[PATCH] ipv6: try not to take rtnl_lock in ip6mr_sk_done

[Francesco Ruggeri]

commit 9634257773c30ce13d74fa4918329612c60d84a8
Author: Francesco Ruggeri <frugg...@arista.com>
Date:   Mon Nov 6 11:01:59 2017 -0800

    ipv6: try not to take rtnl_lock in ip6mr_sk_done
    
    mrt->mroute6_sk can only be set to a non-NULL value in ip6mr_sk_init()
    if sk->sk_type == SOCK_RAW && inet_sk(sk)->inet_num == IPPROTO_ICMPV6.
    Use that not to unnecessarily take the rtn_lock in ip6mr_sk_done()
    when it is invoked from rawv6_close().

Signed-off-by: Francesco Ruggeri <frugg...@arista.com>

diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index f5500f5..e1bb2d8 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -1617,6 +1617,10 @@ int ip6mr_sk_done(struct sock *sk)
        struct net *net = sock_net(sk);
        struct mr6_table *mrt;
 
+       if (sk->sk_type != SOCK_RAW ||
+           inet_sk(sk)->inet_num != IPPROTO_ICMPV6)
+               return err;
+
        rtnl_lock();
        ip6mr_for_each_table(mrt, net) {
                if (sk == mrt->mroute6_sk) {