netfilter buglog - Dec 2019 - [Bug 1386] New: nftables.py cmd doesn't read updated counter values after first read

https://bugzilla.netfilter.org/show_bug.cgi?id=1386

            Bug ID: 1386
           Summary: nftables.py cmd doesn't read updated counter values
                    after first read
           Product: nftables
           Version: unspecified
          Hardware: x86_64
                OS: Gentoo
            Status: NEW
          Severity: major
          Priority: P5
         Component: nft
          Assignee: pablo at netfilter.org
          Reporter: karel at unitednetworks.cz

Created attachment 577
  --> https://bugzilla.netfilter.org/attachment.cgi?id=577&action=edit
example of nftables.py not reading updated counter state

System:

Gentoo 5.4.1 x86_64
nft up to date from GIT as of 4.12.2019
CPython 3.6.9


Overview:

nft commands which read named counters actually read counter values only first
time, subsequent reads returns values from first read.


Detailed info:

Consider this ruleset:

add table ip table1
add counter ip table1 counter1
add chain ip table1 chain1 { type filter hook input priority 0; }
add rule ip table1 chain1 counter name counter1

Then ping several times localhost, after that call nftables.py cmd:

list counter table1 counter1

and you will see some packets added to this counter. Ping localhost several
times again and call nftables.py cmd again:

list counter table1 counter1

and you will see same counter values as in first call without adding some
packets from second pinging. But when running nft from shell:

nft list counter table1 counter1

the values returned will be different from second call through nftables.py cmd
and will account packets from second pinging.


See attached example.

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https://bugzilla.netfilter.org/show_bug.cgi?id=1386

Karel Rericha <karel at unitednetworks.cz> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
 Attachment #577 is|0                           |1
           obsolete|                            |

--- Comment #1 from Karel Rericha <karel at unitednetworks.cz> ---
Created attachment 585
  --> https://bugzilla.netfilter.org/attachment.cgi?id=585&action=edit
example of nftables.py not reading updated counter state, v2

Bug still present on

Gentoo x86_64 kernel 5.4.14 x86_64
nftables from GIT as of 31.1.2020

Posted improved example.

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https://bugzilla.netfilter.org/show_bug.cgi?id=1386

Pablo Neira Ayuso <pablo at netfilter.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED

--- Comment #2 from Pablo Neira Ayuso <pablo at netfilter.org> ---
https://patchwork.ozlabs.org/project/netfilter-devel/patch/20200806112139.1977-1-pablo
at netfilter.org/

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--- Comment #3 from Karel Rericha <karel at unitednetworks.cz> ---
I can confirm that after applying Pablo's patch reading updated counters
works,
bug is fixed.

Thanks a lot again Pablo!

And again I will close this after patch will land in nftables git.

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Karel Rericha <karel at unitednetworks.cz> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

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