Re: [PATCH v2 11/25] tcp: authopt: Implement Sequence Number Extension

[Eric Dumazet]

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));