Patrick McHardy wrote:
>  int xfrm_state_mtu(struct xfrm_state *x, int mtu)
>  {
> -	int res = mtu;
> -
> -	res -= x->props.header_len;
> -
> -	for (;;) {
> -		int m = res;
> -
> -		if (m < 68)
> -			return 68;
> -
> -		spin_lock_bh(&x->lock);
> -		if (x->km.state == XFRM_STATE_VALID &&
> -		    x->type && x->type->get_max_size)
> -			m = x->type->get_max_size(x, m);
> -		else
> -			m += x->props.header_len;
> -		spin_unlock_bh(&x->lock);
> -
> -		if (m <= mtu)
> -			break;
> -		res -= (m - mtu);
> -	}
> +	int res;
>  
> +	spin_lock_bh(&x->lock);
> +	if (x->km.state == XFRM_STATE_VALID &&
> +	    x->type && x->type->get_mtu)
> +		res = x->type->get_mtu(x, mtu);
> +	else
> +		res = mtu;
> +	spin_unlock_bh(&x->lock);
>  	return res;
>  }


That broke estimation for AH. This one should be fine.