linux-kernel - Re: [PATCH RESEND net-next] ipv6: mcast: Add ip6_mc_find

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Message-ID: <739c6d25-7421-4f8f-bb61-f613a1c8b3ce@linux.intel.com>
Date: Mon, 18 Aug 2025 15:47:31 +0200
From: Dawid Osuchowski <dawid.osuchowski@...ux.intel.com>
To: Yue Haibing <yuehaibing@...wei.com>, davem@...emloft.net,
 dsahern@...nel.org, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
 horms@...nel.org
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND net-next] ipv6: mcast: Add ip6_mc_find_idev()
 helper

On 2025-08-18 12:10 PM, Yue Haibing wrote:
> __ipv6_sock_mc_join() has the same code as ip6_mc_find_dev() to find dev,
> extract this into ip6_mc_find_dev() and add ip6_mc_find_idev() to reduce
> code duplication and improve readability.

nit: the commit msg is a tad bit confusing

> 
> Signed-off-by: Yue Haibing <yuehaibing@...wei.com>

Regardless of the nit above,

Reviewed-by: Dawid Osuchowski <dawid.osuchowski@...ux.intel.com>

Thanks,
Dawid

> ---
>   net/ipv6/mcast.c | 76 ++++++++++++++++++++++--------------------------
>   1 file changed, 35 insertions(+), 41 deletions(-)
> 
> diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
> index 36ca27496b3c..75430ad55c3d 100644
> --- a/net/ipv6/mcast.c
> +++ b/net/ipv6/mcast.c
> @@ -169,6 +169,29 @@ static int unsolicited_report_interval(struct inet6_dev *idev)
>   	return iv > 0 ? iv : 1;
>   }
>   
> +static struct net_device *ip6_mc_find_dev(struct net *net,
> +					  const struct in6_addr *group,
> +					  int ifindex)
> +{
> +	struct net_device *dev = NULL;
> +	struct rt6_info *rt;
> +
> +	if (ifindex == 0) {
> +		rcu_read_lock();
> +		rt = rt6_lookup(net, group, NULL, 0, NULL, 0);
> +		if (rt) {
> +			dev = dst_dev(&rt->dst);
> +			dev_hold(dev);
> +			ip6_rt_put(rt);
> +		}
> +		rcu_read_unlock();
> +	} else {
> +		dev = dev_get_by_index(net, ifindex);
> +	}
> +
> +	return dev;
> +}
> +
>   /*
>    *	socket join on multicast group
>    */
> @@ -191,28 +214,13 @@ static int __ipv6_sock_mc_join(struct sock *sk, int ifindex,
>   	}
>   
>   	mc_lst = sock_kmalloc(sk, sizeof(struct ipv6_mc_socklist), GFP_KERNEL);
> -
>   	if (!mc_lst)
>   		return -ENOMEM;
>   
>   	mc_lst->next = NULL;
>   	mc_lst->addr = *addr;
>   
> -	if (ifindex == 0) {
> -		struct rt6_info *rt;
> -
> -		rcu_read_lock();
> -		rt = rt6_lookup(net, addr, NULL, 0, NULL, 0);
> -		if (rt) {
> -			dev = dst_dev(&rt->dst);
> -			dev_hold(dev);
> -			ip6_rt_put(rt);
> -		}
> -		rcu_read_unlock();
> -	} else {
> -		dev = dev_get_by_index(net, ifindex);
> -	}
> -
> +	dev = ip6_mc_find_dev(net, addr, ifindex);
>   	if (!dev) {
>   		sock_kfree_s(sk, mc_lst, sizeof(*mc_lst));
>   		return -ENODEV;
> @@ -302,32 +310,18 @@ int ipv6_sock_mc_drop(struct sock *sk, int ifindex, const struct in6_addr *addr)
>   }
>   EXPORT_SYMBOL(ipv6_sock_mc_drop);
>   
> -static struct inet6_dev *ip6_mc_find_dev(struct net *net,
> -					 const struct in6_addr *group,
> -					 int ifindex)
> +static struct inet6_dev *ip6_mc_find_idev(struct net *net,
> +					  const struct in6_addr *group,
> +					  int ifindex)
>   {
> -	struct net_device *dev = NULL;
> -	struct inet6_dev *idev;
> -
> -	if (ifindex == 0) {
> -		struct rt6_info *rt;
> +	struct inet6_dev *idev = NULL;
> +	struct net_device *dev;
>   
> -		rcu_read_lock();
> -		rt = rt6_lookup(net, group, NULL, 0, NULL, 0);
> -		if (rt) {
> -			dev = dst_dev(&rt->dst);
> -			dev_hold(dev);
> -			ip6_rt_put(rt);
> -		}
> -		rcu_read_unlock();
> -	} else {
> -		dev = dev_get_by_index(net, ifindex);
> +	dev = ip6_mc_find_dev(net, group, ifindex);
> +	if (dev) {
> +		idev = in6_dev_get(dev);
> +		dev_put(dev);
>   	}
> -	if (!dev)
> -		return NULL;
> -
> -	idev = in6_dev_get(dev);
> -	dev_put(dev);
>   
>   	return idev;
>   }
> @@ -374,7 +368,7 @@ int ip6_mc_source(int add, int omode, struct sock *sk,
>   	if (!ipv6_addr_is_multicast(group))
>   		return -EINVAL;
>   
> -	idev = ip6_mc_find_dev(net, group, pgsr->gsr_interface);
> +	idev = ip6_mc_find_idev(net, group, pgsr->gsr_interface);
>   	if (!idev)
>   		return -ENODEV;
>   
> @@ -509,7 +503,7 @@ int ip6_mc_msfilter(struct sock *sk, struct group_filter *gsf,
>   	    gsf->gf_fmode != MCAST_EXCLUDE)
>   		return -EINVAL;
>   
> -	idev = ip6_mc_find_dev(net, group, gsf->gf_interface);
> +	idev = ip6_mc_find_idev(net, group, gsf->gf_interface);
>   	if (!idev)
>   		return -ENODEV;
>