|  | 
        In the table below, X denotes
        a socket option class, a
        denotes a value of X, p denotes a value that meets the protocol requirements, and u denotes an identifier.
      
Table 27. SettableSocketOption requirements
| expression | type | 
                  assertion/note | 
|---|---|---|
| 
                   | 
                   | 
                  Returns a value suitable for passing as the level
                  argument to POSIX  | 
| 
                   | 
                   | 
                  Returns a value suitable for passing as the option_name
                  argument to POSIX  | 
| 
                   | 
                  a pointer, convertible to  | 
                  Returns a pointer suitable for passing as the option_value
                  argument to POSIX  | 
| 
                   | 
                   | 
                  Returns a value suitable for passing as the option_len
                  argument to POSIX  |