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https://github.com/systemd/systemd
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login: add sd_login_monitor_get_timeout() public api call
We don't need this right now, but we should keep our options open, in case we need more than just an fd for waking up.
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@ -48,6 +48,7 @@
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<refname>sd_login_monitor_flush</refname>
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<refname>sd_login_monitor_get_fd</refname>
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<refname>sd_login_monitor_get_events</refname>
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<refname>sd_login_monitor_get_timeout</refname>
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<refname>sd_login_monitor</refname>
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<refpurpose>Monitor login sessions, seats and users</refpurpose>
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</refnamediv>
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@ -82,6 +83,12 @@
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<paramdef>sd_login_monitor* <parameter>m</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_login_monitor_get_timeout</function></funcdef>
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<paramdef>sd_login_monitor* <parameter>m</parameter></paramdef>
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<paramdef>uint64_t* <parameter>timeout_usec</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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@ -130,7 +137,9 @@
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or a similar interface. The application should include
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the returned file descriptor as wake-up source for the
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events mask returned by
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<function>sd_login_monitor_get_events()</function>. Whenever
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<function>sd_login_monitor_get_events()</function>. It
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should pass a timeout value as returned by
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<function>sd_login_monitor_get_timeout()</function>. Whenever
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a wake-up is triggered the file descriptor needs to be
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reset via
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<function>sd_login_monitor_flush()</function>. An
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@ -146,15 +155,51 @@
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and similar to fill into the
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<literal>.events</literal> field of <literal>struct
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pollfd</literal>.</para>
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<para><function>sd_login_monitor_get_timeout()</function>
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will return a timeout value for usage in
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<function>poll()</function>. This returns a value in
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microseconds since the epoch of CLOCK_MONOTONIC for
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timing out <function>poll()</function> in
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<literal>timeout_usec</literal>. See
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<citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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for details about
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<literal>CLOCK_MONOTONIC</literal>. If there's no
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timeout to wait for this will fill in
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<literal>(uint64_t) -1</literal> instead. Note that
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<function>poll()</function> takes a relative timeout
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in milliseconds rather than an absolute timeout in
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microseconds. To convert the absolute 'us' timeout into
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relative 'ms', use code like the following:</para>
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<programlisting>uint64_t t;
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int msec;
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sd_login_monitor_get_timeout(m, &t);
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if (t == (uint64_t) -1)
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msec = -1;
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else {
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struct timespec ts;
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uint64_t n;
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clock_getttime(CLOCK_MONOTONIC, &ts);
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n = (uint64_t) ts.tv_sec * 1000000 + ts.tv_nsec / 1000;
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msec = t > n ? (int) ((t - n + 999) / 1000) : 0;
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}</programlisting>
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<para>The code above does not do any error checking
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for brevity's sake. The calculated <literal>msec</literal>
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integer can be passed directly as
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<function>poll()</function>'s timeout
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parameter.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>On success
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<function>sd_login_monitor_new()</function> and
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<function>sd_login_monitor_flush()</function> return 0
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or a positive integer. On success
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<function>sd_login_monitor_new()</function>,
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<function>sd_login_monitor_flush()</function> and
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<function>sd_login_monitor_get_timeout()</function>
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return 0 or a positive integer. On success
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<function>sd_login_monitor_get_fd()</function> returns
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a Unix file descriptor. On success
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<function>sd_login_monitor_get_events()</function>
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@ -173,8 +218,9 @@
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<para>The <function>sd_login_monitor_new()</function>,
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<function>sd_login_monitor_unref()</function>,
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<function>sd_login_monitor_flush()</function>,
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<function>sd_login_monitor_get_fd()</function> and
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<function>sd_login_monitor_get_events()</function>
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<function>sd_login_monitor_get_fd()</function>,
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<function>sd_login_monitor_get_events()</function> and
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<function>sd_login_monitor_get_timeout()</function>
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interfaces are available as shared library, which can
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be compiled and linked to with the
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<literal>libsystemd-login</literal>
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@ -189,7 +235,8 @@
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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<citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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</para>
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</refsect1>
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@ -62,4 +62,5 @@ global:
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LIBSYSTEMD_LOGIN_201 {
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global:
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sd_login_monitor_get_events;
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sd_login_monitor_get_timeout;
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} LIBSYSTEMD_LOGIN_198;
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@ -804,5 +804,23 @@ _public_ int sd_login_monitor_get_events(sd_login_monitor *m) {
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if (!m)
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return -EINVAL;
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/* For now we will only return POLLIN here, since we don't
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* need anything else ever for inotify. However, let's have
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* this API to keep our options open should we later on need
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* it. */
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return POLLIN;
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}
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_public_ int sd_login_monitor_get_timeout(sd_login_monitor *m, uint64_t *timeout_usec) {
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if (!m)
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return -EINVAL;
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if (!timeout_usec)
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return -EINVAL;
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/* For now we will only return (uint64_t) -1, since we don't
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* need any timeout. However, let's have this API to keep our
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* options open should we later on need it. */
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*timeout_usec = (uint64_t) -1;
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return 0;
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}
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@ -183,12 +183,23 @@ int main(int argc, char* argv[]) {
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r = sd_login_monitor_new("session", &m);
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assert_se(r >= 0);
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zero(pollfd);
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pollfd.fd = sd_login_monitor_get_fd(m);
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pollfd.events = sd_login_monitor_get_events(m);
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for (n = 0; n < 5; n++) {
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r = poll(&pollfd, 1, -1);
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usec_t timeout, nw;
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zero(pollfd);
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assert_se((pollfd.fd = sd_login_monitor_get_fd(m)) >= 0);
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assert_se((pollfd.events = sd_login_monitor_get_events(m)) >= 0);
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assert_se(sd_login_monitor_get_timeout(m, &timeout) >= 0);
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nw = now(CLOCK_MONOTONIC);
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r = poll(&pollfd, 1,
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timeout == (uint64_t) -1 ? -1 :
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timeout > nw ? (int) ((timeout - nw) / 1000) :
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0);
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assert_se(r >= 0);
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sd_login_monitor_flush(m);
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@ -23,6 +23,7 @@
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***/
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#include <sys/types.h>
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#include <inttypes.h>
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#ifdef __cplusplus
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extern "C" {
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@ -159,6 +160,9 @@ int sd_login_monitor_get_fd(sd_login_monitor *m);
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/* Get poll() mask to monitor */
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int sd_login_monitor_get_events(sd_login_monitor *m);
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/* Get timeout for poll(), as usec value relative to CLOCK_MONOTONIC's epoch */
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int sd_login_monitor_get_timeout(sd_login_monitor *m, uint64_t *timeout_usec);
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#ifdef __cplusplus
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}
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#endif
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