pppoe_disc.c

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

#include <u.h>
#include <libc.h>
#include <ip.h>
#include "dat.h"
#include "protos.h"

typedef struct Hdr Hdr;
struct Hdr {
	uchar verstype;
	uchar code;
	uchar sessid[2];
	uchar length[2];	/* of payload */
};
enum
{
	HDRSIZE = 1+1+2+2
};

static Mux p_mux[] =
{
	{"ppp",		0,	} ,
	{0}
};

enum
{
	Overs,
	Otype,
	Ocode,
	Osess,
};

static Field p_fields[] = 
{
	{"v",	Fnum,	Overs,	"version",	} ,
	{"t",	Fnum,	Otype,	"type",	} ,
	{"c",	Fnum,	Ocode,	"code" } ,
	{"s",	Fnum,	Osess,	"sessid" } ,
	{0}
};

static void
p_compilesess(Filter *f)
{
//	Mux *m;

	if(f->op == '='){
		compile_cmp(pppoe_sess.name, f, p_fields);
		return;
	}
/*
	for(m = p_mux; m->name != nil; m++)
		if(strcmp(f->s, m->name) == 0){
			f->pr = m->pr;
			f->ulv = m->val;
			f->subop = Ot;
			return;
		}
*/
	sysfatal("unknown pppoe field or protocol: %s", f->s);
}
static void
p_compiledisc(Filter *f)
{
//	Mux *m;

	if(f->op == '='){
		compile_cmp(pppoe_disc.name, f, p_fields);
		return;
	}
/*
	for(m = p_mux; m->name != nil; m++)
		if(strcmp(f->s, m->name) == 0){
			f->pr = m->pr;
			f->ulv = m->val;
			f->subop = Ot;
			return;
		}
*/
	sysfatal("unknown pppoe field or protocol: %s", f->s);
}

static int
p_filter(Filter *f, Msg *m)
{
	Hdr *h;

	if(m->pe - m->ps < HDRSIZE)
		return 0;

	h = (Hdr*)m->ps;
	m->ps += HDRSIZE;

	switch(f->subop){
	case Overs:
		return (h->verstype>>4) == f->ulv;
	case Otype:
		return (h->verstype&0xF) == f->ulv;
	case Ocode:
		return h->code == f->ulv;
	case Osess:
		return NetS(h->sessid) == f->ulv;
	}
	return 0;
}

/* BUG: print all the discovery types */
static int
p_seprintdisc(Msg *m)
{
	Hdr *h;
	int len;

	len = m->pe - m->ps;
	if(len < HDRSIZE)
		return -1;

	h = (Hdr*)m->ps;
	m->ps += HDRSIZE;

	m->pr = nil;

	m->p = seprint(m->p, m->e, "v=%d t=%d c=0x%x s=0x%ux, len=%d",
		h->verstype>>4, h->verstype&0xF, h->code, NetS(h->sessid), NetS(h->length));

	return 0;
}

static int
p_seprintsess(Msg *m)
{
	Hdr *h;
	int len;

	len = m->pe - m->ps;
	if(len < HDRSIZE)
		return -1;

	h = (Hdr*)m->ps;
	m->ps += HDRSIZE;

	/* this will call ppp for me */
	demux(p_mux, 0, 0, m, &dump);

	m->p = seprint(m->p, m->e, "v=%d t=%d c=0x%x s=0x%ux, len=%d",
		h->verstype>>4, h->verstype&0xF, h->code, NetS(h->sessid), NetS(h->length));

	return 0;
}

Proto pppoe_disc =
{
	"pppoe_disc",
	p_compiledisc,
	p_filter,
	p_seprintdisc,
	p_mux,
	"%lud",
	p_fields,
	defaultframer
};

Proto pppoe_sess =
{
	"pppoe_sess",
	p_compilesess,
	p_filter,
	p_seprintsess,
	p_mux,
	"%lud",
	p_fields,
	defaultframer
};