nat: Fix bad bug, make sure the fd is not overwritten..

The adding of the innocent looking code was actually overwrote
the fd and then stupid things happened. Rename variables to avoid
that. rc,ret should be scratch variables...
diff --git a/openbsc/src/nat/bsc_nat.c b/openbsc/src/nat/bsc_nat.c
index b9a1584..90df41f 100644
--- a/openbsc/src/nat/bsc_nat.c
+++ b/openbsc/src/nat/bsc_nat.c
@@ -717,17 +717,17 @@
 static int ipaccess_listen_bsc_cb(struct bsc_fd *bfd, unsigned int what)
 {
 	struct bsc_connection *bsc;
-	int ret, on;
+	int fd, rc, on;
 	struct sockaddr_in sa;
 	socklen_t sa_len = sizeof(sa);
 
 	if (!(what & BSC_FD_READ))
 		return 0;
 
-	ret = accept(bfd->fd, (struct sockaddr *) &sa, &sa_len);
-	if (ret < 0) {
+	fd = accept(bfd->fd, (struct sockaddr *) &sa, &sa_len);
+	if (fd < 0) {
 		perror("accept");
-		return ret;
+		return fd;
 	}
 
 	/* count the reconnect */
@@ -738,13 +738,13 @@
 	 */
 	if (!msc_con->is_connected) {
 		LOGP(DNAT, LOGL_NOTICE, "Disconnecting BSC due lack of MSC connection.\n");
-		close(ret);
+		close(fd);
 		return 0;
 	}
 
 	on = 1;
-	ret = setsockopt(bfd->fd, IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on));
-	if (ret != 0)
+	rc = setsockopt(bfd->fd, IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on));
+	if (rc != 0)
                 LOGP(DNAT, LOGL_ERROR, "Failed to set TCP_NODELAY: %s\n", strerror(errno));
 
 	/* todo... do something with the connection */
@@ -756,24 +756,24 @@
 	bsc = bsc_connection_alloc(nat);
 	if (!bsc) {
 		LOGP(DNAT, LOGL_ERROR, "Failed to allocate BSC struct.\n");
-		close(ret);
+		close(fd);
 		return -1;
 	}
 
 	bsc->write_queue.bfd.data = bsc;
-	bsc->write_queue.bfd.fd = ret;
+	bsc->write_queue.bfd.fd = fd;
 	bsc->write_queue.read_cb = ipaccess_bsc_read_cb;
 	bsc->write_queue.write_cb = ipaccess_bsc_write_cb;
 	bsc->write_queue.bfd.when = BSC_FD_READ;
 	if (bsc_register_fd(&bsc->write_queue.bfd) < 0) {
 		LOGP(DNAT, LOGL_ERROR, "Failed to register BSC fd.\n");
-		close(ret);
+		close(fd);
 		talloc_free(bsc);
 		return -2;
 	}
 
 	LOGP(DNAT, LOGL_NOTICE, "BSC connection on %d with IP: %s\n",
-		ret, inet_ntoa(sa.sin_addr));
+		fd, inet_ntoa(sa.sin_addr));
 	llist_add(&bsc->list_entry, &nat->bsc_connections);
 	send_id_ack(bsc);
 	send_id_req(bsc);