core: add basic lookup by name/pidref in io.systemd.Unit.List

src/core/varlink-unit.c

@@ -3,11 +3,13 @@
 #include "sd-json.h"
 
 #include "bitfield.h"
+#include "cgroup.h"
 #include "condition.h"
 #include "execute.h"
 #include "install.h"
 #include "json-util.h"
 #include "manager.h"
+#include "pidref.h"
 #include "set.h"
 #include "strv.h"
 #include "unit.h"
@@ -316,17 +318,85 @@ static int list_unit_one(sd_varlink *link, Unit *unit, bool more) {
         return sd_varlink_reply(link, v);
 }
 
+static int lookup_unit_by_pidref(sd_varlink *link, Manager *manager, PidRef *pidref, Unit **ret_unit) {
+        _cleanup_(pidref_done) PidRef peer = PIDREF_NULL;
+        Unit *unit;
+        int r;
+
+        assert(link);
+        assert(manager);
+        assert(ret_unit);
+
+        if (pidref_is_automatic(pidref)) {
+                r = varlink_get_peer_pidref(link, &peer);
+                if (r < 0)
+                        return log_debug_errno(r, "Failed to get peer pidref: %m");
+
+                pidref = &peer;
+        } else if (!pidref_is_set(pidref))
+                return -EINVAL;
+
+        unit = manager_get_unit_by_pidref(manager, pidref);
+        if (!unit)
+                return -ESRCH;
+
+        *ret_unit = unit;
+        return 0;
+}
+
+typedef struct UnitLookupParameters {
+        const char *name;
+        PidRef pidref;
+} UnitLookupParameters;
+
+static void unit_lookup_parameters_done(UnitLookupParameters *p) {
+        assert(p);
+        pidref_done(&p->pidref);
+}
+
 int vl_method_list_units(sd_varlink *link, sd_json_variant *parameters, sd_varlink_method_flags_t flags, void *userdata) {
+        static const sd_json_dispatch_field dispatch_table[] = {
+                { "name", SD_JSON_VARIANT_STRING,        json_dispatch_const_unit_name, offsetof(UnitLookupParameters, name),   0 /* allows UNIT_NAME_PLAIN | UNIT_NAME_INSTANCE */ },
+                { "pid",  _SD_JSON_VARIANT_TYPE_INVALID, json_dispatch_pidref,          offsetof(UnitLookupParameters, pidref), SD_JSON_RELAX /* allows PID_AUTOMATIC */            },
+                {}
+        };
+
         Manager *manager = ASSERT_PTR(userdata);
+         _cleanup_(unit_lookup_parameters_done) UnitLookupParameters p = {
+                 .pidref = PIDREF_NULL,
+        };
         int r;
 
         assert(link);
         assert(parameters);
 
-        r = sd_varlink_dispatch(link, parameters, /* dispatch_table = */ NULL, /* userdata = */ NULL);
+        r = sd_varlink_dispatch(link, parameters, dispatch_table, &p);
         if (r != 0)
                 return r;
 
+        if (p.name) {
+                Unit *unit = manager_get_unit(manager, p.name);
+                if (!unit)
+                        return sd_varlink_error(link, VARLINK_ERROR_UNIT_NO_SUCH_UNIT, NULL);
+
+                return list_unit_one(link, unit, /* more = */ false);
+        }
+
+        if (pidref_is_set(&p.pidref) || pidref_is_automatic(&p.pidref)) {
+                Unit *unit;
+                r = lookup_unit_by_pidref(link, manager, &p.pidref, &unit);
+                if (r == -EINVAL)
+                        return sd_varlink_error_invalid_parameter_name(link, "pid");
+                if (r == -ESRCH)
+                        return sd_varlink_error(link, VARLINK_ERROR_UNIT_NO_SUCH_UNIT, NULL);
+                if (r < 0)
+                        return r;
+
+                return list_unit_one(link, unit, /* more = */ false);
+        }
+
+        // TODO lookup by invocationID, CGroup
+
         if (!FLAGS_SET(flags, SD_VARLINK_METHOD_MORE))
                 return sd_varlink_error(link, SD_VARLINK_ERROR_EXPECTED_MORE, NULL);
 

src/core/varlink-unit.h

@@ -3,4 +3,6 @@
 
 #include "sd-varlink.h"
 
+#define VARLINK_ERROR_UNIT_NO_SUCH_UNIT "io.systemd.Unit.NoSuchUnit"
+
 int vl_method_list_units(sd_varlink *link, sd_json_variant *parameters, sd_varlink_method_flags_t flags, void *userdata);

src/shared/varlink-io.systemd.Unit.c

@@ -225,6 +225,10 @@ static SD_VARLINK_DEFINE_ERROR(NoSuchUnit);
 static SD_VARLINK_DEFINE_METHOD_FULL(
                 List,
                 SD_VARLINK_SUPPORTS_MORE,
+                SD_VARLINK_FIELD_COMMENT("If non-null the name of a unit."),
+                SD_VARLINK_DEFINE_INPUT(name, SD_VARLINK_STRING, SD_VARLINK_NULLABLE),
+                SD_VARLINK_FIELD_COMMENT("If non-null the PID of a unit. Special value 0 means to take pid of the caller."),
+                SD_VARLINK_DEFINE_INPUT_BY_TYPE(pid, ProcessId, SD_VARLINK_NULLABLE),
                 SD_VARLINK_FIELD_COMMENT("Configuration of the unit"),
                 SD_VARLINK_DEFINE_OUTPUT_BY_TYPE(context, UnitContext, 0),
                 SD_VARLINK_FIELD_COMMENT("Runtime information of the unit"),
@@ -246,5 +250,7 @@ SD_VARLINK_DEFINE_INTERFACE(
                 &vl_type_Timestamp,
                 SD_VARLINK_SYMBOL_COMMENT("An object to represent a unit's activation details"),
                 &vl_type_ActivationDetails,
+                SD_VARLINK_SYMBOL_COMMENT("An object for referencing UNIX processes"),
+                &vl_type_ProcessId,
                 SD_VARLINK_SYMBOL_COMMENT("No matching unit found"),
                 &vl_error_NoSuchUnit);