EHOSTUNREACH    Errno = 23
	EIDRM           Errno = 24
	EILSEQ          Errno = 25
	EINPROGRESS     Errno = 26
	EINTR           Errno = 27
	EINVAL          Errno = 28
	EIO             Errno = 29
	EISCONN         Errno = 30
	EISDIR          Errno = 31
	ELOOP           Errno = 32
	EMFILE          Errno = 33
	EMLINK          Errno = 34
	EMSGSIZE        Errno = 35
	EMULTIHOP       Errno = 36
	ENAMETOOLONG    Errno = 37

	// because fd is not yet accessible to user,
	// so no concurrent operations are possible.
	switch err := connectFunc(fd.pfd.Sysfd, ra); err {
	case syscall.EINPROGRESS, syscall.EALREADY, syscall.EINTR:
	case nil, syscall.EISCONN:
		select {
		case <-ctx.Done():
			return nil, mapErr(ctx.Err())
		default:
		}
		if err := fd.pfd.Init(fd.net, true); err != nil {
			return nil, err
		}
		runtime.KeepAlive(fd)
		return nil, nil

	ECONNRESET
	EDEADLK
	EDEADLOCK
	EDESTADDRREQ
	EDOM
	EDOTDOT
	EDQUOT
	EEXIST
	EFAULT
	EFBIG
	EHOSTDOWN
	EHOSTUNREACH
	EIDRM
	EILSEQ
	EINPROGRESS
	EINTR
	EINVAL
	EIO
	EISCONN
	EISDIR
	EISNAM
	EKEYEXPIRED
	EKEYREJECTED
	EKEYREVOKED
	EL2HLT
	EL2NSYNC
	EL3HLT
	EL3RST
	ELIBACC
	ELIBBAD
	ELIBEXEC
	ELIBMAX
	ELIBSCN
	ELNRNG
	ELOOP
	EMEDIUMTYPE
	EMFILE

	"ENETDOWN":        ENETDOWN,
	"ENETUNREACH":     ENETUNREACH,
	"ENETRESET":       ENETRESET,
	"ECONNABORTED":    ECONNABORTED,
	"ECONNRESET":      ECONNRESET,
	"ENOBUFS":         ENOBUFS,
	"EISCONN":         EISCONN,
	"ENOTCONN":        ENOTCONN,
	"ESHUTDOWN":       ESHUTDOWN,
	"ETOOMANYREFS":    ETOOMANYREFS,
	"ETIMEDOUT":       ETIMEDOUT,
	"ECONNREFUSED":    ECONNREFUSED,
	"EHOSTDOWN":       EHOSTDOWN,

	if err = af.apply(so); err != nil {
		return -1, err
	}

	if so.Err != nil {
		return -1, so.Err
	}
	if opt == syscall.SO_ERROR && (so.SocketErr == syscall.Errno(0) || so.SocketErr == syscall.EISCONN) {
		sw.smu.Lock()
		sw.stats.getLocked(so.Cookie).Connected++
		sw.smu.Unlock()
	}
	return soerr, nil

	EHOSTUNREACH    = syscall.Errno(0x71)
	EHWPOISON       = syscall.Errno(0x85)
	EIDRM           = syscall.Errno(0x2b)
	EILSEQ          = syscall.Errno(0x54)
	EINPROGRESS     = syscall.Errno(0x73)
	EISCONN         = syscall.Errno(0x6a)
	EISNAM          = syscall.Errno(0x78)
	EKEYEXPIRED     = syscall.Errno(0x7f)
	EKEYREJECTED    = syscall.Errno(0x81)
	EKEYREVOKED     = syscall.Errno(0x80)

	EHWPOISON       = syscall.Errno(0xa8)
	EIDRM           = syscall.Errno(0x24)
	EILSEQ          = syscall.Errno(0x58)
	EINIT           = syscall.Errno(0x8d)
	EINPROGRESS     = syscall.Errno(0x96)
	EISCONN         = syscall.Errno(0x85)
	EISNAM          = syscall.Errno(0x8b)
	EKEYEXPIRED     = syscall.Errno(0xa2)
	EKEYREJECTED    = syscall.Errno(0xa4)
	EKEYREVOKED     = syscall.Errno(0xa3)

	EHOSTUNREACH    = syscall.Errno(0x71)
	EHWPOISON       = syscall.Errno(0x85)
	EIDRM           = syscall.Errno(0x2b)
	EILSEQ          = syscall.Errno(0x54)
	EINPROGRESS     = syscall.Errno(0x73)
	EISCONN         = syscall.Errno(0x6a)
	EISNAM          = syscall.Errno(0x78)
	EKEYEXPIRED     = syscall.Errno(0x7f)
	EKEYREJECTED    = syscall.Errno(0x81)
	EKEYREVOKED     = syscall.Errno(0x80)

	EHOSTUNREACH    = syscall.Errno(0x71)
	EHWPOISON       = syscall.Errno(0x85)
	EIDRM           = syscall.Errno(0x2b)
	EILSEQ          = syscall.Errno(0x54)
	EINPROGRESS     = syscall.Errno(0x73)
	EISCONN         = syscall.Errno(0x6a)
	EISNAM          = syscall.Errno(0x78)
	EKEYEXPIRED     = syscall.Errno(0x7f)
	EKEYREJECTED    = syscall.Errno(0x81)
	EKEYREVOKED     = syscall.Errno(0x80)

	EHOSTUNREACH    = syscall.Errno(0x71)
	EHWPOISON       = syscall.Errno(0x85)
	EIDRM           = syscall.Errno(0x2b)
	EILSEQ          = syscall.Errno(0x54)
	EINPROGRESS     = syscall.Errno(0x73)
	EISCONN         = syscall.Errno(0x6a)
	EISNAM          = syscall.Errno(0x78)
	EKEYEXPIRED     = syscall.Errno(0x7f)
	EKEYREJECTED    = syscall.Errno(0x81)
	EKEYREVOKED     = syscall.Errno(0x80)