Re: [PATCH 1/1] vxlan: insert ipv6 macro

Hi, Jiri

How to explain the following source code? As you mentioned,  are the
#ifdefs in the following source pointless?
As to the previous patch, I will compile and analyze it. But now I am
busy with something else. After I draw a conclusion, I will let you
know.

Thanks for your reply.

 static void vxlan_sock_release(struct vxlan_dev *vxlan)
{
        bool ipv4 = __vxlan_sock_release_prep(vxlan->vn4_sock);
#if IS_ENABLED(CONFIG_IPV6)
        bool ipv6 = __vxlan_sock_release_prep(vxlan->vn6_sock);
#endif
        synchronize_net();
        if (ipv4) {
                udp_tunnel_sock_release(vxlan->vn4_sock->sock);
                kfree(vxlan->vn4_sock);
        }
#if IS_ENABLED(CONFIG_IPV6)
        if (ipv6) {
                udp_tunnel_sock_release(vxlan->vn6_sock->sock);
                kfree(vxlan->vn6_sock);
        }
#endif
}

On Tue, Oct 11, 2016 at 10:06 PM, Jiri Benc [off-list ref] wrote:

On Tue, 11 Oct 2016 16:23:31 +0800, zyjzyj2000@gmail.com wrote:

quoted

--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c

@@ -2647,15 +2647,15 @@ static struct socket *vxlan_create_sock(struct net *net, bool ipv6,
      int err;

      memset(&udp_conf, 0, sizeof(udp_conf));
-
+#if IS_ENABLED(CONFIG_IPV6)
      if (ipv6) {
              udp_conf.family = AF_INET6;
              udp_conf.use_udp6_rx_checksums =
                  !(flags & VXLAN_F_UDP_ZERO_CSUM6_RX);
              udp_conf.ipv6_v6only = 1;
-     } else {
+     } else
+#endif
              udp_conf.family = AF_INET;
-     }

Zhu Yanjun, before posting patches such as the previous ones or
this one, please test whether they make any difference. In this case,
try to compile the code with IPv6 disabled before and after this patch,
disassemble and compare the results. You'll see that this patch is
pointless.

It's pretty obvious from the code but to be really sure, I've just
quickly built the vxlan module with IPv6 disabled. And indeed, as
expected, the compiler just inlined everything into vxlan_open. The
whole chain vxlan_open -> vxlan_sock_add -> __vxlan_sock_add (note that
there's only a single caller of __vxlan_sock_add with IPv6 disabled) ->
vxlan_socket_create -> vxlan_create_sock is inlined.

It also means the code in the "if (ipv6)" branch is completely
eliminated by the compiler even without ugly #ifdefs.

 Jiri