#ifndef VJBSDHDR_H#define VJBSDHDR_H#include "lwip/tcp.h"/* * Structure of an internet header, naked of options. * * We declare ip_len and ip_off to be short, rather than u_short * pragmatically since otherwise unsigned comparisons can result * against negative integers quite easily, and fail in subtle ways. */PACK_STRUCT_BEGINstruct ip{#if defined(NO_CHAR_BITFIELDS)	u_char ip_hl_v;	/* bug in GCC for mips means the bitfield stuff will sometimes break - so we use a char for both and get round it with macro's instead... */#else#if BYTE_ORDER == LITTLE_ENDIAN	unsigned ip_hl:4,				/* header length */		ip_v:4;						/* version */#elif BYTE_ORDER == BIG_ENDIAN 	unsigned ip_v:4,					/* version */		ip_hl:4;					/* header length */#else	COMPLAIN - NO BYTE ORDER SELECTED!#endif#endif	u_char	ip_tos;					/* type of service */	u_short	ip_len;					/* total length */	u_short	ip_id;					/* identification */	u_short	ip_off;					/* fragment offset field */#define	IP_DF 0x4000				/* dont fragment flag */#define	IP_MF 0x2000				/* more fragments flag */#define	IP_OFFMASK 0x1fff			/* mask for fragmenting bits */	u_char	ip_ttl;					/* time to live */	u_char	ip_p;					/* protocol */	u_short	ip_sum;					/* checksum */	struct	in_addr ip_src,ip_dst;	/* source and dest address */};PACK_STRUCT_ENDtypedef u32_t tcp_seq;/* * TCP header. * Per RFC 793, September, 1981. */PACK_STRUCT_BEGINstruct tcphdr  {	u_short	th_sport;		/* source port */	u_short	th_dport;		/* destination port */	tcp_seq	th_seq;			/* sequence number */	tcp_seq	th_ack;			/* acknowledgement number */#if defined(NO_CHAR_BITFIELDS)	u_char th_x2_off;#else#if BYTE_ORDER == LITTLE_ENDIAN	unsigned	th_x2:4,		/* (unused) */			th_off:4;		/* data offset */#endif#if BYTE_ORDER == BIG_ENDIAN 	unsigned	th_off:4,		/* data offset */			th_x2:4;		/* (unused) */#endif#endif	u_char	th_flags;	u_short	th_win;			/* window */	u_short	th_sum;			/* checksum */	u_short	th_urp;			/* urgent pointer */};PACK_STRUCT_END#endif /* VJBSDHDR_H */