Add new --level-prefix option

This prepends a syslog-style priority level such as <3> to each line of diagnostic output, so that the diagnostic output can be parsed by tools like `systemd-cat --level-prefix=1`. A future version of Steam's pressure-vessel is likely to use this to make warnings and fatal errors from bubblewrap more visible. Signed-off-by: Simon McVittie <[email protected]>
containers · Jul 24, 2024 · db40f0b · db40f0b
1 parent 60feac9
commit db40f0b
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Showing 6 changed files with 27 additions and 0 deletions.
diff --git a/bind-mount.c b/bind-mount.c
@@ -560,6 +560,9 @@ die_with_bind_result (bind_mount_result res,
   bool want_errno = TRUE;
   char *message;
 
+  if (bwrap_level_prefix)
+    fprintf (stderr, "<%d>", LOG_ERR);
+
   fprintf (stderr, "bwrap: ");
 
   va_start (args, format);

diff --git a/bubblewrap.c b/bubblewrap.c
@@ -311,6 +311,7 @@ usage (int ecode, FILE *out)
            "    --version                    Print version\n"
            "    --args FD                    Parse NUL-separated args from FD\n"
            "    --argv0 VALUE                Set argv[0] to the value VALUE before running the program\n"
+           "    --level-prefix               Prepend e.g. <3> to diagnostic messages\n"
            "    --unshare-all                Unshare every namespace we support by default\n"
            "    --share-net                  Retain the network namespace (can only combine with --unshare-all)\n"
            "    --unshare-user               Create new user namespace (may be automatically implied if not setuid)\n"
@@ -1752,6 +1753,10 @@ parse_args_recurse (int          *argcp,
           argv++;
           argc--;
         }
+      else if (strcmp (arg, "--level-prefix") == 0)
+        {
+          bwrap_level_prefix = TRUE;
+        }
       else if (strcmp (arg, "--unshare-all") == 0)
         {
           /* Keep this in order with the older (legacy) --unshare arguments,

diff --git a/bwrap.xml b/bwrap.xml
@@ -96,6 +96,15 @@
       <term><option>--argv0 <arg choice="plain">VALUE</arg></option></term>
       <listitem><para>Set argv[0] to the value <arg choice="plain">VALUE</arg> before running the program</para></listitem>
     </varlistentry>
+    <varlistentry>
+      <term><option>--level-prefix</option></term>
+      <listitem>
+        <para>Add a syslog-style level prefix to each line of diagnostic
+          output, for example <literal>&lt;4&gt;</literal> for a warning.
+          These prefixes can be parsed by tools such as
+          <literal>systemd-cat --level-prefix=1</literal>.</para>
+      </listitem>
+    </varlistentry>
   </variablelist>
   <para>Options related to kernel namespaces:</para>
   <variablelist>

diff --git a/tests/test-run.sh b/tests/test-run.sh
@@ -568,4 +568,7 @@ ok "argv0 manipulation"
 $RUN --chdir / --chdir / true > stdout 2>&1
 assert_file_has_content stdout '^bwrap: Only the last --chdir option will take effect$'
 
+$RUN --level-prefix --chdir / --chdir / true > stdout 2>&1
+assert_file_has_content stdout '^<4>bwrap: Only the last --chdir option will take effect$'
+
 done_testing
diff --git a/utils.c b/utils.c
@@ -34,12 +34,17 @@
 #define security_check_context(x) security_check_context ((security_context_t) x)
 #endif
 
+bool bwrap_level_prefix = FALSE;
+
 __attribute__((format(printf, 2, 0))) static void
 bwrap_logv (int level,
             const char *format,
             va_list args,
             const char *detail)
 {
+  if (bwrap_level_prefix)
+    fprintf (stderr, "<%d>", level);
+
   fprintf (stderr, "bwrap: ");
   vfprintf (stderr, format, args);
 

diff --git a/utils.h b/utils.h
@@ -53,6 +53,8 @@ typedef int bool;
 #define PR_SET_CHILD_SUBREAPER 36
 #endif
 
+extern bool bwrap_level_prefix;
+
 void  bwrap_log (int level,
                  const char *format,
                  ...) __attribute__((format (printf, 2, 3)));