Historically we had two top level XSL files for top level and nested documents which only differ in what they pass for 'href_base' to the main 'page.xsl' file. We can instead pass the variable as argument from the build system so that we have just one XSL file and also allow for more nested document trees in the future. The '404' page is special even with the current XSL way so we add a special case for it. Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- docs/go/meson.build | 5 +++-- docs/internals/meson.build | 5 +++-- docs/kbase/meson.build | 5 +++-- docs/manpages/meson.build | 5 +++-- docs/meson.build | 12 ++++++++---- docs/site.xsl | 12 +----------- docs/subsite.xsl | 24 ------------------------ 7 files changed, 21 insertions(+), 47 deletions(-) delete mode 100644 docs/subsite.xsl diff --git a/docs/go/meson.build b/docs/go/meson.build index 0ae0216ce3..c0e19c4182 100644 --- a/docs/go/meson.build +++ b/docs/go/meson.build @@ -3,7 +3,6 @@ docs_go_files = [ 'libvirtxml', ] -html_xslt_gen_xslt = subsite_xsl html_xslt_gen_install_dir = docs_html_dir / 'go' html_xslt_gen = [] @@ -14,6 +13,7 @@ foreach name : docs_go_files 'name': name, 'file': docs_rst2html5_gen.process(rst_file), 'source': 'docs' / 'go' / rst_file, + 'href_base': '../', } endforeach @@ -33,8 +33,9 @@ foreach data : html_xslt_gen '--stringparam', 'pagesrc', data.get('source', ''), '--stringparam', 'builddir', meson.build_root(), '--stringparam', 'timestamp', docs_timestamp, + '--stringparam', 'href_base', data.get('href_base', ''), '--nonet', - html_xslt_gen_xslt, + site_xsl, '@INPUT@', ], depends: data.get('depends', []), diff --git a/docs/internals/meson.build b/docs/internals/meson.build index 2d0ae6195c..298a55dd88 100644 --- a/docs/internals/meson.build +++ b/docs/internals/meson.build @@ -5,7 +5,6 @@ internals_in_files = [ 'rpc', ] -html_xslt_gen_xslt = subsite_xsl html_xslt_gen_install_dir = docs_html_dir / 'internals' html_xslt_gen = [] @@ -13,6 +12,7 @@ foreach name : internals_in_files html_xslt_gen += { 'name': name, 'source': 'docs' / 'internals' / name + '.html.in', + 'href_base': '../' } endforeach @@ -32,8 +32,9 @@ foreach data : html_xslt_gen '--stringparam', 'pagesrc', data.get('source', ''), '--stringparam', 'builddir', meson.build_root(), '--stringparam', 'timestamp', docs_timestamp, + '--stringparam', 'href_base', data.get('href_base', ''), '--nonet', - html_xslt_gen_xslt, + site_xsl, '@INPUT@', ], depends: data.get('depends', []), diff --git a/docs/kbase/meson.build b/docs/kbase/meson.build index 4114fc81d1..e37feb6d30 100644 --- a/docs/kbase/meson.build +++ b/docs/kbase/meson.build @@ -24,7 +24,6 @@ docs_kbase_files = [ 'virtiofs', ] -html_xslt_gen_xslt = subsite_xsl html_xslt_gen_install_dir = docs_html_dir / 'kbase' html_xslt_gen = [] @@ -35,6 +34,7 @@ foreach name : docs_kbase_files 'name': name, 'file': docs_rst2html5_gen.process(rst_file), 'source': 'docs' / 'kbase' / rst_file, + 'href_base': '../', } endforeach @@ -54,8 +54,9 @@ foreach data : html_xslt_gen '--stringparam', 'pagesrc', data.get('source', ''), '--stringparam', 'builddir', meson.build_root(), '--stringparam', 'timestamp', docs_timestamp, + '--stringparam', 'href_base', data.get('href_base', ''), '--nonet', - html_xslt_gen_xslt, + site_xsl, '@INPUT@', ], depends: data.get('depends', []), diff --git a/docs/manpages/meson.build b/docs/manpages/meson.build index d9fcb6b057..ba673cf472 100644 --- a/docs/manpages/meson.build +++ b/docs/manpages/meson.build @@ -1,4 +1,3 @@ -html_xslt_gen_xslt = subsite_xsl html_xslt_gen_install_dir = docs_html_dir / 'manpages' html_xslt_gen = [] @@ -130,6 +129,7 @@ foreach data : docs_man_files 'name': data['name'], 'file': html_in, 'source': 'docs' / 'manpages' / rst_in_file, + 'href_base': '../', } endforeach @@ -149,8 +149,9 @@ foreach data : html_xslt_gen '--stringparam', 'pagesrc', data.get('source', ''), '--stringparam', 'builddir', meson.build_root(), '--stringparam', 'timestamp', docs_timestamp, + '--stringparam', 'href_base', data.get('href_base', ''), '--nonet', - html_xslt_gen_xslt, + site_xsl, '@INPUT@', ], depends: data.get('depends', []), diff --git a/docs/meson.build b/docs/meson.build index 2295fbf752..75b5e4c08f 100644 --- a/docs/meson.build +++ b/docs/meson.build @@ -18,7 +18,6 @@ docs_assets = [ ] docs_html_in_files = [ - '404', 'docs', 'formatcaps', 'formatdomaincaps', @@ -132,7 +131,6 @@ docs_timestamp = run_command( ).stdout().strip() site_xsl = files('site.xsl') -subsite_xsl = files('subsite.xsl') page_xsl = files('page.xsl') newapi_xsl = files('newapi.xsl') @@ -218,7 +216,6 @@ docs_rst2html5_gen = generator( # html_xslt_gen config -html_xslt_gen_xslt = site_xsl html_xslt_gen_install_dir = docs_html_dir html_xslt_gen = [] @@ -251,6 +248,12 @@ html_xslt_gen += { 'depends': aclperms_gen, } +html_xslt_gen += { + 'name': '404', + 'source': 'docs' / '404.html.in', + 'href_base': '/', +} + hvsupport_html_in = custom_target( 'hvsupport.html.in', output: 'hvsupport.html.in', @@ -302,8 +305,9 @@ foreach data : html_xslt_gen '--stringparam', 'pagesrc', data.get('source', ''), '--stringparam', 'builddir', meson.build_root(), '--stringparam', 'timestamp', docs_timestamp, + '--stringparam', 'href_base', data.get('href_base', ''), '--nonet', - html_xslt_gen_xslt, + site_xsl, '@INPUT@', ], depends: data.get('depends', []), diff --git a/docs/site.xsl b/docs/site.xsl index 931e26272f..f56eb67b8a 100644 --- a/docs/site.xsl +++ b/docs/site.xsl @@ -13,21 +13,11 @@ encoding="UTF-8" indent="yes"/> - <xsl:variable name="href_base"> - <xsl:choose> - <xsl:when test="$pagesrc = 'docs/404.html.in'"> - <xsl:value-of select="'/'"/> - </xsl:when> - <xsl:otherwise> - <xsl:value-of select="''"/> - </xsl:otherwise> - </xsl:choose> - </xsl:variable> - <xsl:template match="/"> <xsl:apply-templates select="." mode="page"> <xsl:with-param name="pagesrc" select="$pagesrc"/> <xsl:with-param name="timestamp" select="$timestamp"/> + <xsl:with-param name="href_base" select="$href_base"/> </xsl:apply-templates> </xsl:template> diff --git a/docs/subsite.xsl b/docs/subsite.xsl deleted file mode 100644 index 2bdfcbb9b1..0000000000 --- a/docs/subsite.xsl +++ /dev/null @@ -1,24 +0,0 @@ -<?xml version="1.0"?> -<xsl:stylesheet - xmlns:xsl="http://www.w3.org/1999/XSL/Transform" - xmlns:exsl="http://exslt.org/common" - exclude-result-prefixes="xsl exsl" - version="1.0"> - - <xsl:import href="page.xsl"/> - - <xsl:output - method="xml" - encoding="UTF-8" - indent="yes"/> - - <xsl:variable name="href_base" select="'../'"/> - - <xsl:template match="/"> - <xsl:apply-templates select="." mode="page"> - <xsl:with-param name="pagesrc" select="$pagesrc"/> - <xsl:with-param name="timestamp" select="$timestamp"/> - </xsl:apply-templates> - </xsl:template> - -</xsl:stylesheet> -- 2.35.1

Along with the conversion we need to adapt the stylesheets to apply to the new document similarly to how we do that in the knowledge base. Note that one visible difference is that now a 'Documentation' heading is visible on top of the page. Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- docs/css/libvirt.css | 17 ++-- docs/docs.html.in | 188 ------------------------------------------- docs/docs.rst | 175 ++++++++++++++++++++++++++++++++++++++++ docs/meson.build | 2 +- 4 files changed, 188 insertions(+), 194 deletions(-) delete mode 100644 docs/docs.html.in create mode 100644 docs/docs.rst diff --git a/docs/css/libvirt.css b/docs/css/libvirt.css index b08271ea4d..2ae80f8595 100644 --- a/docs/css/libvirt.css +++ b/docs/css/libvirt.css @@ -105,8 +105,8 @@ } #index.document, -#docs.document, #hvsupport.document, +#documentation.document, #knowledge-base.document { width: inherit; @@ -397,6 +397,7 @@ h6:hover > a.headerlink { } div.panel, +#documentation .section, #knowledge-base .section { width: 24%; @@ -406,6 +407,7 @@ div.panel, } div.panel h2, +#documentation .section h1, #knowledge-base .section h1 { margin-top: 0px; padding: 0.5em; @@ -423,15 +425,12 @@ div.panel h2, height: 300px; } +#documentation.document > h1, #knowledge-base.document > h1 { text-align: center; padding: 1em; } -#docs.document h1 { - visibility: hidden; -} - br.clear { clear: both; border: 0px; @@ -485,11 +484,13 @@ br.clear { } div.panel dd, +#documentation dd, #knowledge-base dd { font-size: smaller; } div.panel a, +#documentation a, #knowledge-base a { text-decoration: none; } @@ -497,6 +498,9 @@ div.panel a, div.panel ul, div.panel p, div.panel dl, +#documentation ul, +#documentation p, +#documentation dl, #knowledge-base ul, #knowledge-base p, #knowledge-base dl { @@ -505,16 +509,19 @@ div.panel dl, } div.panel ul, +#documentation ul, #knowledge-base ul { margin-left: 1em; } div.panel dt, +#documentation dt, #knowledge-base dt { margin: 0px; } div.panel dd, +#documentation dd, #knowledge-base dd { margin: 0px; margin-bottom: 1em; diff --git a/docs/docs.html.in b/docs/docs.html.in deleted file mode 100644 index ff7a95fae7..0000000000 --- a/docs/docs.html.in +++ /dev/null @@ -1,188 +0,0 @@ -<?xml version="1.0" encoding="UTF-8"?> -<!DOCTYPE html> -<html xmlns="http://www.w3.org/1999/xhtml"> - <body id="docs"> - <h1>Documentation</h1> - <div class="panel"> - <h2>Deployment / operation</h2> - - <dl> - <dt><a href="apps.html">Applications</a></dt> - <dd>Applications known to use libvirt</dd> - - <dt><a href="manpages/index.html">Manual pages</a></dt> - <dd>Manual pages for libvirt tools / daemons</dd> - - <dt><a href="windows.html">Windows</a></dt> - <dd>Downloads for Windows</dd> - - <dt><a href="macos.html">macOS</a></dt> - <dd>Working with libvirt on macOS</dd> - - <dt><a href="migration.html">Migration</a></dt> - <dd>Migrating guests between machines</dd> - - <dt><a href="daemons.html">Daemons</a></dt> - <dd>Overview of the daemons provided by libvirt</dd> - - <dt><a href="remote.html">Remote access</a></dt> - <dd>Enable remote access over TCP</dd> - - <dt><a href="auth.html">Authentication</a></dt> - <dd>Configure authentication for the libvirt daemon</dd> - - <dt><a href="acl.html">Access control</a></dt> - <dd>Configure access control libvirt APIs with <a href="aclpolkit.html">polkit</a></dd> - - <dt><a href="logging.html">Logging</a></dt> - <dd>The library and the daemon logging support</dd> - - <dt><a href="auditlog.html">Audit log</a></dt> - <dd>Audit trail logs for host operations</dd> - - <dt><a href="firewall.html">Firewall</a></dt> - <dd>Firewall and network filter configuration</dd> - - <dt><a href="hooks.html">Hooks</a></dt> - <dd>Hooks for system specific management</dd> - - <dt><a href="nss.html">NSS module</a></dt> - <dd>Enable domain host name translation to IP addresses</dd> - - <dt><a href="https://wiki.libvirt.org/page/FAQ">FAQ</a></d... - <dd>Frequently asked questions</dd> - </dl> - - </div> - - <div class="panel"> - <h2>Application development</h2> - <dl> - <dt><a href="html/index.html">API reference</a></dt> - <dd>Reference manual for the C public API, split in - <a href="html/libvirt-libvirt-common.html">common</a>, - <a href="html/libvirt-libvirt-domain.html">domain</a>, - <a href="html/libvirt-libvirt-domain-checkpoint.html">domain checkpoint</a>, - <a href="html/libvirt-libvirt-domain-snapshot.html">domain snapshot</a>, - <a href="html/libvirt-virterror.html">error</a>, - <a href="html/libvirt-libvirt-event.html">event</a>, - <a href="html/libvirt-libvirt-host.html">host</a>, - <a href="html/libvirt-libvirt-interface.html">interface</a>, - <a href="html/libvirt-libvirt-network.html">network</a>, - <a href="html/libvirt-libvirt-nodedev.html">node device</a>, - <a href="html/libvirt-libvirt-nwfilter.html">network filter</a>, - <a href="html/libvirt-libvirt-secret.html">secret</a>, - <a href="html/libvirt-libvirt-storage.html">storage</a>, - <a href="html/libvirt-libvirt-stream.html">stream</a> - and - <a href="html/index-admin.html">admin</a>, - <a href="html/index-qemu.html">QEMU</a>, - <a href="html/index-lxc.html">LXC</a> libs - </dd> - - <dt><a href="bindings.html">Language bindings and API modules</a></dt> - <dd>Bindings of the libvirt API for - <a href="csharp.html">c#</a>, - <a href="https://pkg.go.dev/libvirt.org/go/libvirt">go</a>;, - <a href="java.html">java</a>, - <a href="https://libvirt.org/ocaml/">ocaml</a>;, - <a href="https://search.cpan.org/dist/Sys-Virt/">perl</a>;, - <a href="python.html">python</a>, - <a href="php.html">php</a>, - <a href="https://libvirt.org/ruby/">ruby</a> - and integration API modules for - <a href="dbus.html">D-Bus</a></dd> - - - <dt><a href="format.html">XML schemas</a></dt> - <dd>Description of the XML schemas for - <a href="formatdomain.html">domains</a>, - <a href="formatnetwork.html">networks</a>, - <a href="formatnetworkport.html">network ports</a>, - <a href="formatnwfilter.html">network filtering</a>, - <a href="formatstorage.html">storage</a>, - <a href="formatstorageencryption.html">storage encryption</a>, - <a href="formatcaps.html">capabilities</a>, - <a href="formatdomaincaps.html">domain capabilities</a>, - <a href="formatstoragecaps.html">storage pool capabilities</a>, - <a href="formatnode.html">node devices</a>, - <a href="formatsecret.html">secrets</a>, - <a href="formatsnapshot.html">snapshots</a>, - <a href="formatcheckpoint.html">checkpoints</a>, - <a href="formatbackup.html">backup jobs</a></dd> - - <dt><a href="uri.html">URI format</a></dt> - <dd>The URI formats used for connecting to libvirt</dd> - - <dt><a href="cgroups.html">CGroups</a></dt> - <dd>Control groups integration</dd> - - <dt><a href="drivers.html">Drivers</a></dt> - <dd>Hypervisor specific driver information</dd> - - <dt><a href="support.html">Support guarantees</a></dt> - <dd>Details of support status for various interfaces</dd> - - <dt><a href="hvsupport.html">Driver support</a></dt> - <dd>matrix of API support per hypervisor per release</dd> - - <dt><a href="kbase/index.html">Knowledge Base</a></dt> - <dd>Task oriented guides to key features</dd> - </dl> - </div> - - <div class="panel"> - <h2>Project development</h2> - <dl> - <dt><a href="hacking.html">Contributor guidelines</a></dt> - <dd>General hacking guidelines for contributors</dd> - - <dt><a href="styleguide.html">Docs style guide</a></dt> - <dd>Style guidelines for reStructuredText docs</dd> - - <dt><a href="strategy.html">Project strategy</a></dt> - <dd>Sets a vision for future direction &amp; technical choices</dd> - - <dt><a href="ci.html">CI Testing</a></dt> - <dd>Details of the Continuous Integration testing strategy</dd> - - <dt><a href="bugs.html">Bug reports</a></dt> - <dd>How and where to report bugs and request features</dd> - - <dt><a href="compiling.html">Compiling</a></dt> - <dd>How to compile libvirt</dd> - - <dt><a href="goals.html">Goals</a></dt> - <dd>Terminology and goals of libvirt API</dd> - - <dt><a href="api.html">API concepts</a></dt> - <dd>The libvirt API concepts</dd> - - <dt><a href="api_extension.html">API extensions</a></dt> - <dd>Adding new public libvirt APIs</dd> - - <dt><a href="internals/eventloop.html">Event loop and worker pool</a></dt> - <dd>Libvirt's event loop and worker pool mode</dd> - - <dt><a href="internals/command.html">Spawning commands</a></dt> - <dd>Spawning commands from libvirt driver code</dd> - - <dt><a href="internals/rpc.html">RPC protocol &amp; APIs</a></dt> - <dd>RPC protocol information and API / dispatch guide</dd> - - <dt><a href="internals/locking.html">Lock managers</a></dt> - <dd>Use lock managers to protect disk content</dd> - - <dt><a href="testsuites.html">Functional testing</a></dt> - <dd>Testing libvirt with <a href="testtck.html">TCK test suite</a> and - <a href="testapi.html">Libvirt-test-API</a></dd> - - <dt><a href="newreposetup.html">New repo setup</a></dt> - <dd>Procedure for configuring new git repositories for libvirt</dd> - </dl> - </div> - - <br class="clear"/> - - </body> -</html> diff --git a/docs/docs.rst b/docs/docs.rst new file mode 100644 index 0000000000..299c26d09b --- /dev/null +++ b/docs/docs.rst @@ -0,0 +1,175 @@ +============= +Documentation +============= + +Deployment / operation +---------------------- + +`Applications <apps.html>`__ + Applications known to use libvirt + +`Manual pages <manpages/index.html>`__ + Manual pages for libvirt tools / daemons + +`Windows <windows.html>`__ + Downloads for Windows + +`macOS <macos.html>`__ + Working with libvirt on macOS + +`Migration <migration.html>`__ + Migrating guests between machines + +`Daemons <daemons.html>`__ + Overview of the daemons provided by libvirt + +`Remote access <remote.html>`__ + Enable remote access over TCP + +`TLS certs <tlscerts.html>`__ + Generate and deploy x509 certificates for TLS + +`Authentication <auth.html>`__ + Configure authentication for the libvirt daemon + +`Access control <acl.html>`__ + Configure access control libvirt APIs with `polkit <aclpolkit.html>`__ + +`Logging <logging.html>`__ + The library and the daemon logging support + +`Audit log <auditlog.html>`__ + Audit trail logs for host operations + +`Firewall <firewall.html>`__ + Firewall and network filter configuration + +`Hooks <hooks.html>`__ + Hooks for system specific management + +`NSS module <nss.html>`__ + Enable domain host name translation to IP addresses + +`FAQ <https://wiki.libvirt.org/page/FAQ>`__ + Frequently asked questions + +Application development +----------------------- + +`API reference <html/index.html>`__ + Reference manual for the C public API, split in + `common <html/libvirt-libvirt-common.html>`__, + `domain <html/libvirt-libvirt-domain.html>`__, + `domain checkpoint <html/libvirt-libvirt-domain-checkpoint.html>`__, + `domain snapshot <html/libvirt-libvirt-domain-snapshot.html>`__, + `error <html/libvirt-virterror.html>`__, + `event <html/libvirt-libvirt-event.html>`__, + `host <html/libvirt-libvirt-host.html>`__, + `interface <html/libvirt-libvirt-interface.html>`__, + `network <html/libvirt-libvirt-network.html>`__, + `node device <html/libvirt-libvirt-nodedev.html>`__, + `network filter <html/libvirt-libvirt-nwfilter.html>`__, + `secret <html/libvirt-libvirt-secret.html>`__, + `storage <html/libvirt-libvirt-storage.html>`__, + `stream <html/libvirt-libvirt-stream.html>`__ and + `admin <html/index-admin.html>`__, + `QEMU <html/index-qemu.html>`__, + `LXC <html/index-lxc.html>`__ libs + +`Language bindings and API modules <bindings.html>`__ + Bindings of the libvirt API for + `c# <csharp.html>`__, + `go <https://pkg.go.dev/libvirt.org/go/libvirt>`__, + `java <java.html>`__, + `ocaml <https://libvirt.org/ocaml/>`__, + `perl <https://search.cpan.org/dist/Sys-Virt/>`__, + `python <python.html>`__, + `php <php.html>`__, + `ruby <https://libvirt.org/ruby/>`__ + and integration API modules for + `D-Bus <dbus.html>`__ + +`XML schemas <format.html>`__ + Description of the XML schemas for + `domains <formatdomain.html>`__, + `networks <formatnetwork.html>`__, + `network ports <formatnetworkport.html>`__, + `network filtering <formatnwfilter.html>`__, + `storage <formatstorage.html>`__, + `storage encryption <formatstorageencryption.html>`__, + `capabilities <formatcaps.html>`__, + `domain capabilities <formatdomaincaps.html>`__, + `storage pool capabilities <formatstoragecaps.html>`__, + `node devices <formatnode.html>`__, + `secrets <formatsecret.html>`__, + `snapshots <formatsnapshot.html>`__, + `checkpoints <formatcheckpoint.html>`__, + `backup jobs <formatbackup.html>`__ + +`URI format <uri.html>`__ + The URI formats used for connecting to libvirt + +`CGroups <cgroups.html>`__ + Control groups integration + +`Drivers <drivers.html>`__ + Hypervisor specific driver information + +`Support guarantees <support.html>`__ + Details of support status for various interfaces + +`Driver support <hvsupport.html>`__ + matrix of API support per hypervisor per release + +`Knowledge Base <kbase/index.html>`__ + Task oriented guides to key features + +Project development +------------------- + +`Contributor guidelines <hacking.html>`__ + General hacking guidelines for contributors + +`Docs style guide <styleguide.html>`__ + Style guidelines for reStructuredText docs + +`Project strategy <strategy.html>`__ + Sets a vision for future direction & technical choices + +`CI Testing <ci.html>`__ + Details of the Continuous Integration testing strategy + +`Bug reports <bugs.html>`__ + How and where to report bugs and request features + +`Compiling <compiling.html>`__ + How to compile libvirt + +`Goals <goals.html>`__ + Terminology and goals of libvirt API + +`API concepts <api.html>`__ + The libvirt API concepts + +`API extensions <api_extension.html>`__ + Adding new public libvirt APIs + +`Event loop and worker pool <internals/eventloop.html>`__ + Libvirt's event loop and worker pool mode + +`Spawning commands <internals/command.html>`__ + Spawning commands from libvirt driver code + +`RPC protocol & APIs <internals/rpc.html>`__ + RPC protocol information and API / dispatch guide + +`Lock managers <internals/locking.html>`__ + Use lock managers to protect disk content + +`Functional testing <testsuites.html>`__ + Testing libvirt with + `TCK test suite <testtck.html>`__ and + `Libvirt-test-API <testapi.html>`__ + +`New repo setup <newreposetup.html>`__ + Procedure for configuring new git repositories for libvirt diff --git a/docs/meson.build b/docs/meson.build index 75b5e4c08f..9e69a0dc05 100644 --- a/docs/meson.build +++ b/docs/meson.build @@ -18,7 +18,6 @@ docs_assets = [ ] docs_html_in_files = [ - 'docs', 'formatcaps', 'formatdomaincaps', 'formatnetwork', @@ -53,6 +52,7 @@ docs_rst_files = [ 'csharp', 'daemons', 'dbus', + 'docs', 'downloads', 'drivers', 'drvbhyve', -- 2.35.1

Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- docs/docs.rst | 3 - docs/internals/eventloop.html.in | 106 ----------------------------- docs/internals/meson.build | 1 - docs/kbase/index.rst | 3 + docs/kbase/internals/eventloop.rst | 84 +++++++++++++++++++++++ docs/kbase/internals/meson.build | 1 + 6 files changed, 88 insertions(+), 110 deletions(-) delete mode 100644 docs/internals/eventloop.html.in create mode 100644 docs/kbase/internals/eventloop.rst diff --git a/docs/docs.rst b/docs/docs.rst index a92c7c26ab..4496206d6a 100644 --- a/docs/docs.rst +++ b/docs/docs.rst @@ -154,9 +154,6 @@ Project development `API extensions <api_extension.html>`__ Adding new public libvirt APIs -`Event loop and worker pool <internals/eventloop.html>`__ - Libvirt's event loop and worker pool mode - `RPC protocol & APIs <internals/rpc.html>`__ RPC protocol information and API / dispatch guide diff --git a/docs/internals/eventloop.html.in b/docs/internals/eventloop.html.in deleted file mode 100644 index 1a24254fc5..0000000000 --- a/docs/internals/eventloop.html.in +++ /dev/null @@ -1,106 +0,0 @@ -<?xml version="1.0" encoding="UTF-8"?> -<!DOCTYPE html> -<html xmlns="http://www.w3.org/1999/xhtml"> - <body> - <h1>Libvirt's event loop</h1> - - <ul id="toc"></ul> - - <p> - This page describes the event loop approach used in - libvirt. Both server and client. - </p> - - <h2><a id="event_loop">Event driven programming</a></h2> - - <p>Traditionally, a program simply ran once, then terminated. - This type of program was very common in the early days of - computing, and lacked any form of user interactivity. This is - still used frequently, particularly in small one purpose - programs.</p> - - <p>However, that approach is not suitable for all the types - of applications. For instance graphical applications spend - most of their run time waiting for an input from user. Only - after it happened (in our example a button was clicked, a key - pressed, etc.) an event is generated to which they respond - by executing desired function. If generalized, this is how - many long running programs (daemons) work. Even those who are - not waiting for direct user input and have no graphical - interface. Such as Libvirt.</p> - - <img alt="event loop" src="../images/event_loop_simple.png"/> - - <p>In Libvirt this approach is used in combination with - <code>poll(2)</code> as all the communication with its - clients (and domains it manages too) happens through sockets. - Therefore whenever new client connects, it is given exclusive - file descriptor which is then watched for incoming events, - e.g. messages. </p> - - <h2><a id="api">The event loop API</a></h2> - - <p>To work with event loop from our code we have plenty of - APIs.</p> - - <ul> - <li><code>virEventAddHandle</code>: Registers a - callback for monitoring file handle events.</li> - <li><code>virEventUpdateHandle</code>: Change set of events - monitored file handle is being watched for.</li> - <li><code>virEventRemoveHandle</code>: Unregisters - previously registered file handle so that it is no - longer monitored for any events.</li> - <li><code>virEventAddTimeout</code>: Registers a - callback for timer event.</li> - <li><code>virEventUpdateTimeout</code>: Changes frequency - for a timer.</li> - <li><code>virEventRemoveTimeout</code>: Unregisters - a timer.</li> - </ul> - - <p>For more information on these APIs continue reading <a - href="../html/libvirt-libvirt-event.html">here</a>.</p> - - <h2><a id="worker_pool">Worker pool</a></h2> - - <p>Looking back at the image above we can see one big - limitation. While processing a message event loop is blocked - and for an outside observer unresponsive. This is not - acceptable for Libvirt. Therefore we have came up with the - following solution.</p> - - <img alt="event loop" src="../images/event_loop_worker.png"/> - - <p>The event loop does only necessary minimum and hand over - message processing to another thread. In fact, there can be - as many processing threads as configured increasing - processing power.</p> - - <p>To break this high level description into smaller pieces, - here is what happens when user calls an API:</p> - <ol> - <li>User (or management application) calls a Libvirt API. - Depending on the connection URI, this may or may not - involve server. Well, for the sake of our - demonstration we assume the former.</li> - <li>Remote driver encodes the API among it's arguments - into an <a href="rpc.html">RPC message</a> and sends - it to the server.</li> - <li>Here, server is waiting in <code>poll(2)</code> for - an event, like incoming message.</li> - <li>As soon as the first bytes of message are received, - even loop wakes up and server starts reading the - whole message.</li> - <li>Once fully read, the event loop notifies threads - known as worker threads from which one picks the incoming - message, decodes and process it.</li> - <li>As soon as API execution is finished, a reply is sent - to the client.</li> - </ol> - - <p>In case that there's no free worker to process an incoming - message in step 5, message is placed at the end of a message - queue and is processed in next iteration.</p> - </body> -</html> diff --git a/docs/internals/meson.build b/docs/internals/meson.build index e5f4bb0a4b..5baf444bf9 100644 --- a/docs/internals/meson.build +++ b/docs/internals/meson.build @@ -1,5 +1,4 @@ internals_in_files = [ - 'eventloop', 'locking', 'rpc', ] diff --git a/docs/kbase/index.rst b/docs/kbase/index.rst index 01ec5a070d..47cfc0505c 100644 --- a/docs/kbase/index.rst +++ b/docs/kbase/index.rst @@ -88,3 +88,6 @@ Internals `Spawning commands <internals/command.html>`__ Spawning commands from libvirt driver code + +`Event loop and worker pool <internals/eventloop.html>`__ + Libvirt's event loop and worker pool mode diff --git a/docs/kbase/internals/eventloop.rst b/docs/kbase/internals/eventloop.rst new file mode 100644 index 0000000000..f25e97ab14 --- /dev/null +++ b/docs/kbase/internals/eventloop.rst @@ -0,0 +1,84 @@ +==================== +Libvirt's event loop +==================== + +.. contents:: + +This page describes the event loop approach used in libvirt. Both server and +client. + +Event driven programming +------------------------ + +Traditionally, a program simply ran once, then terminated. This type of program +was very common in the early days of computing, and lacked any form of user +interactivity. This is still used frequently, particularly in small one purpose +programs. + +However, that approach is not suitable for all the types of applications. For +instance graphical applications spend most of their run time waiting for an +input from user. Only after it happened (in our example a button was clicked, a +key pressed, etc.) an event is generated to which they respond by executing +desired function. If generalized, this is how many long running programs +(daemons) work. Even those who are not waiting for direct user input and have no +graphical interface. Such as Libvirt. + +.. image:: ../images/event_loop_simple.png + :alt: event loop + +In Libvirt this approach is used in combination with ``poll(2)`` as all the +communication with its clients (and domains it manages too) happens through +sockets. Therefore whenever new client connects, it is given exclusive file +descriptor which is then watched for incoming events, e.g. messages. + +The event loop API +------------------ + +To work with event loop from our code we have plenty of APIs. + +- ``virEventAddHandle``: Registers a callback for monitoring file handle + events. +- ``virEventUpdateHandle``: Change set of events monitored file handle is being + watched for. +- ``virEventRemoveHandle``: Unregisters previously registered file handle so + that it is no longer monitored for any events. +- ``virEventAddTimeout``: Registers a callback for timer event. +- ``virEventUpdateTimeout``: Changes frequency for a timer. +- ``virEventRemoveTimeout``: Unregisters a timer. + +For more information on these APIs continue reading +`here <../html/libvirt-libvirt-event.html>`__. + +Worker pool +----------- + +Looking back at the image above we can see one big limitation. While processing +a message event loop is blocked and for an outside observer unresponsive. This +is not acceptable for Libvirt. Therefore we have came up with the following +solution. + +.. image:: ../images/event_loop_worker.png + :alt: event loop + +The event loop does only necessary minimum and hand over message processing to +another thread. In fact, there can be as many processing threads as configured +increasing processing power. + +To break this high level description into smaller pieces, here is what happens +when user calls an API: + +#. User (or management application) calls a Libvirt API. Depending on the + connection URI, this may or may not involve server. Well, for the sake of our + demonstration we assume the former. +#. Remote driver encodes the API among it's arguments into an `RPC + message <rpc.html>`__ and sends it to the server. +#. Here, server is waiting in ``poll(2)`` for an event, like incoming message. +#. As soon as the first bytes of message are received, even loop wakes up and + server starts reading the whole message. +#. Once fully read, the event loop notifies threads known as worker threads from + which one picks the incoming message, decodes and process it. +#. As soon as API execution is finished, a reply is sent to the client. + +In case that there's no free worker to process an incoming message in step 5, +message is placed at the end of a message queue and is processed in next +iteration. diff --git a/docs/kbase/internals/meson.build b/docs/kbase/internals/meson.build index 3486b21852..5f61f5dba4 100644 --- a/docs/kbase/internals/meson.build +++ b/docs/kbase/internals/meson.build @@ -1,5 +1,6 @@ docs_kbase_internals_files = [ 'command', + 'eventloop', 'incremental-backup', 'migration', ] -- 2.35.1

Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- docs/api.rst | 2 +- docs/docs.rst | 3 - docs/internals/meson.build | 1 - docs/internals/rpc.html.in | 914 ------------------------------- docs/kbase/index.rst | 3 + docs/kbase/internals/meson.build | 1 + docs/kbase/internals/rpc.rst | 781 ++++++++++++++++++++++++++ 7 files changed, 786 insertions(+), 919 deletions(-) delete mode 100644 docs/internals/rpc.html.in create mode 100644 docs/kbase/internals/rpc.rst diff --git a/docs/api.rst b/docs/api.rst index d9f01fb403..325b9b840c 100644 --- a/docs/api.rst +++ b/docs/api.rst @@ -219,7 +219,7 @@ Daemon and Remote Access Access to libvirt drivers is primarily handled by the libvirtd daemon through the `remote <remote.html>`__ driver via an -`RPC <internals/rpc.html>`__. Some hypervisors do support client-side +`RPC <kbase/internals/rpc.html>`__. Some hypervisors do support client-side connections and responses, such as Test, OpenVZ, VMware, VirtualBox (vbox), ESX, Hyper-V, Xen, and Virtuozzo. The libvirtd daemon service is started on the host at system boot time and can also be restarted at any diff --git a/docs/docs.rst b/docs/docs.rst index 3387dacce8..0a698913be 100644 --- a/docs/docs.rst +++ b/docs/docs.rst @@ -154,9 +154,6 @@ Project development `API extensions <api_extension.html>`__ Adding new public libvirt APIs -`RPC protocol & APIs <internals/rpc.html>`__ - RPC protocol information and API / dispatch guide - `Functional testing <testsuites.html>`__ Testing libvirt with `TCK test suite <testtck.html>`__ and diff --git a/docs/internals/meson.build b/docs/internals/meson.build index 68a2e70a3d..cbf0623c08 100644 --- a/docs/internals/meson.build +++ b/docs/internals/meson.build @@ -1,5 +1,4 @@ internals_in_files = [ - 'rpc', ] html_xslt_gen_install_dir = docs_html_dir / 'internals' diff --git a/docs/internals/rpc.html.in b/docs/internals/rpc.html.in deleted file mode 100644 index ceb7dba5f2..0000000000 --- a/docs/internals/rpc.html.in +++ /dev/null @@ -1,914 +0,0 @@ -<?xml version="1.0" encoding="UTF-8"?> -<!DOCTYPE html> -<html xmlns="http://www.w3.org/1999/xhtml"> - <body> - <h1>libvirt RPC infrastructure</h1> - - <ul id="toc"></ul> - - <p> - libvirt includes a basic protocol and code to implement - an extensible, secure client/server RPC service. This was - originally designed for communication between the libvirt - client library and the libvirtd daemon, but the code is - now isolated to allow reuse in other areas of libvirt code. - This document provides an overview of the protocol and - structure / operation of the internal RPC library APIs. - </p> - - - <h2><a id="protocol">RPC protocol</a></h2> - - <p> - libvirt uses a simple, variable length, packet based RPC protocol. - All structured data within packets is encoded using the - <a href="https://en.wikipedia.org/wiki/External_Data_Representation&quo... standard</a> - as currently defined by <a href="https://tools.ietf.org/html/rfc4506">RFC 4506</a>. - On any connection running the RPC protocol, there can be multiple - programs active, each supporting one or more versions. A program - defines a set of procedures that it supports. The procedures can - support call+reply method invocation, asynchronous events, - and generic data streams. Method invocations can be overlapped, - so waiting for a reply to one will not block the receipt of the - reply to another outstanding method. The protocol was loosely - inspired by the design of SunRPC. The definition of the RPC - protocol is in the file <code>src/rpc/virnetprotocol.x</code> - in the libvirt source tree. - </p> - - <h3><a href="protocolframing">Packet framing</a></h3> - - <p> - On the wire, there is no explicit packet framing marker. Instead - each packet is preceded by an unsigned 32-bit integer giving - the total length of the packet in bytes. This length includes - the 4-bytes of the length word itself. Conceptually the framing - looks like this: - </p> - -<pre> -|~~~ Packet 1 ~~~|~~~ Packet 2 ~~~|~~~ Packet 3 ~~~|~~~ - -+-------+------------+-------+------------+-------+------------+... -| n=U32 | (n-4) * U8 | n=U32 | (n-4) * U8 | n=U32 | (n-4) * U8 | -+-------+------------+-------+------------+-------+------------+... - -|~ Len ~|~ Data ~|~ Len ~|~ Data ~|~ Len ~|~ Data ~|~ - -</pre> - - <h3><a href="protocoldata">Packet data</a></h3> - - <p> - The data in each packet is split into two parts, a short - fixed length header, followed by a variable length payload. - So a packet from the illustration above is more correctly - shown as - </p> - -<pre> - -+-------+-------------+---------------....---+ -| n=U32 | 6*U32 | (n-(7*4))*U8 | -+-------+-------------+---------------....---+ - -|~ Len ~|~ Header ~|~ Payload .... ~| -</pre> - - - <h3><a href="protocolheader">Packet header</a></h3> - <p> - The header contains 6 fields, encoded as signed/unsigned 32-bit - integers. - </p> - - <pre> -+---------------+ -| program=U32 | -+---------------+ -| version=U32 | -+---------------+ -| procedure=S32 | -+---------------+ -| type=S32 | -+---------------+ -| serial=U32 | -+---------------+ -| status=S32 | -+---------------+ - </pre> - - <dl> - <dt><code>program</code></dt> - <dd> - This is an arbitrarily chosen number that will uniquely - identify the "service" running over the stream. - </dd> - <dt><code>version</code></dt> - <dd> - This is the version number of the program, by convention - starting from '1'. When an incompatible change is made - to a program, the version number is incremented. Ideally - both versions will then be supported on the wire in - parallel for backwards compatibility. - </dd> - <dt><code>procedure</code></dt> - <dd> - This is an arbitrarily chosen number that will uniquely - identify the method call, or event associated with the - packet. By convention, procedure numbers start from 1 - and are assigned monotonically thereafter. - </dd> - <dt><code>type</code></dt> - <dd> - <p> - This can be one of the following enumeration values - </p> - <ol> - <li>call: invocation of a method call</li> - <li>reply: completion of a method call</li> - <li>event: an asynchronous event</li> - <li>stream: control info or data from a stream</li> - </ol> - </dd> - <dt><code>serial</code></dt> - <dd> - This is a number that starts from 1 and increases - each time a method call packet is sent. A reply or - stream packet will have a serial number matching the - original method call packet serial. Events always - have the serial number set to 0. - </dd> - <dt><code>status</code></dt> - <dd> - <p> - This can one of the following enumeration values - </p> - <ol> - <li>ok: a normal packet. this is always set for method calls or events. - For replies it indicates successful completion of the method. For - streams it indicates confirmation of the end of file on the stream.</li> - <li>error: for replies this indicates that the method call failed - and error information is being returned. For streams this indicates - that not all data was sent and the stream has aborted</li> - <li>continue: for streams this indicates that further data packets - will be following</li> - </ol> - </dd> - </dl> - - <h3><a href="protocolpayload">Packet payload</a></h3> - - <p> - The payload of a packet will vary depending on the <code>type</code> - and <code>status</code> fields from the header. - </p> - - <ul> - <li>type=call: the in parameters for the method call, XDR encoded</li> - <li>type=call-with-fds: number of file handles, then the in parameters for the method call, XDR encoded, followed by the file handles</li> - <li>type=reply+status=ok: the return value and/or out parameters for the method call, XDR encoded</li> - <li>type=reply+status=error: the error information for the method, a virErrorPtr XDR encoded</li> - <li>type=reply-with-fds+status=ok: number of file handles, the return value and/or out parameters for the method call, XDR encoded, followed by the file handles</li> - <li>type=reply-with-fds+status=error: number of file handles, the error information for the method, a virErrorPtr XDR encoded, followed by the file handles</li> - <li>type=event: the parameters for the event, XDR encoded</li> - <li>type=stream+status=ok: no payload</li> - <li>type=stream+status=error: the error information for the method, a virErrorPtr XDR encoded</li> - <li>type=stream+status=continue: the raw bytes of data for the stream. No XDR encoding</li> - </ul> - - <p> - With the two packet types that support passing file descriptors, in - between the header and the payload there will be a 4-byte integer - specifying the number of file descriptors which are being sent. - The actual file handles are sent after the payload has been sent. - Each file handle has a single dummy byte transmitted as a carrier - for the out of band file descriptor. While the sender should always - send '\0' as the dummy byte value, the receiver ought to ignore the - value for the sake of robustness. - </p> - - <p> - For the exact payload information for each procedure, consult the XDR protocol - definition for the program+version in question - </p> - - <h3><a id="wireexamples">Wire examples</a></h3> - - <p> - The following diagrams illustrate some example packet exchanges - between a client and server - </p> - - <h4><a id="wireexamplescall">Method call</a></h4> - - <p> - A single method call and successful - reply, for a program=8, version=1, procedure=3, which 10 bytes worth - of input args, and 4 bytes worth of return values. The overall input - packet length is 4 + 24 + 10 == 38, and output packet length 32 - </p> - - <pre> - +--+-----------------------+-----------+ -C --&gt; |38| 8 | 1 | 3 | 0 | 1 | 0 | .o.oOo.o. | --&gt; S (call) - +--+-----------------------+-----------+ - - +--+-----------------------+--------+ -C &lt;-- |32| 8 | 1 | 3 | 1 | 1 | 0 | .o.oOo | &lt;-- S (reply) - +--+-----------------------+--------+ - </pre> - - <h4><a id="wireexamplescallerr">Method call with error</a></h4> - - <p> - An unsuccessful method call will instead return an error object - </p> - - <pre> - +--+-----------------------+-----------+ -C --&gt; |38| 8 | 1 | 3 | 0 | 1 | 0 | .o.oOo.o. | --&gt; S (call) - +--+-----------------------+-----------+ - - +--+-----------------------+--------------------------+ -C &lt;-- |48| 8 | 1 | 3 | 2 | 1 | 0 | .o.oOo.o.oOo.o.oOo.o.oOo | &lt;-- S (error) - +--+-----------------------+--------------------------+ - </pre> - - <h4><a id="wireexamplescallup">Method call with upload stream</a></h4> - - <p> - A method call which also involves uploading some data over - a stream will result in - </p> - - <pre> - +--+-----------------------+-----------+ -C --&gt; |38| 8 | 1 | 3 | 0 | 1 | 0 | .o.oOo.o. | --&gt; S (call) - +--+-----------------------+-----------+ - - +--+-----------------------+--------+ -C &lt;-- |32| 8 | 1 | 3 | 1 | 1 | 0 | .o.oOo | &lt;-- S (reply) - +--+-----------------------+--------+ - - +--+-----------------------+-------------....-------+ -C --&gt; |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --&gt; S (stream data up) - +--+-----------------------+-------------....-------+ - +--+-----------------------+-------------....-------+ -C --&gt; |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --&gt; S (stream data up) - +--+-----------------------+-------------....-------+ - +--+-----------------------+-------------....-------+ -C --&gt; |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --&gt; S (stream data up) - +--+-----------------------+-------------....-------+ - ... - +--+-----------------------+-------------....-------+ -C --&gt; |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --&gt; S (stream data up) - +--+-----------------------+-------------....-------+ - +--+-----------------------+ -C --&gt; |24| 8 | 1 | 3 | 3 | 1 | 0 | --&gt; S (stream finish) - +--+-----------------------+ - +--+-----------------------+ -C &lt;-- |24| 8 | 1 | 3 | 3 | 1 | 0 | &lt;-- S (stream finish) - +--+-----------------------+ - </pre> - - <h4><a id="wireexamplescallbi">Method call bidirectional stream</a></h4> - - <p> - A method call which also involves a bi-directional stream will - result in - </p> - - <pre> - +--+-----------------------+-----------+ -C --&gt; |38| 8 | 1 | 3 | 0 | 1 | 0 | .o.oOo.o. | --&gt; S (call) - +--+-----------------------+-----------+ - - +--+-----------------------+--------+ -C &lt;-- |32| 8 | 1 | 3 | 1 | 1 | 0 | .o.oOo | &lt;-- S (reply) - +--+-----------------------+--------+ - - +--+-----------------------+-------------....-------+ -C --&gt; |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --&gt; S (stream data up) - +--+-----------------------+-------------....-------+ - +--+-----------------------+-------------....-------+ -C --&gt; |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --&gt; S (stream data up) - +--+-----------------------+-------------....-------+ - +--+-----------------------+-------------....-------+ -C &lt;-- |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | &lt;-- S (stream data down) - +--+-----------------------+-------------....-------+ - +--+-----------------------+-------------....-------+ -C --&gt; |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --&gt; S (stream data up) - +--+-----------------------+-------------....-------+ - +--+-----------------------+-------------....-------+ -C --&gt; |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --&gt; S (stream data up) - +--+-----------------------+-------------....-------+ - +--+-----------------------+-------------....-------+ -C &lt;-- |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | &lt;-- S (stream data down) - +--+-----------------------+-------------....-------+ - +--+-----------------------+-------------....-------+ -C &lt;-- |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | &lt;-- S (stream data down) - +--+-----------------------+-------------....-------+ - +--+-----------------------+-------------....-------+ -C &lt;-- |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | &lt;-- S (stream data down) - +--+-----------------------+-------------....-------+ - +--+-----------------------+-------------....-------+ -C --&gt; |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --&gt; S (stream data up) - +--+-----------------------+-------------....-------+ - .. - +--+-----------------------+-------------....-------+ -C --&gt; |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --&gt; S (stream data up) - +--+-----------------------+-------------....-------+ - +--+-----------------------+ -C --&gt; |24| 8 | 1 | 3 | 3 | 1 | 0 | --&gt; S (stream finish) - +--+-----------------------+ - +--+-----------------------+ -C &lt;-- |24| 8 | 1 | 3 | 3 | 1 | 0 | &lt;-- S (stream finish) - +--+-----------------------+ - </pre> - - - <h4><a id="wireexamplescallmany">Method calls overlapping</a></h4> - <pre> - +--+-----------------------+-----------+ -C --&gt; |38| 8 | 1 | 3 | 0 | 1 | 0 | .o.oOo.o. | --&gt; S (call 1) - +--+-----------------------+-----------+ - +--+-----------------------+-----------+ -C --&gt; |38| 8 | 1 | 3 | 0 | 2 | 0 | .o.oOo.o. | --&gt; S (call 2) - +--+-----------------------+-----------+ - +--+-----------------------+--------+ -C &lt;-- |32| 8 | 1 | 3 | 1 | 2 | 0 | .o.oOo | &lt;-- S (reply 2) - +--+-----------------------+--------+ - +--+-----------------------+-----------+ -C --&gt; |38| 8 | 1 | 3 | 0 | 3 | 0 | .o.oOo.o. | --&gt; S (call 3) - +--+-----------------------+-----------+ - +--+-----------------------+--------+ -C &lt;-- |32| 8 | 1 | 3 | 1 | 3 | 0 | .o.oOo | &lt;-- S (reply 3) - +--+-----------------------+--------+ - +--+-----------------------+-----------+ -C --&gt; |38| 8 | 1 | 3 | 0 | 4 | 0 | .o.oOo.o. | --&gt; S (call 4) - +--+-----------------------+-----------+ - +--+-----------------------+--------+ -C &lt;-- |32| 8 | 1 | 3 | 1 | 1 | 0 | .o.oOo | &lt;-- S (reply 1) - +--+-----------------------+--------+ - +--+-----------------------+--------+ -C &lt;-- |32| 8 | 1 | 3 | 1 | 4 | 0 | .o.oOo | &lt;-- S (reply 4) - +--+-----------------------+--------+ - </pre> - - <h4><a id="wireexamplescallfd">Method call with passed FD</a></h4> - - <p> - A single method call with 2 passed file descriptors and successful - reply, for a program=8, version=1, procedure=3, which 10 bytes worth - of input args, and 4 bytes worth of return values. The number of - file descriptors is encoded as a 32-bit int. Each file descriptor - then has a 1 byte dummy payload. The overall input - packet length is 4 + 24 + 4 + 2 + 10 == 44, and output packet length 32. - </p> - - <pre> - +--+-----------------------+---------------+-------+ -C --&gt; |44| 8 | 1 | 3 | 0 | 1 | 0 | 2 | .o.oOo.o. | 0 | 0 | --&gt; S (call) - +--+-----------------------+---------------+-------+ - - +--+-----------------------+--------+ -C &lt;-- |32| 8 | 1 | 3 | 1 | 1 | 0 | .o.oOo | &lt;-- S (reply) - +--+-----------------------+--------+ - </pre> - - - <h2><a id="security">RPC security</a></h2> - - <p> - There are various things to consider to ensure an implementation - of the RPC protocol can be satisfactorily secured - </p> - - <h3><a id="securitytls">Authentication/encryption</a></h3> - - <p> - The basic RPC protocol does not define or require any specific - authentication/encryption capabilities. A generic solution to - providing encryption for the protocol is to run the protocol - over a TLS encrypted data stream. x509 certificate checks can - be done to form a crude authentication mechanism. It is also - possible for an RPC program to negotiate an encryption / - authentication capability, such as SASL, which may then also - provide per-packet data encryption. Finally the protocol data - stream can of course be tunnelled over transports such as SSH. - </p> - - <h3><a id="securitylimits">Data limits</a></h3> - - <p> - Although the protocol itself defines many arbitrary sized data values in the - payloads, to avoid denial of service attack there are a number of size limit - checks prior to encoding or decoding data. There is a limit on the maximum - size of a single RPC message, limit on the maximum string length, and limits - on any other parameter which uses a variable length array. These limits can - be raised, subject to agreement between client/server, without otherwise - breaking compatibility of the RPC data on the wire. - </p> - - <h3><a id="securityvalidate">Data validation</a></h3> - - <p> - It is important that all data be fully validated before performing - any actions based on the data. When reading an RPC packet, the - first four bytes must be read and the max packet size limit validated, - before any attempt is made to read the variable length packet data. - After a complete packet has been read, the header must be decoded - and all 6 fields fully validated, before attempting to dispatch - the payload. Once dispatched, the payload can be decoded and passed - on to the appropriate API for execution. The RPC code must not take - any action based on the payload, since it has no way to validate - the semantics of the payload data. It must delegate this to the - execution API (e.g. corresponding libvirt public API). - </p> - - <h2><a id="internals">RPC internal APIs</a></h2> - - <p> - The generic internal RPC library code lives in the <code>src/rpc/</code> - directory of the libvirt source tree. Unless otherwise noted, the - objects are all threadsafe. The core object types and their - purposes are: - </p> - - <h3><a id="apioverview">Overview of RPC objects</a></h3> - - <p> - The following is a high level overview of the role of each - of the main RPC objects - </p> - - <dl> - <dt><code>virNetSASLContext *</code> (virnetsaslcontext.h)</dt> - <dd>The virNetSASLContext APIs maintain SASL state for a network - service (server or client). This is primarily used on the server - to provide an access control list of SASL usernames permitted as - clients. - </dd> - - <dt><code>virNetSASLSession *</code> (virnetsaslcontext.h)</dt> - <dd>The virNetSASLSession APIs maintain SASL state for a single - network connection (socket). This is used to perform the multi-step - SASL handshake and perform encryption/decryption of data once - authenticated, via integration with virNetSocket. - </dd> - - <dt><code>virNetTLSContext *</code> (virnettlscontext.h)</dt> - <dd>The virNetTLSContext APIs maintain TLS state for a network - service (server or client). This is primarily used on the server - to provide an access control list of x509 distinguished names, as - well as diffie-hellman keys. It can also do validation of - x509 certificates prior to initiating a connection, in order - to improve detection of configuration errors. - </dd> - - <dt><code>virNetTLSSession *</code> (virnettlscontext.h)</dt> - <dd>The virNetTLSSession APIs maintain TLS state for a single - network connection (socket). This is used to perform the multi-step - TLS handshake and perform encryption/decryption of data once - authenticated, via integration with virNetSocket. - </dd> - - <dt><code>virNetSocket *</code> (virnetsocket.h)</dt> - <dd>The virNetSocket APIs provide a higher level wrapper around - the raw BSD sockets and getaddrinfo APIs. They allow for creation - of both server and client sockets. Data transports supported are - TCP, UNIX, SSH tunnel or external command tunnel. Internally the - TCP socket impl uses the getaddrinfo info APIs to ensure correct - protocol-independent behaviour, thus supporting both IPv4 and IPv6. - The socket APIs can be associated with a virNetSASLSession *or - virNetTLSSession *object to allow seamless encryption/decryption - of all writes and reads. For UNIX sockets it is possible to obtain - the remote client user ID and process ID. Integration with the - libvirt event loop also allows use of callbacks for notification - of various I/O conditions - </dd> - - <dt><code>virNetMessage *</code> (virnetmessage.h)</dt> - <dd>The virNetMessage APIs provide a wrapper around the libxdr - API calls, to facilitate processing and creation of RPC - packets. There are convenience APIs for encoding/encoding the - packet headers, encoding/decoding the payload using an XDR - filter, encoding/decoding a raw payload (for streams), and - encoding a virErrorPtr object. There is also a means to - add to/serve from a linked-list queue of messages.</dd> - - <dt><code>virNetClient *</code> (virnetclient.h)</dt> - <dd>The virNetClient APIs provide a way to connect to a - remote server and run one or more RPC protocols over - the connection. Connections can be made over TCP, UNIX - sockets, SSH tunnels, or external command tunnels. There - is support for both TLS and SASL session encryption. - The client also supports management of multiple data streams - over each connection. Each client object can be used from - multiple threads concurrently, with method calls/replies - being interleaved on the wire as required. - </dd> - - <dt><code>virNetClientProgram *</code> (virnetclientprogram.h)</dt> - <dd>The virNetClientProgram APIs are used to register a - program+version with the connection. This then enables - invocation of method calls, receipt of asynchronous - events and use of data streams, within that program+version. - When created a set of callbacks must be supplied to take - care of dispatching any incoming asynchronous events. - </dd> - - <dt><code>virNetClientStream *</code> (virnetclientstream.h)</dt> - <dd>The virNetClientStream APIs are used to control transmission and - receipt of data over a stream active on a client. Streams provide - a low latency, unlimited length, bi-directional raw data exchange - mechanism layered over the RPC connection - </dd> - - <dt><code>virNetServer *</code> (virnetserver.h)</dt> - <dd>The virNetServer APIs are used to manage a network server. A - server exposed one or more programs, over one or more services. - It manages multiple client connections invoking multiple RPC - calls in parallel, with dispatch across multiple worker threads. - </dd> - - <dt><code>virNetDaemon *</code> (virnetdaemon.h)</dt> - <dd>The virNetDaemon APIs are used to manage a daemon process. A - daemon is a process that might expose one or more servers. It - handles most process-related details, network-related should - be part of the underlying server. - </dd> - - <dt><code>virNetServerClient *</code> (virnetserverclient.h)</dt> - <dd>The virNetServerClient APIs are used to manage I/O related - to a single client network connection. It handles initial - validation and routing of incoming RPC packets, and transmission - of outgoing packets. - </dd> - - <dt><code>virNetServerProgram *</code> (virnetserverprogram.h)</dt> - <dd>The virNetServerProgram APIs are used to provide the implementation - of a single program/version set. Primarily this includes a set of - callbacks used to actually invoke the APIs corresponding to - program procedure numbers. It is responsible for all the serialization - of payloads to/from XDR.</dd> - - <dt><code>virNetServerService *</code> (virnetserverservice.h)</dt> - <dd>The virNetServerService APIs are used to connect the server to - one or more network protocols. A single service may involve multiple - sockets (ie both IPv4 and IPv6). A service also has an associated - authentication policy for incoming clients. - </dd> - </dl> - - <h3><a id="apiclientdispatch">Client RPC dispatch</a></h3> - - <p> - The client RPC code must allow for multiple overlapping RPC method - calls to be invoked, transmission and receipt of data for multiple - streams and receipt of asynchronous events. Understandably this - involves coordination of multiple threads. - </p> - - <p> - The core requirement in the client dispatch code is that only - one thread is allowed to be performing I/O on the socket at - any time. This thread is said to be "holding the buck". When - any other thread comes along and needs to do I/O it must place - its packets on a queue and delegate processing of them to the - thread that has the buck. This thread will send out the method - call, and if it sees a reply will pass it back to the waiting - thread. If the other thread's reply hasn't arrived, by the time - the main thread has got its own reply, then it will transfer - responsibility for I/O to the thread that has been waiting the - longest. It is said to be "passing the buck" for I/O. - </p> - - <p> - When no thread is performing any RPC method call, or sending - stream data there is still a need to monitor the socket for - incoming I/O related to asynchronous events, or stream data - receipt. For this task, a watch is registered with the event - loop which triggers whenever the socket is readable. This - watch is automatically disabled whenever any other thread - grabs the buck, and re-enabled when the buck is released. - </p> - - <h4><a id="apiclientdispatchex1">Example with buck passing</a></h4> - - <p> - In the first example, a second thread issues an API call - while the first thread holds the buck. The reply to the - first call arrives first, so the buck is passed to the - second thread. - </p> - - <pre> - Thread-1 - | - V - Call API1() - | - V - Grab Buck - | Thread-2 - V | - Send method1 V - | Call API2() - V | - Wait I/O V - |&lt;--------Queue method2 - V | - Send method2 V - | Wait for buck - V | - Wait I/O | - | | - V | - Recv reply1 | - | | - V | - Pass the buck-----&gt;| - | V - V Wait I/O - Return API1() | - V - Recv reply2 - | - V - Release the buck - | - V - Return API2() - </pre> - - <h4><a id="apiclientdispatchex2">Example without buck passing</a></h4> - - <p> - In this second example, a second thread issues an API call - which is sent and replied to, before the first thread's - API call has completed. The first thread thus notifies - the second that its reply is ready, and there is no need - to pass the buck - </p> - - <pre> - Thread-1 - | - V - Call API1() - | - V - Grab Buck - | Thread-2 - V | - Send method1 V - | Call API2() - V | - Wait I/O V - |&lt;--------Queue method2 - V | - Send method2 V - | Wait for buck - V | - Wait I/O | - | | - V | - Recv reply2 | - | | - V | - Notify reply2------&gt;| - | V - V Return API2() - Wait I/O - | - V - Recv reply1 - | - V - Release the buck - | - V - Return API1() - </pre> - - <h4><a id="apiclientdispatchex3">Example with async events</a></h4> - - <p> - In this example, only one thread is present and it has to - deal with some async events arriving. The events are actually - dispatched to the application from the event loop thread - </p> - - <pre> - Thread-1 - | - V - Call API1() - | - V - Grab Buck - | - V - Send method1 - | - V - Wait I/O - | Event thread - V ... - Recv event1 | - | V - V Wait for timer/fd - Queue event1 | - | V - V Timer fires - Wait I/O | - | V - V Emit event1 - Recv reply1 | - | V - V Wait for timer/fd - Return API1() | - ... - </pre> - - <h3><a id="apiserverdispatch">Server RPC dispatch</a></h3> - - <p> - The RPC server code must support receipt of incoming RPC requests from - multiple client connections, and parallel processing of all RPC - requests, even many from a single client. This goal is achieved through - a combination of event driven I/O, and multiple processing threads. - </p> - - <p> - The main libvirt event loop thread is responsible for performing all - socket I/O. It will read incoming packets from clients and will - transmit outgoing packets to clients. It will handle the I/O to/from - streams associated with client API calls. When doing client I/O it - will also pass the data through any applicable encryption layer - (through use of the virNetSocket / virNetTLSSession and virNetSASLSession - integration). What is paramount is that the event loop thread never - do any task that can take a non-trivial amount of time. - </p> - - <p> - When reading packets, the event loop will first read the 4 byte length - word. This is validated to make sure it does not exceed the maximum - permissible packet size, and the client is set to allow receipt of the - rest of the packet data. Once a complete packet has been received, the - next step is to decode the RPC header. The header is validated to - ensure the request is sensible, ie the server should not receive a - method reply from a client. If the client has not yet authenticated, - an access control list check is also performed to make sure the procedure - is one of those allowed prior to auth. If the packet is a method - call, it will be placed on a global processing queue. The event loop - thread is now done with the packet for the time being. - </p> - - <p> - The server has a pool of worker threads, which wait for method call - packets to be queued. One of them will grab the new method call off - the queue for processing. The first step is to decode the payload of - the packet to extract the method call arguments. The worker does not - attempt to do any semantic validation of the arguments, except to make - sure the size of any variable length fields is below defined limits. - </p> - - <p> - The worker now invokes the libvirt API call that corresponds to the - procedure number in the packet header. The worker is thus kept busy - until the API call completes. The implementation of the API call - is responsible for doing semantic validation of parameters and any - MAC security checks on the objects affected. - </p> - - <p> - Once the API call has completed, the worker thread will take the - return value and output parameters, or error object and encode - them into a reply packet. Again it does not attempt to do any - semantic validation of output data, aside from variable length - field limit checks. The worker thread puts the reply packet on - the transmission queue for the client. The worker is now finished - and goes back to wait for another incoming method call. - </p> - - <p> - The main event loop is back in charge and when the client socket - becomes writable, it will start sending the method reply packet - back to the client. - </p> - - <p> - At any time the libvirt connection object can emit asynchronous - events. These are handled by callbacks in the main event thread. - The callback will simply encode the event parameters into a new - data packet and place the packet on the client transmission - queue. - </p> - - <p> - Incoming and outgoing stream packets are also directly handled - by the main event thread. When an incoming stream packet is - received, instead of placing it in the global dispatch queue - for the worker threads, it is sidetracked into a per-stream - processing queue. When the stream becomes writable, queued - incoming stream packets will be processed, passing their data - payload on the stream. Conversely when the stream becomes - readable, chunks of data will be read from it, encoded into - new outgoing packets, and placed on the client's transmit - queue. - </p> - - <h4><a id="apiserverdispatchex1">Example with overlapping methods</a></h4> - - <p> - This example illustrates processing of two incoming methods with - overlapping execution - </p> - - <pre> - Event thread Worker 1 Worker 2 - | | | - V V V - Wait I/O Wait Job Wait Job - | | | - V | | - Recv method1 | | - | | | - V | | - Queue method1 V | - | Serve method1 | - V | | - Wait I/O V | - | Call API1() | - V | | - Recv method2 | | - | | | - V | | - Queue method2 | V - | | Serve method2 - V V | - Wait I/O Return API1() V - | | Call API2() - | V | - V Queue reply1 | - Send reply1 | | - | V V - V Wait Job Return API2() - Wait I/O | | - | ... V - V Queue reply2 - Send reply2 | - | V - V Wait Job - Wait I/O | - | ... - ... - </pre> - - <h4><a id="apiserverdispatchex2">Example with stream data</a></h4> - - <p> - This example illustrates processing of stream data - </p> - - <pre> - Event thread - | - V - Wait I/O - | - V - Recv stream1 - | - V - Queue stream1 - | - V - Wait I/O - | - V - Recv stream2 - | - V - Queue stream2 - | - V - Wait I/O - | - V - Write stream1 - | - V - Write stream2 - | - V - Wait I/O - | - ... - </pre> - - </body> -</html> diff --git a/docs/kbase/index.rst b/docs/kbase/index.rst index 2125bf4252..31711d908b 100644 --- a/docs/kbase/index.rst +++ b/docs/kbase/index.rst @@ -94,3 +94,6 @@ Internals `Lock managers <internals/locking.html>`__ Use lock managers to protect disk content + +`RPC protocol & APIs <internals/rpc.html>`__ + RPC protocol information and API / dispatch guide diff --git a/docs/kbase/internals/meson.build b/docs/kbase/internals/meson.build index 8195d7caf0..879c4b2de8 100644 --- a/docs/kbase/internals/meson.build +++ b/docs/kbase/internals/meson.build @@ -4,6 +4,7 @@ docs_kbase_internals_files = [ 'incremental-backup', 'locking', 'migration', + 'rpc', ] diff --git a/docs/kbase/internals/rpc.rst b/docs/kbase/internals/rpc.rst new file mode 100644 index 0000000000..02bc880044 --- /dev/null +++ b/docs/kbase/internals/rpc.rst @@ -0,0 +1,781 @@ +========================== +libvirt RPC infrastructure +========================== + +.. contents:: + +libvirt includes a basic protocol and code to implement an extensible, secure +client/server RPC service. This was originally designed for communication +between the libvirt client library and the libvirtd daemon, but the code is now +isolated to allow reuse in other areas of libvirt code. This document provides +an overview of the protocol and structure / operation of the internal RPC +library APIs. + +RPC protocol +------------ + +libvirt uses a simple, variable length, packet based RPC protocol. All +structured data within packets is encoded using the `XDR +standard <https://en.wikipedia.org/wiki/External_Data_Representation>`__ as +currently defined by `RFC 4506 <https://tools.ietf.org/html/rfc4506>`__. On any +connection running the RPC protocol, there can be multiple programs active, each +supporting one or more versions. A program defines a set of procedures that it +supports. The procedures can support call+reply method invocation, asynchronous +events, and generic data streams. Method invocations can be overlapped, so +waiting for a reply to one will not block the receipt of the reply to another +outstanding method. The protocol was loosely inspired by the design of SunRPC. +The definition of the RPC protocol is in the file ``src/rpc/virnetprotocol.x`` +in the libvirt source tree. + +`Packet framing <protocolframing>`__ +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +On the wire, there is no explicit packet framing marker. Instead each packet is +preceded by an unsigned 32-bit integer giving the total length of the packet in +bytes. This length includes the 4-bytes of the length word itself. Conceptually +the framing looks like this: + +:: + + |~~~ Packet 1 ~~~|~~~ Packet 2 ~~~|~~~ Packet 3 ~~~|~~~ + + +-------+------------+-------+------------+-------+------------+... + | n=U32 | (n-4) * U8 | n=U32 | (n-4) * U8 | n=U32 | (n-4) * U8 | + +-------+------------+-------+------------+-------+------------+... + + |~ Len ~|~ Data ~|~ Len ~|~ Data ~|~ Len ~|~ Data ~|~ + +`Packet data <protocoldata>`__ +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The data in each packet is split into two parts, a short fixed length header, +followed by a variable length payload. So a packet from the illustration above +is more correctly shown as + +:: + + + +-------+-------------+---------------....---+ + | n=U32 | 6*U32 | (n-(7*4))*U8 | + +-------+-------------+---------------....---+ + + |~ Len ~|~ Header ~|~ Payload .... ~| + +`Packet header <protocolheader>`__ +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The header contains 6 fields, encoded as signed/unsigned 32-bit integers. + +:: + + +---------------+ + | program=U32 | + +---------------+ + | version=U32 | + +---------------+ + | procedure=S32 | + +---------------+ + | type=S32 | + +---------------+ + | serial=U32 | + +---------------+ + | status=S32 | + +---------------+ + +``program`` + This is an arbitrarily chosen number that will uniquely identify the + "service" running over the stream. +``version`` + This is the version number of the program, by convention starting from '1'. + When an incompatible change is made to a program, the version number is + incremented. Ideally both versions will then be supported on the wire in + parallel for backwards compatibility. +``procedure`` + This is an arbitrarily chosen number that will uniquely identify the method + call, or event associated with the packet. By convention, procedure numbers + start from 1 and are assigned monotonically thereafter. +``type`` + This can be one of the following enumeration values + + #. call: invocation of a method call + #. reply: completion of a method call + #. event: an asynchronous event + #. stream: control info or data from a stream + +``serial`` + This is a number that starts from 1 and increases each time a method call + packet is sent. A reply or stream packet will have a serial number matching + the original method call packet serial. Events always have the serial number + set to 0. +``status`` + This can one of the following enumeration values + + #. ok: a normal packet. this is always set for method calls or events. For + replies it indicates successful completion of the method. For streams it + indicates confirmation of the end of file on the stream. + #. error: for replies this indicates that the method call failed and error + information is being returned. For streams this indicates that not all + data was sent and the stream has aborted + #. continue: for streams this indicates that further data packets will be + following + +`Packet payload <protocolpayload>`__ +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The payload of a packet will vary depending on the ``type`` and ``status`` +fields from the header. + +- type=call: the in parameters for the method call, XDR encoded +- type=call-with-fds: number of file handles, then the in parameters for the + method call, XDR encoded, followed by the file handles +- type=reply+status=ok: the return value and/or out parameters for the method + call, XDR encoded +- type=reply+status=error: the error information for the method, a virErrorPtr + XDR encoded +- type=reply-with-fds+status=ok: number of file handles, the return value + and/or out parameters for the method call, XDR encoded, followed by the file + handles +- type=reply-with-fds+status=error: number of file handles, the error + information for the method, a virErrorPtr XDR encoded, followed by the file + handles +- type=event: the parameters for the event, XDR encoded +- type=stream+status=ok: no payload +- type=stream+status=error: the error information for the method, a virErrorPtr + XDR encoded +- type=stream+status=continue: the raw bytes of data for the stream. No XDR + encoding + +With the two packet types that support passing file descriptors, in between the +header and the payload there will be a 4-byte integer specifying the number of +file descriptors which are being sent. The actual file handles are sent after +the payload has been sent. Each file handle has a single dummy byte transmitted +as a carrier for the out of band file descriptor. While the sender should always +send '\0' as the dummy byte value, the receiver ought to ignore the value for +the sake of robustness. + +For the exact payload information for each procedure, consult the XDR protocol +definition for the program+version in question + +Wire examples +~~~~~~~~~~~~~ + +The following diagrams illustrate some example packet exchanges between a client +and server + +Method call +^^^^^^^^^^^ + +A single method call and successful reply, for a program=8, version=1, +procedure=3, which 10 bytes worth of input args, and 4 bytes worth of return +values. The overall input packet length is 4 + 24 + 10 == 38, and output packet +length 32 + +:: + + +--+-----------------------+-----------+ + C --> |38| 8 | 1 | 3 | 0 | 1 | 0 | .o.oOo.o. | --> S (call) + +--+-----------------------+-----------+ + + +--+-----------------------+--------+ + C <-- |32| 8 | 1 | 3 | 1 | 1 | 0 | .o.oOo | <-- S (reply) + +--+-----------------------+--------+ + +Method call with error +^^^^^^^^^^^^^^^^^^^^^^ + +An unsuccessful method call will instead return an error object + +:: + + +--+-----------------------+-----------+ + C --> |38| 8 | 1 | 3 | 0 | 1 | 0 | .o.oOo.o. | --> S (call) + +--+-----------------------+-----------+ + + +--+-----------------------+--------------------------+ + C <-- |48| 8 | 1 | 3 | 2 | 1 | 0 | .o.oOo.o.oOo.o.oOo.o.oOo | <-- S (error) + +--+-----------------------+--------------------------+ + +Method call with upload stream +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +A method call which also involves uploading some data over a stream will result +in + +:: + + +--+-----------------------+-----------+ + C --> |38| 8 | 1 | 3 | 0 | 1 | 0 | .o.oOo.o. | --> S (call) + +--+-----------------------+-----------+ + + +--+-----------------------+--------+ + C <-- |32| 8 | 1 | 3 | 1 | 1 | 0 | .o.oOo | <-- S (reply) + +--+-----------------------+--------+ + + +--+-----------------------+-------------....-------+ + C --> |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --> S (stream data up) + +--+-----------------------+-------------....-------+ + +--+-----------------------+-------------....-------+ + C --> |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --> S (stream data up) + +--+-----------------------+-------------....-------+ + +--+-----------------------+-------------....-------+ + C --> |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --> S (stream data up) + +--+-----------------------+-------------....-------+ + ... + +--+-----------------------+-------------....-------+ + C --> |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --> S (stream data up) + +--+-----------------------+-------------....-------+ + +--+-----------------------+ + C --> |24| 8 | 1 | 3 | 3 | 1 | 0 | --> S (stream finish) + +--+-----------------------+ + +--+-----------------------+ + C <-- |24| 8 | 1 | 3 | 3 | 1 | 0 | <-- S (stream finish) + +--+-----------------------+ + +Method call bidirectional stream +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +A method call which also involves a bi-directional stream will result in + +:: + + +--+-----------------------+-----------+ + C --> |38| 8 | 1 | 3 | 0 | 1 | 0 | .o.oOo.o. | --> S (call) + +--+-----------------------+-----------+ + + +--+-----------------------+--------+ + C <-- |32| 8 | 1 | 3 | 1 | 1 | 0 | .o.oOo | <-- S (reply) + +--+-----------------------+--------+ + + +--+-----------------------+-------------....-------+ + C --> |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --> S (stream data up) + +--+-----------------------+-------------....-------+ + +--+-----------------------+-------------....-------+ + C --> |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --> S (stream data up) + +--+-----------------------+-------------....-------+ + +--+-----------------------+-------------....-------+ + C <-- |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | <-- S (stream data down) + +--+-----------------------+-------------....-------+ + +--+-----------------------+-------------....-------+ + C --> |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --> S (stream data up) + +--+-----------------------+-------------....-------+ + +--+-----------------------+-------------....-------+ + C --> |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --> S (stream data up) + +--+-----------------------+-------------....-------+ + +--+-----------------------+-------------....-------+ + C <-- |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | <-- S (stream data down) + +--+-----------------------+-------------....-------+ + +--+-----------------------+-------------....-------+ + C <-- |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | <-- S (stream data down) + +--+-----------------------+-------------....-------+ + +--+-----------------------+-------------....-------+ + C <-- |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | <-- S (stream data down) + +--+-----------------------+-------------....-------+ + +--+-----------------------+-------------....-------+ + C --> |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --> S (stream data up) + +--+-----------------------+-------------....-------+ + .. + +--+-----------------------+-------------....-------+ + C --> |38| 8 | 1 | 3 | 3 | 1 | 2 | .o.oOo.o.oOo....o.oOo. | --> S (stream data up) + +--+-----------------------+-------------....-------+ + +--+-----------------------+ + C --> |24| 8 | 1 | 3 | 3 | 1 | 0 | --> S (stream finish) + +--+-----------------------+ + +--+-----------------------+ + C <-- |24| 8 | 1 | 3 | 3 | 1 | 0 | <-- S (stream finish) + +--+-----------------------+ + +Method calls overlapping +^^^^^^^^^^^^^^^^^^^^^^^^ + +:: + + +--+-----------------------+-----------+ + C --> |38| 8 | 1 | 3 | 0 | 1 | 0 | .o.oOo.o. | --> S (call 1) + +--+-----------------------+-----------+ + +--+-----------------------+-----------+ + C --> |38| 8 | 1 | 3 | 0 | 2 | 0 | .o.oOo.o. | --> S (call 2) + +--+-----------------------+-----------+ + +--+-----------------------+--------+ + C <-- |32| 8 | 1 | 3 | 1 | 2 | 0 | .o.oOo | <-- S (reply 2) + +--+-----------------------+--------+ + +--+-----------------------+-----------+ + C --> |38| 8 | 1 | 3 | 0 | 3 | 0 | .o.oOo.o. | --> S (call 3) + +--+-----------------------+-----------+ + +--+-----------------------+--------+ + C <-- |32| 8 | 1 | 3 | 1 | 3 | 0 | .o.oOo | <-- S (reply 3) + +--+-----------------------+--------+ + +--+-----------------------+-----------+ + C --> |38| 8 | 1 | 3 | 0 | 4 | 0 | .o.oOo.o. | --> S (call 4) + +--+-----------------------+-----------+ + +--+-----------------------+--------+ + C <-- |32| 8 | 1 | 3 | 1 | 1 | 0 | .o.oOo | <-- S (reply 1) + +--+-----------------------+--------+ + +--+-----------------------+--------+ + C <-- |32| 8 | 1 | 3 | 1 | 4 | 0 | .o.oOo | <-- S (reply 4) + +--+-----------------------+--------+ + +Method call with passed FD +^^^^^^^^^^^^^^^^^^^^^^^^^^ + +A single method call with 2 passed file descriptors and successful reply, for a +program=8, version=1, procedure=3, which 10 bytes worth of input args, and 4 +bytes worth of return values. The number of file descriptors is encoded as a +32-bit int. Each file descriptor then has a 1 byte dummy payload. The overall +input packet length is 4 + 24 + 4 + 2 + 10 == 44, and output packet length 32. + +:: + + +--+-----------------------+---------------+-------+ + C --> |44| 8 | 1 | 3 | 0 | 1 | 0 | 2 | .o.oOo.o. | 0 | 0 | --> S (call) + +--+-----------------------+---------------+-------+ + + +--+-----------------------+--------+ + C <-- |32| 8 | 1 | 3 | 1 | 1 | 0 | .o.oOo | <-- S (reply) + +--+-----------------------+--------+ + +RPC security +------------ + +There are various things to consider to ensure an implementation of the RPC +protocol can be satisfactorily secured + +Authentication/encryption +~~~~~~~~~~~~~~~~~~~~~~~~~ + +The basic RPC protocol does not define or require any specific +authentication/encryption capabilities. A generic solution to providing +encryption for the protocol is to run the protocol over a TLS encrypted data +stream. x509 certificate checks can be done to form a crude authentication +mechanism. It is also possible for an RPC program to negotiate an encryption / +authentication capability, such as SASL, which may then also provide per-packet +data encryption. Finally the protocol data stream can of course be tunnelled +over transports such as SSH. + +Data limits +~~~~~~~~~~~ + +Although the protocol itself defines many arbitrary sized data values in the +payloads, to avoid denial of service attack there are a number of size limit +checks prior to encoding or decoding data. There is a limit on the maximum size +of a single RPC message, limit on the maximum string length, and limits on any +other parameter which uses a variable length array. These limits can be raised, +subject to agreement between client/server, without otherwise breaking +compatibility of the RPC data on the wire. + +Data validation +~~~~~~~~~~~~~~~ + +It is important that all data be fully validated before performing any actions +based on the data. When reading an RPC packet, the first four bytes must be read +and the max packet size limit validated, before any attempt is made to read the +variable length packet data. After a complete packet has been read, the header +must be decoded and all 6 fields fully validated, before attempting to dispatch +the payload. Once dispatched, the payload can be decoded and passed on to the +appropriate API for execution. The RPC code must not take any action based on +the payload, since it has no way to validate the semantics of the payload data. +It must delegate this to the execution API (e.g. corresponding libvirt public +API). + +RPC internal APIs +----------------- + +The generic internal RPC library code lives in the ``src/rpc/`` directory of the +libvirt source tree. Unless otherwise noted, the objects are all threadsafe. The +core object types and their purposes are: + +Overview of RPC objects +~~~~~~~~~~~~~~~~~~~~~~~ + +The following is a high level overview of the role of each of the main RPC +objects + +``virNetSASLContext *`` (virnetsaslcontext.h) + The virNetSASLContext APIs maintain SASL state for a network service (server + or client). This is primarily used on the server to provide an access control + list of SASL usernames permitted as clients. +``virNetSASLSession *`` (virnetsaslcontext.h) + The virNetSASLSession APIs maintain SASL state for a single network + connection (socket). This is used to perform the multi-step SASL handshake + and perform encryption/decryption of data once authenticated, via integration + with virNetSocket. +``virNetTLSContext *`` (virnettlscontext.h) + The virNetTLSContext APIs maintain TLS state for a network service (server or + client). This is primarily used on the server to provide an access control + list of x509 distinguished names, as well as diffie-hellman keys. It can also + do validation of x509 certificates prior to initiating a connection, in order + to improve detection of configuration errors. +``virNetTLSSession *`` (virnettlscontext.h) + The virNetTLSSession APIs maintain TLS state for a single network connection + (socket). This is used to perform the multi-step TLS handshake and perform + encryption/decryption of data once authenticated, via integration with + virNetSocket. +``virNetSocket *`` (virnetsocket.h) + The virNetSocket APIs provide a higher level wrapper around the raw BSD + sockets and getaddrinfo APIs. They allow for creation of both server and + client sockets. Data transports supported are TCP, UNIX, SSH tunnel or + external command tunnel. Internally the TCP socket impl uses the getaddrinfo + info APIs to ensure correct protocol-independent behaviour, thus supporting + both IPv4 and IPv6. The socket APIs can be associated with a + virNetSASLSession \*or virNetTLSSession \*object to allow seamless + encryption/decryption of all writes and reads. For UNIX sockets it is + possible to obtain the remote client user ID and process ID. Integration with + the libvirt event loop also allows use of callbacks for notification of + various I/O conditions +``virNetMessage *`` (virnetmessage.h) + The virNetMessage APIs provide a wrapper around the libxdr API calls, to + facilitate processing and creation of RPC packets. There are convenience APIs + for encoding/encoding the packet headers, encoding/decoding the payload using + an XDR filter, encoding/decoding a raw payload (for streams), and encoding a + virErrorPtr object. There is also a means to add to/serve from a linked-list + queue of messages. +``virNetClient *`` (virnetclient.h) + The virNetClient APIs provide a way to connect to a remote server and run one + or more RPC protocols over the connection. Connections can be made over TCP, + UNIX sockets, SSH tunnels, or external command tunnels. There is support for + both TLS and SASL session encryption. The client also supports management of + multiple data streams over each connection. Each client object can be used + from multiple threads concurrently, with method calls/replies being + interleaved on the wire as required. +``virNetClientProgram *`` (virnetclientprogram.h) + The virNetClientProgram APIs are used to register a program+version with the + connection. This then enables invocation of method calls, receipt of + asynchronous events and use of data streams, within that program+version. + When created a set of callbacks must be supplied to take care of dispatching + any incoming asynchronous events. +``virNetClientStream *`` (virnetclientstream.h) + The virNetClientStream APIs are used to control transmission and receipt of + data over a stream active on a client. Streams provide a low latency, + unlimited length, bi-directional raw data exchange mechanism layered over the + RPC connection +``virNetServer *`` (virnetserver.h) + The virNetServer APIs are used to manage a network server. A server exposed + one or more programs, over one or more services. It manages multiple client + connections invoking multiple RPC calls in parallel, with dispatch across + multiple worker threads. +``virNetDaemon *`` (virnetdaemon.h) + The virNetDaemon APIs are used to manage a daemon process. A daemon is a + process that might expose one or more servers. It handles most + process-related details, network-related should be part of the underlying + server. +``virNetServerClient *`` (virnetserverclient.h) + The virNetServerClient APIs are used to manage I/O related to a single client + network connection. It handles initial validation and routing of incoming RPC + packets, and transmission of outgoing packets. +``virNetServerProgram *`` (virnetserverprogram.h) + The virNetServerProgram APIs are used to provide the implementation of a + single program/version set. Primarily this includes a set of callbacks used + to actually invoke the APIs corresponding to program procedure numbers. It is + responsible for all the serialization of payloads to/from XDR. +``virNetServerService *`` (virnetserverservice.h) + The virNetServerService APIs are used to connect the server to one or more + network protocols. A single service may involve multiple sockets (ie both + IPv4 and IPv6). A service also has an associated authentication policy for + incoming clients. + +Client RPC dispatch +~~~~~~~~~~~~~~~~~~~ + +The client RPC code must allow for multiple overlapping RPC method calls to be +invoked, transmission and receipt of data for multiple streams and receipt of +asynchronous events. Understandably this involves coordination of multiple +threads. + +The core requirement in the client dispatch code is that only one thread is +allowed to be performing I/O on the socket at any time. This thread is said to +be "holding the buck". When any other thread comes along and needs to do I/O it +must place its packets on a queue and delegate processing of them to the thread +that has the buck. This thread will send out the method call, and if it sees a +reply will pass it back to the waiting thread. If the other thread's reply +hasn't arrived, by the time the main thread has got its own reply, then it will +transfer responsibility for I/O to the thread that has been waiting the longest. +It is said to be "passing the buck" for I/O. + +When no thread is performing any RPC method call, or sending stream data there +is still a need to monitor the socket for incoming I/O related to asynchronous +events, or stream data receipt. For this task, a watch is registered with the +event loop which triggers whenever the socket is readable. This watch is +automatically disabled whenever any other thread grabs the buck, and re-enabled +when the buck is released. + +Example with buck passing +^^^^^^^^^^^^^^^^^^^^^^^^^ + +In the first example, a second thread issues an API call while the first thread +holds the buck. The reply to the first call arrives first, so the buck is passed +to the second thread. + +:: + + Thread-1 + | + V + Call API1() + | + V + Grab Buck + | Thread-2 + V | + Send method1 V + | Call API2() + V | + Wait I/O V + |<--------Queue method2 + V | + Send method2 V + | Wait for buck + V | + Wait I/O | + | | + V | + Recv reply1 | + | | + V | + Pass the buck----->| + | V + V Wait I/O + Return API1() | + V + Recv reply2 + | + V + Release the buck + | + V + Return API2() + +Example without buck passing +^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +In this second example, a second thread issues an API call which is sent and +replied to, before the first thread's API call has completed. The first thread +thus notifies the second that its reply is ready, and there is no need to pass +the buck + +:: + + Thread-1 + | + V + Call API1() + | + V + Grab Buck + | Thread-2 + V | + Send method1 V + | Call API2() + V | + Wait I/O V + |<--------Queue method2 + V | + Send method2 V + | Wait for buck + V | + Wait I/O | + | | + V | + Recv reply2 | + | | + V | + Notify reply2------>| + | V + V Return API2() + Wait I/O + | + V + Recv reply1 + | + V + Release the buck + | + V + Return API1() + +Example with async events +^^^^^^^^^^^^^^^^^^^^^^^^^ + +In this example, only one thread is present and it has to deal with some async +events arriving. The events are actually dispatched to the application from the +event loop thread + +:: + + Thread-1 + | + V + Call API1() + | + V + Grab Buck + | + V + Send method1 + | + V + Wait I/O + | Event thread + V ... + Recv event1 | + | V + V Wait for timer/fd + Queue event1 | + | V + V Timer fires + Wait I/O | + | V + V Emit event1 + Recv reply1 | + | V + V Wait for timer/fd + Return API1() | + ... + +Server RPC dispatch +~~~~~~~~~~~~~~~~~~~ + +The RPC server code must support receipt of incoming RPC requests from multiple +client connections, and parallel processing of all RPC requests, even many from +a single client. This goal is achieved through a combination of event driven +I/O, and multiple processing threads. + +The main libvirt event loop thread is responsible for performing all socket I/O. +It will read incoming packets from clients and will transmit outgoing packets to +clients. It will handle the I/O to/from streams associated with client API +calls. When doing client I/O it will also pass the data through any applicable +encryption layer (through use of the virNetSocket / virNetTLSSession and +virNetSASLSession integration). What is paramount is that the event loop thread +never do any task that can take a non-trivial amount of time. + +When reading packets, the event loop will first read the 4 byte length word. +This is validated to make sure it does not exceed the maximum permissible packet +size, and the client is set to allow receipt of the rest of the packet data. +Once a complete packet has been received, the next step is to decode the RPC +header. The header is validated to ensure the request is sensible, ie the server +should not receive a method reply from a client. If the client has not yet +authenticated, an access control list check is also performed to make sure the +procedure is one of those allowed prior to auth. If the packet is a method call, +it will be placed on a global processing queue. The event loop thread is now +done with the packet for the time being. + +The server has a pool of worker threads, which wait for method call packets to +be queued. One of them will grab the new method call off the queue for +processing. The first step is to decode the payload of the packet to extract the +method call arguments. The worker does not attempt to do any semantic validation +of the arguments, except to make sure the size of any variable length fields is +below defined limits. + +The worker now invokes the libvirt API call that corresponds to the procedure +number in the packet header. The worker is thus kept busy until the API call +completes. The implementation of the API call is responsible for doing semantic +validation of parameters and any MAC security checks on the objects affected. + +Once the API call has completed, the worker thread will take the return value +and output parameters, or error object and encode them into a reply packet. +Again it does not attempt to do any semantic validation of output data, aside +from variable length field limit checks. The worker thread puts the reply packet +on the transmission queue for the client. The worker is now finished and goes +back to wait for another incoming method call. + +The main event loop is back in charge and when the client socket becomes +writable, it will start sending the method reply packet back to the client. + +At any time the libvirt connection object can emit asynchronous events. These +are handled by callbacks in the main event thread. The callback will simply +encode the event parameters into a new data packet and place the packet on the +client transmission queue. + +Incoming and outgoing stream packets are also directly handled by the main event +thread. When an incoming stream packet is received, instead of placing it in the +global dispatch queue for the worker threads, it is sidetracked into a +per-stream processing queue. When the stream becomes writable, queued incoming +stream packets will be processed, passing their data payload on the stream. +Conversely when the stream becomes readable, chunks of data will be read from +it, encoded into new outgoing packets, and placed on the client's transmit +queue. + +Example with overlapping methods +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +This example illustrates processing of two incoming methods with overlapping +execution + +:: + + Event thread Worker 1 Worker 2 + | | | + V V V + Wait I/O Wait Job Wait Job + | | | + V | | + Recv method1 | | + | | | + V | | + Queue method1 V | + | Serve method1 | + V | | + Wait I/O V | + | Call API1() | + V | | + Recv method2 | | + | | | + V | | + Queue method2 | V + | | Serve method2 + V V | + Wait I/O Return API1() V + | | Call API2() + | V | + V Queue reply1 | + Send reply1 | | + | V V + V Wait Job Return API2() + Wait I/O | | + | ... V + V Queue reply2 + Send reply2 | + | V + V Wait Job + Wait I/O | + | ... + ... + +Example with stream data +^^^^^^^^^^^^^^^^^^^^^^^^ + +This example illustrates processing of stream data + +:: + + Event thread + | + V + Wait I/O + | + V + Recv stream1 + | + V + Queue stream1 + | + V + Wait I/O + | + V + Recv stream2 + | + V + Queue stream2 + | + V + Wait I/O + | + V + Write stream1 + | + V + Write stream2 + | + V + Wait I/O + | + ... -- 2.35.1

Note that this document was not referenced from any top level page. This patch does a straight conversion and leaves it unreferenced. Next patch will then modify it to serve as an overview (hence the new name) of how an API call happens. Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- docs/internals.html.in | 119 ------------------------------ docs/kbase/internals/meson.build | 1 + docs/kbase/internals/overview.rst | 117 +++++++++++++++++++++++++++++ docs/meson.build | 1 - 4 files changed, 118 insertions(+), 120 deletions(-) delete mode 100644 docs/internals.html.in create mode 100644 docs/kbase/internals/overview.rst diff --git a/docs/internals.html.in b/docs/internals.html.in deleted file mode 100644 index e474f7ddd7..0000000000 --- a/docs/internals.html.in +++ /dev/null @@ -1,119 +0,0 @@ -<?xml version="1.0" encoding="UTF-8"?> -<!DOCTYPE html> -<html xmlns="http://www.w3.org/1999/xhtml"> - <body> - <h1>libvirt internals</h1> - - <p> - This section provides documents useful to those working on the libvirt - internals, adding new public APIs, new hypervisor drivers or extending - the libvirtd daemon code. - </p> - - <ul> - <li>Introduction to basic rules and guidelines for - <a href="hacking.html">hacking</a> on libvirt code</li> - <li>Guide to adding <a href="api_extension.html">public APIs</a></li> - <li>Insight into libvirt <a href="internals/eventloop.html">event loop and worker pool</a></li> - <li>Approach for <a href="internals/command.html">spawning commands</a> - from libvirt driver code</li> - <li>The libvirt <a href="internals/rpc.html">RPC infrastructure</a></li> - <li>The <a href="internals/locking.html">Resource Lock Manager</a></li> - </ul> - - <p>Before adding new code it will be important to get a basic understanding - of the many elements involved with making any call or change to the libvirt - code. The architecture <a href="goals.html">goals</a> must be adhered to - when submitting new code. Understanding the many places that need to be - touched and the interactions between various subsystems within libvirt - will directly correlate to the ability to be successful in getting new - code accepted.</p> - <p>The following diagram depicts code flow from a client application, in - this case the libvirt provided <code>virsh</code> command through the - various layers to elicit a response from some chosen hypervisor. - </p> - - <p class="image"> - <img alt="virConnectOpen calling sequence" - src="images/libvirt-virConnect-example.png"/> - </p> - <ul> - <li>"virsh -c qemu:///system list --all" - <p>After the virsh code processes the input arguments, it eventually - will make a call to open the connection using a default set of - authentication credentials (virConnectAuthDefault). </p></li> - <li>virConnectOpenAuth() - <p>Each of the virConnectOpen APIs will first call virInitialize() and - then revector through the local "do_open():" call.</p> - <ul> - <li>virInitialize() - <p>Calls the registration API for each of the drivers with - client-side only capabilities and then call the remoteRegister() - API last. This ensures the virDriverTab[] tries local drivers - first before using the remote driver.</p></li> - <li>Loop through virDriverTab[] entries trying to call their - respective "open" entry point (in our case remoteOpen())</li> - <li>After successful return from the virDriverTab[] open() - API, attempt to find and open other drivers (network, interface, - storage, etc.)</li> - </ul> - </li> - <li>remoteOpen() - <p>After a couple of URI checks, a call to doRemoteOpen() is made</p> - <ul> - <li>Determine network transport and host/port to use from URI - <p>The transport will be either tls, unix, ssh, libssh2, ext, - or tcp with the default of tls. Decode the host/port if provided - or default to "localhost".</p></li> - <li>virNetClientRegisterAsyncIO() - <p>Register an I/O callback mechanism to get returned data via - virNetClientIncomingEvent()</p></li> - <li>"call(...REMOTE_PROC_OPEN...)" - <p>Eventually routes into virNetClientProgramCall() which will - call virNetClientSendWithReply() and eventually uses - virNetClientIO()to send the message to libvirtd and - then waits for a response using virNetClientIOEventLoop()</p></li> - <li>virNetClientIncomingEvent() - <p>Receives the returned packet and processes through - virNetClientIOUpdateCallback()</p></li> - </ul> - </li> - <li>libvirtd Daemon - <p></p> - <ul> - <li>Daemon Startup - <p>The daemon initialization processing will declare itself - as a daemon via a virNetDaemonNew() call, then creates new server - using virNetServerNew() and adds that server to the main daemon - struct with virNetDaemonAddServer() call. It will then use - virDriverLoadModule() to find/load all known drivers, - set up an RPC server program using the <code>remoteProcs[]</code> - table via a virNetServerProgramNew() call. The table is the - corollary to the <code>remote_procedure</code> enum list in - the client. It lists all the functions to be called in - the same order. Once RPC is set up, networking server sockets - are opened, the various driver state initialization routines - are run from the <code>virStateDriverTab[]</code>, the network - links are enabled, and the daemon waits for work.</p></li> - <li>RPC - <p>When a message is received, the <code>remoteProcs[]</code> - table is referenced for the 'REMOTE_PROC_OPEN' call entry. - This results in remoteDispatchOpen() being called via the - virNetServerProgramDispatchCall().</p></li> - <li>remoteDispatchOpen() - <p>The API will read the argument passed picking out the - <code>name</code> of the driver to be opened. The code - will then call virConnectOpen() or virConnectOpenReadOnly() - depending on the argument <code>flags</code>.</p></li> - <li>virConnectOpen() or virConnectOpenReadOnly() - <p>Just like the client except that upon entry the URI - is what was passed from the client and will be found - and opened to process the data.</p> - <p>The returned structure data is returned via the - virNetServer interfaces to the remote driver which then - returns it to the client application.</p></li> - </ul> - </li> - </ul> - </body> -</html> diff --git a/docs/kbase/internals/meson.build b/docs/kbase/internals/meson.build index 879c4b2de8..8b5daad1f9 100644 --- a/docs/kbase/internals/meson.build +++ b/docs/kbase/internals/meson.build @@ -4,6 +4,7 @@ docs_kbase_internals_files = [ 'incremental-backup', 'locking', 'migration', + 'overview', 'rpc', ] diff --git a/docs/kbase/internals/overview.rst b/docs/kbase/internals/overview.rst new file mode 100644 index 0000000000..84ea7858db --- /dev/null +++ b/docs/kbase/internals/overview.rst @@ -0,0 +1,117 @@ +========================== +libvirt internals overview +========================== + +This section provides documents useful to those working on the libvirt +internals, adding new public APIs, new hypervisor drivers or extending the +libvirtd daemon code. + +- Introduction to basic rules and guidelines for `hacking <../../hacking.html>`__ on + libvirt code +- Guide to adding `public APIs <../../api_extension.html>`__ +- Insight into libvirt `event loop and worker + pool <eventloop.html>`__ +- Approach for `spawning commands <command.html>`__ from libvirt + driver code +- The libvirt `RPC infrastructure <rpc.html>`__ +- The `Resource Lock Manager <locking.html>`__ + +Before adding new code it will be important to get a basic understanding of the +many elements involved with making any call or change to the libvirt code. The +architecture `goals <../../goals.html>`__ must be adhered to when submitting new code. +Understanding the many places that need to be touched and the interactions +between various subsystems within libvirt will directly correlate to the ability +to be successful in getting new code accepted. + +The following diagram depicts code flow from a client application, in this case +the libvirt provided ``virsh`` command through the various layers to elicit a +response from some chosen hypervisor. + +.. image:: ../../images/libvirt-virConnect-example.png + :alt: virConnectOpen calling sequence + +- "virsh -c qemu:///system list --all" + + After the virsh code processes the input arguments, it eventually will make a + call to open the connection using a default set of authentication credentials + (virConnectAuthDefault). + +- virConnectOpenAuth() + + Each of the virConnectOpen APIs will first call virInitialize() and then + revector through the local "do_open():" call. + + - virInitialize() + + Calls the registration API for each of the drivers with client-side only + capabilities and then call the remoteRegister() API last. This ensures the + virDriverTab[] tries local drivers first before using the remote driver. + + - Loop through virDriverTab[] entries trying to call their respective "open" + entry point (in our case remoteOpen()) + + - After successful return from the virDriverTab[] open() API, attempt to + find and open other drivers (network, interface, storage, etc.) + +- remoteOpen() + + After a couple of URI checks, a call to doRemoteOpen() is made + + - Determine network transport and host/port to use from URI + + The transport will be either tls, unix, ssh, libssh2, ext, or tcp with the + default of tls. Decode the host/port if provided or default to + "localhost". + + - virNetClientRegisterAsyncIO() + + Register an I/O callback mechanism to get returned data via + virNetClientIncomingEvent() + + - "call(...REMOTE_PROC_OPEN...)" + + Eventually routes into virNetClientProgramCall() which will call + virNetClientSendWithReply() and eventually uses virNetClientIO()to send + the message to libvirtd and then waits for a response using + virNetClientIOEventLoop() + + - virNetClientIncomingEvent() + + Receives the returned packet and processes through + virNetClientIOUpdateCallback() + +- libvirtd Daemon + + - Daemon Startup + + The daemon initialization processing will declare itself as a daemon via a + virNetDaemonNew() call, then creates new server using virNetServerNew() + and adds that server to the main daemon struct with + virNetDaemonAddServer() call. It will then use virDriverLoadModule() to + find/load all known drivers, set up an RPC server program using the + ``remoteProcs[]`` table via a virNetServerProgramNew() call. The table is + the corollary to the ``remote_procedure`` enum list in the client. It + lists all the functions to be called in the same order. Once RPC is set + up, networking server sockets are opened, the various driver state + initialization routines are run from the ``virStateDriverTab[]``, the + network links are enabled, and the daemon waits for work. + + - RPC + + When a message is received, the ``remoteProcs[]`` table is referenced for + the 'REMOTE_PROC_OPEN' call entry. This results in remoteDispatchOpen() + being called via the virNetServerProgramDispatchCall(). + + - remoteDispatchOpen() + + The API will read the argument passed picking out the ``name`` of the + driver to be opened. The code will then call virConnectOpen() or + virConnectOpenReadOnly() depending on the argument ``flags``. + + - virConnectOpen() or virConnectOpenReadOnly() + + Just like the client except that upon entry the URI is what was passed + from the client and will be found and opened to process the data. + + The returned structure data is returned via the virNetServer interfaces to + the remote driver which then returns it to the client application. diff --git a/docs/meson.build b/docs/meson.build index 4291dea6f5..9f1f1ed80d 100644 --- a/docs/meson.build +++ b/docs/meson.build @@ -25,7 +25,6 @@ docs_html_in_files = [ 'formatnwfilter', 'formatstoragecaps', 'index', - 'internals', 'remote', 'storage', 'uri', -- 2.35.1