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SubjectRe: [PATCH v2 11/25] tcp: authopt: Implement Sequence Number Extension
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On 11/1/21 10:54 PM, Eric Dumazet wrote:
> On 11/1/21 9:34 AM, Leonard Crestez wrote:
>> Add a compute_sne function which finds the value of SNE for a certain
>> SEQ given an already known "recent" SNE/SEQ. This is implemented using
>> the standard tcp before/after macro and will work for SEQ values that
>> are without 2^31 of the SEQ for which we know the SNE.
>
>> }
>> +void __tcp_authopt_update_rcv_sne(struct tcp_sock *tp, struct tcp_authopt_info *info, u32 seq);
>> +static inline void tcp_authopt_update_rcv_sne(struct tcp_sock *tp, u32 seq)
>> +{
>> + struct tcp_authopt_info *info;
>> +
>> + if (static_branch_unlikely(&tcp_authopt_needed)) {
>> + rcu_read_lock();
>> + info = rcu_dereference(tp->authopt_info);
>> + if (info)
>> + __tcp_authopt_update_rcv_sne(tp, info, seq);
>> + rcu_read_unlock();
>> + }
>> +}
>> +void __tcp_authopt_update_snd_sne(struct tcp_sock *tp, struct tcp_authopt_info *info, u32 seq);
>> +static inline void tcp_authopt_update_snd_sne(struct tcp_sock *tp, u32 seq)
>> +{
>> + struct tcp_authopt_info *info;
>> +
>> + if (static_branch_unlikely(&tcp_authopt_needed)) {
>> + rcu_read_lock();
>> + info = rcu_dereference(tp->authopt_info);
>> + if (info)
>> + __tcp_authopt_update_snd_sne(tp, info, seq);
>> + rcu_read_unlock();
>> + }
>> +}
>>
>
> I would think callers of these helpers own socket lock,
> so no rcu_read_lock()/unlock() should be needed.
>
> Perhaps instead
> rcu_dereference_protected(tp->authopt_info, lockdep_sock_is_held(sk));

Yes, all the callers hold the socket lock and replacing rcu_read_lock
doesn't trigger any RCU warnings.

--
Regards,
Leonard

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