Re: [PATCH v12 net-next 06/23] net/tcp: Add TCP-AO sign to outgoing packets

[Paolo Abeni]

On Mon, 2023-09-18 at 20:00 +0100, Dmitry Safonov wrote:
> @@ -1361,16 +1385,48 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
>  		th->window	= htons(min(tp->rcv_wnd, 65535U));
>  	}
>  
> -	tcp_options_write(th, tp, &opts);
> +	tcp_options_write(th, tp, &opts, &key);
>  
> +	if (tcp_key_is_md5(&key)) {
>  #ifdef CONFIG_TCP_MD5SIG
> -	/* Calculate the MD5 hash, as we have all we need now */
> -	if (md5) {
> +		/* Calculate the MD5 hash, as we have all we need now */
>  		sk_gso_disable(sk);
>  		tp->af_specific->calc_md5_hash(opts.hash_location,
> -					       md5, sk, skb);
> -	}
> +					       key.md5_key, sk, skb);
>  #endif
> +	} else if (tcp_key_is_ao(&key)) {
> +#ifdef CONFIG_TCP_AO
> +		struct tcp_ao_info *ao;
> +		void *tkey_buf = NULL;
> +		u8 *traffic_key;
> +		__be32 disn;
> +
> +		ao = rcu_dereference_protected(tcp_sk(sk)->ao_info,
> +					       lockdep_sock_is_held(sk));
> +		if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
> +			if (tcb->tcp_flags & TCPHDR_ACK)
> +				disn = ao->risn;
> +			else
> +				disn = 0;
> +
> +			tkey_buf = kmalloc(tcp_ao_digest_size(key.ao_key),
> +					   GFP_ATOMIC);
> +			if (!tkey_buf) {
> +				kfree_skb_reason(skb, SKB_DROP_REASON_NOMEM);
> +				return -ENOMEM;
> +			}
> +			traffic_key = tkey_buf;
> +			tp->af_specific->ao_calc_key_sk(key.ao_key, traffic_key,
> +							sk, ao->lisn, disn, true);
> +		} else {
> +			traffic_key = snd_other_key(key.ao_key);
> +		}
> +		tp->af_specific->calc_ao_hash(opts.hash_location, key.ao_key,
> +					      sk, skb, traffic_key,
> +					      opts.hash_location - (u8 *)th, 0);
> +		kfree(tkey_buf);
> +#endif

I'm sorry for the incremental feedback.

The above could possibly deserve being moved to a specific helper, for
both readability and code locality when TCP_AO is enabled at compile
time but not used.

Cheers,

Paolo