linux-kernel - Re: [PATCH net] bonding: check xdp prog when set bond mode

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Message-ID: <21d52659-622a-4b2a-b091-787bf0f5d67f@blackwall.org>
Date: Fri, 14 Mar 2025 12:22:47 +0200
From: Nikolay Aleksandrov <razor@...ckwall.org>
To: Toke Høiland-Jørgensen <toke@...hat.com>,
 Wang Liang <wangliang74@...wei.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 3/14/25 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
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
should have that flag set.

Cheers,
 Nik