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#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},
};
int
parthdrlen(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;
}
int
parsehdr(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 void
p_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 int
p_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 int
p_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,
};
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