#include <u.h>#include <libc.h>#include <ip.h>#include "dat.h"#include "protos.h"/* GRE version 0 is specified in rfc1701. GRE version 0 has been respecified in rfc2784 as a subset of rfc1701. GRE version 1, as used by pptp, has been specified in rfc2637.*//* GRE flag bits */enum {	GRE_chksum	= (1<<15),	GRE_routing	= (1<<14),	GRE_key		= (1<<13),	GRE_seq		= (1<<12),	GRE_srcrt		= (1<<11),	GRE_recur	= (7<<8),	GRE_ack		= (1<<7),	GRE_version	= 0x7,};typedef struct Hdr	Hdr;struct Hdr{	ushort flags;	ushort proto;	uchar version;	ushort chksum;	ushort offset;	ulong key;	ulong seq;	ulong route;	ulong ack;};enum{	Oproto,};static Field p_fields[] = {	{"proto",		Fnum,	Oproto,	"encapsulated protocol",	} ,	{0}};static Mux p_mux[] ={	{"pup",	0x0200, },	{"xns",	0x0600, },	{"ip",		0x0800, },	{"chaos",	0x0804, },	{"arp",	0x0806, },	{"frarp",	0x0808, },	{"vines",	0x0bad, },	{"vinesecho",	0x0bae, },	{"vinesloop",	0x0baf, },	{"ppp",	0x880b, },	{"llc",	0x007a, },	{"dot1q",	0x8100, },	{"eapol",	0x888e, },	{0},};intparthdrlen(ushort flags){	return 4 + 		(flags&GRE_chksum || flags&GRE_routing) ? 4 : 0 +		flags&GRE_key ? 4 : 0 +		flags&GRE_seq ? 4 : 0 +		flags&GRE_ack ? 4 : 0;}intparsehdr(Hdr *h, uchar *s, uchar *e){	uchar *p;	uchar n;	if(e - s < 4)		return -1;	p = s;	h->flags = NetS(p);	p += 2;	h->proto = NetS(p);	p += 2;	h->version = h->flags&GRE_version;	if(parthdrlen(h->flags) > e - s)		return -1;	if(h->flags&(GRE_chksum|GRE_routing)){		h->chksum = NetS(p);		p += 2;		h->offset = NetS(p);		p += 2;	}	if(h->flags&GRE_key){		h->key = NetL(p);		p += 4;	}	if(h->flags&GRE_seq){		h->seq = NetL(p);		p += 4;	}	if(h->flags&GRE_ack){		h->ack = NetL(p);		p += 4;	}	if(h->flags&GRE_routing){		for(;;){			if(e - p < 4)				return -1;			if((n = p[3]) == 0)				break;			p += n;		}	}	return p - s;}static voidp_compile(Filter *f){	Mux *m;	if(f->op == '='){		compile_cmp(gre.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 = Oproto;			return;		}	sysfatal("unknown gre field or protocol: %s", f->s);}static intp_filter(Filter *f, Msg *m){	Hdr h;	int len;	len = parsehdr(&h, m->ps, m->pe);	if(len < 0)		return -1;	m->ps += len;	switch(f->subop){	case Oproto:		return h.proto == f->ulv;	}	return 0;}static intp_seprint(Msg *m){	Hdr h;	int len;	len = parsehdr(&h, m->ps, m->pe);	if(len < 0)		return -1;	m->ps += len;	demux(p_mux, h.proto, h.proto, m, &dump);	m->p = seprint(m->p, m->e, "version=%d proto=%#ux flags=%#.4ux", h.version, h.proto, h.flags);	if(h.flags&GRE_chksum)		m->p = seprint(m->p, m->e, " checksum=%#.4ux", h.chksum);	if(h.flags&GRE_key)		m->p = seprint(m->p, m->e, " key=%#.8ulx", h.key);	if(h.flags&GRE_seq)		m->p = seprint(m->p, m->e, " seq=%#.8ulx", h.seq);	if(h.flags&GRE_ack)		m->p = seprint(m->p, m->e, " ack=%#.8ulx", h.ack);	if(h.flags&GRE_routing)		m->p = seprint(m->p, m->e, " offset=%#ux haverouting", h.offset);	if(h.version == 0)		m->p = seprint(m->p, m->e, " recursion=%ud", (h.flags&GRE_recur)>>8);		return 0;}Proto gre ={	"gre",	p_compile,	p_filter,	p_seprint,	p_mux,	"%#.4ux",	p_fields,	defaultframer,};