| 20 | var errUnexpectedRead = errors.New("unexpected read from socket") |
| 21 | |
| 22 | func connCheck(conn net.Conn) error { |
| 23 | var sysErr error |
| 24 | |
| 25 | sysConn, ok := conn.(syscall.Conn) |
| 26 | if !ok { |
| 27 | return nil |
| 28 | } |
| 29 | rawConn, err := sysConn.SyscallConn() |
| 30 | if err != nil { |
| 31 | return err |
| 32 | } |
| 33 | |
| 34 | err = rawConn.Read(func(fd uintptr) bool { |
| 35 | var buf [1]byte |
| 36 | n, err := syscall.Read(int(fd), buf[:]) |
| 37 | switch { |
| 38 | case n == 0 && err == nil: |
| 39 | sysErr = io.EOF |
| 40 | case n > 0: |
| 41 | sysErr = errUnexpectedRead |
| 42 | case err == syscall.EAGAIN || err == syscall.EWOULDBLOCK: |
| 43 | sysErr = nil |
| 44 | default: |
| 45 | sysErr = err |
| 46 | } |
| 47 | return true |
| 48 | }) |
| 49 | if err != nil { |
| 50 | return err |
| 51 | } |
| 52 | |
| 53 | return sysErr |
| 54 | } |