linux-kernel - Re: [External] Re: [PATCH bpf-next v2] bpf: Fix bpf_get/setsockopt to tos not take effect when TCP over IPv4 via INET6 API

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Message-ID: <6c75215b-0bdc-4b5a-b267-6dce0faec496@bytedance.com>
Date: Tue, 27 Aug 2024 16:08:12 +0800
From: Feng Zhou <zhoufeng.zf@...edance.com>
To: Eric Dumazet <edumazet@...gle.com>,
 Martin KaFai Lau <martin.lau@...ux.dev>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, ast@...nel.org,
 daniel@...earbox.net, andrii@...nel.org, eddyz87@...il.com, song@...nel.org,
 yonghong.song@...ux.dev, john.fastabend@...il.com, kpsingh@...nel.org,
 sdf@...ichev.me, haoluo@...gle.com, jolsa@...nel.org, dsahern@...nel.org,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
 yangzhenze@...edance.com, wangdongdong.6@...edance.com
Subject: Re: [External] Re: [PATCH bpf-next v2] bpf: Fix bpf_get/setsockopt to
 tos not take effect when TCP over IPv4 via INET6 API

在 2024/8/24 02:53, Eric Dumazet 写道:
> On Fri, Aug 23, 2024 at 8:49 PM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>>
>> On 8/23/24 6:35 AM, Eric Dumazet wrote:
>>> On Fri, Aug 23, 2024 at 10:53 AM Feng zhou <zhoufeng.zf@...edance.com> wrote:
>>>>
>>>> From: Feng Zhou <zhoufeng.zf@...edance.com>
>>>>
>>>> when TCP over IPv4 via INET6 API, bpf_get/setsockopt with ipv4 will
>>>> fail, because sk->sk_family is AF_INET6. With ipv6 will success, not
>>>> take effect, because inet_csk(sk)->icsk_af_ops is ipv6_mapped and
>>>> use ip_queue_xmit, inet_sk(sk)->tos.
>>>>
>>>> So bpf_get/setsockopt needs add the judgment of this case. Just check
>>>> "inet_csk(sk)->icsk_af_ops == &ipv6_mapped".
>>>>
>>>> | Reported-by: kernel test robot <lkp@...el.com>
>>>> | Closes: https://lore.kernel.org/oe-kbuild-all/202408152034.lw9Ilsj6-lkp@intel.com/
>>>> Signed-off-by: Feng Zhou <zhoufeng.zf@...edance.com>
>>>> ---
>>>> Changelog:
>>>> v1->v2: Addressed comments from kernel test robot
>>>> - Fix compilation error
>>>> Details in here:
>>>> https://lore.kernel.org/bpf/202408152058.YXAnhLgZ-lkp@intel.com/T/
>>>>
>>>>    include/net/tcp.h   | 2 ++
>>>>    net/core/filter.c   | 6 +++++-
>>>>    net/ipv6/tcp_ipv6.c | 6 ++++++
>>>>    3 files changed, 13 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/include/net/tcp.h b/include/net/tcp.h
>>>> index 2aac11e7e1cc..ea673f88c900 100644
>>>> --- a/include/net/tcp.h
>>>> +++ b/include/net/tcp.h
>>>> @@ -493,6 +493,8 @@ struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
>>>>                                               struct tcp_options_received *tcp_opt,
>>>>                                               int mss, u32 tsoff);
>>>>
>>>> +bool is_tcp_sock_ipv6_mapped(struct sock *sk);
>>>> +
>>>>    #if IS_ENABLED(CONFIG_BPF)
>>>>    struct bpf_tcp_req_attrs {
>>>>           u32 rcv_tsval;
>>>> diff --git a/net/core/filter.c b/net/core/filter.c
>>>> index ecf2ddf633bf..02a825e35c4d 100644
>>>> --- a/net/core/filter.c
>>>> +++ b/net/core/filter.c
>>>> @@ -5399,7 +5399,11 @@ static int sol_ip_sockopt(struct sock *sk, int optname,
>>>>                             char *optval, int *optlen,
>>>>                             bool getopt)
>>>>    {
>>>> -       if (sk->sk_family != AF_INET)
>>>> +       if (sk->sk_family != AF_INET
>>>> +#if IS_BUILTIN(CONFIG_IPV6)
>>>> +           && !is_tcp_sock_ipv6_mapped(sk)
>>>> +#endif
>>>> +           )
>>>>                   return -EINVAL;
>>>
>>> This does not look right to me.
>>>
>>> I would remove the test completely.
>>>
>>> SOL_IP socket options are available on AF_INET6 sockets just fine.
>>
>> Good point on the SOL_IP options.
>>
>> The sk could be neither AF_INET nor AF_INET6. e.g. the bpf_get/setsockopt
>> calling from the bpf_lsm's socket_post_create). so the AF_INET test is still needed.
>>
> 
> OK, then I suggest using sk_is_inet() helper.
> 
>> Adding "&& sk->sk_family != AF_INET6" should do. From ipv6_setsockopt, I think
>> it also needs to consider the "sk->sk_type != SOCK_RAW".
>>
>> Please add a test in the next re-spin.
>>
>> pw-bot: cr

Thanks for your suggestion, I will add it in the next version.