alternatively, we could define it in sys/socket.h since SO* is
reserved there, and tcp.h includes sys/socket.h in extensions mode.
note that SOL_TCP is simply wrong and it's only here for compatibility
with broken applications. the correct argument to pass for setting TCP
socket options is IPPROTO_TCP, which of course has the same value as
SOL_TCP but works everywhere.
#define TCP_CONGESTION 13
#define TCP_MD5SIG 14
#define TCP_CONGESTION 13
#define TCP_MD5SIG 14
#if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
#if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
#include <sys/types.h>
#include <sys/socket.h>
#endif
#include <sys/types.h>
#include <sys/socket.h>
#endif