Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Sat, 6 Oct 2018 21:43:48 +0200
From:   Eugene Syromiatnikov <esyr@redhat.com>
To:     "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc:     linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        davem@davemloft.net, gregkh@linuxfoundation.org
Subject: Re: [PATCH net-next v7 28/28] net: WireGuard secure network tunnel
Message-ID: <20181006194348.GK32759@asgard.redhat.com>
References: <20181006025709.4019-1-Jason@zx2c4.com>
 <20181006025709.4019-29-Jason@zx2c4.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20181006025709.4019-29-Jason@zx2c4.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Sat, Oct 06, 2018 at 04:57:09AM +0200, Jason A. Donenfeld wrote:
> +static int get_allowedips(void *ctx, const u8 *ip, u8 cidr, int family)
> +{
> +	struct allowedips_ctx *actx = ctx;
> +	struct nlattr *allowedip_nest;
> +
> +	allowedip_nest = nla_nest_start(actx->skb, actx->i++);

Second parameter of nl_nest_start is an attribute type; (ab)using it as
array index leads to special handling of such structures in parsers.
It's better to have some type like WGDEVICE_A_PEER_ITEM and provide an
additional attribute inside it for index (WGPEER_A_INDEX?).
See, for example, commit v4.12-rc1~119^2~131 ("nbd: add a status netlink
command").

> +static int get_peer(struct wireguard_peer *peer, unsigned int index,
> +		    struct allowedips_cursor *rt_cursor, struct sk_buff *skb)
> +{
> +	struct nlattr *allowedips_nest, *peer_nest = nla_nest_start(skb, index);

Same here.