typedef struct Udphdr Udphdr;struct Udphdr{	uchar	d[6];		/* Ethernet destination */	uchar	s[6];		/* Ethernet source */	uchar	type[2];	/* Ethernet packet type */ 	uchar	vihl;		/* Version and header length */	uchar	tos;		/* Type of service */	uchar	length[2];	/* packet length */	uchar	id[2];		/* Identification */	uchar	frag[2];	/* Fragment information */ 	/* Udp pseudo ip really starts here */	uchar	ttl;		uchar	udpproto;	/* Protocol */	uchar	udpplen[2];	/* Header plus data length */	uchar	udpsrc[4];	/* Ip source */	uchar	udpdst[4];	/* Ip destination */	uchar	udpsport[2];	/* Source port */	uchar	udpdport[2];	/* Destination port */	uchar	udplen[2];	/* data length */	uchar	udpcksum[2];	/* Checksum */}; typedef struct Etherhdr Etherhdr;struct Etherhdr{	uchar	d[6];	uchar	s[6];	uchar	type[2]; 	/* Now we have the ip fields */	uchar	vihl;		/* Version and header length */	uchar	tos;		/* Type of service */	uchar	length[2];	/* packet length */	uchar	id[2];		/* Identification */	uchar	frag[2];	/* Fragment information */	uchar	ttl;		/* Time to live */	uchar	proto;		/* Protocol */	uchar	cksum[2];	/* Header checksum */	uchar	src[4];		/* Ip source */	uchar	dst[4];		/* Ip destination */}; enum{	IP_VER4		= 0x40,	IP_VER6		= 0x60,	IP_HLEN		= 0x05,			 	UDP_EHSIZE	= 22,	UDP_PHDRSIZE	= 12,	UDP_HDRSIZE	= 20,	ETHER_HDR	= 14,	IP_UDPPROTO	= 17,	ET_IP		= 0x800,	Bcastip		= 0xffffffff,	BPportsrc	= 68,	BPportdst	= 67,	TFTPport	= 69,	Timeout		= 2500,	/* milliseconds */	Bootrequest 	= 1,	Bootreply   	= 2,	Tftp_READ	= 1,	Tftp_WRITE	= 2,	Tftp_DATA	= 3,	Tftp_ACK	= 4,	Tftp_ERROR	= 5,	Segsize		= 512,	TFTPSZ		= Segsize+10,}; typedef struct Bootp Bootp;struct Bootp{	uchar	op;		/* opcode */	uchar	htype;		/* hardware type */	uchar	hlen;		/* hardware address len */	uchar	hops;		/* hops */	uchar	xid[4];		/* a random number */	uchar	secs[2];	/* elapsed since client started booting */	uchar	pad[2];	uchar	ciaddr[4];	/* client IP address (client tells server) */	uchar	yiaddr[4];	/* client IP address (server tells client) */	uchar	siaddr[4];	/* server IP address */	uchar	giaddr[4];	/* gateway IP address */	uchar	chaddr[16];	/* client hardware address */	char	sname[64];	/* server host name (optional) */	char	file[128];	/* boot file name */	char	vend[128];	/* vendor-specific goo */}; typedef struct Netaddr Netaddr;struct Netaddr{	ulong	ip;	ushort	port;	char	ea[Eaddrlen];}; extern int	eipfmt(Fmt*);