Ethereal-dev: Re: [Ethereal-dev] Need an extra bit in the packet-header struct.
Guy Harris wrote:
On Mon, Jun 28, 2004 at 11:44:26PM -0700, Ben Greear wrote:
I have need for an extra bit in the header for each packet.
This is to tell me whether the packet was received or transmitted
on this interface.
To which "packet header structure" are you referring?
I wasn't aware I had more than once choice. I'm
talking about this one from pcap.h:
struct pcap_pkthdr {
struct timeval ts; /* timestamp */
bpf_u_int32 caplen; /* length of portion present */
bpf_u_int32 len; /* length this packet (off wire) */
};
Since the length fields are 32-bit, and there is no 4GB packet to be
had, I was thinking I could just use the high-bit there.
If it's "wtap_pkthdr", you might as well just add an entire field -
especially given that "received or transmitted" don't cover all the
possibilities; there's also
unknown (if you really don't know whether the packet was
received or transmitted)
received {unicast,broadcast,multicast} (some packet capture
mechanisms supply this information; current libpcap doesn't pass
that through, but it might do so in the future)
along with "transmitted" and "received but that's all I know about it".
If it's "frame_data", there's already a flag field, although, again, the
direction indicator should be more than one bit.
A quick google leads me to believe these are specific to ethereal. I'll
grab the source and poke around.
Thanks,
Ben
--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc http://www.candelatech.com
