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Date: Tue, 8 Sep 2026 09:56:54 -0600
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Subject: Re: [PATCH net-next 1/3] rtnetlink: add AF_PACKET multicast dumps
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To: Yuyang Huang <sigefriedhyy@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>,
 Donald Hunter <donald.hunter@gmail.com>, Eric Dumazet <edumazet@google.com>,
 Ido Schimmel <idosch@nvidia.com>, Jakub Kicinski <kuba@kernel.org>,
 Kuniyuki Iwashima <kuniyu@google.com>,
 Nikolaos Gkarlis <nickgarlis@gmail.com>, Paolo Abeni <pabeni@redhat.com>,
 Sabrina Dubroca <sd@queasysnail.net>, Shuah Khan <shuah@kernel.org>,
 Simon Horman <horms@kernel.org>, Stanislav Fomichev <sdf.kernel@gmail.com>,
 linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
 netdev@vger.kernel.org
References: <20260905093932.43726-1-sigefriedhyy@gmail.com>
 <20260905093932.43726-2-sigefriedhyy@gmail.com>
From: David Ahern <dsahern@kernel.org>
In-Reply-To: <20260905093932.43726-2-sigefriedhyy@gmail.com>
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On 9/5/26 4:39 AM, Yuyang Huang wrote:
> +static int rtnl_dump_mcaddr(struct sk_buff *skb, struct netlink_callback *cb)
> +{
> +	struct net *net = sock_net(skb->sk);
> +	unsigned int flags = NLM_F_MULTI;
> +	struct {
> +		unsigned long ifindex;
> +		int addr_idx;
> +	} *ctx = (void *)cb->ctx;
> +	struct net_device *dev;
> +	int ifindex = 0;
> +	int err = 0;
> +
> +	if (cb->strict_check) {

this is new code. It should only work with strict checking.

> +		err = rtnl_valid_dump_mcaddr_req(cb->nlh, cb->extack,
> +						 &ifindex);
> +		if (err < 0)
> +			return err;
> +	}
> +
> +	rcu_read_lock();
> +
> +	if (ifindex) {
> +		cb->answer_flags |= NLM_F_DUMP_FILTERED;
> +		flags |= NLM_F_DUMP_FILTERED;
> +		dev = dev_get_by_index_rcu(net, ifindex);
> +		if (!dev) {
> +			err = -ENODEV;
> +			goto out;
> +		}
> +		err = rtnl_dump_mcaddr_dev(dev, skb, cb, &ctx->addr_idx, flags);
> +		goto out;
> +	}
> +
> +	for_each_netdev_dump(net, dev, ctx->ifindex) {
> +		err = rtnl_dump_mcaddr_dev(dev, skb, cb, &ctx->addr_idx,
> +					   flags);
> +		if (err < 0)
> +			break;
> +	}
> +out:
> +	rcu_read_unlock();
> +	return err;
> +}
> +
>  struct sk_buff *rtmsg_ifinfo_build_skb(int type, struct net_device *dev,
>  				       unsigned int change,
>  				       u32 event, gfp_t flags, int *new_nsid,