netdev - Re: [PATCH RESEND net-next, v3] netlink: support dumping IPv4 multicast addresses

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Message-ID: <8ba3c7f0-4a14-46bb-82b0-ff9fbc0f71b7@kernel.org>
Date: Wed, 8 Jan 2025 12:56:42 -0700
From: David Ahern <dsahern@...nel.org>
To: Yuyang Huang <yuyanghuang@...gle.com>
Cc: "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
 roopa@...ulusnetworks.com, jiri@...nulli.us, stephen@...workplumber.org,
 jimictw@...gle.com, prohr@...gle.com, liuhangbin@...il.com,
 nicolas.dichtel@...nd.com, andrew@...n.ch, netdev@...r.kernel.org,
 Maciej Żenczykowski <maze@...gle.com>,
 Lorenzo Colitti <lorenzo@...gle.com>
Subject: Re: [PATCH RESEND net-next, v3] netlink: support dumping IPv4
 multicast addresses

On 1/4/25 7:02 PM, Yuyang Huang wrote:
> @@ -1850,21 +1851,46 @@ static int in_dev_dump_addr(struct in_device *in_dev, struct sk_buff *skb,
>  			    struct netlink_callback *cb, int *s_ip_idx,
>  			    struct inet_fill_args *fillargs)
>  {
> +	struct ip_mc_list *im;
>  	struct in_ifaddr *ifa;
>  	int ip_idx = 0;
>  	int err;
>  
> -	in_dev_for_each_ifa_rcu(ifa, in_dev) {
> -		if (ip_idx < *s_ip_idx) {
> +	switch (fillargs->type) {
> +	case UNICAST_ADDR:
> +		fillargs->event = RTM_NEWADDR;
> +		in_dev_for_each_ifa_rcu(ifa, in_dev) {
> +			if (ip_idx < *s_ip_idx) {
> +				ip_idx++;
> +				continue;
> +			}
> +			err = inet_fill_ifaddr(skb, ifa, fillargs);
> +			if (err < 0)
> +				goto done;
> +
> +			nl_dump_check_consistent(cb, nlmsg_hdr(skb));
>  			ip_idx++;
> -			continue;
>  		}
> -		err = inet_fill_ifaddr(skb, ifa, fillargs);
> -		if (err < 0)
> -			goto done;
> +		break;

Almost all of the logic is under the switch cases, you are not really
saving a lot here. I think it would be simpler just to have simpler
in_dev_dump_addr for each type.

> +	case MULTICAST_ADDR:
> +		for (im = rcu_dereference(in_dev->mc_list);
> +		     im;
> +		     im = rcu_dereference(im->next_rcu)) {
> +			if (ip_idx < *s_ip_idx) {
> +				ip_idx++;
> +				continue;
> +			}
> +			err = inet_fill_ifmcaddr(skb, in_dev->dev, im,
> +						 RTM_GETMULTICAST, NLM_F_MULTI);
> +			if (err < 0)
> +				goto done;
>  
> -		nl_dump_check_consistent(cb, nlmsg_hdr(skb));
> -		ip_idx++;
> +			nl_dump_check_consistent(cb, nlmsg_hdr(skb));
> +			ip_idx++;
> +		}
> +		break;
> +	default:
> +		break;
>  	}
>  	err = 0;
>  	ip_idx = 0;