uninitialized symbol 'err'.
err is not initialized, because returning 0 is expected, initialize err
to 0.
Fixes: 3c171f496ef5 ("netfilter: bridge: add connection tracking system")
Reported-by: k2ci <kernel-bot@kylinos.cn>
Signed-off-by: Linkui Xiao <xiaolinkui@kylinos.cn>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
W=1 builds warn on missing MODULE_DESCRIPTION, add them. Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>