Accept AF_VSOCK listen addresses in socket unit files. Both guest and
host can now take advantage of socket activation.
The QEMU guest agent has recently been modified to support socket
activation and can run over AF_VSOCK with this patch.
The AF_VSOCK address family facilitates guest<->host communication on
VMware and KVM (virtio-vsock). Adding support to systemd allows guest
agents to be launched through .socket unit files. Today guest agents
are stand-alone daemons running inside guests that do not take advantage
of systemd socket activation.
sockaddr_port() either returns a >= 0 port number or a negative errno.
This works for AF_INET and AF_INET6 because port ranges are only 16-bit.
In AF_VSOCK ports are 32-bit so an int cannot represent all port number
and negative errnos. Separate the port and the return code.
Ubuntu 14.04 (Trusty) kernel header packages ship without
<linux/vm_sockets.h>. Only struct sockaddr_vm and VMADDR_CID_ANY will
be needed by systemd and they are simple enough to go in missing.h.
CentOS 7 <sys/socket.h> does not define AF_VSOCK. Define it so the code
can compile although actual socket(2) calls may fail at runtime if the
address family isn't available.
Stefan Hajnoczi