Re: Request for a DLT code for IPMB packet

[Guy Harris <guy () alum mit edu>]

Toeung, Chanthy wrote:

> I'm doing a project on creating a plugins of packet IPMB ( with I2C
> interface ) in Wireshark.
>
> Now i need a specific DLT code for this packet so that i can put my
> code in Open Source of Wirshark. Can you please assign me one number ?

So presumably the first byte of the packet data will be the slave
address, followed by the netFn and LUN, followed by the checksum, etc.?

> Moreover, Can you tell me how to add a new Capture type to libpcap ?

Capture type, or DLT_ type?

If you mean "capture type", i.e. a new mechanism for capturing traffic
(so that you can capture traffic on the I2C bus), you'd have to modify
the pcap-*.c file for the OS on which you're doing this (pcap-win32.c
for Windows, pcap-linux.c for Linux, pcap-bpf.c for various BSDs
including OS X, pcap-dlpi.c for Solaris and some other UN*Xes, etc.).

See, for example, pcap-linux.c's "pcap_open_live()" routine.  It checks
for some special device names - any name with "dag" in it is assumed to
be an Endace DAG device, any name with "septel" in it is assumed to be
an Intel SS7 device, etc. - and, for each of the special device name
types, calls a special open_live routine.

If you want to add an I2C/IPMB capture device, you'd add a similar chunk
of code to the open_live routine for the OS you're using, and have it
call an open_live routine for I2C/IPMB.  That routine would check the
device name (it might, for example, be "i2c" or "ipmb"), allocate a
pcap_t data structure, and fill it in appropriately.

Some of the items to fill in are pointers to routines to, for example,
read a new packet from the device.

See, for example, the Linux Bluetooth and USB capture devices for
examples.  Unfortunately, there's no "how to add a new type of capture
device" documentation - and the interface for that will probably change
at some point.

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