netdev - Re: pull-request: bpf-next 2025-04-17

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Message-ID: <35f0089e-57a6-4f40-a278-aee4bcfeafac@linux.dev>
Date: Tue, 22 Apr 2025 11:49:26 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Jakub Kicinski <kuba@...nel.org>
Cc: David Miller <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>,
 Andrii Nakryiko <andrii@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Martin KaFai Lau <martin.lau@...nel.org>, netdev@...r.kernel.org,
 bpf@...r.kernel.org, Amery Hung <ameryhung@...il.com>
Subject: Re: pull-request: bpf-next 2025-04-17

On 4/21/25 6:54 PM, Jakub Kicinski wrote:
> On Thu, 17 Apr 2025 11:43:37 -0700 Martin KaFai Lau wrote:
>> 1) bpf qdisc support, from Amery Hung.
>>     A qdisc can be implemented in bpf struct_ops programs and
>>     can be used the same as other existing qdiscs in the
>>     "tc qdisc" command.
> 
> Hm, it doesn't build in allmodconfig. Is there a strong reason for it?

The bpf_qdisc.c is enforcing some correctness in the bpf 
Qdisc_op.{init,reset,destroy}. For example, it ensures that 
qdisc_watchdog_cancel is done in reset/destroy.

It is done by patching the bpf .reset prog and call a kfunc to ensure the 
cleanup work is done. Patching with mod kfunc is not supported now. We can 
consider to directly use BPF_EMIT_CALL to support mod helper call which should 
be simpler verifier changes.