netdev - Re: [PATCH] Add skb_store_bytes() for BPF_PROG_TYPE_CGROUP

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Date:   Thu, 6 Jan 2022 14:35:53 -0800
From:   Yonghong Song <yhs@...com>
To:     "Tyler Wear (QUIC)" <quic_twear@...cinc.com>,
        Martin KaFai Lau <kafai@...com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "maze@...gle.com" <maze@...gle.com>
Subject: Re: [PATCH] Add skb_store_bytes() for BPF_PROG_TYPE_CGROUP_SKB



On 1/6/22 9:18 AM, Tyler Wear (QUIC) wrote:
> 
> 
>> -----Original Message-----
>> From: Yonghong Song <yhs@...com>
>> Sent: Wednesday, January 5, 2022 11:51 PM
>> To: Tyler Wear (QUIC) <quic_twear@...cinc.com>; Martin KaFai Lau <kafai@...com>
>> Cc: netdev@...r.kernel.org; bpf@...r.kernel.org; maze@...gle.com
>> Subject: Re: [PATCH] Add skb_store_bytes() for BPF_PROG_TYPE_CGROUP_SKB
>>
>> WARNING: This email originated from outside of Qualcomm. Please be wary of any links or attachments, and do not enable macros.
>>
>> On 1/4/22 4:27 PM, Tyler Wear (QUIC) wrote:
>>>
>>>
>>>> -----Original Message-----
>>>> From: Martin KaFai Lau <kafai@...com>
>>>> Sent: Wednesday, December 29, 2021 1:06 PM
>>>> To: Tyler Wear <twear@...cinc.com>
>>>> Cc: Yonghong Song <yhs@...com>; Tyler Wear (QUIC)
>>>> <quic_twear@...cinc.com>; netdev@...r.kernel.org;
>>>> bpf@...r.kernel.org; maze@...gle.com
>>>> Subject: Re: [PATCH] Add skb_store_bytes() for
>>>> BPF_PROG_TYPE_CGROUP_SKB
>>>>
>>>> WARNING: This email originated from outside of Qualcomm. Please be wary of any links or attachments, and do not enable
>> macros.
>>>>
>>>> On Wed, Dec 29, 2021 at 06:29:05PM +0000, Tyler Wear wrote:
>>>>> Unable to run any bpf tests do to errors below. These occur with and without the new patch. Is this a known issue?
>>>>> Is the new test case required since bpf_skb_store_bytes() is already a tested function for other prog types?
>>>>>
>>>>> libbpf: failed to find BTF for extern 'bpf_testmod_invalid_mod_kfunc'
>>>>> [18] section: -2
>>>>> Error: failed to open BPF object file: No such file or directory
>>>>> libbpf: failed to find BTF info for global/extern symbol 'my_tid'
>>>>> Error: failed to link
>>>>> '/local/mnt/workspace/linux-stable/tools/testing/selftests/bpf/linke
>>>>> d_
>>>>> funcs1.o': Unknown error -2 (-2)
>>>>> libbpf: failed to find BTF for extern 'bpf_kfunc_call_test1' [27]
>>>>> section: -2
>>>> tools/testing/selftests/bpf/README.rst has details on these.
>>>>
>>>> Ensure the llvm and pahole are up to date.
>>>> Also take a look at the "Testing patches" and "LLVM" section in Documentation/bpf/bpf_devel_QA.rst.
>>>
>>> This will also require adding the l3/l4_ csum_replace() api's then. Adding the csum_replace() to a cgroup test case results in the
>> below error during bpf program validation:
>>> "BPF_LD_[ABS|IND] instructions not allowed for this program type"
>>
>> I saw you posted a new patch, so it seems you have resolved this BPF_LD_[ABS|IND] issue. Do you know what is the reason for this
>> verification error? Here, the program type is cgroup_skb which should not mess up with BPF_LD_[ABS|IND] which is mostly for classic
>> bpf to extended bpf conversion. Did I miss anything here?
>>
> 
> Was an issue with using bpf_legacy.h to load bytes.

Okay, I see. that makes sense. The helper bpf_skb_load_bytes() is the 
way to go.