Message-ID: <6ea34ad0-8456-4e49-8eb1-372cf571d91b@blackwall.org>
Date: Mon, 17 Mar 2025 09:39:09 +0200
From: Nikolay Aleksandrov <razor@...ckwall.org>
To: Wang Liang <wangliang74@...wei.com>,
 Toke Høiland-Jørgensen <toke@...hat.com>,
 jv@...sburgh.net, andrew+netdev@...n.ch, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, ast@...nel.org,
 daniel@...earbox.net, hawk@...nel.org, john.fastabend@...il.com,
 joamaki@...il.com
Cc: yuehaibing@...wei.com, zhangchangzhong@...wei.com,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH net] bonding: check xdp prog when set bond mode

On 3/17/25 06:07, Wang Liang wrote:
> 
> 在 2025/3/14 18:44, Nikolay Aleksandrov 写道:
>> On 3/14/25 12:22 PM, Nikolay Aleksandrov wrote:
>>> On 3/14/25 12:13 PM, Toke Høiland-Jørgensen wrote:
>>>> Wang Liang <wangliang74@...wei.com> writes:
>>>>
>>>>> Following operations can trigger a warning[1]:
>>>>>
>>>>>      ip netns add ns1
>>>>>      ip netns exec ns1 ip link add bond0 type bond mode balance-rr
>>>>>      ip netns exec ns1 ip link set dev bond0 xdp obj af_xdp_kern.o sec xdp
>>>>>      ip netns exec ns1 ip link set bond0 type bond mode broadcast
>>>>>      ip netns del ns1
>>>>>
>>>>> When delete the namespace, dev_xdp_uninstall() is called to remove xdp
>>>>> program on bond dev, and bond_xdp_set() will check the bond mode. If bond
>>>>> mode is changed after attaching xdp program, the warning may occur.
>>>>>
>>>>> Some bond modes (broadcast, etc.) do not support native xdp. Set bond mode
>>>>> with xdp program attached is not good. Add check for xdp program when set
>>>>> bond mode.
>>>>>
>>>>>      [1]
>>>>>      ------------[ cut here ]------------
>>>>>      WARNING: CPU: 0 PID: 11 at net/core/dev.c:9912 unregister_netdevice_many_notify+0x8d9/0x930
>>>>>      Modules linked in:
>>>>>      CPU: 0 UID: 0 PID: 11 Comm: kworker/u4:0 Not tainted 6.14.0-rc4 #107
>>>>>      Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
>>>>>      Workqueue: netns cleanup_net
>>>>>      RIP: 0010:unregister_netdevice_many_notify+0x8d9/0x930
>>>>>      Code: 00 00 48 c7 c6 6f e3 a2 82 48 c7 c7 d0 b3 96 82 e8 9c 10 3e ...
>>>>>      RSP: 0018:ffffc90000063d80 EFLAGS: 00000282
>>>>>      RAX: 00000000ffffffa1 RBX: ffff888004959000 RCX: 00000000ffffdfff
>>>>>      RDX: 0000000000000000 RSI: 00000000ffffffea RDI: ffffc90000063b48
>>>>>      RBP: ffffc90000063e28 R08: ffffffff82d39b28 R09: 0000000000009ffb
>>>>>      R10: 0000000000000175 R11: ffffffff82d09b40 R12: ffff8880049598e8
>>>>>      R13: 0000000000000001 R14: dead000000000100 R15: ffffc90000045000
>>>>>      FS:  0000000000000000(0000) GS:ffff888007a00000(0000) knlGS:0000000000000000
>>>>>      CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>>      CR2: 000000000d406b60 CR3: 000000000483e000 CR4: 00000000000006f0
>>>>>      Call Trace:
>>>>>       <TASK>
>>>>>       ? __warn+0x83/0x130
>>>>>       ? unregister_netdevice_many_notify+0x8d9/0x930
>>>>>       ? report_bug+0x18e/0x1a0
>>>>>       ? handle_bug+0x54/0x90
>>>>>       ? exc_invalid_op+0x18/0x70
>>>>>       ? asm_exc_invalid_op+0x1a/0x20
>>>>>       ? unregister_netdevice_many_notify+0x8d9/0x930
>>>>>       ? bond_net_exit_batch_rtnl+0x5c/0x90
>>>>>       cleanup_net+0x237/0x3d0
>>>>>       process_one_work+0x163/0x390
>>>>>       worker_thread+0x293/0x3b0
>>>>>       ? __pfx_worker_thread+0x10/0x10
>>>>>       kthread+0xec/0x1e0
>>>>>       ? __pfx_kthread+0x10/0x10
>>>>>       ? __pfx_kthread+0x10/0x10
>>>>>       ret_from_fork+0x2f/0x50
>>>>>       ? __pfx_kthread+0x10/0x10
>>>>>       ret_from_fork_asm+0x1a/0x30
>>>>>       </TASK>
>>>>>      ---[ end trace 0000000000000000 ]---
>>>>>
>>>>> Fixes: 9e2ee5c7e7c3 ("net, bonding: Add XDP support to the bonding driver")
>>>>> Signed-off-by: Wang Liang <wangliang74@...wei.com>
>>>>> ---
>>>>>   drivers/net/bonding/bond_options.c | 3 +++
>>>>>   1 file changed, 3 insertions(+)
>>>>>
>>>>> diff --git a/drivers/net/bonding/bond_options.c b/drivers/net/bonding/bond_options.c
>>>>> index 327b6ecdc77e..127181866829 100644
>>>>> --- a/drivers/net/bonding/bond_options.c
>>>>> +++ b/drivers/net/bonding/bond_options.c
>>>>> @@ -868,6 +868,9 @@ static bool bond_set_xfrm_features(struct bonding *bond)
>>>>>   static int bond_option_mode_set(struct bonding *bond,
>>>>>                   const struct bond_opt_value *newval)
>>>>>   {
>>>>> +    if (bond->xdp_prog)
>>>>> +        return -EOPNOTSUPP;
>>>>> +
>>>> Should we allow changing as long as the new mode also supports XDP?
>>>>
>>>> -Toke
>>>>
>>>>
>>> +1
>>> I think we should allow it, the best way probably is to add a new option
>>> BOND_VALFLAG_XDP_UNSUPP (for example) as a bond option flag and to set
>>> it in bond_options.c for each mode that doesn't support XDP, then you
>>> can do the check in a generic way (for any option) in
>>> bond_opt_check_deps. Any bond option that can't be changed with XDP prog
>> err, I meant any bond option's value that isn't supported with XDP, for
>> a whole option it would be a bit different
> Thanks for your suggestions!
> 
> When install xdp prog, bond_xdp_set() use bond_xdp_check() to check whether the bond mode support xdp.
> 
> When uninstall xdp prog, the paramter prog of bond_xdp_set() is NULL. How about not call bond_xdp_check() to avoid the warning when the prog is NULL, like:
> 
> static int bond_xdp_set(struct net_device *dev, struct bpf_prog *prog,
>             struct netlink_ext_ack *extack)
>     ...
>     if (prog && !bond_xdp_check(bond))

No, this could cause other problems. Actually, for -net I think the best would be to stick to
a simpler fix and just do bond_xdp_check() if there's a XDP program attached when changing
the mode so it can be backported easier. The option value flag can be done in the future
if more option values (or options) need to be disabled for XDP.

Cheers,
 Nik

>>> should have that flag set.
>>>
>>> Cheers,
>>>   Nik
>>>
>>

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