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Bug 1900565 - Further improve performance of JSON echo functionality
Summary: Further improve performance of JSON echo functionality
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: nftables
Version: 8.4
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: rc
: 8.4
Assignee: Phil Sutter
QA Contact: Tomas Dolezal
URL:
Whiteboard:
Depends On: 1835300
Blocks:
TreeView+ depends on / blocked
 
Reported: 2020-11-23 11:56 UTC by Phil Sutter
Modified: 2021-05-18 15:10 UTC (History)
3 users (show)

Fixed In Version: nftables-0.9.3-17.el8
Doc Type: Enhancement
Doc Text:
Feature: Performance of 'nft --echo --json' has been improved. The required mapping from kernel response containing assigned handles to user input was slow if user input was huge, e.g. when restoring a set with many elements. Via introduction of a hash table for this purpose, the delay is avoided entirely. Reason: Firewalld is a user of libnftables' JSON API, maintaining blacklists in there could lead to significant startup delay depending on list size. Result: No slowdown in firewalld anymore.
Clone Of: 1835300
Environment:
Last Closed: 2021-05-18 15:10:15 UTC
Type: Bug
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)

Comment 3 Phil Sutter 2020-12-07 14:54:11 UTC 
There's a required follow-up, above improvement by itself does not work and breaks JSON echo functionality:

commit 299ec575faa6b070940b483dc517ecd883b9f1a4
Author: Phil Sutter <phil>
Date:   Wed Dec 2 23:07:11 2020 +0100

    json: Fix seqnum_to_json() functionality
    
    Introduction of json_cmd_assoc_hash missed that by the time the hash
    table insert happens, the struct cmd object's 'seqnum' field which is
    used as key is not initialized yet. This doesn't happen until
    nft_netlink() prepares the batch object which records the lowest seqnum.
    Therefore push all json_cmd_assoc objects into a temporary list until
    the first lookup happens. At this time, all referenced cmd objects have
    their seqnum set and the list entries can be moved into the hash table
    for fast lookups.
    
    To expose such problems in the future, make json_events_cb() emit an
    error message if the passed message has a handle but no assoc entry is
    found for its seqnum.
    
    Fixes: 389a0e1edc89a ("json: echo: Speedup seqnum_to_json()")
    Cc: Derek Dai <daiderek>
    Signed-off-by: Phil Sutter <phil>
Comment 4 Phil Sutter 2021-01-12 14:49:01 UTC 
And one more follow-up to the original backport:

commit 48917d876d51cd6ba5bff07172acef05c9e12474
Author: Florian Westphal <fw>
Date:   Mon Dec 14 16:53:29 2020 +0100

    json: don't leave dangling pointers on hlist
    
    unshare -n tests/json_echo/run-test.py
    [..]
    Adding chain c
    free(): double free detected in tcache 2
    Aborted (core dumped)
    
    The element must be deleted from the hlist prior to freeing it.
    
    Fixes: 389a0e1edc89a ("json: echo: Speedup seqnum_to_json()")
    Signed-off-by: Florian Westphal <fw>
Comment 6 Phil Sutter 2021-01-21 15:59:53 UTC 
One more follow-up to the original backport:

commit 48917d876d51cd6ba5bff07172acef05c9e12474
Author: Florian Westphal <fw>
Date:   Mon Dec 14 16:53:29 2020 +0100

    json: don't leave dangling pointers on hlist
    
    unshare -n tests/json_echo/run-test.py
    [..]
    Adding chain c
    free(): double free detected in tcache 2
    Aborted (core dumped)
    
    The element must be deleted from the hlist prior to freeing it.
    
    Fixes: 389a0e1edc89a ("json: echo: Speedup seqnum_to_json()")
    Signed-off-by: Florian Westphal <fw>
Comment 14 errata-xmlrpc 2021-05-18 15:10:15 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 (nftables bug fix and enhancement update), 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://access.redhat.com/errata/RHEA-2021:1722
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