Modify flow table offload to cache the last ct info status that was passed
to the driver offload callbacks by extending enum nf_flow_flags with new
"NF_FLOW_HW_ESTABLISHED" flag. Set the flag if ctinfo was 'established'
during last act_ct meta actions fill call. This infrastructure change is
necessary to optimize promoting of UDP connections from 'new' to
'established' in following patches in this series.
Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Modify flow table offload to support unidirectional connections by
extending enum nf_flow_flags with new "NF_FLOW_HW_BIDIRECTIONAL" flag. Only
offload reply direction when the flag is set. This infrastructure change is
necessary to support offloading UDP NEW connections in original direction
in following patches in series.
Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The for-loop was broken from the start. It translates to:
for (i = 0; i < 4; i += 4)
which means the loop statement is run only once, so only the highest
32-bit of the IPv6 address gets mangled.
Fix the loop increment.
Fixes: 0e07e25b48 ("netfilter: flowtable: fix NAT IPv6 offload mangling")
Fixes: 5c27d8d76c ("netfilter: nf_flow_table_offload: add IPv6 support")
Signed-off-by: Qingfang DENG <dqfext@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
flow_offload_queue_work() can be called in workqueue without
bh disabled, like the call trace showed in my act_ct testing,
calling NF_FLOW_TABLE_STAT_INC() there would cause a call
trace:
BUG: using __this_cpu_add() in preemptible [00000000] code: kworker/u4:0/138560
caller is flow_offload_queue_work+0xec/0x1b0 [nf_flow_table]
Workqueue: act_ct_workqueue tcf_ct_flow_table_cleanup_work [act_ct]
Call Trace:
<TASK>
dump_stack_lvl+0x33/0x46
check_preemption_disabled+0xc3/0xf0
flow_offload_queue_work+0xec/0x1b0 [nf_flow_table]
nf_flow_table_iterate+0x138/0x170 [nf_flow_table]
nf_flow_table_free+0x140/0x1a0 [nf_flow_table]
tcf_ct_flow_table_cleanup_work+0x2f/0x2b0 [act_ct]
process_one_work+0x6a3/0x1030
worker_thread+0x8a/0xdf0
This patch fixes it by using NF_FLOW_TABLE_STAT_INC_ATOMIC()
instead in flow_offload_queue_work().
Note that for FLOW_CLS_REPLACE branch in flow_offload_queue_work(),
it may not be called in preemptible path, but it's good to use
NF_FLOW_TABLE_STAT_INC_ATOMIC() for all cases in
flow_offload_queue_work().
Fixes: b038177636 ("netfilter: nf_flow_table: count pending offload workqueue tasks")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
nf_flow_table_block_setup and the driver TC_SETUP_FT call can modify the flow
block cb list while they are being traversed elsewhere, causing a crash.
Add a write lock around the calls to protect readers
Fixes: c29f74e0df ("netfilter: nf_flow_table: hardware offload support")
Reported-by: Chad Monroe <chad.monroe@smartrg.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
To clear the flow table on flow table free, the following sequence
normally happens in order:
1) gc_step work is stopped to disable any further stats/del requests.
2) All flow table entries are set to teardown state.
3) Run gc_step which will queue HW del work for each flow table entry.
4) Waiting for the above del work to finish (flush).
5) Run gc_step again, deleting all entries from the flow table.
6) Flow table is freed.
But if a flow table entry already has pending HW stats or HW add work
step 3 will not queue HW del work (it will be skipped), step 4 will wait
for the pending add/stats to finish, and step 5 will queue HW del work
which might execute after freeing of the flow table.
To fix the above, this patch flushes the pending work, then it sets the
teardown flag to all flows in the flowtable and it forces a garbage
collector run to queue work to remove the flows from hardware, then it
flushes this new pending work and (finally) it forces another garbage
collector run to remove the entry from the software flowtable.
Stack trace:
[47773.882335] BUG: KASAN: use-after-free in down_read+0x99/0x460
[47773.883634] Write of size 8 at addr ffff888103b45aa8 by task kworker/u20:6/543704
[47773.885634] CPU: 3 PID: 543704 Comm: kworker/u20:6 Not tainted 5.12.0-rc7+ #2
[47773.886745] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009)
[47773.888438] Workqueue: nf_ft_offload_del flow_offload_work_handler [nf_flow_table]
[47773.889727] Call Trace:
[47773.890214] dump_stack+0xbb/0x107
[47773.890818] print_address_description.constprop.0+0x18/0x140
[47773.892990] kasan_report.cold+0x7c/0xd8
[47773.894459] kasan_check_range+0x145/0x1a0
[47773.895174] down_read+0x99/0x460
[47773.899706] nf_flow_offload_tuple+0x24f/0x3c0 [nf_flow_table]
[47773.907137] flow_offload_work_handler+0x72d/0xbe0 [nf_flow_table]
[47773.913372] process_one_work+0x8ac/0x14e0
[47773.921325]
[47773.921325] Allocated by task 592159:
[47773.922031] kasan_save_stack+0x1b/0x40
[47773.922730] __kasan_kmalloc+0x7a/0x90
[47773.923411] tcf_ct_flow_table_get+0x3cb/0x1230 [act_ct]
[47773.924363] tcf_ct_init+0x71c/0x1156 [act_ct]
[47773.925207] tcf_action_init_1+0x45b/0x700
[47773.925987] tcf_action_init+0x453/0x6b0
[47773.926692] tcf_exts_validate+0x3d0/0x600
[47773.927419] fl_change+0x757/0x4a51 [cls_flower]
[47773.928227] tc_new_tfilter+0x89a/0x2070
[47773.936652]
[47773.936652] Freed by task 543704:
[47773.937303] kasan_save_stack+0x1b/0x40
[47773.938039] kasan_set_track+0x1c/0x30
[47773.938731] kasan_set_free_info+0x20/0x30
[47773.939467] __kasan_slab_free+0xe7/0x120
[47773.940194] slab_free_freelist_hook+0x86/0x190
[47773.941038] kfree+0xce/0x3a0
[47773.941644] tcf_ct_flow_table_cleanup_work
Original patch description and stack trace by Paul Blakey.
Fixes: c29f74e0df ("netfilter: nf_flow_table: hardware offload support")
Reported-by: Paul Blakey <paulb@nvidia.com>
Tested-by: Paul Blakey <paulb@nvidia.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
To improve hardware offload debuggability count pending 'add', 'del' and
'stats' flow_table offload workqueue tasks. Counters are incremented before
scheduling new task and decremented when workqueue handler finishes
executing. These counters allow user to diagnose congestion on hardware
offload workqueues that can happen when either CPU is starved and workqueue
jobs are executed at lower rate than new ones are added or when
hardware/driver can't keep up with the rate.
Implement the described counters as percpu counters inside new struct
netns_ft which is stored inside struct net. Expose them via new procfs file
'/proc/net/stats/nf_flowtable' that is similar to existing 'nf_conntrack'
file.
Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
Signed-off-by: Oz Shlomo <ozsh@nvidia.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Pablo Neira Ayuso says:
====================
Netfilter updates for net-next
1) Revert CHECKSUM_UNNECESSARY for UDP packet from conntrack.
2) Reject unsupported families when creating tables, from Phil Sutter.
3) GRE support for the flowtable, from Toshiaki Makita.
4) Add GRE offload support for act_ct, also from Toshiaki.
5) Update mlx5 driver to support for GRE flowtable offload,
from Toshiaki Makita.
6) Oneliner to clean up incorrect indentation in nf_conntrack_bridge,
from Jiapeng Chong.
* git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf-next:
netfilter: bridge: clean up some inconsistent indenting
net/mlx5: Support GRE conntrack offload
act_ct: Support GRE offload
netfilter: flowtable: Support GRE
netfilter: nf_tables: Reject tables of unsupported family
Revert "netfilter: conntrack: mark UDP zero checksum as CHECKSUM_UNNECESSARY"
====================
Link: https://lore.kernel.org/r/20220315091513.66544-1-pablo@netfilter.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
After cited commit optimizted hw insertion, flow table entries are
populated with ifindex information which was intended to only be used
for HW offload. This tuple ifindex is hashed in the flow table key, so
it must be filled for lookup to be successful. But tuple ifindex is only
relevant for the netfilter flowtables (nft), so it's not filled in
act_ct flow table lookup, resulting in lookup failure, and no SW
offload and no offload teardown for TCP connection FIN/RST packets.
To fix this, add new tc ifindex field to tuple, which will
only be used for offloading, not for lookup, as it will not be
part of the tuple hash.
Fixes: 9795ded7f9 ("net/sched: act_ct: Fill offloading tuple iifidx")
Signed-off-by: Paul Blakey <paulb@nvidia.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Previously the IPv6 addresses in the key were clobbered and the mask was
left unset.
I haven't tested this; I noticed it while skimming the code to
understand an unrelated issue.
Fixes: cfab6dbd0e ("netfilter: flowtable: add tunnel match offload support")
Cc: wenxu <wenxu@ucloud.cn>
Signed-off-by: Will Mortensen <willmo@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Currently, when creating an ingress qdisc on an indirect device before
the driver registered for callbacks, the driver will not have a chance
to register its filter configuration callbacks.
To fix that, modify the code such that it keeps track of all the ingress
qdiscs that call flow_indr_dev_setup_offload(). When a driver calls
flow_indr_dev_register(), go through the list of tracked ingress qdiscs
and call the driver callback entry point so as to give it a chance to
register its callback.
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Eli Cohen <elic@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The 'if (dev)' statement already move into dev_{put , hold}, so remove
redundant if statements.
Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
Signed-off-by: David S. Miller <davem@davemloft.net>
Currently the aging period for tcp/udp connections is hard coded to
30 seconds. Aged tcp/udp connections configure a hard coded 120/30
seconds pickup timeout for conntrack.
This configuration may be too aggressive or permissive for some users.
Dynamically configure the nf flow table GC timeout intervals according
to the user defined values.
Signed-off-by: Oz Shlomo <ozsh@nvidia.com>
Reviewed-by: Paul Blakey <paulb@nvidia.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Offloading conns could fail for multiple reasons and a hw refresh bit is
set to try to reoffload it in next sw packet.
But it could be in some cases and future points that the hw refresh bit
is not set but a refresh could succeed.
Remove the hw refresh bit and do offload refresh if requested.
There won't be a new work entry if a work is already pending
anyway as there is the hw pending bit.
Fixes: 8b3646d6e0 ("net/sched: act_ct: Support refreshing the flow table entries")
Signed-off-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Pablo Neira Ayuso says:
====================
Netfilter updates for net-next
The following patchset contains Netfilter updates for net-next:
1) Add vlan match and pop actions to the flowtable offload,
patches from wenxu.
2) Reduce size of the netns_ct structure, which itself is
embedded in struct net Make netns_ct a read-mostly structure.
Patches from Florian Westphal.
3) Add FLOW_OFFLOAD_XMIT_UNSPEC to skip dst check from garbage
collector path, as required by the tc CT action. From Roi Dayan.
4) VLAN offload fixes for nftables: Allow for matching on both s-vlan
and c-vlan selectors. Fix match of VLAN id due to incorrect
byteorder. Add a new routine to properly populate flow dissector
ethertypes.
5) Missing keys in ip{6}_route_me_harder() results in incorrect
routes. This includes an update for selftest infra. Patches
from Ido Schimmel.
6) Add counter hardware offload support through FLOW_CLS_STATS.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
- keep the ZC code, drop the code related to reinit
net/bridge/netfilter/ebtables.c
- fix build after move to net_generic
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This patch adds vlan pop action offload in the flowtable offload.
Signed-off-by: wenxu <wenxu@ucloud.cn>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This patch adds support for vlan_id, vlan_priority and vlan_proto match
for flowtable offload.
Signed-off-by: wenxu <wenxu@ucloud.cn>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Add a PPPoE push action if layer 2 protocol is ETH_P_PPP_SES to add
PPPoE flowtable hardware offload support.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
The switch might have already added the VLAN tag through PVID hardware
offload. Keep this extra VLAN in the flowtable but skip it on egress.
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
If there is a forward path to reach an ethernet device and hardware
offload is enabled, then use the direct xmit path.
Moreover, store the real device in the direct xmit path info since
software datapath uses dev_hard_header() to push the layer encapsulation
headers while hardware offload refers to the real device.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
When the flow tuple xmit_type is set to FLOW_OFFLOAD_XMIT_DIRECT, the
dst_cache pointer is not valid, and the h_source/h_dest/ifidx out fields
need to be used.
This patch also adds the FLOW_ACTION_VLAN_PUSH action to pass the VLAN
tag to the driver.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Currently the flow table offload replace, destroy and stats work items are
executed on a single workqueue. As such, DESTROY and STATS commands may
be backloged after a burst of REPLACE work items. This scenario can bloat
up memory and may cause active connections to age.
Instatiate add, del and stats workqueues to avoid backlogs of non-dependent
actions. Provide sysfs control over the workqueue attributes, allowing
userspace applications to control the workqueue cpumask.
Signed-off-by: Oz Shlomo <ozsh@nvidia.com>
Reviewed-by: Paul Blakey <paulb@nvidia.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Previously, shared blocks were only relevant for the pseudo-qdiscs ingress
and clsact. Recently, a qevent facility was introduced, which allows to
bind blocks to well-defined slots of a qdisc instance. RED in particular
got two qevents: early_drop and mark. Drivers that wish to offload these
blocks will be sent the usual notification, and need to know which qdisc it
is related to.
To that end, extend flow_block_offload with a "sch" pointer, and initialize
as appropriate. This prompts changes in the indirect block facility, which
now tracks the scheduler in addition to the netdevice. Update signatures of
several functions similarly.
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
If the representor is removed, then identify the indirect flow_blocks
that need to be removed by the release callback and the port representor
structure. To identify the port representor structure, a new
indr.cb_priv field needs to be introduced. The flow_block also needs to
be removed from the driver list from the cleanup path.
Fixes: 1fac52da59 ("net: flow_offload: consolidate indirect flow_block infrastructure")
Signed-off-by: wenxu <wenxu@ucloud.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Drivers do not register to netdev events to set up indirect blocks
anymore. Remove __flow_indr_block_cb_register() and
__flow_indr_block_cb_unregister().
The frontends set up the callbacks through flow_indr_dev_setup_block()
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Update existing frontends to use flow_indr_dev_setup_offload().
This new function must be called if ->ndo_setup_tc is unset to deal
with tunnel devices.
If there is no driver that is subscribed to new tunnel device
flow_block bindings, then this function bails out with EOPNOTSUPP.
If the driver module is removed, the ->cleanup() callback removes the
entries that belong to this tunnel device. This cleanup procedures is
triggered when the device unregisters the tunnel device offload handler.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Move the bpf verifier trace check into the new switch statement in
HEAD.
Resolve the overlapping changes in hinic, where bug fixes overlap
the addition of VF support.
Signed-off-by: David S. Miller <davem@davemloft.net>
Gc step can queue offloaded flow del work or stats work.
Those work items can race each other and a flow could be freed
before the stats work is executed and querying it.
To avoid that, add a pending bit that if a work exists for a flow
don't queue another work for it.
This will also avoid adding multiple stats works in case stats work
didn't complete but gc step started again.
Signed-off-by: Paul Blakey <paulb@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This bit indicates that the conntrack entry is offloaded to hardware
flow table. nf_conntrack entry will be tagged with [HW_OFFLOAD] if
it's offload to hardware.
cat /proc/net/nf_conntrack
ipv4 2 tcp 6 \
src=1.1.1.17 dst=1.1.1.16 sport=56394 dport=5001 \
src=1.1.1.16 dst=1.1.1.17 sport=5001 dport=56394 [HW_OFFLOAD] \
mark=0 zone=0 use=3
Note that HW_OFFLOAD/OFFLOAD/ASSURED are mutually exclusive.
Changelog:
* V1->V2:
- Remove check of lastused from stats. It was meant for cases such
as removing driver module while traffic still running. Better to
handle such cases from garbage collector.
Signed-off-by: Bodong Wang <bodong@mellanox.com>
Reviewed-by: Oz Shlomo <ozsh@mellanox.com>
Reviewed-by: Paul Blakey <paulb@mellanox.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Pablo Neira Ayuso says:
====================
Netfilter/IPVS updates for net-next
The following patchset contains Netfilter/IPVS updates for net-next:
1) Add support to specify a stateful expression in set definitions,
this allows users to specify e.g. counters per set elements.
2) Flowtable software counter support.
3) Flowtable hardware offload counter support, from wenxu.
3) Parallelize flowtable hardware offload requests, from Paul Blakey.
This includes a patch to add one work entry per offload command.
4) Several patches to rework nf_queue refcount handling, from Florian
Westphal.
4) A few fixes for the flowtable tunnel offload: Fix crash if tunneling
information is missing and set up indirect flow block as TC_SETUP_FT,
patch from wenxu.
5) Stricter netlink attribute sanity check on filters, from Romain Bellan
and Florent Fourcot.
5) Annotations to make sparse happy, from Jules Irenge.
6) Improve icmp errors in debugging information, from Haishuang Yan.
7) Fix warning in IPVS icmp error debugging, from Haishuang Yan.
8) Fix endianess issue in tcp extension header, from Sergey Marinkevich.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
Store the conntrack counters to the conntrack entry in the
HW flowtable offload.
Signed-off-by: wenxu <wenxu@ucloud.cn>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
To allow offload commands to execute in parallel, create workqueue
for flow table offload, and use a work entry per offload command.
Signed-off-by: Paul Blakey <paulb@mellanox.com>
Reviewed-by: Oz Shlomo <ozsh@mellanox.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Currently flow offload threads are synchronized by the flow block mutex.
Use rw lock instead to increase flow insertion (read) concurrency.
Signed-off-by: Paul Blakey <paulb@mellanox.com>
Reviewed-by: Oz Shlomo <ozsh@mellanox.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
The indirect block setup should use TC_SETUP_FT as the type instead of
TC_SETUP_BLOCK. Adjust existing users of the indirect flow block
infrastructure.
Fixes: b5140a36da ("netfilter: flowtable: add indr block setup support")
Signed-off-by: wenxu <wenxu@ucloud.cn>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Overlapping header include additions in macsec.c
A bug fix in 'net' overlapping with the removal of 'version'
string in ena_netdev.c
Overlapping test additions in selftests Makefile
Overlapping PCI ID table adjustments in iwlwifi driver.
Signed-off-by: David S. Miller <davem@davemloft.net>
nf_flow_rule_match() sets control.addr_type in key, so needs to also set
the corresponding mask. An exact match is wanted, so mask is all ones.
Fixes: c29f74e0df ("netfilter: nf_flow_table: hardware offload support")
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
The tc ct action does not cache the route in the flowtable entry.
Fixes: 88bf6e4114 ("netfilter: flowtable: add tunnel encap/decap action offload support")
Fixes: cfab6dbd0e ("netfilter: flowtable: add tunnel match offload support")
Signed-off-by: wenxu <wenxu@ucloud.cn>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This patch add tunnel encap decap action offload in the flowtable
offload.
Signed-off-by: wenxu <wenxu@ucloud.cn>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This patch support both ipv4 and ipv6 tunnel_id, tunnel_src and
tunnel_dst match for flowtable offload
Signed-off-by: wenxu <wenxu@ucloud.cn>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Add etfilter flowtable support indr-block setup. It makes flowtable offload
vlan and tunnel device.
Signed-off-by: wenxu <wenxu@ucloud.cn>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
NF flow table API associate 5-tuple rule with an action list by calling
the flow table type action() CB to fill the rule's actions.
In action CB of act_ct, populate the ct offload entry actions with a new
ct_metadata action. Initialize the ct_metadata with the ct mark, label and
zone information. If ct nat was performed, then also append the relevant
packet mangle actions (e.g. ipv4/ipv6/tcp/udp header rewrites).
Drivers that offload the ft entries may match on the 5-tuple and perform
the action list.
Signed-off-by: Paul Blakey <paulb@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Let drivers to add their cb allowing them to receive flow offload events
of type TC_SETUP_CLSFLOWER (REPLACE/DEL/STATS) for flows managed by the
flow table.
Signed-off-by: Paul Blakey <paulb@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
nftables test case
tests/shell/testcases/flowtable/0001flowtable_0
results in a crash. After the refactor, if we leave early via
nf_flowtable_hw_offload(), then "struct flow_block_offload" is left
in an uninitialized state, but later users assume its initialised.
Fixes: a7965d58dd ("netfilter: flowtable: add nf_flow_table_offload_cmd()")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>