musl/include/netinet/tcp.h

#ifndef _NETINET_TCP_H
#define _NETINET_TCP_H

#include <features.h>

#define TCP_NODELAY 1
#define TCP_MAXSEG	 2
#define TCP_CORK	 3
#define TCP_KEEPIDLE	 4
#define TCP_KEEPINTVL	 5
#define TCP_KEEPCNT	 6
#define TCP_SYNCNT	 7
#define TCP_LINGER2	 8
#define TCP_DEFER_ACCEPT 9
#define TCP_WINDOW_CLAMP 10
#define TCP_INFO	 11
#define	TCP_QUICKACK	 12
#define TCP_CONGESTION	 13
#define TCP_MD5SIG	 14
#define TCP_THIN_LINEAR_TIMEOUTS 16
#define TCP_THIN_DUPACK  17
#define TCP_USER_TIMEOUT 18
#define TCP_REPAIR       19
#define TCP_REPAIR_QUEUE 20
#define TCP_QUEUE_SEQ    21
#define TCP_REPAIR_OPTIONS 22
#define TCP_FASTOPEN     23
#define TCP_TIMESTAMP    24

#if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
#define SOL_TCP 6
#include <sys/types.h>
#include <sys/socket.h>
#include <endian.h>

struct tcphdr
{
	u_int16_t source;
	u_int16_t dest;
	u_int32_t seq;
	u_int32_t ack_seq;
#if __BYTE_ORDER == __LITTLE_ENDIAN
	u_int16_t res1:4;
	u_int16_t doff:4;
	u_int16_t fin:1;
	u_int16_t syn:1;
	u_int16_t rst:1;
	u_int16_t psh:1;
	u_int16_t ack:1;
	u_int16_t urg:1;
	u_int16_t res2:2;
#else
	u_int16_t doff:4;
	u_int16_t res1:4;
	u_int16_t res2:2;
	u_int16_t urg:1;
	u_int16_t ack:1;
	u_int16_t psh:1;
	u_int16_t rst:1;
	u_int16_t syn:1;
	u_int16_t fin:1;
#endif
	u_int16_t window;
	u_int16_t check;
	u_int16_t urg_ptr;
};
#endif

#endif