ENOTTY          Errno = 59
	ENXIO           Errno = 60
	EOVERFLOW       Errno = 61
	EOWNERDEAD      Errno = 62
	EPERM           Errno = 63
	EPIPE           Errno = 64
	EPROTO          Errno = 65
	EPROTONOSUPPORT Errno = 66
	EPROTOTYPE      Errno = 67
	ERANGE          Errno = 68
	EROFS           Errno = 69
	ESPIPE          Errno = 70
	ESRCH           Errno = 71
	ESTALE          Errno = 72
	ETIMEDOUT       Errno = 73

	s, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
	if err == nil {
		syscall.Close(s)
	}
	wantSock := err != syscall.EPROTONOSUPPORT && err != syscall.EINVAL
	gotSock := unix.SupportSockNonblockCloexec()
	if wantSock != gotSock {
		t.Fatalf("SupportSockNonblockCloexec, got %t; want %t", gotSock, wantSock)
	}

	"EUSERS":          EUSERS,
	"ENOTSOCK":        ENOTSOCK,
	"EDESTADDRREQ":    EDESTADDRREQ,
	"EMSGSIZE":        EMSGSIZE,
	"EPROTOTYPE":      EPROTOTYPE,
	"ENOPROTOOPT":     ENOPROTOOPT,
	"EPROTONOSUPPORT": EPROTONOSUPPORT,
	"ESOCKTNOSUPPORT": ESOCKTNOSUPPORT,
	"EOPNOTSUPP":      EOPNOTSUPP,
	"EPFNOSUPPORT":    EPFNOSUPPORT,
	"EAFNOSUPPORT":    EAFNOSUPPORT,
	"EADDRINUSE":      EADDRINUSE,

	ENOTEMPTY
	ENOTNAM
	ENOTRECOVERABLE
	ENOTSOCK
	ENOTSUP
	ENOTTY
	ENOTUNIQ
	ENXIO
	EOPNOTSUPP
	EOVERFLOW
	EOWNERDEAD
	EPERM
	EPFNOSUPPORT
	EPIPE
	EPROTO
	EPROTONOSUPPORT
	EPROTOTYPE
	ERANGE
	EREMCHG
	EREMOTE
	EREMOTEIO
	ERESTART
	EROFS
	ESHUTDOWN
	ESOCKTNOSUPPORT
	ESPIPE
	ESRCH
	ESRMNT
	ESTALE
	ESTRPIPE
	ETIME
	ETIMEDOUT

		family = syscall.AF_INET
	case *syscall.SockaddrInet6:
		family = syscall.AF_INET6
	case *syscall.SockaddrUnix:
		family = syscall.AF_UNIX
	default:
		poll.CloseFunc(s)
		return nil, syscall.EPROTONOSUPPORT
	}
	fd, err := newFD(s, family, sotype, "")
	if err != nil {
		poll.CloseFunc(s)
		return nil, err
	}
	laddr := fd.addrFunc()(lsa)
	raddr := fd.addrFunc()(rsa)
	fd.net = laddr.Network()

	s, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
	if err == nil {
		syscall.Close(s)
		return true
	}
	if err != syscall.EPROTONOSUPPORT && err != syscall.EINVAL {
		// Something wrong with socket(), fall back to checking the kernel version.
		major, minor := KernelVersion()
		if runtime.GOOS == "illumos" {

// looking at the returned error if any.
func initMPTCPavailable() {
	s, err := sysSocket(syscall.AF_INET, syscall.SOCK_STREAM, _IPPROTO_MPTCP)
	switch {
	case errors.Is(err, syscall.EPROTONOSUPPORT): // Not supported: >= v5.6
	case errors.Is(err, syscall.EINVAL): // Not supported: < v5.6
	case err == nil: // Supported and no error
		poll.CloseFunc(s)
		fallthrough
	default:

}

// testNet tests network operations.
func testNet(wg *sync.WaitGroup) {
	ln, err := net.Listen("tcp4", "127.0.0.1:0")
	if err != nil {
		if errors.Is(err, syscall.EAFNOSUPPORT) || errors.Is(err, syscall.EPROTONOSUPPORT) {
			return
		}
		log.Fatal(err)
	}
	wg.Add(2)
	go func() {
		defer wg.Done()
		defer ln.Close()
		c, err := ln.Accept()
		if err != nil {
			log.Fatal(err)
		}

	EOPNOTSUPP      = syscall.Errno(0x7a)
	EOVERFLOW       = syscall.Errno(0x4f)
	EOWNERDEAD      = syscall.Errno(0xa5)
	EPFNOSUPPORT    = syscall.Errno(0x7b)
	EPROTO          = syscall.Errno(0x47)
	EPROTONOSUPPORT = syscall.Errno(0x78)
	EPROTOTYPE      = syscall.Errno(0x62)
	EREMCHG         = syscall.Errno(0x52)
	EREMDEV         = syscall.Errno(0x8e)
	EREMOTE         = syscall.Errno(0x42)
	EREMOTEIO       = syscall.Errno(0x8c)

	EOPNOTSUPP      = syscall.Errno(0x5f)
	EOVERFLOW       = syscall.Errno(0x4b)
	EOWNERDEAD      = syscall.Errno(0x82)
	EPFNOSUPPORT    = syscall.Errno(0x60)
	EPROTO          = syscall.Errno(0x47)
	EPROTONOSUPPORT = syscall.Errno(0x5d)
	EPROTOTYPE      = syscall.Errno(0x5b)
	EREMCHG         = syscall.Errno(0x4e)
	EREMOTE         = syscall.Errno(0x42)
	EREMOTEIO       = syscall.Errno(0x79)
	ERESTART        = syscall.Errno(0x55)