core: treat JobTimeout=0 as equivalent to JobTimeout=infinity

Corrects an incompatibility introduced with 36c16a7.

Fixes: #2537

man/systemd.unit.xml

@@ -728,20 +728,14 @@
         <term><varname>JobTimeoutAction=</varname></term>
         <term><varname>JobTimeoutRebootArgument=</varname></term>
 
-        <listitem><para>When a job for this unit is queued, a time-out
-        may be configured. If this time limit is reached, the job will
-        be cancelled, the unit however will not change state or even
-        enter the <literal>failed</literal> mode. This value defaults
-        to 0 (job timeouts disabled), except for device units. NB:
-        this timeout is independent from any unit-specific timeout
-        (for example, the timeout set with
-        <varname>TimeoutStartSec=</varname> in service units) as the
-        job timeout has no effect on the unit itself, only on the job
-        that might be pending for it. Or in other words: unit-specific
-        timeouts are useful to abort unit state changes, and revert
-        them. The job timeout set with this option however is useful
-        to abort only the job waiting for the unit state to
-        change.</para>
+        <listitem><para>When a job for this unit is queued, a time-out may be configured. If this time limit is
+        reached, the job will be cancelled, the unit however will not change state or even enter the
+        <literal>failed</literal> mode. This value defaults to <literal>infinity</literal> (job timeouts disabled),
+        except for device units. NB: this timeout is independent from any unit-specific timeout (for example, the
+        timeout set with <varname>TimeoutStartSec=</varname> in service units) as the job timeout has no effect on the
+        unit itself, only on the job that might be pending for it. Or in other words: unit-specific timeouts are useful
+        to abort unit state changes, and revert them. The job timeout set with this option however is useful to abort
+        only the job waiting for the unit state to change.</para>
 
         <para><varname>JobTimeoutAction=</varname>
         optionally configures an additional

src/core/load-fragment-gperf.gperf.m4

@@ -161,7 +161,7 @@ Unit.OnFailureJobMode,           config_parse_job_mode,              0,
 Unit.OnFailureIsolate,           config_parse_job_mode_isolate,      0,                             offsetof(Unit, on_failure_job_mode)
 Unit.IgnoreOnIsolate,            config_parse_bool,                  0,                             offsetof(Unit, ignore_on_isolate)
 Unit.IgnoreOnSnapshot,           config_parse_warn_compat,           DISABLED_LEGACY,               0
-Unit.JobTimeoutSec,              config_parse_sec,                   0,                             offsetof(Unit, job_timeout)
+Unit.JobTimeoutSec,              config_parse_sec_fix_0,             0,                             offsetof(Unit, job_timeout)
 Unit.JobTimeoutAction,           config_parse_failure_action,        0,                             offsetof(Unit, job_timeout_action)
 Unit.JobTimeoutRebootArgument,   config_parse_string,                0,                             offsetof(Unit, job_timeout_reboot_arg)
 Unit.StartLimitInterval,         config_parse_sec,                   0,                             offsetof(Unit, start_limit.interval)

src/core/load-fragment.c

@@ -1757,6 +1757,42 @@ int config_parse_service_timeout(
         return 0;
 }
 
+int config_parse_sec_fix_0(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        usec_t *usec = data;
+        int r;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(usec);
+
+        /* This is pretty much like config_parse_sec(), except that this treats a time of 0 as infinity, for
+         * compatibility with older versions of systemd where 0 instead of infinity was used as indicator to turn off a
+         * timeout. */
+
+        r = parse_sec(rvalue, usec);
+        if (r < 0) {
+                log_syntax(unit, LOG_ERR, filename, line, r, "Failed to parse %s= parameter, ignoring: %s", lvalue, rvalue);
+                return 0;
+        }
+
+        if (*usec <= 0)
+                *usec = USEC_INFINITY;
+
+        return 0;
+}
+
 int config_parse_busname_service(
                 const char *unit,
                 const char *filename,

src/core/load-fragment.h

@@ -109,6 +109,7 @@ int config_parse_bus_name(const char* unit, const char *filename, unsigned line,
 int config_parse_exec_utmp_mode(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_working_directory(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_fdname(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
+int config_parse_sec_fix_0(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 
 /* gperf prototypes */
 const struct ConfigPerfItem* load_fragment_gperf_lookup(const char *key, unsigned length);