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Bug 1176612 - The initial packet is not displayed with libpcap-1.5.3-3.el7_0.1 when traffic is monitored with tcpdump
Summary: The initial packet is not displayed with libpcap-1.5.3-3.el7_0.1 when traffic...
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: libpcap
Version: 7.1
Hardware: Unspecified
OS: Unspecified
high
high
Target Milestone: rc
: ---
Assignee: Michal Sekletar
QA Contact: Tomas Dolezal
URL:
Whiteboard:
Depends On:
Blocks: 1168850 1179458 1191023 1207666
TreeView+ depends on / blocked
 
Reported: 2014-12-22 15:15 UTC by Patrik Kis
Modified: 2015-11-19 11:46 UTC (History)
11 users (show)

Fixed In Version: libpcap-1.5.3-7.el7
Doc Type: Bug Fix
Doc Text:
Prior to this update, the libpcap library filtering mechanism did not correctly detect the initial network packet if capturing on all interfaces was requested. As a consequence, the tcpdump utility failed to capture the initial packet. The libpcap code has been patched to account for the additional SLL header automatically added by the kernel, thus fixing this bug. As a result, tcpdump now also captures initial packet.
Clone Of:
: 1207666 (view as bug list)
Environment:
Last Closed: 2015-11-19 11:46:27 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2015:2130 0 normal SHIPPED_LIVE libpcap bug fix update 2015-11-19 10:30:52 UTC

Comment 2 Patrik Kis 2014-12-22 15:22:52 UTC 
Created attachment 972069 [details]
packets captured by wireshark
Comment 3 Michal Sekletar 2014-12-22 20:31:25 UTC 
Are you observing the same behavior on other architectures too? Can you rerun the test but tell tcpdump to capture on specific interface, i.e. eth0 on server? So we can possibly rule out issues with cooked mode. Also try to retest but don't disable promiscuous mode.

It is weird that it works in Wireshark, because it uses libpcap too.
Comment 5 Michal Sekletar 2015-01-06 09:24:52 UTC 
Knowing that it works when capturing on specific interface, is very valuable. Thanks for sharing test results.

Although, so far I have no idea where is the problem. I have to investigate further.
Comment 7 Michal Sekletar 2015-01-10 11:11:40 UTC 
I think I was able to pin down the problem. I started an upstream discussion about the issue. Hopefully we get some response from upstream maintainers soon.

https://github.com/the-tcpdump-group/libpcap/issues/405

My current fix is bit of a hack, I figure that proper fix will be more involved and will require further work upstream.

In the meantime here are the test packages,

https://msekleta.fedorapeople.org/libpcap-1176612/
Comment 8 Michal Sekletar 2015-01-13 14:59:25 UTC 
I agree with Honza, let's defer it to 7.2.
Comment 10 Michal Sekletar 2015-01-15 10:22:42 UTC 
Seems like this can't be deferred. There was no response from upstream. Though, I was able to come up with "safer" fix for the issue which seems to be working.
Comment 14 Michal Sekletar 2015-03-31 11:34:04 UTC 
http://pkgs.devel.redhat.com/cgit/rpms/libpcap/commit/?h=rhel-7.2&id=69fae2c0eb7868254b763b24b6b555d1268e459e -> MODIFIED
Comment 24 errata-xmlrpc 2015-11-19 11:46:27 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2015-2130.html
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