systemd-analyze: make dump work for large # of units

If there is a large number of units, the size of the generated dump
string can overstep DBus message size limit. So let's pass that string
via a fd.

1 files changed, 45 insertions, 7 deletions

diff --git a/src/analyze/analyze.c b/src/analyze/analyze.c
index 5e1766b053..580bc30e12 100644
--- a/src/analyze/analyze.c
+++ b/src/analyze/analyze.c
@@ -21,6 +21,8 @@
 #include "calendarspec.h"
 #include "def.h"
 #include "conf-files.h"
+#include "copy.h"
+#include "fd-util.h"
 #include "glob-util.h"
 #include "hashmap.h"
 #include "locale-util.h"
@@ -1279,11 +1281,39 @@ static int dot(int argc, char *argv[], void *userdata) {
         return 0;
 }
 
+static int dump_fallback(sd_bus *bus) {
+        _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+        _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
+        const char *text = NULL;
+        int r;
+
+        assert(bus);
+
+        r = sd_bus_call_method(
+                        bus,
+                        "org.freedesktop.systemd1",
+                        "/org/freedesktop/systemd1",
+                        "org.freedesktop.systemd1.Manager",
+                        "Dump",
+                        &error,
+                        &reply,
+                        NULL);
+        if (r < 0)
+                return log_error_errno(r, "Failed to issue method call Dump: %s", bus_error_message(&error, r));
+
+        r = sd_bus_message_read(reply, "s", &text);
+        if (r < 0)
+                return bus_log_parse_error(r);
+
+        fputs(text, stdout);
+        return 0;
+}
+
 static int dump(int argc, char *argv[], void *userdata) {
         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
         _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
         _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
-        const char *text = NULL;
+        int fd = -1;
         int r;
 
         r = acquire_bus(&bus, NULL);
@@ -1292,24 +1322,32 @@ static int dump(int argc, char *argv[], void *userdata) {
 
         (void) pager_open(arg_no_pager, false);
 
+        if (!sd_bus_can_send(bus, SD_BUS_TYPE_UNIX_FD))
+                return dump_fallback(bus);
+
         r = sd_bus_call_method(
                         bus,
                         "org.freedesktop.systemd1",
                         "/org/freedesktop/systemd1",
                         "org.freedesktop.systemd1.Manager",
-                        "Dump",
+                        "DumpByFileDescriptor",
                         &error,
                         &reply,
                         NULL);
-        if (r < 0)
-                return log_error_errno(r, "Failed to issue method call: %s", bus_error_message(&error, r));
+        if (r < 0) {
+                /* fall back to Dump if DumpByFileDescriptor is not supported */
+                if (!IN_SET(r, -EACCES, -EBADR))
+                        return log_error_errno(r, "Failed to issue method call DumpByFileDescriptor: %s", bus_error_message(&error, r));
 
-        r = sd_bus_message_read(reply, "s", &text);
+                return dump_fallback(bus);
+        }
+
+        r = sd_bus_message_read(reply, "h", &fd);
         if (r < 0)
                 return bus_log_parse_error(r);
 
-        fputs(text, stdout);
-        return 0;
+        fflush(stdout);
+        return copy_bytes(fd, STDOUT_FILENO, (uint64_t) -1, 0);
 }
 
 static int cat_config(int argc, char *argv[], void *userdata) {