Stephen Hemminger wrote:

On Tue, 27 Feb 2018 14:06:51 +0200
Serhey Popovych [off-list ref] wrote:

quoted

diff --git a/include/compat/libc/bits/socket.h b/include/compat/libc/bits/socket.h
new file mode 100644
index 0000000..25ef0d5
--- /dev/null
+++ b/include/compat/libc/bits/socket.h

@@ -0,0 +1,15 @@
+#ifndef _IP_COMPAT_BITS_SOCKET_H
+#define _IP_COMPAT_BITS_SOCKET_H
+
+#include_next <bits/socket.h>
+
+#ifndef AF_VSOCK
+#define PF_VSOCK	40
+#define AF_VSOCK	PF_VSOCK
+#undef PF_MAX
+#undef AF_MAX
+#define PF_MAX		41
+#define AF_MAX		PF_MAX
+#endif /* AF_VSOCK */
+
+#endif /* _IP_COMPAT_BITS_SOCKET_H */

It makes more sense to change ss.c to ifdef out the code related to AF_VSOCK
if it is not defined.  Rather than asking for unknown address family.

Yes, I did this as v0 before sending series. But now I'm thinking that
single place for all compat stuff would ease tracking of changes.