[PATCH net-next] ipv6: mcast: Add ip6_mc_find_idev() helper

[PATCH net-next] ipv6: mcast: Add ip6_mc_find_idev() helper

[Yue Haibing]

__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.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
---
 net/ipv6/mcast.c | 76 +++++++++++++++++++++++-------------------------
 1 file changed, 36 insertions(+), 40 deletions(-)

diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 36ca27496b3c..3fdff47c7b84 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -169,6 +169,30 @@ 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;
+
+	if (ifindex == 0) {
+		struct rt6_info *rt;
+
+		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
  */
@@ -198,21 +222,7 @@ static int __ipv6_sock_mc_join(struct sock *sk, int ifindex,
 	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 +312,18 @@ 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 +370,7 @@ 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 +505,7 @@ 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;
 
-- 
2.34.1

Re: [PATCH net-next] ipv6: mcast: Add ip6_mc_find_idev() helper

[Jakub Kicinski]

On Thu, 24 Jul 2025 19:56:31 +0800 Yue Haibing wrote:
>  net/ipv6/mcast.c | 76 +++++++++++++++++++++++-------------------------
>  1 file changed, 36 insertions(+), 40 deletions(-)

Dunno if this is worth the churn to save 4 lines.
I was waiting to see if anyone will offer a review tag
but it's getting a bit later in the review cycle, 
please try again after the merge window.
-- 
pw-bot: defer

Re: [PATCH net-next] ipv6: mcast: Add ip6_mc_find_idev() helper

[Yue Haibing]

On 2025/7/26 5:45, Jakub Kicinski wrote:
> On Thu, 24 Jul 2025 19:56:31 +0800 Yue Haibing wrote:
>>  net/ipv6/mcast.c | 76 +++++++++++++++++++++++-------------------------
>>  1 file changed, 36 insertions(+), 40 deletions(-)
> 
> Dunno if this is worth the churn to save 4 lines.
> I was waiting to see if anyone will offer a review tag
> but it's getting a bit later in the review cycle, 
> please try again after the merge window.

Ok, thank you for your review.