support: Provide a way to reorder responses within the DNS test server

support/Makefile

@@ -35,6 +35,8 @@ libsupport-routines = \
   ignore_stderr \
   next_to_fault \
   oom_error \
+  resolv_response_context_duplicate \
+  resolv_response_context_free \
   resolv_test \
   set_fortify_handler \
   support-xfstat \

support/resolv_response_context_duplicate.c

@@ -0,0 +1,37 @@
+/* Duplicate a response context used in DNS resolver tests.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <string.h>
+#include <support/resolv_test.h>
+#include <support/support.h>
+
+struct resolv_response_context *
+resolv_response_context_duplicate (const struct resolv_response_context *ctx)
+{
+  struct resolv_response_context *result = xmalloc (sizeof (*result));
+  memcpy (result, ctx, sizeof (*result));
+  if (result->client_address != NULL)
+    {
+      result->client_address = xmalloc (result->client_address_length);
+      memcpy (result->client_address, ctx->client_address,
+              result->client_address_length);
+    }
+  result->query_buffer = xmalloc (result->query_length);
+  memcpy (result->query_buffer, ctx->query_buffer, result->query_length);
+  return result;
+}

support/resolv_response_context_free.c

@@ -0,0 +1,28 @@
+/* Free a response context used in DNS resolver tests.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stdlib.h>
+#include <support/resolv_test.h>
+
+void
+resolv_response_context_free (struct resolv_response_context *ctx)
+{
+  free (ctx->query_buffer);
+  free (ctx->client_address);
+  free (ctx);
+}

support/resolv_test.c

@@ -434,9 +434,9 @@ resolv_response_buffer (const struct resolv_response_builder *b)
   return result;
 }
 
-static struct resolv_response_builder *
-response_builder_allocate
-  (const unsigned char *query_buffer, size_t query_length)
+struct resolv_response_builder *
+resolv_response_builder_allocate (const unsigned char *query_buffer,
+                                  size_t query_length)
 {
   struct resolv_response_builder *b = xmalloc (sizeof (*b));
   memset (b, 0, offsetof (struct resolv_response_builder, buffer));
@@ -445,8 +445,8 @@ response_builder_allocate
   return b;
 }
 
-static void
-response_builder_free (struct resolv_response_builder *b)
+void
+resolv_response_builder_free (struct resolv_response_builder *b)
 {
   tdestroy (b->compression_offsets, free);
   free (b);
@@ -661,13 +661,17 @@ server_thread_udp_process_one (struct resolv_test *obj, int server_index)
 
   struct resolv_response_context ctx =
     {
+      .test = obj,
+      .client_address = &peer,
+      .client_address_length = peerlen,
       .query_buffer = query,
       .query_length = length,
       .server_index = server_index,
       .tcp = false,
       .edns = qinfo.edns,
     };
-  struct resolv_response_builder *b = response_builder_allocate (query, length);
+  struct resolv_response_builder *b
+    = resolv_response_builder_allocate (query, length);
   obj->config.response_callback
     (&ctx, b, qinfo.qname, qinfo.qclass, qinfo.qtype);
 
@@ -684,7 +688,7 @@ server_thread_udp_process_one (struct resolv_test *obj, int server_index)
           if (b->offset >= 12)
             printf ("info: UDP server %d: sending response:"
                     " %zu bytes, RCODE %d (for %s/%u/%u)\n",
-                    server_index, b->offset, b->buffer[3] & 0x0f,
+                    ctx.server_index, b->offset, b->buffer[3] & 0x0f,
                     qinfo.qname, qinfo.qclass, qinfo.qtype);
           else
             printf ("info: UDP server %d: sending response: %zu bytes"
@@ -694,23 +698,31 @@ server_thread_udp_process_one (struct resolv_test *obj, int server_index)
           if (b->truncate_bytes > 0)
             printf ("info:    truncated by %u bytes\n", b->truncate_bytes);
         }
-      size_t to_send = b->offset;
-      if (to_send < b->truncate_bytes)
-        to_send = 0;
-      else
-        to_send -= b->truncate_bytes;
-
-      /* Ignore most errors here because the other end may have closed
-         the socket. */
-      if (sendto (obj->servers[server_index].socket_udp,
-                  b->buffer, to_send, 0,
-                  (struct sockaddr *) &peer, peerlen) < 0)
-        TEST_VERIFY_EXIT (errno != EBADF);
+      resolv_response_send_udp (&ctx, b);
     }
-  response_builder_free (b);
+  resolv_response_builder_free (b);
   return true;
 }
 
+void
+resolv_response_send_udp (const struct resolv_response_context *ctx,
+                          struct resolv_response_builder *b)
+{
+  TEST_VERIFY_EXIT (!ctx->tcp);
+  size_t to_send = b->offset;
+  if (to_send < b->truncate_bytes)
+    to_send = 0;
+  else
+    to_send -= b->truncate_bytes;
+
+  /* Ignore most errors here because the other end may have closed
+     the socket.  */
+  if (sendto (ctx->test->servers[ctx->server_index].socket_udp,
+              b->buffer, to_send, 0,
+              ctx->client_address, ctx->client_address_length) < 0)
+    TEST_VERIFY_EXIT (errno != EBADF);
+}
+
 /* UDP thread_callback function.  Variant for one thread per
    server.  */
 static void
@@ -897,14 +909,15 @@ server_thread_tcp_client (void *arg)
 
       struct resolv_response_context ctx =
         {
+          .test = closure->obj,
           .query_buffer = query_buffer,
           .query_length = query_length,
           .server_index = closure->server_index,
           .tcp = true,
           .edns = qinfo.edns,
         };
-      struct resolv_response_builder *b = response_builder_allocate
-        (query_buffer, query_length);
+      struct resolv_response_builder *b
+        = resolv_response_builder_allocate (query_buffer, query_length);
       closure->obj->config.response_callback
         (&ctx, b, qinfo.qname, qinfo.qclass, qinfo.qtype);
 
@@ -936,7 +949,7 @@ server_thread_tcp_client (void *arg)
           writev_fully (closure->client_socket, buffers, 2);
         }
       bool close_flag = b->close;
-      response_builder_free (b);
+      resolv_response_builder_free (b);
       free (query_buffer);
       if (close_flag)
         break;

support/resolv_test.h

@@ -35,25 +35,36 @@ struct resolv_edns_info
   uint16_t payload_size;
 };
 
+/* This opaque struct collects information about the resolver testing
+   currently in progress.  */
+struct resolv_test;
+
 /* This struct provides context information when the response callback
    specified in struct resolv_redirect_config is invoked. */
 struct resolv_response_context
 {
-  const unsigned char *query_buffer;
+  struct resolv_test *test;
+  void *client_address;
+  size_t client_address_length;
+  unsigned char *query_buffer;
   size_t query_length;
   int server_index;
   bool tcp;
   struct resolv_edns_info edns;
 };
 
+/* Produces a deep copy of the context.  */
+struct resolv_response_context *
+  resolv_response_context_duplicate (const struct resolv_response_context *);
+
+/* Frees the copy.  For the context passed to the response function,
+   this happens implicitly.  */
+void resolv_response_context_free (struct resolv_response_context *);
+
 /* This opaque struct is used to construct responses from within the
    response callback function.  */
 struct resolv_response_builder;
 
-/* This opaque struct collects information about the resolver testing
-   currently in progress.  */
-struct resolv_test;
-
 enum
   {
     /* Maximum number of test servers supported by the framework.  */
@@ -188,6 +199,22 @@ void resolv_response_close (struct resolv_response_builder *);
 /* The size of the response packet built so far.  */
 size_t resolv_response_length (const struct resolv_response_builder *);
 
+/* Allocates a response builder tied to a specific query packet,
+   starting at QUERY_BUFFER, containing QUERY_LENGTH bytes.  */
+struct resolv_response_builder *
+  resolv_response_builder_allocate (const unsigned char *query_buffer,
+                                    size_t query_length);
+
+/* Deallocates a response buffer.  */
+void resolv_response_builder_free (struct resolv_response_builder *);
+
+/* Sends a UDP response using a specific context.  This can be used to
+   reorder or duplicate responses, along with
+   resolv_response_context_duplicate and
+   response_builder_allocate.  */
+void resolv_response_send_udp (const struct resolv_response_context *,
+                               struct resolv_response_builder *);
+
 __END_DECLS
 
 #endif /* SUPPORT_RESOLV_TEST_H */