Re: [PATCH net-next v5 03/15] bpf: introduce timestamp_used to allow UDP socket fetched in bpf prog

[Martin KaFai Lau <martin.lau@linux.dev>]

On 1/17/25 5:58 PM, Jason Xing wrote:
>> On 1/15/25 5:12 PM, Jason Xing wrote:
>>>>> Also, I need to set allow_direct_access to one as long as there is
>>>>> "sock_ops.is_fullsock = 1;" in the existing callbacks.
>>>> Only set allow_direct_access when the sk is fullsock in the "existing" sockops
>>>> callback.
>>> Only "existing"? Then how can the bpf program access those members of
>>> the tcp socket structure in the current/new timestamping callbacks?
>> There is at least one sk write:
>>
>>          case offsetof(struct bpf_sock_ops, sk_txhash):
>>                  SOCK_OPS_GET_OR_SET_FIELD(sk_txhash, sk_txhash,
>>                                           struct sock, type);
>>
>> afaict, the kernel always writes sk->sk_txhash with the sk lock held. The new
>> timestamping callbacks cannot write because it does not hold the lock.
> Surely, I will handle the sk_txhash case as you suggested 🙂

to be clear, not setting the allow_tcp_access in the new timestamping cb should do.