sunrpc: Improvements for UDP client timeout handling [BZ #20257]

This commit fixes various aspects in the UDP client timeout handling.
Timeouts are now applied in a more consistent fashion.  Discarded UDP
packets no longer prevent the timeout from happening at all.

1 files changed, 402 insertions, 0 deletions

diff --git a/sunrpc/tst-udp-timeout.c b/sunrpc/tst-udp-timeout.c
new file mode 100644
index 0000000000..db9943a03e
--- /dev/null
+++ b/sunrpc/tst-udp-timeout.c
@@ -0,0 +1,402 @@
+/* Test timeout handling in the UDP client.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <netinet/in.h>
+#include <rpc/clnt.h>
+#include <rpc/svc.h>
+#include <stdbool.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/namespace.h>
+#include <support/test-driver.h>
+#include <support/xsocket.h>
+#include <support/xunistd.h>
+#include <sys/socket.h>
+#include <time.h>
+#include <unistd.h>
+
+/* Test data serialization and deserialization.   */
+
+struct test_query
+{
+  uint32_t a;
+  uint32_t b;
+  uint32_t timeout_ms;
+  uint32_t wait_for_seq;
+  uint32_t garbage_packets;
+};
+
+static bool_t
+xdr_test_query (XDR *xdrs, void *data, ...)
+{
+  struct test_query *p = data;
+  return xdr_uint32_t (xdrs, &p->a)
+    && xdr_uint32_t (xdrs, &p->b)
+    && xdr_uint32_t (xdrs, &p->timeout_ms)
+    && xdr_uint32_t (xdrs, &p->wait_for_seq)
+    && xdr_uint32_t (xdrs, &p->garbage_packets);
+}
+
+struct test_response
+{
+  uint32_t seq;
+  uint32_t sum;
+};
+
+static bool_t
+xdr_test_response (XDR *xdrs, void *data, ...)
+{
+  struct test_response *p = data;
+  return xdr_uint32_t (xdrs, &p->seq)
+    && xdr_uint32_t (xdrs, &p->sum);
+}
+
+/* Implementation of the test server.  */
+
+enum
+  {
+    /* RPC parameters, chosen at random.  */
+    PROGNUM = 15717,
+    VERSNUM = 13689,
+
+    /* Main RPC operation.  */
+    PROC_ADD = 1,
+
+    /* Reset the sequence number.  */
+    PROC_RESET_SEQ,
+
+    /* Request process termination.  */
+    PROC_EXIT,
+
+    /* Special exit status to mark successful processing.  */
+    EXIT_MARKER = 55,
+  };
+
+static void
+server_dispatch (struct svc_req *request, SVCXPRT *transport)
+{
+  /* Query sequence number.  */
+  static uint32_t seq = 0;
+  ++seq;
+
+  if (test_verbose)
+    printf ("info: server_dispatch seq=%u rq_proc=%lu\n",
+            seq, request->rq_proc);
+
+  switch (request->rq_proc)
+    {
+    case PROC_ADD:
+      {
+        struct test_query query;
+        memset (&query, 0xc0, sizeof (query));
+        TEST_VERIFY_EXIT
+          (svc_getargs (transport, xdr_test_query,
+                        (void *) &query));
+
+        if (test_verbose)
+          printf ("  a=%u b=%u timeout_ms=%u wait_for_seq=%u"
+                  " garbage_packets=%u\n",
+                  query.a, query.b, query.timeout_ms, query.wait_for_seq,
+                  query.garbage_packets);
+
+        if (seq < query.wait_for_seq)
+          {
+            /* No response at this point.  */
+            if (test_verbose)
+              printf ("  skipped response\n");
+            break;
+          }
+
+        if (query.garbage_packets > 0)
+          {
+            int per_packet_timeout;
+            if (query.timeout_ms > 0)
+              per_packet_timeout
+                = query.timeout_ms * 1000 / query.garbage_packets;
+            else
+              per_packet_timeout = 0;
+
+            char buf[20];
+            memset (&buf, 0xc0, sizeof (buf));
+            for (int i = 0; i < query.garbage_packets; ++i)
+              {
+                /* 13 is relatively prime to 20 = sizeof (buf) + 1, so
+                   the len variable will cover the entire interval
+                   [0, 20] if query.garbage_packets is sufficiently
+                   large.  */
+                size_t len = (i * 13 + 1) % (sizeof (buf) + 1);
+                TEST_VERIFY (sendto (transport->xp_sock,
+                                     buf, len, MSG_NOSIGNAL,
+                                     (struct sockaddr *) &transport->xp_raddr,
+                                     transport->xp_addrlen) == len);
+                if (per_packet_timeout > 0)
+                  usleep (per_packet_timeout);
+              }
+          }
+        else if (query.timeout_ms > 0)
+          usleep (query.timeout_ms * 1000);
+
+        struct test_response response =
+          {
+            .seq = seq,
+            .sum = query.a + query.b,
+          };
+        TEST_VERIFY (svc_sendreply (transport, xdr_test_response,
+                                    (void *) &response));
+      }
+      break;
+
+    case PROC_RESET_SEQ:
+      seq = 0;
+      TEST_VERIFY (svc_sendreply (transport, (xdrproc_t) xdr_void, NULL));
+      break;
+
+    case PROC_EXIT:
+      TEST_VERIFY (svc_sendreply (transport, (xdrproc_t) xdr_void, NULL));
+      _exit (EXIT_MARKER);
+      break;
+
+    default:
+      FAIL_EXIT1 ("invalid rq_proc value: %lu", request->rq_proc);
+      break;
+    }
+}
+
+/* Implementation of the test client.  */
+
+static struct test_response
+test_call (CLIENT *clnt, int proc, struct test_query query,
+           struct timeval timeout)
+{
+  if (test_verbose)
+    printf ("info: test_call proc=%d timeout=%lu.%06lu\n",
+            proc, (unsigned long) timeout.tv_sec,
+            (unsigned long) timeout.tv_usec);
+  struct test_response response;
+  TEST_VERIFY_EXIT (clnt_call (clnt, proc,
+                               xdr_test_query, (void *) &query,
+                               xdr_test_response, (void *) &response,
+                               timeout)
+                    == RPC_SUCCESS);
+  return response;
+}
+
+static void
+test_call_timeout (CLIENT *clnt, int proc, struct test_query query,
+                   struct timeval timeout)
+{
+  struct test_response response;
+  TEST_VERIFY (clnt_call (clnt, proc,
+                          xdr_test_query, (void *) &query,
+                          xdr_test_response, (void *) &response,
+                          timeout)
+               == RPC_TIMEDOUT);
+}
+
+/* Complete one regular RPC call to drain the server socket
+   buffer.  Resets the sequence number.  */
+static void
+test_call_flush (CLIENT *clnt)
+{
+  /* This needs a longer timeout to flush out all pending requests.
+     The choice of 5 seconds is larger than the per-response timeouts
+     requested via the timeout_ms field.  */
+  if (test_verbose)
+    printf ("info: flushing pending queries\n");
+  TEST_VERIFY_EXIT (clnt_call (clnt, PROC_RESET_SEQ,
+                               (xdrproc_t) xdr_void, NULL,
+                               (xdrproc_t) xdr_void, NULL,
+                               ((struct timeval) { 5, 0 }))
+                    == RPC_SUCCESS);
+}
+
+/* Return the number seconds since an arbitrary point in time.  */
+static double
+get_ticks (void)
+{
+  {
+    struct timespec ts;
+    if (clock_gettime (CLOCK_MONOTONIC, &ts) == 0)
+      return ts.tv_sec + ts.tv_nsec * 1e-9;
+  }
+  {
+    struct timeval tv;
+    TEST_VERIFY_EXIT (gettimeofday (&tv, NULL) == 0);
+    return tv.tv_sec + tv.tv_usec * 1e-6;
+  }
+}
+
+static void
+test_udp_server (int port)
+{
+  struct sockaddr_in sin =
+    {
+      .sin_family = AF_INET,
+      .sin_addr.s_addr = htonl (INADDR_LOOPBACK),
+      .sin_port = htons (port)
+    };
+  int sock = RPC_ANYSOCK;
+
+  /* The client uses a 1.5 second timeout for retries.  The timeouts
+     are arbitrary, but chosen so that there is a substantial gap
+     between them, but the total time spent waiting is not too
+     large.  */
+  CLIENT *clnt = clntudp_create (&sin, PROGNUM, VERSNUM,
+                                 (struct timeval) { 1, 500 * 1000 },
+                                 &sock);
+  TEST_VERIFY_EXIT (clnt != NULL);
+
+  /* Basic call/response test.  */
+  struct test_response response = test_call
+    (clnt, PROC_ADD,
+     (struct test_query) { .a = 17, .b = 4 },
+     (struct timeval) { 3, 0 });
+  TEST_VERIFY (response.sum == 21);
+  TEST_VERIFY (response.seq == 1);
+
+  /* Check that garbage packets do not interfere with timeout
+     processing.  */
+  double before = get_ticks ();
+  response = test_call
+    (clnt, PROC_ADD,
+     (struct test_query) {
+       .a = 19, .b = 4, .timeout_ms = 500, .garbage_packets = 21,
+     },
+     (struct timeval) { 3, 0 });
+  TEST_VERIFY (response.sum == 23);
+  TEST_VERIFY (response.seq == 2);
+  double after = get_ticks ();
+  if (test_verbose)
+    printf ("info: 21 garbage packets took %f seconds\n", after - before);
+  /* Expected timeout is 0.5 seconds.  Add some slack in case process
+     scheduling delays processing the query or response, but do not
+     accept a retry (which would happen at 1.5 seconds).  */
+  TEST_VERIFY (0.5 <= after - before);
+  TEST_VERIFY (after - before < 1.2);
+  test_call_flush (clnt);
+
+  /* Check that missing a response introduces a 1.5 second timeout, as
+     requested when calling clntudp_create.  */
+  before = get_ticks ();
+  response = test_call
+    (clnt, PROC_ADD,
+     (struct test_query) { .a = 170, .b = 40, .wait_for_seq = 2 },
+     (struct timeval) { 3, 0 });
+  TEST_VERIFY (response.sum == 210);
+  TEST_VERIFY (response.seq == 2);
+  after = get_ticks ();
+  if (test_verbose)
+    printf ("info: skipping one response took %f seconds\n",
+            after - before);
+  /* Expected timeout is 1.5 seconds.  Do not accept a second retry
+     (which would happen at 3 seconds).  */
+  TEST_VERIFY (1.5 <= after - before);
+  TEST_VERIFY (after - before < 2.9);
+  test_call_flush (clnt);
+
+  /* Check that the overall timeout wins against the per-query
+     timeout.  */
+  before = get_ticks ();
+  test_call_timeout
+    (clnt, PROC_ADD,
+     (struct test_query) { .a = 170, .b = 41, .wait_for_seq = 2 },
+     (struct timeval) { 0, 750 * 1000 });
+  after = get_ticks ();
+  if (test_verbose)
+    printf ("info: 0.75 second timeout took %f seconds\n",
+            after - before);
+  TEST_VERIFY (0.75 <= after - before);
+  TEST_VERIFY (after - before < 1.4);
+  test_call_flush (clnt);
+
+  for (int with_garbage = 0; with_garbage < 2; ++with_garbage)
+    {
+      /* Check that no response at all causes the client to bail out.  */
+      before = get_ticks ();
+      test_call_timeout
+        (clnt, PROC_ADD,
+         (struct test_query) {
+           .a = 170, .b = 40, .timeout_ms = 1200,
+           .garbage_packets = with_garbage * 21
+         },
+         (struct timeval) { 0, 750 * 1000 });
+      after = get_ticks ();
+      if (test_verbose)
+        printf ("info: test_udp_server: 0.75 second timeout took %f seconds"
+                " (garbage %d)\n",
+                after - before, with_garbage);
+      TEST_VERIFY (0.75 <= after - before);
+      TEST_VERIFY (after - before < 1.4);
+      test_call_flush (clnt);
+
+      /* As above, but check the total timeout.  */
+      before = get_ticks ();
+      test_call_timeout
+        (clnt, PROC_ADD,
+         (struct test_query) {
+           .a = 170, .b = 40, .timeout_ms = 3000,
+           .garbage_packets = with_garbage * 30
+         },
+         (struct timeval) { 2, 300 * 1000 });
+      after = get_ticks ();
+      if (test_verbose)
+        printf ("info: test_udp_server: 2.3 second timeout took %f seconds"
+                " (garbage %d)\n",
+                after - before, with_garbage);
+      TEST_VERIFY (2.3 <= after - before);
+      TEST_VERIFY (after - before < 3.0);
+      test_call_flush (clnt);
+    }
+
+  TEST_VERIFY_EXIT (clnt_call (clnt, PROC_EXIT,
+                               (xdrproc_t) xdr_void, NULL,
+                               (xdrproc_t) xdr_void, NULL,
+                               ((struct timeval) { 5, 0 }))
+                    == RPC_SUCCESS);
+  clnt_destroy (clnt);
+}
+
+static int
+do_test (void)
+{
+  support_become_root ();
+  support_enter_network_namespace ();
+
+  SVCXPRT *transport = svcudp_create (RPC_ANYSOCK);
+  TEST_VERIFY_EXIT (transport != NULL);
+  TEST_VERIFY (svc_register (transport, PROGNUM, VERSNUM, server_dispatch, 0));
+
+  pid_t pid = xfork ();
+  if (pid == 0)
+    {
+      svc_run ();
+      FAIL_EXIT1 ("supposed to be unreachable");
+    }
+  test_udp_server (transport->xp_port);
+
+  int status;
+  xwaitpid (pid, &status, 0);
+  TEST_VERIFY (WIFEXITED (status) && WEXITSTATUS (status) == EXIT_MARKER);
+
+  SVC_DESTROY (transport);
+  return 0;
+}
+
+/* The minimum run time is around 17 seconds.  */
+#define TIMEOUT 25
+#include <support/test-driver.c>