VSOCK(7)                   Linux Programmer's Manual                  VSOCK(7)

       vsock - Linux VSOCK address family

       #include <sys/socket.h>
       #include <linux/vm_sockets.h>

       stream_socket = socket(AF_VSOCK, SOCK_STREAM, 0);
       datagram_socket = socket(AF_VSOCK, SOCK_DGRAM, 0);

       The  VSOCK address family facilitates communication between virtual ma-
       chines and the host they are running on.  This address family  is  used
       by  guest  agents  and  hypervisor  services that need a communications
       channel that is independent of virtual machine network configuration.

       Valid socket types are SOCK_STREAM and  SOCK_DGRAM.   SOCK_STREAM  pro-
       vides connection-oriented byte streams with guaranteed, in-order deliv-
       ery.  SOCK_DGRAM provides a connectionless datagram packet service with
       best-effort  delivery  and best-effort ordering.  Availability of these
       socket types is dependent on the underlying hypervisor.

       A new socket is created with

           socket(AF_VSOCK, socket_type, 0);

       When a process wants to establish a  connection,  it  calls  connect(2)
       with  a  given destination socket address.  The socket is automatically
       bound to a free port if unbound.

       A process can listen for incoming connections by  first  binding  to  a
       socket address using bind(2) and then calling listen(2).

       Data  is  transmitted  using the send(2) or write(2) families of system
       calls and data is received using the recv(2)  or  read(2)  families  of
       system calls.

   Address format
       A  socket address is defined as a combination of a 32-bit Context Iden-
       tifier (CID) and a 32-bit port number.  The CID identifies  the  source
       or  destination,  which  is  either a virtual machine or the host.  The
       port number differentiates between multiple services running on a  sin-
       gle machine.

           struct sockaddr_vm {
               sa_family_t    svm_family;     /* Address family: AF_VSOCK */
               unsigned short svm_reserved1;
               unsigned int   svm_port;       /* Port # in host byte order */
               unsigned int   svm_cid;        /* Address in host byte order */
               unsigned char  svm_zero[sizeof(struct sockaddr) -
                                       sizeof(sa_family_t) -
                                       sizeof(unsigned short) -
                                       sizeof(unsigned int) -
                                       sizeof(unsigned int)];

       svm_family  is  always set to AF_VSOCK.  svm_reserved1 is always set to
       0.  svm_port contains the port number in host  byte  order.   The  port
       numbers  below  1024  are called privileged ports.  Only a process with
       the CAP_NET_BIND_SERVICE capability may bind(2) to these port  numbers.
       svm_zero must be zero-filled.

       There are several special addresses: VMADDR_CID_ANY (-1U) means any ad-
       dress for binding; VMADDR_CID_HYPERVISOR (0) is reserved  for  services
       built  into  the  hypervisor; VMADDR_CID_RESERVED (1) must not be used;
       VMADDR_CID_HOST (2) is the well-known address of the host.

       The special constant VMADDR_PORT_ANY (-1U) means any  port  number  for

   Live migration
       Sockets  are affected by live migration of virtual machines.  Connected
       SOCK_STREAM sockets become disconnected when the  virtual  machine  mi-
       grates to a new host.  Applications must reconnect when this happens.

       The  local  CID  may change across live migration if the old CID is not
       available on the new host.  Bound sockets are automatically updated  to
       the new CID.

              Get  the CID of the local machine.  The argument is a pointer to
              an unsigned int.

                  ioctl(socket, IOCTL_VM_SOCKETS_GET_LOCAL_CID, &cid);

              Consider using VMADDR_CID_ANY when binding  instead  of  getting
              the local CID with IOCTL_VM_SOCKETS_GET_LOCAL_CID.

       EACCES Unable    to   bind   to   a   privileged   port   without   the
              CAP_NET_BIND_SERVICE capability.

              Unable to bind to a port that is already in use.

              Unable to find a free port for binding or unable to  bind  to  a
              nonlocal CID.

       EINVAL Invalid  parameters.  This includes: attempting to bind a socket
              that is already bound, providing an invalid struct  sockaddr_vm,
              and other input validation errors.

              Invalid socket option in setsockopt(2) or getsockopt(2).

              Unable to perform operation on an unconnected socket.

              Operation  not  supported.  This includes: the MSG_OOB flag that
              is not implemented  for  the  send(2)  family  of  syscalls  and
              MSG_PEEK for the recv(2) family of syscalls.

              Invalid  socket  protocol number.  The protocol should always be

              Unsupported socket type  in  socket(2).   Only  SOCK_STREAM  and
              SOCK_DGRAM are valid.

       Support  for  VMware  (VMCI)  has  been available since Linux 3.9.  KVM
       (virtio) is supported since Linux  4.8.   Hyper-V  is  supported  since
       Linux 4.14.

       bind(2),  connect(2), listen(2), recv(2), send(2), socket(2), capabili-

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Linux                             2020-02-09                          VSOCK(7)
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