On Wed, Sep 07, 2022 at 11:53:03AM -0400, Ben Cotton wrote: > https://fedoraproject.org/wiki/Changes/KTLSSupportForGnuTLS > > This document represents a proposed Change. As part of the Changes > process, proposals are publicly announced in order to receive > community feedback. This proposal will only be implemented if approved > by the Fedora Engineering Steering Committee. > > == Summary == > Acceleration of GnuTLS with software ''Kernel TLS'' (KTLS) > > == Owner == > * Name: [[User:Fkrenzel| František Krenželok]], [[User:Ueno| Daiki Ueno]] > * Email: fkrenzel@xxxxxxxxxx, dueno@xxxxxxxxxx > > > == Detailed Description == > The goal of this change is to provide GnuTLS users with a high > throughput data transfer mechanism on encrypted channels, with > emphasis on ''network block devices'' (NBD). > > We accomplish this with KTLS which offloads enc/decryption (TLS > record) to the kernel, while GnuTLS handles initial connection (TLS > handshake). > > GNUTLS will detect whether the kernel supports kTLS and will > automatically enable its usage when compatible. Any package built > against GNUTLS, is likely to see some performance benefit from kTLS, > provided it has not installed custom push/pull I/O function callbacks. > > kTLS enables a reduction in context switching and reduced data copies > when using send_file(). With suitable NIC hardware the encryption > operations can be offloaded, freeing time on the main CPUs for > application usage. Without offload hardware, kTLS may still improve > parallelism for applications as the kernel can perform encryption > operations on a differen host CPU to that running the application > threads > > == Feedback == > <!-- Summarize the feedback from the community and address why you > chose not to accept proposed alternatives. This section is optional > for all change proposals but is strongly suggested. Incorporating > feedback here as it is raised gives FESCo a clearer view of your > proposal and leaves a good record for the future. If you get no > feedback, that is useful to note in this section as well. For > innovative or possibly controversial ideas, consider collecting > feedback before you file the change proposal. --> > > == Benefit to Fedora == > The improvement lies in acceleration of large data transfers trough > encrypted channels. > The send_file function enables us to send data directly trough socket > without entering user space, saving us from 2 context switches and 2 > additional user space buffers. This is especially useful for NBD > > '''Benefits''' > * Acceleration of ''live VM migration'', which should mitigate the > downtime for various services used by both the users and the > developers. > > * Increased speed at which files can be retrieved from NBD via > encrypted channel and less CPU and memory strain on NBD server. > > packages that might benefit: {{package|nbd}} {{package|nbdkit}} {{package|qemu}} Also: {{package|libnbd}} >From the point of the packages above, kTLS has been enabled already for a while, but it does require the gnutls default to change. > == Scope == > * Proposal owners: Support for KTLS key update in GnuTLS ''track'': > [https://gitlab.com/gnutls/gnutls/-/merge_requests/1625 gitlab] > * Other developers: Support for TLS1.3 key update in KTLS (tls kernel module) > * Release engineering: not needed for this Change > * Policies and guidelines: not needed for this Change > * Trademark approval: not needed for this Change > * Alignment with Objectives: None > > == Upgrade/compatibility impact == > Although this feature will be enabled by default, users will not > notice any change, as in case of failure to initialize KTLS, GnuTLS > will fallback to the currently used mode of operation. > > Users will be also provided with means to disable this feature trough > crypto-policies > > == How To Test == > '''To enable this feature user has to:''' > # load TLS kernel module (`modprobe tls`) It would be nice if manually loading the module wasn't necessary. > # enable ktls with crypto policies > {{admon/note|Once proposal accepted|KTLS will be enabled by default > and this step will not be needed.}} > <pre>$ cat > /etc/crypto-policies/local.d/gnutls-ktls.config <<EOF > [global] > ktls = true > EOF > </pre> > <pre>$ update-crypto-policies</pre> > {{admon/important||KTLS will not initialize if app uses custom > push/pull callback for GnuTLS.}} > > == User Experience == > This change should accelerate large data transfers especially that of files. > This will affect users that use applications which utilize GnuTLS for > encrypting communication channels. > > == Dependencies == > > Currently '''KTLS doesn't support key_update''' (The keys delivered to > the kernel can’t be set more than once per session) so a kernel module > patch would be needed for this functionality. > This not only impacts key_update invokation by user of either side, > but also by [https://datatracker.ietf.org/doc/html/rfc8446#section-5.5 > AES-GCM key usage limit]. As this could weaken the security of TLS > protocol, GnuTLS will disable KTLS for rest of the session and > fallback to default mode of operation i.e. move encryption and > decryption back to usersace after the key_update is called. > > {{admon/note|GnuTLS supports KTLS key_update| This feature is > supported if apropriate kernel patch is applied}} > > == Contingency Plan == > * Contingency mechanism: Feature will be disabled by default in crypto-policies. > * Contingency deadline: 2023-02-21 > * Blocks release? No > > > == Documentation == > === API === > '''[https://gnutls.org/manual/gnutls.html#index-gnutls_005ftransport_005fis_005fktls_005fenabled > gnutls_transport_is_ktls_enabled()]''' > To check if KTLS was properly initialized on the interfaces: > {{admon/important||it has to be invoked no earlier that after a TLS-handshake}} > <pre> gnutls_transport_ktls_enable_flags_t > gnutls_transport_is_ktls_enabled(gnutls_session_t session);</pre> > > > '''[https://gnutls.org/manual/gnutls.html#index-gnutls_005frecord_005fsend_005ffile > gnutls_record_send_file()]''' > To send data directly from a file descriptor in a zero-copy manner if > KTLS is enabled; otherwise it will just iteratively read from the file > descriptor: > <pre> ssize_t gnutls_record_send_file(gnutls_session_t session, int > fd, off_t *offset, size_t count);</pre> > > == Release Notes == > > > > -- > Ben Cotton > He / Him / His > Fedora Program Manager > Red Hat > TZ=America/Indiana/Indianapolis Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-builder quickly builds VMs from scratch http://libguestfs.org/virt-builder.1.html _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx Do not reply to spam, report it: https://pagure.io/fedora-infrastructure/new_issue
