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Nadia Pinaeva writes: I am working on a tool that allows collecting network performance metrics by using conntrack events. Start time of a conntrack entry is used to evaluate seen_reply latency, therefore the sooner it is timestamped, the better the precision is. In particular, when using this tool to compare the performance of the same feature implemented using iptables/nftables/OVS it is crucial to have the entry timestamped earlier to see any difference. At this time, conntrack events can only get timestamped at recv time in userspace, so there can be some delay between the event being generated and the userspace process consuming the message. There is sys/net/netfilter/nf_conntrack_timestamp, which adds a 64bit timestamp (ns resolution) that records start and stop times, but its not suited for this either, start time is the 'hashtable insertion time', not 'conntrack allocation time'. There is concern that moving the start-time moment to conntrack allocation will add overhead in case of flooding, where conntrack entries are allocated and released right away without getting inserted into the hashtable. Also, even if this was changed it would not with events other than new (start time) and destroy (stop time). Pablo suggested to add new CTA_TIMESTAMP_EVENT, this adds this feature. The timestamp is recorded in case both events are requested and the sys/net/netfilter/nf_conntrack_timestamp toggle is enabled. Reported-by: Nadia Pinaeva <n.m.pinaeva@gmail.com> Suggested-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> |
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| fs | ||
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| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
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| net | ||
| rust | ||
| samples | ||
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| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.