[glib: 6/13] gthreadedresolver: Don’t warn on unrecognised record types

[Philip Withnall <pwithnall src gnome org>]

commit 81193c5aac04059455dc24aa573b06e1e773d700
Author: Philip Withnall <pwithnall endlessos org>
Date:   Fri Mar 18 15:52:18 2022 +0000

    gthreadedresolver: Don’t warn on unrecognised record types
    
    Otherwise the code isn’t forwards-compatible, and may be DOSed by
    servers returning unknown records, if `G_DEBUG=fatal-warnings` is
    enabled for some reason.
    
    Signed-off-by: Philip Withnall <pwithnall endlessos org>

 gio/gthreadedresolver.c      |  2 +-
 gio/tests/resolver-parsing.c | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)
---
diff --git a/gio/gthreadedresolver.c b/gio/gthreadedresolver.c
index 59f229a16c..5682102038 100644
--- a/gio/gthreadedresolver.c
+++ b/gio/gthreadedresolver.c
@@ -780,7 +780,7 @@ g_resolver_records_from_res_query (const gchar      *rrname,
           record = parse_res_txt (answer, p + rdlength, &p);
           break;
         default:
-          g_warn_if_reached ();
+          g_debug ("Unrecognised DNS record type %u", rrtype);
           record = NULL;
           break;
         }
diff --git a/gio/tests/resolver-parsing.c b/gio/tests/resolver-parsing.c
index bf1ba1b736..909917be86 100644
--- a/gio/tests/resolver-parsing.c
+++ b/gio/tests/resolver-parsing.c
@@ -146,6 +146,42 @@ test_invalid_header (void)
     }
 }
 
+static void
+test_unknown_record_type (void)
+{
+#ifndef HAVE_DN_COMP
+  g_test_skip ("The dn_comp() function was not available.");
+  return;
+#else
+  GByteArray *answer = NULL;
+  GList *records = NULL;
+  GError *local_error = NULL;
+  const guint type_id = 20;  /* ISDN, not supported anywhere */
+
+  /* An answer with an unsupported type chosen from
+   * https://en.wikipedia.org/wiki/List_of_DNS_record_types#[1]_Obsolete_record_types */
+  answer = dns_header ();
+  dns_builder_add_domain (answer, "example.org");
+  dns_builder_add_uint16 (answer, type_id);
+  dns_builder_add_uint16 (answer, 1); /* qclass=C_IN */
+  dns_builder_add_uint32 (answer, 0); /* ttl (ignored) */
+  dns_builder_add_uint16 (answer, 0); /* rdlength */
+
+  records = g_resolver_records_from_res_query ("example.org",
+                                               type_id,
+                                               answer->data,
+                                               answer->len,
+                                               0,
+                                               &local_error);
+
+  g_assert_error (local_error, G_RESOLVER_ERROR, G_RESOLVER_ERROR_NOT_FOUND);
+  g_assert_null (records);
+  g_clear_error (&local_error);
+
+  g_byte_array_free (answer, TRUE);
+#endif
+}
+
 int
 main (int   argc,
       char *argv[])
@@ -153,6 +189,7 @@ main (int   argc,
   g_test_init (&argc, &argv, G_TEST_OPTION_ISOLATE_DIRS, NULL);
 
   g_test_add_func ("/gresolver/invalid-header", test_invalid_header);
+  g_test_add_func ("/gresolver/unknown-record-type", test_unknown_record_type);
 
   return g_test_run ();
 }