case *OpError:
		if err := err.isValid(); err != nil {
			return err
		}
		nestedErr = err.Err
		goto second
	}
	return fmt.Errorf("unexpected type on 1st nested level: %T", nestedErr)

second:
	if isPlatformError(nestedErr) {
		return nil
	}
	switch err := nestedErr.(type) {
	case *AddrError, *timeoutError, *DNSError, InvalidAddrError, *ParseError, *poll.DeadlineExceededError, UnknownNetworkError:
		return nil

// license that can be found in the LICENSE file.

package net

import "syscall"

var (
	errOpNotSupported = syscall.EPLAN9

	abortedConnRequestErrors []error
)

func isPlatformError(err error) bool {
	_, ok := err.(syscall.ErrorString)
	return ok
}

func isENOBUFS(err error) bool {
	return false // ENOBUFS is Unix-specific

package net

import (
	"errors"
	"os"
	"syscall"
)

var (
	errOpNotSupported = syscall.EOPNOTSUPP

	abortedConnRequestErrors = []error{syscall.ECONNABORTED} // see accept in fd_unix.go
)

func isPlatformError(err error) bool {
	_, ok := err.(syscall.Errno)
	return ok
}

func samePlatformError(err, want error) bool {
	if op, ok := err.(*OpError); ok {
		err = op.Err
	}
	if sys, ok := err.(*os.SyscallError); ok {

	"errors"
	"syscall"
)

var (
	errOpNotSupported = syscall.EOPNOTSUPP

	abortedConnRequestErrors = []error{syscall.ERROR_NETNAME_DELETED, syscall.WSAECONNRESET} // see accept in fd_windows.go
)

func isPlatformError(err error) bool {
	_, ok := err.(syscall.Errno)
	return ok
}

func isENOBUFS(err error) bool {
	// syscall.ENOBUFS is a completely made-up value on Windows: we don't expect