当传递src_addr参数时recvfrom返回invalid argument

这个问题很可能出在addrlen参数上，以下是man文档的解释

If  src_addr  is  not  NULL,  and  the underlying protocol provides the
source address, this source address is filled  in.   When  src_addr  is
NULL,  nothing  is  filled  in;  in this case, addrlen is not used, and
should also be NULL.  The argument addrlen is a value-result  argument,
which  the  caller should initialize before the call to the size of the
buffer associated with src_addr, and modified on return to indicate the
actual  size  of the source address.  The returned address is truncated
if the buffer provided is too small; in this case, addrlen will  return
a value greater than was supplied to the call.