2013/4/3 Eric Wong <normalperson / yhbt.net>:

>> This is Linux-specific and only defined in linux headers
>> such as /usr/include/linux/in.h.
>>
>> I'm not sure applications can safely use such headers.
>
> We already have Linux-specific constants (e.g. TCP_CORK) and
> *BSD-specific constants (e.g. TCP_NOPUSH), so I don't think we should
> make it hard for users to take advantage of non-portable features on
> their favorite OS.

It is not my concern.
TCP_CORK is defined in /usr/include/netinet/tcp.h which is a glibc header.
-- 
Tanaka Akira