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/*
* Radio tap as exported by BSD and Linux.
* The wireless ethernet devices return this format on Linux
* when running in monitor mode.
*
* TODO: Automatically determine whether the ethernet
* device is radio or ether, so that -h is not needed.
*/
#include <u.h>
#include <libc.h>
#include <ip.h>
#include "dat.h"
#include "protos.h"
static Mux p_mux[] =
{
{ "802.11", 0 },
{ 0 }
};
typedef struct Hdr Hdr;
struct Hdr
{
uchar vers;
uchar pad;
ushort len;
ulong present;
};
static int
unpackhdr(uchar *p, uchar *ep, Hdr *h)
{
if(p+sizeof(Hdr) > ep)
return -1;
h->vers = p[0];
h->pad = p[1];
h->len = LittleS(p+2);
h->present = LittleL(p+4);
// can be more present fields if 0x80000000 is set in each along the chain.
if(p+h->len > ep)
return -1;
return 0;
}
enum
{
Ot,
};
static Field p_fields[] =
{
{ 0 }
};
static void
p_compile(Filter *f)
{
Mux *m;
if(f->op == '='){
compile_cmp(radiotap.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 radiotap field or protocol: %s", f->s);
}
static int
p_filter(Filter *f, Msg *m)
{
Hdr h;
memset(&h, 0, sizeof h);
if(unpackhdr(m->ps, m->pe, &h) < 0)
return 0;
m->ps += h.len;
switch(f->subop){
case Ot:
return 1;
}
return 0;
}
static int
p_seprint(Msg *m)
{
Hdr h;
memset(&h, 0, sizeof h);
if(unpackhdr(m->ps, m->pe, &h) < 0)
return -1;
m->p = seprint(m->p, m->e, "%.*H", h.len, m->ps);
m->ps += h.len;
m->pr = &p80211;
return 0;
}
Proto radiotap =
{
"radiotap",
p_compile,
p_filter,
p_seprint,
p_mux,
nil,
nil,
defaultframer
};
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