sk_err_soft和 sk_err有什么区别？

1. *        @sk_err: last error
   
2.   *        @sk_err_soft: errors that don't cause failure but are the cause of a
   
3.   *                      persistent failure not just 'timed out'

QUOTE:

EINPROGRESS
              The socket is nonblocking and the connection cannot be completed immediately.  It is possible to select(2) or  poll(2)  for  completion  by
              selecting the socket for writing.  After select(2) indicates writability, use getsockopt(2) to read the SO_ERROR option at level SOL_SOCKET
              to determine whether connect() completed successfully (SO_ERROR is zero) or unsuccessfully (SO_ERROR is one of the usual error codes listed
              here, explaining the reason for the failure).