machined: add API for querying the OS release of a machine image

This adds a bus call GetImageOSRelease() to the Manager interface that
retrieves the /etc/os-release file of a machine image. It matches the existing
GetMachineOSRelease() call, however operates on a disk image rather than a
running container.

The backend for this call on .raw images is implemented via the generalized
image dissector, which makes this scheme relatively easy to implement.

1 files changed, 20 insertions, 13 deletions

diff --git a/src/machine/machinectl.c b/src/machine/machinectl.c
index 9c754b4327..3294ea7821 100644
--- a/src/machine/machinectl.c
+++ b/src/machine/machinectl.c
@@ -138,7 +138,7 @@ static void clean_machine_info(MachineInfo *machines, size_t n_machines) {
         free(machines);
 }
 
-static int get_os_release_property(sd_bus *bus, const char *name, const char *query, ...) {
+static int call_get_os_release(sd_bus *bus, const char *method, const char *name, const char *query, ...) {
         _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
         const char *k, *v, *iter, **query_res = NULL;
         size_t count = 0, awaited_args = 0;
@@ -153,12 +153,13 @@ static int get_os_release_property(sd_bus *bus, const char *name, const char *qu
                 awaited_args++;
         query_res = newa0(const char *, awaited_args);
 
-        r = sd_bus_call_method(bus,
-                "org.freedesktop.machine1",
-                "/org/freedesktop/machine1",
-                "org.freedesktop.machine1.Manager",
-                "GetMachineOSRelease",
-                NULL, &reply, "s", name);
+        r = sd_bus_call_method(
+                        bus,
+                        "org.freedesktop.machine1",
+                        "/org/freedesktop/machine1",
+                        "org.freedesktop.machine1.Manager",
+                        method,
+                        NULL, &reply, "s", name);
         if (r < 0)
                 return r;
 
@@ -193,7 +194,7 @@ static int get_os_release_property(sd_bus *bus, const char *name, const char *qu
                         val = strdup(query_res[count]);
                         if (!val) {
                                 va_end(ap);
-                                return log_oom();
+                                return -ENOMEM;
                         }
                         *out = val;
                 }
@@ -249,8 +250,12 @@ static int list_machines(int argc, char *argv[], void *userdata) {
 
                 machines[n_machines].os = NULL;
                 machines[n_machines].version_id = NULL;
-                r = get_os_release_property(bus, name,
-                                "ID\0" "VERSION_ID\0",
+                r = call_get_os_release(
+                                bus,
+                                "GetMachineOSRelease",
+                                name,
+                                "ID\0"
+                                "VERSION_ID\0",
                                 &machines[n_machines].os,
                                 &machines[n_machines].version_id);
                 if (r < 0)
@@ -610,7 +615,7 @@ static int print_addresses(sd_bus *bus, const char *name, int ifi, const char *p
         return 0;
 }
 
-static int print_os_release(sd_bus *bus, const char *name, const char *prefix) {
+static int print_os_release(sd_bus *bus, const char *method, const char *name, const char *prefix) {
         _cleanup_free_ char *pretty = NULL;
         int r;
 
@@ -618,7 +623,7 @@ static int print_os_release(sd_bus *bus, const char *name, const char *prefix) {
         assert(name);
         assert(prefix);
 
-        r = get_os_release_property(bus, name, "PRETTY_NAME\0", &pretty, NULL);
+        r = call_get_os_release(bus, method, name, "PRETTY_NAME\0", &pretty, NULL);
         if (r < 0)
                 return r;
 
@@ -729,7 +734,7 @@ static void print_machine_status_info(sd_bus *bus, MachineStatusInfo *i) {
                        "\n\t          ",
                        ALL_IP_ADDRESSES);
 
-        print_os_release(bus, i->name, "\t      OS: ");
+        print_os_release(bus, "GetMachineOSRelease", i->name, "\t      OS: ");
 
         if (i->unit) {
                 printf("\t    Unit: %s\n", i->unit);
@@ -927,6 +932,8 @@ static void print_image_status_info(sd_bus *bus, ImageStatusInfo *i) {
         if (i->path)
                 printf("\t    Path: %s\n", i->path);
 
+        print_os_release(bus, "GetImageOSRelease", i->name, "\t      OS: ");
+
         printf("\t      RO: %s%s%s\n",
                i->read_only ? ansi_highlight_red() : "",
                i->read_only ? "read-only" : "writable",