Re: [PATCH] VSOCK: fix uapi/linux/vm_sockets.h incomplete types

This patch fixes the following compiler errors when userspace
applications use the vm_sockets.h header:

  include/uapi/linux/vm_sockets.h:148:32: error: invalid application of ‘sizeof’ to incomplete type ‘struct sockaddr’
    unsigned char svm_zero[sizeof(struct sockaddr) -
                                  ^~~~~~
  include/uapi/linux/vm_sockets.h:149:18: error: ‘sa_family_t’ undeclared here (not in a function)
             sizeof(sa_family_t) -
                    ^~~~~~~~~~~

Two issues:
1. In the kernel struct sockaddr comes in via <linux/socket.h> but in
   userspace <sys/socket.h> is required.
2. struct sockaddr_vm has a __kernel_sa_family_t field so let's be
   consistent and use the same type for the sizeof(sa_family_t)
   calculation.

Currently userspace applications work around this broken header by first
including <sys/socket.h>.  In the kernel there is no compiler error
because <linux/socket.h> provides everything.  It's worth fixing the
header file though.

Cc: Jorgen Hansen <redacted>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 include/uapi/linux/vm_sockets.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/vm_sockets.h b/include/uapi/linux/vm_sockets.h
index b4ed5d895699..4ae5c625ac56 100644
--- a/include/uapi/linux/vm_sockets.h
+++ b/include/uapi/linux/vm_sockets.h

@@ -18,6 +18,10 @@
 
 #include <linux/socket.h>
 
+#ifndef __KERNEL__
+#include <sys/socket.h> /* struct sockaddr */
+#endif
+