unix: add flags to SockaddrVM

The Flags member was added to struct sockaddr_vm in Linux kernel 5.11
and successively into RawSockaddrVM when updating to that kernel version
in CL 291637. Add the flags to SockaddrVM as well.

While at it, also update the list of CID values with VMADDR_CID_LOCAL.

Change-Id: I08828136f4c5ded3cca2fd07aefac066b9977b13
Reviewed-on: https://go-review.googlesource.com/c/sys/+/308990
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/syscall_linux.go

@@ -857,16 +857,19 @@ type SockaddrVM struct {
 	// CID and Port specify a context ID and port address for a VM socket.
 	// Guests have a unique CID, and hosts may have a well-known CID of:
 	//  - VMADDR_CID_HYPERVISOR: refers to the hypervisor process.
+	//  - VMADDR_CID_LOCAL: refers to local communication (loopback).
 	//  - VMADDR_CID_HOST: refers to other processes on the host.
-	CID  uint32
-	Port uint32
-	raw  RawSockaddrVM
+	CID   uint32
+	Port  uint32
+	Flags uint8
+	raw   RawSockaddrVM
 }
 
 func (sa *SockaddrVM) sockaddr() (unsafe.Pointer, _Socklen, error) {
 	sa.raw.Family = AF_VSOCK
 	sa.raw.Port = sa.Port
 	sa.raw.Cid = sa.CID
+	sa.raw.Flags = sa.Flags
 
 	return unsafe.Pointer(&sa.raw), SizeofSockaddrVM, nil
 }
@@ -1171,8 +1174,9 @@ func anyToSockaddr(fd int, rsa *RawSockaddrAny) (Sockaddr, error) {
 	case AF_VSOCK:
 		pp := (*RawSockaddrVM)(unsafe.Pointer(rsa))
 		sa := &SockaddrVM{
-			CID:  pp.Cid,
-			Port: pp.Port,
+			CID:   pp.Cid,
+			Port:  pp.Port,
+			Flags: pp.Flags,
 		}
 		return sa, nil
 	case AF_BLUETOOTH: