Re: [PATCH bpf-next v3 1/3] x86/cfi,bpf: Add a stub function for get_info of struct tcp_congestion_ops.

[Kui-Feng Lee <sinquersw@gmail.com>]

On 2/20/24 09:38, Alexei Starovoitov wrote:
> On Fri, Feb 16, 2024 at 11:34 AM <thinker.li@gmail.com> wrote:
>>
>> From: Kui-Feng Lee <thinker.li@gmail.com>
>>
>> struct tcp_congestion_ops is missing a stub function for get_info.  This is
>> required for checking the consistency of cfi_stubs of struct_ops.
>>
>> Cc: Peter Zijlstra <peterz@infradead.org>
>> Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
>> ---
>>   net/ipv4/bpf_tcp_ca.c | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
>> index 7f518ea5f4ac..6ab5d9c36416 100644
>> --- a/net/ipv4/bpf_tcp_ca.c
>> +++ b/net/ipv4/bpf_tcp_ca.c
>> @@ -321,6 +321,12 @@ static u32 bpf_tcp_ca_sndbuf_expand(struct sock *sk)
>>          return 0;
>>   }
>>
>> +static size_t bpf_tcp_ca_get_info(struct sock *sk, u32 ext, int *attr,
>> +                                 union tcp_cc_info *info)
>> +{
>> +       return 0;
>> +}
>> +
>>   static void __bpf_tcp_ca_init(struct sock *sk)
>>   {
>>   }
>> @@ -340,6 +346,7 @@ static struct tcp_congestion_ops __bpf_ops_tcp_congestion_ops = {
>>          .cong_control = bpf_tcp_ca_cong_control,
>>          .undo_cwnd = bpf_tcp_ca_undo_cwnd,
>>          .sndbuf_expand = bpf_tcp_ca_sndbuf_expand,
>> +       .get_info = bpf_tcp_ca_get_info,
> 
> No. It was explicitly skipped.
> The plan is to use NULL in cfi_stubs to remove
> static u32 unsupported_ops[] = {
>          offsetof(struct tcp_congestion_ops, get_info),
> };
> and manual check of such fields in is_unsupported().


Ok! That means I have to check the result of st_ops->check() to skip
unsupported ops.


> NULL is cfi_stubs will be such an indication.
> 
> pw-bot: cr