[NET] NETNS: Omit namespace comparision without CONFIG_NET_NS.

Introduce an inline net_eq() to compare two namespaces.
Without CONFIG_NET_NS, since no namespace other than &init_net
exists, it is always 1.

We do not need to convert 1) inline vs inline and
2) inline vs &init_net comparisons.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index db266ff..aacbc82 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -70,7 +70,7 @@
 	sk_for_each(sk, node, &udptable[hnum & (UDP_HTABLE_SIZE - 1)]) {
 		struct inet_sock *inet = inet_sk(sk);
 
-		if (sock_net(sk) == net && sk->sk_hash == hnum &&
+		if (net_eq(sock_net(sk), net) && sk->sk_hash == hnum &&
 				sk->sk_family == PF_INET6) {
 			struct ipv6_pinfo *np = inet6_sk(sk);
 			int score = 0;