dumpcap w/ pcapng produces out of order/negative times

dumpcap w/ pcapng produces out of order/negative times

[Ben Magistro]

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While utilizing dumpcap with our app, we have observed the captured file
producing out of order timestamps to include negative times.  We are still
investigating the root cause but believe it is in lib/pcapng.  While doing
some testing of this issue, this behavior was not observed with pcap.  In
the attached pcap, there are 5 streams (same curl multiple times a few
seconds apart), with streams 1 and 3 showing oddities.  Specifically,
stream 1 is in the future relative to the packet order and stream 3 has a
negative time.

Not sure if the pcap file will actual post/attach, if it doesn't will try
something.

System: CentOS7 + devtoolset 9
DPDK: v21.11

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Re: dumpcap w/ pcapng produces out of order/negative times

[Stephen Hemminger]

On Thu, 13 Jan 2022 21:38:06 -0500
Ben Magistro <koncept1@gmail.com> wrote:

> While utilizing dumpcap with our app, we have observed the captured file
> producing out of order timestamps to include negative times.  We are still
> investigating the root cause but believe it is in lib/pcapng.  While doing
> some testing of this issue, this behavior was not observed with pcap.  In
> the attached pcap, there are 5 streams (same curl multiple times a few
> seconds apart), with streams 1 and 3 showing oddities.  Specifically,
> stream 1 is in the future relative to the packet order and stream 3 has a
> negative time.
> 
> Not sure if the pcap file will actual post/attach, if it doesn't will try
> something.
> 
> System: CentOS7 + devtoolset 9
> DPDK: v21.11

The library hast convert from TSC (cpu clock) to nanoseconds since 1/1/1970
The function pcapng_init computes the offset. 

Re: dumpcap w/ pcapng produces out of order/negative times

[Ben Magistro]

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In case others wind up here, the issue described here appears to be
addressed by "libpcapng: fix timestamp wrapping in output files".  Thanks
for the patch!

https://patches.dpdk.org/project/dpdk/patch/20220517100115.157888-1-quentin@armitage.org.uk/

On Fri, Jan 14, 2022 at 11:15 AM Stephen Hemminger <
stephen@networkplumber.org> wrote:

> On Thu, 13 Jan 2022 21:38:06 -0500
> Ben Magistro <koncept1@gmail.com> wrote:
>
> > While utilizing dumpcap with our app, we have observed the captured file
> > producing out of order timestamps to include negative times.  We are
> still
> > investigating the root cause but believe it is in lib/pcapng.  While
> doing
> > some testing of this issue, this behavior was not observed with pcap.  In
> > the attached pcap, there are 5 streams (same curl multiple times a few
> > seconds apart), with streams 1 and 3 showing oddities.  Specifically,
> > stream 1 is in the future relative to the packet order and stream 3 has a
> > negative time.
> >
> > Not sure if the pcap file will actual post/attach, if it doesn't will try
> > something.
> >
> > System: CentOS7 + devtoolset 9
> > DPDK: v21.11
>
> The library hast convert from TSC (cpu clock) to nanoseconds since 1/1/1970
> The function pcapng_init computes the offset.
>

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