diff options
Diffstat (limited to 'man/sd_listen_fds.xml')
| -rw-r--r-- | man/sd_listen_fds.xml | 133 |
1 files changed, 107 insertions, 26 deletions
diff --git a/man/sd_listen_fds.xml b/man/sd_listen_fds.xml index 9b9705eb2e..ea55671e4f 100644 --- a/man/sd_listen_fds.xml +++ b/man/sd_listen_fds.xml @@ -1,4 +1,4 @@ -<?xml version='1.0'?> <!--*-nxml-*--> +<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> @@ -45,6 +45,7 @@ <refnamediv> <refname>sd_listen_fds</refname> + <refname>sd_listen_fds_with_names</refname> <refname>SD_LISTEN_FDS_START</refname> <refpurpose>Check for file descriptors passed by the system manager</refpurpose> </refnamediv> @@ -59,23 +60,26 @@ <funcdef>int <function>sd_listen_fds</function></funcdef> <paramdef>int <parameter>unset_environment</parameter></paramdef> </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_listen_fds_with_names</function></funcdef> + <paramdef>int <parameter>unset_environment</parameter></paramdef> + <paramdef>char*** <parameter>names</parameter></paramdef> + </funcprototype> </funcsynopsis> </refsynopsisdiv> <refsect1> <title>Description</title> - <para><function>sd_listen_fds()</function> shall be called by a - daemon to check for file descriptors passed by the init system as - part of the socket-based activation logic.</para> - - <para>If the <parameter>unset_environment</parameter> parameter is - non-zero, <function>sd_listen_fds()</function> will unset the - <varname>$LISTEN_FDS</varname> and <varname>$LISTEN_PID</varname> - environment variables before returning (regardless of whether the - function call itself succeeded or not). Further calls to - <function>sd_listen_fds()</function> will then fail, but the - variables are no longer inherited by child processes.</para> + <para><function>sd_listen_fds()</function> may be invoked by a + daemon to check for file descriptors passed by the service manager as + part of the socket-based activation logic. It returns the number + of received file descriptors. If no file descriptors have been + received zero is returned. The first file descriptor may be found + at file descriptor number 3 + (i.e. <constant>SD_LISTEN_FDS_START</constant>), the remaining + descriptors follow at 4, 5, 6, ..., if any.</para> <para>If a daemon receives more than one file descriptor, they will be passed in the same order as configured in the systemd @@ -108,12 +112,86 @@ <literal>FDSTORE=1</literal> messages, these file descriptors are passed last, in arbitrary order, and with duplicates removed.</para> + + <para>If the <parameter>unset_environment</parameter> parameter is + non-zero, <function>sd_listen_fds()</function> will unset the + <varname>$LISTEN_FDS</varname>, <varname>$LISTEN_PID</varname> and + <varname>$LISTEN_FDNAMES</varname> environment variables before + returning (regardless of whether the function call itself + succeeded or not). Further calls to + <function>sd_listen_fds()</function> will then return zero, but the + variables are no longer inherited by child processes.</para> + + <para><function>sd_listen_fds_with_names()</function> is like + <function>sd_listen_fds()</function> but optionally also returns + an array of strings with identification names for the passed file + descriptors, if that is available, and the + <parameter>names</parameter> parameter is non-NULL. This + information is read from the <varname>$LISTEN_FDNAMES</varname> + variable, which may contain a colon-separated list of names. For + socket-activated services, these names may be configured with the + <varname>FileDescriptorName=</varname> setting in socket unit + files, see + <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry> + for details. For file descriptors pushed into the file descriptor + store (see above) the name is set via the + <varname>FDNAME=</varname> field transmitted via + <function>sd_pid_notify_with_fds()</function>. The primary usecase + for these names are services which accept a variety of file + descriptors which are not recognizable with functions like + <function>sd_is_socket()</function> alone, and thus require + identification via a name. It is recommended to rely on named file + descriptors only if identification via + <function>sd_is_socket()</function> and related calls is not + sufficient. Note that the names used are not unique in any + way. The returned array of strings has as many entries as file + descriptors has been received, plus a final NULL pointer + terminating the array. The caller needs to free the array itself + and each of its elements with libc's <varname>free()</varname> + call after use. If the <parameter>names</parameter> parameter is + NULL the call is entirely equivalent to + <function>sd_listen_fds()</function>.</para> + + <para>Under specific conditions the following automatic file + descriptor names are returned: + + <table> + <title> + <command>Special names</command> + </title> + + <tgroup cols='2'> + <thead> + <row> + <entry>Name</entry> + <entry>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry><literal>unknown</literal></entry> + <entry>The process received no name for the specific file descriptor from the service manager.</entry> + </row> + + <row> + <entry><literal>stored</literal></entry> + <entry>The file descriptor originates in the service manager's per-service file descriptor store, and the <varname>FDNAME=</varname> field was absent when the file descriptor was submitted to the service manager.</entry> + </row> + + <row> + <entry><literal>connection</literal></entry> + <entry>The service was activated in per-connection style using <varname>Accept=yes</varname> in the socket unit file, and the file descriptor is the connection socket.</entry> + </row> + </tbody> + </tgroup> + </table> + </para> </refsect1> <refsect1> <title>Return Value</title> - <para>On failure, this call returns a negative errno-style error + <para>On failure, these calls returns a negative errno-style error code. If <varname>$LISTEN_FDS</varname>/<varname>$LISTEN_PID</varname> was not set or was not correctly set for this daemon and hence no file @@ -128,13 +206,16 @@ <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> - <para>Internally, this function checks whether the - <varname>$LISTEN_PID</varname> environment variable equals the - daemon PID. If not, it returns immediately. Otherwise, it parses - the number passed in the <varname>$LISTEN_FDS</varname> + <para>Internally, <function>sd_listen_fds()</function> checks + whether the <varname>$LISTEN_PID</varname> environment variable + equals the daemon PID. If not, it returns immediately. Otherwise, + it parses the number passed in the <varname>$LISTEN_FDS</varname> environment variable, then sets the FD_CLOEXEC flag for the parsed number of file descriptors starting from SD_LISTEN_FDS_START. - Finally, it returns the parsed number.</para> + Finally, it returns the parsed + number. <function>sd_listen_fds_with_names()</function> does the + same but also parses <varname>$LISTEN_FDNAMES</varname> if + set.</para> </refsect1> <refsect1> @@ -144,15 +225,14 @@ <varlistentry> <term><varname>$LISTEN_PID</varname></term> <term><varname>$LISTEN_FDS</varname></term> + <term><varname>$LISTEN_FDNAMES</varname></term> - <listitem><para>Set by the init system - for supervised processes that use - socket-based activation. This - environment variable specifies the - data - <function>sd_listen_fds()</function> - parses. See above for - details.</para></listitem> + <listitem><para>Set by the service manager for supervised + processes that use socket-based activation. This environment + variable specifies the data + <function>sd_listen_fds()</function> and + <function>sd_listen_fds_with_names()</function> parses. See + above for details.</para></listitem> </varlistentry> </variablelist> </refsect1> @@ -167,6 +247,7 @@ <citerefentry><refentrytitle>sd_is_socket</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd_is_socket_inet</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd_is_socket_unix</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd_pid_notify_with_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>, <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry> |