netdev - [PATCH net-next 2/2] ip6mr: ip6mr_sk_done() can exit early in common cases

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Date:   Fri,  4 Feb 2022 12:15:46 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>, David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next 2/2] ip6mr: ip6mr_sk_done() can exit early in common cases

From: Eric Dumazet <edumazet@...gle.com>

In many cases, ip6mr_sk_done() is called while no ipmr socket
has been registered.

This removes 4 rtnl acquisitions per netns dismantle,
with following callers:

igmp6_net_exit(), tcpv6_net_exit(), ndisc_net_exit()

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv6/ip6mr.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index 541cd08871293eb5702e47e0645ea16394621e97..8e483e14b5709b1b8a6e9dfd6616a5bde5c273ee 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -1575,6 +1575,9 @@ int ip6mr_sk_done(struct sock *sk)
 	    inet_sk(sk)->inet_num != IPPROTO_ICMPV6)
 		return err;
 
+	if (!atomic_read(&net->ipv6.devconf_all->mc_forwarding))
+		return err;
+
 	rtnl_lock();
 	ip6mr_for_each_table(mrt, net) {
 		if (sk == rtnl_dereference(mrt->mroute_sk)) {
-- 
2.35.0.263.gb82422642f-goog