ipv6: provide and use ipv6 specific version for {recv, send}msg

This will simplify indirect call wrapper invocation in the following
patch.

No functional change intended, any - out-of-tree - IPv6 user of
inet_{recv,send}msg can keep using the existing functions.

SCTP code still uses the existing version even for ipv6: as this series
will not add ICW for SCTP, moving to the new helper would not give
any benefit.

The only other in-kernel user of inet_{recv,send}msg is
pvcalls_conn_back_read(), but psvcalls explicitly creates only IPv4 socket,
so no need to update that code path, too.

v1 -> v2: drop inet6_{recv,send}msg declaration from header file,
   prefer ICW macro instead
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/af_inet6.c

@@ -564,6 +564,33 @@ int inet6_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
 }
 EXPORT_SYMBOL(inet6_ioctl);
 
+int inet6_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
+{
+	struct sock *sk = sock->sk;
+
+	if (unlikely(inet_send_prepare(sk)))
+		return -EAGAIN;
+
+	return sk->sk_prot->sendmsg(sk, msg, size);
+}
+
+int inet6_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
+		  int flags)
+{
+	struct sock *sk = sock->sk;
+	int addr_len = 0;
+	int err;
+
+	if (likely(!(flags & MSG_ERRQUEUE)))
+		sock_rps_record_flow(sk);
+
+	err = sk->sk_prot->recvmsg(sk, msg, size, flags & MSG_DONTWAIT,
+				   flags & ~MSG_DONTWAIT, &addr_len);
+	if (err >= 0)
+		msg->msg_namelen = addr_len;
+	return err;
+}
+
 const struct proto_ops inet6_stream_ops = {
 	.family		   = PF_INET6,
 	.owner		   = THIS_MODULE,
@@ -580,8 +607,8 @@ const struct proto_ops inet6_stream_ops = {
 	.shutdown	   = inet_shutdown,		/* ok		*/
 	.setsockopt	   = sock_common_setsockopt,	/* ok		*/
 	.getsockopt	   = sock_common_getsockopt,	/* ok		*/
-	.sendmsg	   = inet_sendmsg,		/* ok		*/
-	.recvmsg	   = inet_recvmsg,		/* ok		*/
+	.sendmsg	   = inet6_sendmsg,		/* retpoline's sake */
+	.recvmsg	   = inet6_recvmsg,		/* retpoline's sake */
 #ifdef CONFIG_MMU
 	.mmap		   = tcp_mmap,
 #endif
@@ -614,8 +641,8 @@ const struct proto_ops inet6_dgram_ops = {
 	.shutdown	   = inet_shutdown,		/* ok		*/
 	.setsockopt	   = sock_common_setsockopt,	/* ok		*/
 	.getsockopt	   = sock_common_getsockopt,	/* ok		*/
-	.sendmsg	   = inet_sendmsg,		/* ok		*/
-	.recvmsg	   = inet_recvmsg,		/* ok		*/
+	.sendmsg	   = inet6_sendmsg,		/* retpoline's sake */
+	.recvmsg	   = inet6_recvmsg,		/* retpoline's sake */
 	.mmap		   = sock_no_mmap,
 	.sendpage	   = sock_no_sendpage,
 	.set_peek_off	   = sk_set_peek_off,