machine: add OSRelease and UIDShift fields in varlink io.systemd.Machine.List output

This commit adds support of the above mentioned fields. This is equivalent to DBus implementation of:
- GetMachineOSRelease
- GetMachineUIDShift

src/machine/machined-varlink.c

@@ -391,14 +391,38 @@ static int vl_method_get_memberships(sd_varlink *link, sd_json_variant *paramete
         return sd_varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
 }
 
-static int list_machine_one(sd_varlink *link, Machine *m, bool more) {
+static int list_machine_one_and_maybe_read_metadata(sd_varlink *link, Machine *m, bool more, AcquireMetadata am) {
-        int r;
+        _cleanup_strv_free_ char **os_release = NULL;
+        uid_t shift = UID_INVALID;
+        int n, r;
 
         assert(link);
         assert(m);
 
         _cleanup_(sd_json_variant_unrefp) sd_json_variant *v = NULL;
 
+        if (should_acquire_metadata(am)) {
+                r = machine_get_os_release(m, &os_release);
+                if (r < 0 && am == ACQUIRE_METADATA_GRACEFUL)
+                        log_debug_errno(r, "Failed to get OS release (graceful mode), ignoring: %m");
+                else if (r == -ENONET)
+                        return sd_varlink_error(link, "io.systemd.Machine.NoOSReleaseInformation", NULL);
+                else if (ERRNO_IS_NEG_NOT_SUPPORTED(r))
+                        return sd_varlink_error(link, "io.systemd.Machine.NotAvailable", NULL);
+                else if (r < 0)
+                        return log_debug_errno(r, "Failed to get OS release: %m");
+
+                r = machine_get_uid_shift(m, &shift);
+                if (r < 0 && am == ACQUIRE_METADATA_GRACEFUL)
+                        log_debug_errno(r, "Failed to get UID shift (graceful mode), ignoring: %m");
+                else if (r == -ENXIO)
+                        return sd_varlink_error(link, "io.systemd.Machine.NoUIDShift", NULL);
+                else if (ERRNO_IS_NEG_NOT_SUPPORTED(r))
+                        return sd_varlink_error(link, "io.systemd.Machine.NotAvailable", NULL);
+                else if (r < 0)
+                        return log_debug_errno(r, "Failed to get UID shift: %m");
+        }
+
         r = sd_json_buildo(
                         &v,
                         SD_JSON_BUILD_PAIR("name", SD_JSON_BUILD_STRING(m->name)),
@@ -411,7 +435,9 @@ static int list_machine_one(sd_varlink *link, Machine *m, bool more) {
                         SD_JSON_BUILD_PAIR_CONDITION(dual_timestamp_is_set(&m->timestamp), "timestamp", JSON_BUILD_DUAL_TIMESTAMP(&m->timestamp)),
                         SD_JSON_BUILD_PAIR_CONDITION(m->vsock_cid != VMADDR_CID_ANY, "vSockCid", SD_JSON_BUILD_UNSIGNED(m->vsock_cid)),
                         JSON_BUILD_PAIR_STRING_NON_EMPTY("sshAddress", m->ssh_address),
-                        JSON_BUILD_PAIR_STRING_NON_EMPTY("sshPrivateKeyPath", m->ssh_private_key_path));
+                        JSON_BUILD_PAIR_STRING_NON_EMPTY("sshPrivateKeyPath", m->ssh_private_key_path),
+                        SD_JSON_BUILD_PAIR_CONDITION(!strv_isempty(os_release), "OSRelease", JSON_BUILD_STRV_ENV_PAIR(os_release)),
+                        JSON_BUILD_PAIR_UNSIGNED_NOT_EQUAL("UIDShift", shift, UID_INVALID));
         if (r < 0)
                 return r;
 
@@ -424,6 +450,7 @@ static int list_machine_one(sd_varlink *link, Machine *m, bool more) {
 typedef struct MachineLookupParameters {
         const char *name;
         PidRef pidref;
+        AcquireMetadata acquire_metadata;
 } MachineLookupParameters;
 
 static void machine_lookup_parameters_done(MachineLookupParameters *p) {
@@ -437,6 +464,7 @@ static JSON_DISPATCH_ENUM_DEFINE(json_dispatch_acquire_metadata, AcquireMetadata
 static int vl_method_list(sd_varlink *link, sd_json_variant *parameters, sd_varlink_method_flags_t flags, void *userdata) {
         static const sd_json_dispatch_field dispatch_table[] = {
                 VARLINK_DISPATCH_MACHINE_LOOKUP_FIELDS(MachineLookupParameters),
+                { "acquireMetadata", SD_JSON_VARIANT_STRING, json_dispatch_acquire_metadata, offsetof(MachineLookupParameters, acquire_metadata), 0 },
                 VARLINK_DISPATCH_POLKIT_FIELD,
                 {}
         };
@@ -444,7 +472,9 @@ static int vl_method_list(sd_varlink *link, sd_json_variant *parameters, sd_varl
         Manager *m = ASSERT_PTR(userdata);
         _cleanup_(machine_lookup_parameters_done) MachineLookupParameters p = {
                 .pidref = PIDREF_NULL,
+                .acquire_metadata = ACQUIRE_METADATA_NO,
         };
+
         Machine *machine;
         int r;
 
@@ -462,7 +492,7 @@ static int vl_method_list(sd_varlink *link, sd_json_variant *parameters, sd_varl
                 if (r != 0)
                         return r;
 
-                return list_machine_one(link, machine, /* more= */ false);
+                return list_machine_one_and_maybe_read_metadata(link, machine, /* more = */ false, p.acquire_metadata);
         }
 
         if (!FLAGS_SET(flags, SD_VARLINK_METHOD_MORE))
@@ -471,7 +501,7 @@ static int vl_method_list(sd_varlink *link, sd_json_variant *parameters, sd_varl
         Machine *previous = NULL, *i;
         HASHMAP_FOREACH(i, m->machines) {
                 if (previous) {
-                        r = list_machine_one(link, previous, /* more= */ true);
+                        r = list_machine_one_and_maybe_read_metadata(link, previous, /* more = */ true, p.acquire_metadata);
                         if (r < 0)
                                 return r;
                 }
@@ -480,7 +510,7 @@ static int vl_method_list(sd_varlink *link, sd_json_variant *parameters, sd_varl
         }
 
         if (previous)
-                return list_machine_one(link, previous, /* more= */ false);
+                return list_machine_one_and_maybe_read_metadata(link, previous, /* more = */ false, p.acquire_metadata);
 
         return sd_varlink_error(link, "io.systemd.Machine.NoSuchMachine", NULL);
 }

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

@@ -13,6 +13,15 @@
         SD_VARLINK_DEFINE_INPUT_BY_TYPE(pid, ProcessId, SD_VARLINK_NULLABLE),                                                                  \
         VARLINK_DEFINE_POLKIT_INPUT
 
+static SD_VARLINK_DEFINE_ENUM_TYPE(
+                AcquireMetadata,
+                SD_VARLINK_FIELD_COMMENT("Do not include metadata in the output"),
+                SD_VARLINK_DEFINE_ENUM_VALUE(no),
+                SD_VARLINK_FIELD_COMMENT("Include metadata in the output"),
+                SD_VARLINK_DEFINE_ENUM_VALUE(yes),
+                SD_VARLINK_FIELD_COMMENT("Include metadata in the output, but gracefully eat up errors"),
+                SD_VARLINK_DEFINE_ENUM_VALUE(graceful));
+
 static SD_VARLINK_DEFINE_METHOD(
                 Register,
                 SD_VARLINK_DEFINE_INPUT(name,              SD_VARLINK_STRING, 0),
@@ -49,6 +58,8 @@ static SD_VARLINK_DEFINE_METHOD_FULL(
                 List,
                 SD_VARLINK_SUPPORTS_MORE,
                 VARLINK_DEFINE_MACHINE_LOOKUP_AND_POLKIT_INPUT_FIELDS,
+                SD_VARLINK_FIELD_COMMENT("If 'yes' the output will include machine metadata fields such as 'OSRelease' and 'UIDShift'. If 'graceful' it's equal to true but gracefully eats up errors"),
+                SD_VARLINK_DEFINE_INPUT_BY_TYPE(acquireMetadata, AcquireMetadata, SD_VARLINK_NULLABLE),
                 SD_VARLINK_FIELD_COMMENT("Name of the machine"),
                 SD_VARLINK_DEFINE_OUTPUT(name, SD_VARLINK_STRING, 0),
                 SD_VARLINK_FIELD_COMMENT("128bit ID identifying this machine, formatted in hexadecimal"),
@@ -70,10 +81,17 @@ static SD_VARLINK_DEFINE_METHOD_FULL(
                 SD_VARLINK_FIELD_COMMENT("SSH address to connect to"),
                 SD_VARLINK_DEFINE_OUTPUT(sshAddress, SD_VARLINK_STRING, SD_VARLINK_NULLABLE),
                 SD_VARLINK_FIELD_COMMENT("Path to private SSH key"),
-                SD_VARLINK_DEFINE_OUTPUT(sshPrivateKeyPath, SD_VARLINK_STRING, SD_VARLINK_NULLABLE));
+                SD_VARLINK_DEFINE_OUTPUT(sshPrivateKeyPath, SD_VARLINK_STRING, SD_VARLINK_NULLABLE),
+                SD_VARLINK_FIELD_COMMENT("OS release information of the machine. It contains an array of key value pairs read from the os-release(5) file in the image."),
+                SD_VARLINK_DEFINE_OUTPUT(OSRelease, SD_VARLINK_STRING, SD_VARLINK_NULLABLE|SD_VARLINK_ARRAY),
+                SD_VARLINK_FIELD_COMMENT("Return the base UID/GID of the machine"),
+                SD_VARLINK_DEFINE_OUTPUT(UIDShift, SD_VARLINK_INT, SD_VARLINK_NULLABLE));
 
 static SD_VARLINK_DEFINE_ERROR(NoSuchMachine);
 static SD_VARLINK_DEFINE_ERROR(MachineExists);
+static SD_VARLINK_DEFINE_ERROR(NoOSReleaseInformation);
+static SD_VARLINK_DEFINE_ERROR(NoUIDShift);
+static SD_VARLINK_DEFINE_ERROR(NotAvailable);
 
 SD_VARLINK_DEFINE_INTERFACE(
                 io_systemd_Machine,
@@ -82,6 +100,8 @@ SD_VARLINK_DEFINE_INTERFACE(
                 &vl_type_ProcessId,
                 SD_VARLINK_SYMBOL_COMMENT("A timestamp object consisting of both CLOCK_REALTIME and CLOCK_MONOTONIC timestamps"),
                 &vl_type_Timestamp,
+                SD_VARLINK_SYMBOL_COMMENT("A enum field allowing to gracefully get metadata"),
+                &vl_type_AcquireMetadata,
                 &vl_method_Register,
                 &vl_method_Unregister,
                 SD_VARLINK_SYMBOL_COMMENT("Terminate machine, killing its processes"),
@@ -92,4 +112,10 @@ SD_VARLINK_DEFINE_INTERFACE(
                 &vl_method_List,
                 SD_VARLINK_SYMBOL_COMMENT("No matching machine currently running"),
                 &vl_error_NoSuchMachine,
-                &vl_error_MachineExists);
+                &vl_error_MachineExists,
+                SD_VARLINK_SYMBOL_COMMENT("Machine does not contain OS release information"),
+                &vl_error_NoOSReleaseInformation,
+                SD_VARLINK_SYMBOL_COMMENT("Machine uses a complex UID/GID mapping, cannot determine shift"),
+                &vl_error_NoUIDShift,
+                SD_VARLINK_SYMBOL_COMMENT("Requested information is not available"),
+                &vl_error_NotAvailable);