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2aec17f199
Pablo Neira Ayuso says:
====================
the indirect flow_block infrastructure, revisited
This series fixes b5140a36da ("netfilter: flowtable: add indr block
setup support") that adds support for the indirect block for the
flowtable. This patch crashes the kernel with the TC CT action.
[ 630.908086] BUG: kernel NULL pointer dereference, address: 00000000000000f0
[ 630.908233] #PF: error_code(0x0000) - not-present page
[ 630.908304] PGD 800000104addd067 P4D 800000104addd067 PUD 104311d067 PMD 0
[ 630.908380] Oops: 0000 [#1] SMP PTI [ 630.908615] RIP: 0010:nf_flow_table_indr_block_cb+0xc0/0x190 [nf_flow_table]
[ 630.908690] Code: 5b 41 5c 41 5d 41 5e 41 5f 5d c3 4c 89 75 a0 4c 89 65 a8 4d 89 ee 49 89 dd 4c 89 fe 48 c7 c7 b7 64 36 a0 31 c0 e8 ce ed d8 e0 <49> 8b b7 f0 00 00 00 48 c7 c7 c8 64 36 a0 31 c0 e8 b9 ed d8 e0 49[ 630.908790] RSP: 0018:ffffc9000895f8c0 EFLAGS: 00010246
[...]
[ 630.910774] Call Trace:
[ 630.911192] ? mlx5e_rep_indr_setup_block+0x270/0x270 [mlx5_core]
[ 630.911621] ? mlx5e_rep_indr_setup_block+0x270/0x270 [mlx5_core]
[ 630.912040] ? mlx5e_rep_indr_setup_block+0x270/0x270 [mlx5_core]
[ 630.912443] flow_block_cmd+0x51/0x80
[ 630.912844] __flow_indr_block_cb_register+0x26c/0x510
[ 630.913265] mlx5e_nic_rep_netdevice_event+0x9e/0x110 [mlx5_core]
[ 630.913665] notifier_call_chain+0x53/0xa0
[ 630.914063] raw_notifier_call_chain+0x16/0x20
[ 630.914466] call_netdevice_notifiers_info+0x39/0x90
[ 630.914859] register_netdevice+0x484/0x550
[ 630.915256] __ip_tunnel_create+0x12b/0x1f0 [ip_tunnel]
[ 630.915661] ip_tunnel_init_net+0x116/0x180 [ip_tunnel]
[ 630.916062] ipgre_tap_init_net+0x22/0x30 [ip_gre]
[ 630.916458] ops_init+0x44/0x110
[ 630.916851] register_pernet_operations+0x112/0x200
A workaround patch to cure this crash has been proposed. However, there
is another problem: The indirect flow_block still does not work for the
new TC CT action. The problem is that the existing flow_indr_block_entry
callback assumes you can look up for the flowtable from the netdevice to
get the flow_block. This flow_block allows you to offload the flows via
TC_SETUP_CLSFLOWER. Unfortunately, it is not possible to get the
flow_block from the TC CT flowtables because they are _not_ bound to any
specific netdevice.
= What is the indirect flow_block infrastructure?
The indirect flow_block infrastructure allows drivers to offload
tc/netfilter rules that belong to software tunnel netdevices, e.g.
vxlan.
This indirect flow_block infrastructure relates tunnel netdevices with
drivers because there is no obvious way to relate these two things
from the control plane.
= How does the indirect flow_block work before this patchset?
Front-ends register the indirect block callback through
flow_indr_add_block_cb() if they support for offloading tunnel
netdevices.
== Setting up an indirect block
1) Drivers track tunnel netdevices via NETDEV_{REGISTER,UNREGISTER} events.
If there is a new tunnel netdevice that the driver can offload, then the
driver invokes __flow_indr_block_cb_register() with the new tunnel
netdevice and the driver callback. The __flow_indr_block_cb_register()
call iterates over the list of the front-end callbacks.
2) The front-end callback sets up the flow_block_offload structure and it
invokes the driver callback to set up the flow_block.
3) The driver callback now registers the flow_block structure and it
returns the flow_block back to the front-end.
4) The front-end gets the flow_block object and it is now ready to
offload rules for this tunnel netdevice.
A simplified callgraph is represented below.
Front-end Driver
NETDEV_REGISTER
|
__flow_indr_block_cb_register(netdev, cb_priv, driver_cb)
| [1]
.--------------frontend_indr_block_cb(cb_priv, driver_cb)
|
.
setup_flow_block_offload(bo)
| [2]
driver_cb(bo, cb_priv) -----------.
|
\/
set up flow_blocks [3]
|
add rules to flow_block <----------
TC_SETUP_CLSFLOWER [4]
== Releasing the indirect flow_block
There are two possibilities, either tunnel netdevice is removed or
a netdevice (port representor) is removed.
=== Tunnel netdevice is removed
Driver waits for the NETDEV_UNREGISTER event that announces the tunnel
netdevice removal. Then, it calls __flow_indr_block_cb_unregister() to
remove the flow_block and rules. Callgraph is very similar to the one
described above.
=== Netdevice is removed (port representor)
Driver calls __flow_indr_block_cb_unregister() to remove the existing
netfilter/tc rule that belong to the tunnel netdevice.
= How does the indirect flow_block work after this patchset?
Drivers register the indirect flow_block setup callback through
flow_indr_dev_register() if they support for offloading tunnel
netdevices.
== Setting up an indirect flow_block
1) Frontends check if dev->netdev_ops->ndo_setup_tc is unset. If so,
frontends call flow_indr_dev_setup_offload(). This call invokes
the drivers' indirect flow_block setup callback.
2) The indirect flow_block setup callback sets up a flow_block structure
which relates the tunnel netdevice and the driver.
3) The front-end uses flow_block and offload the rules.
Note that the operational to set up (non-indirect) flow_block is very
similar.
== Releasing the indirect flow_block
=== Tunnel netdevice is removed
This calls flow_indr_dev_setup_offload() to set down the flow_block and
remove the offloaded rules. This alternate path is exercised if
dev->netdev_ops->ndo_setup_tc is unset.
=== Netdevice is removed (port representor)
If a netdevice is removed, then it might need to to clean up the
offloaded tc/netfilter rules that belongs to the tunnel netdevice:
1) The driver invokes flow_indr_dev_unregister() when a netdevice is
removed.
2) This call iterates over the existing indirect flow_blocks
and it invokes the cleanup callback to let the front-end remove the
tc/netfilter rules. The cleanup callback already provides the
flow_block that the front-end needs to clean up.
Front-end Driver
|
flow_indr_dev_unregister(...)
|
iterate over list of indirect flow_block
and invoke cleanup callback
|
.-----------------------------
|
.
frontend_flow_block_cleanup(flow_block)
.
|
\/
remove rules to flow_block
TC_SETUP_CLSFLOWER
= About this patchset
This patchset aims to address the existing TC CT problem while
simplifying the indirect flow_block infrastructure. Saving 300 LoC in
the flow_offload core and the drivers. The operational gets aligned with
the (non-indirect) flow_blocks logic. Patchset is composed of:
Patch #1 add nf_flow_table_gc_cleanup() which is required by the
netfilter's flowtable new indirect flow_block approach.
Patch #2 adds the flow_block_indr object which is actually part of
of the flow_block object. This stores the indirect flow_block
metadata such as the tunnel netdevice owner and the cleanup
callback (in case the tunnel netdevice goes away).
This patch adds flow_indr_dev_{un}register() to allow drivers
to offer netdevice tunnel hardware offload to the front-ends.
Then, front-ends call flow_indr_dev_setup_offload() to invoke
the drivers to set up the (indirect) flow_block.
Patch #3 add the tcf_block_offload_init() helper function, this is
a preparation patch to adapt the tc front-end to use this
new indirect flow_block infrastructure.
Patch #4 updates the tc and netfilter front-ends to use the new
indirect flow_block infrastructure.
Patch #5 updates the mlx5 driver to use the new indirect flow_block
infrastructure.
Patch #6 updates the nfp driver to use the new indirect flow_block
infrastructure.
Patch #7 updates the bnxt driver to use the new indirect flow_block
infrastructure.
Patch #8 removes the indirect flow_block infrastructure version 1,
now that frontends and drivers have been translated to
version 2 (coming in this patchset).
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
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