SO_VM_SOCKETS_BUFFER_SIZE might have been useful for VMCI-specific
applications, but we should use SO_RCVBUF and SO_SNDBUF for portable
applications in the future. Those socket options also work with other
address families.
I guess these sockopts are bypassed by AF_VSOCK because it doesn't use
the common skb queuing code in net/core/sock.c:(. But one day we might
migrate to it...
Stefan