Simplify allocations and fix merge and continue actions [BZ #28931]

Allocations for address tuples is currently a bit confusing because of
the pointer chasing through PAT, making it hard to observe the sequence
in which allocations have been made.  Narrow scope of the pointer
chasing through PAT so that it is only used where necessary.

This also tightens actions behaviour with the hosts database in
getaddrinfo to comply with the manual text.  The "continue" action
discards previous results and the "merge" action results in an immedate
lookup failure.  Consequently, chaining of allocations across modules is
no longer necessary, thus opening up cleanup opportunities.

A test has been added that checks some combinations to ensure that they
work correctly.

Resolves: BZ #28931

Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reviewed-by: DJ Delorie <dj@redhat.com>

4 files changed, 659 insertions, 0 deletions

diff --git a/nss/Makefile b/nss/Makefile
index 42a5953..d8b06b4 100644
--- a/nss/Makefile
+++ b/nss/Makefile
@@ -76,6 +76,7 @@ tests-container := \
   tst-nss-db-endgrent \
   tst-nss-db-endpwent \
   tst-nss-files-hosts-long \
+  tst-nss-gai-actions \
   tst-nss-test3 \
   tst-reload1 \
   tst-reload2 \
diff --git a/nss/tst-nss-gai-actions.c b/nss/tst-nss-gai-actions.c
new file mode 100644
index 0000000..efca6cd
--- /dev/null
+++ b/nss/tst-nss-gai-actions.c
@@ -0,0 +1,149 @@
+/* Test continue and merge NSS actions for getaddrinfo.
+   Copyright The GNU Toolchain Authors.
+   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 <dlfcn.h>
+#include <gnu/lib-names.h>
+#include <nss.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <support/check.h>
+#include <support/format_nss.h>
+#include <support/support.h>
+#include <support/xstdio.h>
+#include <support/xunistd.h>
+
+enum
+{
+  ACTION_MERGE = 0,
+  ACTION_CONTINUE,
+};
+
+static const char *
+family_str (int family)
+{
+  switch (family)
+    {
+    case AF_UNSPEC:
+      return "AF_UNSPEC";
+    case AF_INET:
+      return "AF_INET";
+    default:
+      __builtin_unreachable ();
+    }
+}
+
+static const char *
+action_str (int action)
+{
+  switch (action)
+    {
+    case ACTION_MERGE:
+      return "merge";
+    case ACTION_CONTINUE:
+      return "continue";
+    default:
+      __builtin_unreachable ();
+    }
+}
+
+static void
+do_one_test (int action, int family, bool canon)
+{
+  struct addrinfo hints =
+    {
+      .ai_family = family,
+    };
+
+  struct addrinfo *ai;
+
+  if (canon)
+    hints.ai_flags = AI_CANONNAME;
+
+  printf ("***** Testing \"files [SUCCESS=%s] files\" for family %s, %s\n",
+	  action_str (action), family_str (family),
+	  canon ? "AI_CANONNAME" : "");
+
+  int ret = getaddrinfo ("example.org", "80", &hints, &ai);
+
+  switch (action)
+    {
+    case ACTION_MERGE:
+      if (ret == 0)
+	{
+	  char *formatted = support_format_addrinfo (ai, ret);
+
+	  printf ("merge unexpectedly succeeded:\n %s\n", formatted);
+	  support_record_failure ();
+	  free (formatted);
+	}
+      else
+	return;
+    case ACTION_CONTINUE:
+	{
+	  char *formatted = support_format_addrinfo (ai, ret);
+
+	  /* Verify that the result appears exactly once.  */
+	  const char *expected = "address: STREAM/TCP 192.0.0.1 80\n"
+	    "address: DGRAM/UDP 192.0.0.1 80\n"
+	    "address: RAW/IP 192.0.0.1 80\n";
+
+	  const char *contains = strstr (formatted, expected);
+	  const char *contains2 = NULL;
+
+	  if (contains != NULL)
+	    contains2 = strstr (contains + strlen (expected), expected);
+
+	  if (contains == NULL || contains2 != NULL)
+	    {
+	      printf ("continue failed:\n%s\n", formatted);
+	      support_record_failure ();
+	    }
+
+	  free (formatted);
+	  break;
+	}
+    default:
+      __builtin_unreachable ();
+    }
+}
+
+static void
+do_one_test_set (int action)
+{
+  char buf[32];
+
+  snprintf (buf, sizeof (buf), "files [SUCCESS=%s] files",
+	    action_str (action));
+  __nss_configure_lookup ("hosts", buf);
+
+  do_one_test (action, AF_UNSPEC, false);
+  do_one_test (action, AF_INET, false);
+  do_one_test (action, AF_INET, true);
+}
+
+static int
+do_test (void)
+{
+  do_one_test_set (ACTION_CONTINUE);
+  do_one_test_set (ACTION_MERGE);
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/nss/tst-nss-gai-actions.root/etc/host.conf b/nss/tst-nss-gai-actions.root/etc/host.conf
new file mode 100644
index 0000000..d1a59f7
--- /dev/null
+++ b/nss/tst-nss-gai-actions.root/etc/host.conf
@@ -0,0 +1 @@
+multi on
diff --git a/nss/tst-nss-gai-actions.root/etc/hosts b/nss/tst-nss-gai-actions.root/etc/hosts
new file mode 100644
index 0000000..50ce977
--- /dev/null
+++ b/nss/tst-nss-gai-actions.root/etc/hosts
@@ -0,0 +1,508 @@
+192.0.0.1	example.org
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