[Ovmsdev] PCAP CAN bus dump
mark at webb-johnson.net
Sat Apr 28 11:08:50 HKT 2018
All good now.
I wanted to support another format (binary) in the hopes that speed could improve (CRTD involves a lot of conversion), but really not impressed with the PCAP format - takes 24 bytes to store 1 CAN frame (which is almost the same as CRTD in a textually readable format. Haven’t done any speed tests yet.
Are there any other standard CAN dump/log formats in popular use out there? I seem to remember some Nissan Leaf dumps out in the wild in some binary format, but never found out how to read them.
Is this can-do?
But it seems a weirdly over-complex format, with no support for extended IDs (or at least as documented there)?
> On 28 Apr 2018, at 1:02 AM, Greg D. <gregd2350 at gmail.com> wrote:
> Hi Mark,
> Sorry, I missed last night's request for this. I have a number of Wireshark traces during my development of the OBDII ECU code, taken on a Raspberry Pi with a PICAN-2 interface attached. They're saved in PCAPNG format, but I can load and resave them as needed, or take new ones if there's something in particular to capture.
> Any need at this point?
> Mark Webb-Johnson wrote:
>> PCAP support is now in (for RE).
>> OVMS# re start
>> OVMS# re serve format cap
>> OVMS# re serve mode simulate
>> # Capture over Wifi to pcap
>> $ nc OVMS.local 3000 >my.pcap
>> # Replay pcap over Wifi
>> $ nc OVMS.local 3000 <my.pcap >/dev/null
>> Seems to work ok, but I only support big endian micro-second resolution pcaps (at the moment). You’d need to fix byte ordering in the pcap header record to be able to replay your existing pcaps into it.
>> I’ve tested some simulated captures, into Wireshark, and it seems fine for me. Will try in a real car tomorrow. Thanks for your help with the captures. Very helpful to see what is going on with a real example.
>> Regards, Mark.
>>> On 27 Apr 2018, at 1:58 PM, Tom Parker <tom at carrott.org <mailto:tom at carrott.org>> wrote:
>>> https://carrott.org/pcaps/ <https://carrott.org/pcaps/>
>>> These were captured with tcpdump and an USB can interface with slcan driver. I post processed them to byte swap the can ID with https://carrott.org/git/leaf-can-dissector.git/blob/HEAD:/pcap-canid-endian-swap.py <https://carrott.org/git/leaf-can-dissector.git/blob/HEAD:/pcap-canid-endian-swap.py>
>>> I don't know why tcpdump and wireshark disagree on the byte order of the can id.
>>> On Apr 27, 2018 5:24 PM, Mark Webb-Johnson <mark at webb-johnson.net> <mailto:mark at webb-johnson.net> wrote:
>>>> Has anybody got an example of a PCAP format canbus dump file? Some dump from a car in a suitable format for loading into wireshark (pcap not pcapng).
>>>> If so, please eMail to me (mark at webb-johnson.net <mailto:mark at webb-johnson.net>) or give me a link to where I can download from.
>>>> I need it to verify that OVMS can read/write to that format.
>>>> Thanks, Mark.
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