netdev - Re: [PATCH bpf-next v2 1/5] bpf: Support injecting chain calls into BPF programs on load

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Date:   Sat, 05 Oct 2019 12:32:18 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Marek Majkowski <marek@...udflare.com>,
        Lorenz Bauer <lmb@...udflare.com>,
        Alan Maguire <alan.maguire@...cle.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 1/5] bpf: Support injecting chain calls into BPF programs on load

Jakub Kicinski <jakub.kicinski@...ronome.com> writes:

>> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
>> index 5b9d22338606..753abfb78c13 100644
>> --- a/include/linux/bpf.h
>> +++ b/include/linux/bpf.h
>> @@ -383,6 +383,7 @@ struct bpf_prog_aux {
>>  	struct list_head ksym_lnode;
>>  	const struct bpf_prog_ops *ops;
>>  	struct bpf_map **used_maps;
>> +	struct bpf_array *chain_progs;
>>  	struct bpf_prog *prog;
>>  	struct user_struct *user;
>>  	u64 load_time; /* ns since boottime */
>> @@ -443,6 +444,7 @@ struct bpf_array {
>>  
>>  #define BPF_COMPLEXITY_LIMIT_INSNS      1000000 /* yes. 1M insns */
>>  #define MAX_TAIL_CALL_CNT 32
>> +#define BPF_NUM_CHAIN_SLOTS 8
>
> This could be user arg? Also the behaviour of mapping could be user
> controlled? Perhaps even users could pass the snippet to map the
> return code to the location, one day?

(Forgot to reply to this point).

Yeah, we could make it user-configurable. Or just dynamically increase
the size of the array if we run out. Or do something different with
linked list, as I alluded to in the other reply :)

-Toke