ip.h

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

typedef struct	Conv	Conv;
typedef struct	Fs	Fs;
typedef union	Hwaddr	Hwaddr;
typedef struct	IP	IP;
typedef struct	IPaux	IPaux;
typedef struct	Ipself	Ipself;
typedef struct	Ipselftab	Ipselftab;
typedef struct	Iplink	Iplink;
typedef struct	Iplifc	Iplifc;
typedef struct	Ipmulti	Ipmulti;
typedef struct	Ipifc	Ipifc;
typedef struct	Iphash	Iphash;
typedef struct	Ipht	Ipht;
typedef struct	Netlog	Netlog;
typedef struct	Medium	Medium;
typedef struct	Proto	Proto;
typedef struct	Arpent	Arpent;
typedef struct	Arp Arp;
typedef struct	Route	Route;

typedef struct	Routerparams	Routerparams;
typedef struct 	Hostparams	Hostparams;
typedef struct 	v6router	v6router;
typedef struct	v6params	v6params;

#pragma incomplete Arp
#pragma incomplete Ipself
#pragma incomplete Ipselftab
#pragma incomplete IP
#pragma incomplete Netlog

enum
{
	Addrlen=	64,
	Maxproto=	20,
	Nhash=		64,
	Maxincall=	5,
	Nchans=		1024,
	MAClen=		16,		/* longest mac address */

	MAXTTL=		255,
	DFLTTOS=	0,

	IPaddrlen=	16,
	IPv4addrlen=	4,
	IPv4off=	12,
	IPllen=		4,

	/* ip versions */
	V4=		4,
	V6=		6,
	IP_VER4= 	0x40,
	IP_VER6=	0x60,

	/* 2^Lroot trees in the root table */
	Lroot=		10,

	Maxpath =	64,
};

enum
{
	Idle=		0,
	Announcing=	1,
	Announced=	2,
	Connecting=	3,
	Connected=	4,
};

/*
 *  one per conversation directory
 */
struct Conv
{
	QLock;

	int	x;			/* conversation index */
	Proto*	p;

	int	restricted;		/* remote port is restricted */
	uint	ttl;			/* max time to live */
	uint	tos;			/* type of service */
	int	ignoreadvice;		/* don't terminate connection on icmp errors */

	uchar	ipversion;
	uchar	laddr[IPaddrlen];	/* local IP address */
	uchar	raddr[IPaddrlen];	/* remote IP address */
	ushort	lport;			/* local port number */
	ushort	rport;			/* remote port number */

	char	*owner;			/* protections */
	int	perm;
	int	inuse;			/* opens of listen/data/ctl */
	int	length;
	int	state;

	/* udp specific */
	int	headers;		/* data src/dst headers in udp */
	int	reliable;		/* true if reliable udp */

	Conv*	incall;			/* calls waiting to be listened for */
	Conv*	next;

	Queue*	rq;			/* queued data waiting to be read */
	Queue*	wq;			/* queued data waiting to be written */
	Queue*	eq;			/* returned error packets */
	Queue*	sq;			/* snooping queue */
	Ref	snoopers;		/* number of processes with snoop open */

	QLock	car;
	Rendez	cr;
	char	cerr[ERRMAX];

	QLock	listenq;
	Rendez	listenr;

	Ipmulti	*multi;			/* multicast bindings for this interface */

	void*	ptcl;			/* protocol specific stuff */

	Route	*r;			/* last route used */
	ulong	rgen;			/* routetable generation for *r */
};

struct Medium
{
	char	*name;
	int	hsize;		/* medium header size */
	int	mintu;		/* default min mtu */
	int	maxtu;		/* default max mtu */
	int	maclen;		/* mac address length  */
	void	(*bind)(Ipifc*, int, char**);
	void	(*unbind)(Ipifc*);
	void	(*bwrite)(Ipifc *ifc, Block *b, int version, uchar *ip);

	/* for arming interfaces to receive multicast */
	void	(*addmulti)(Ipifc *ifc, uchar *a, uchar *ia);
	void	(*remmulti)(Ipifc *ifc, uchar *a, uchar *ia);

	/* process packets written to 'data' */
	void	(*pktin)(Fs *f, Ipifc *ifc, Block *bp);

	/* routes for router boards */
	void	(*addroute)(Ipifc *ifc, int, uchar*, uchar*, uchar*, int);
	void	(*remroute)(Ipifc *ifc, int, uchar*, uchar*);
	void	(*flushroutes)(Ipifc *ifc);

	/* for routing multicast groups */
	void	(*joinmulti)(Ipifc *ifc, uchar *a, uchar *ia);
	void	(*leavemulti)(Ipifc *ifc, uchar *a, uchar *ia);

	/* address resolution */
	void	(*ares)(Fs*, int, uchar*, uchar*, int, int);	/* resolve */
	void	(*areg)(Ipifc*, uchar*);			/* register */

	/* v6 address generation */
	void	(*pref2addr)(uchar *pref, uchar *ea);

	int	unbindonclose;	/* if non-zero, unbind on last close */
};

/* logical interface associated with a physical one */
struct Iplifc
{
	uchar	local[IPaddrlen];
	uchar	mask[IPaddrlen];
	uchar	remote[IPaddrlen];
	uchar	net[IPaddrlen];
	uchar	tentative;	/* =1 => v6 dup disc on, =0 => confirmed unique */
	uchar	onlink;		/* =1 => onlink, =0 offlink. */
	uchar	autoflag;	/* v6 autonomous flag */
	long 	validlt;	/* v6 valid lifetime */
	long 	preflt;		/* v6 preferred lifetime */
	long	origint;	/* time when addr was added */
	Iplink	*link;		/* addresses linked to this lifc */
	Iplifc	*next;
};

/* binding twixt Ipself and Iplifc */
struct Iplink
{
	Ipself	*self;
	Iplifc	*lifc;
	Iplink	*selflink;	/* next link for this local address */
	Iplink	*lifclink;	/* next link for this ifc */
	ulong	expire;
	Iplink	*next;		/* free list */
	int	ref;
};

/* rfc 2461, pp.40--43. */

/* default values, one per stack */
struct Routerparams {
	int	mflag;
	int	oflag;
	int 	maxraint;
	int	minraint;
	int	linkmtu;
	int	reachtime;
	int	rxmitra;
	int	ttl;
	int	routerlt;	
};

struct Hostparams {
	int	rxmithost;
};

struct Ipifc
{
	RWlock;
	
	Conv	*conv;		/* link to its conversation structure */
	char	dev[64];	/* device we're attached to */
	Medium	*m;		/* Media pointer */
	int	maxtu;		/* Maximum transfer unit */
	int	mintu;		/* Minumum tranfer unit */
	int	mbps;		/* megabits per second */
	void	*arg;		/* medium specific */
	int	reassemble;	/* reassemble IP packets before forwarding */

	/* these are used so that we can unbind on the fly */
	Lock	idlock;
	uchar	ifcid;		/* incremented each 'bind/unbind/add/remove' */
	int	ref;		/* number of proc's using this ipifc */
	Rendez	wait;		/* where unbinder waits for ref == 0 */
	int	unbinding;

	uchar	mac[MAClen];	/* MAC address */

	Iplifc	*lifc;		/* logical interfaces on this physical one */

	ulong	in, out;	/* message statistics */
	ulong	inerr, outerr;	/* ... */

	uchar	sendra6;	/* == 1 => send router advs on this ifc	*/
	uchar	recvra6;	/* == 1 => recv router advs on this ifc */
	Routerparams rp;	/* router parameters as in RFC 2461, pp.40--43. 
					used only if node is router */
};

/*
 *  one per multicast-lifc pair used by a Conv
 */
struct Ipmulti
{
	uchar	ma[IPaddrlen];
	uchar	ia[IPaddrlen];
	Ipmulti	*next;
};

/*
 *  hash table for 2 ip addresses + 2 ports
 */
enum
{
	Nipht=		521,	/* convenient prime */

	IPmatchexact=	0,	/* match on 4 tuple */
	IPmatchany,		/* *!* */
	IPmatchport,		/* *!port */
	IPmatchaddr,		/* addr!* */
	IPmatchpa,		/* addr!port */
};
struct Iphash
{
	Iphash	*next;
	Conv	*c;
	int	match;
};
struct Ipht
{
	Lock;
	Iphash	*tab[Nipht];
};
void iphtadd(Ipht*, Conv*);
void iphtrem(Ipht*, Conv*);
Conv* iphtlook(Ipht *ht, uchar *sa, ushort sp, uchar *da, ushort dp);

/*
 *  one per multiplexed protocol
 */
struct Proto
{
	QLock;
	char*		name;		/* protocol name */
	int		x;		/* protocol index */
	int		ipproto;	/* ip protocol type */

	char*		(*connect)(Conv*, char**, int);
	char*		(*announce)(Conv*, char**, int);
	char*		(*bind)(Conv*, char**, int);
	int		(*state)(Conv*, char*, int);
	void		(*create)(Conv*);
	void		(*close)(Conv*);
	void		(*rcv)(Proto*, Ipifc*, Block*);
	char*		(*ctl)(Conv*, char**, int);
	void		(*advise)(Proto*, Block*, char*);
	int		(*stats)(Proto*, char*, int);
	int		(*local)(Conv*, char*, int);
	int		(*remote)(Conv*, char*, int);
	int		(*inuse)(Conv*);
	int		(*gc)(Proto*);	/* returns true if any conversations are freed */

	Fs		*f;		/* file system this proto is part of */
	Conv		**conv;		/* array of conversations */
	int		ptclsize;	/* size of per protocol ctl block */
	int		nc;		/* number of conversations */
	int		ac;
	Qid		qid;		/* qid for protocol directory */
	ushort		nextport;
	ushort		nextrport;

	void		*priv;
};


/*
 *  one per IP protocol stack
 */
struct Fs
{
	RWlock;
	int	dev;