结构体强制转换问题！！求教

struct sockaddr  tmp111;

struct sockaddr_in *sin111;

char *buf = (char *)malloc(10000);



memset(buf, 0, sizeof(buf));

tmp111 = ipList[asd].fromaddr;

sin111 = (struct sockaddr_in*)&tmp111; 



 memcpy(buff,  sin111->sin_addr, 4);

 memcpy(buff,  (struct in_addr*)&sin111->sin_addr, 4);