resolv: Add tst-resolv-aliases

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

resolv/Makefile

@@ -89,6 +89,7 @@ tests += \
   tst-ns_name_pton \
   tst-res_hconf_reorder \
   tst-res_hnok \
+  tst-resolv-aliases \
   tst-resolv-basic \
   tst-resolv-binary \
   tst-resolv-byaddr \
@@ -259,6 +260,7 @@ $(objpfx)tst-resolv-ai_idn.out: $(gen-locales)
 $(objpfx)tst-resolv-ai_idn-latin1.out: $(gen-locales)
 $(objpfx)tst-resolv-ai_idn-nolibidn2.out: \
   $(gen-locales) $(objpfx)tst-no-libidn2.so
+$(objpfx)tst-resolv-aliases: $(objpfx)libresolv.so $(shared-thread-library)
 $(objpfx)tst-resolv-basic: $(objpfx)libresolv.so $(shared-thread-library)
 $(objpfx)tst-resolv-binary: $(objpfx)libresolv.so $(shared-thread-library)
 $(objpfx)tst-resolv-byaddr: $(objpfx)libresolv.so $(shared-thread-library)

resolv/tst-resolv-aliases.c

@@ -0,0 +1,254 @@
+/* Test alias handling (mainly for gethostbyname).
+   Copyright (C) 2022 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 <array_length.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/check_nss.h>
+#include <support/resolv_test.h>
+#include <support/support.h>
+
+#include "tst-resolv-maybe_insert_sig.h"
+
+/* QNAME format:
+
+   aADDRESSES-cCNAMES.example.net
+
+   CNAMES is the length of the CNAME chain, ADDRESSES is the number of
+   addresses in the response.  The special value 255 means that there
+   are no addresses, and the RCODE is NXDOMAIN.  */
+static void
+response (const struct resolv_response_context *ctx,
+          struct resolv_response_builder *b,
+          const char *qname, uint16_t qclass, uint16_t qtype)
+{
+  TEST_COMPARE (qclass, C_IN);
+  if (qtype != T_A)
+    TEST_COMPARE (qtype, T_AAAA);
+
+  unsigned int addresses, cnames;
+  char *tail;
+  if (sscanf (qname, "a%u-c%u%ms", &addresses, &cnames, &tail) == 3)
+    {
+      if (strcmp (tail, ".example.com") == 0
+          || strcmp (tail, ".example.net.example.net") == 0
+          || strcmp (tail, ".example.net.example.com") == 0)
+        /* These only happen after NXDOMAIN.  */
+        TEST_VERIFY (addresses == 255);
+      else if (strcmp (tail, ".example.net") != 0)
+        FAIL_EXIT1 ("invalid QNAME: %s", qname);
+    }
+  free (tail);
+
+  int rcode;
+  if (addresses == 255)
+    {
+      /* Special case: Use no addresses with NXDOMAIN response.  */
+      rcode = ns_r_nxdomain;
+      addresses = 0;
+    }
+  else
+    rcode = 0;
+
+  struct resolv_response_flags flags = { .rcode = rcode };
+  resolv_response_init (b, flags);
+  resolv_response_add_question (b, qname, qclass, qtype);
+  resolv_response_section (b, ns_s_an);
+  maybe_insert_sig (b, qname);
+
+  /* Provide the requested number of CNAME records.  */
+  char *previous_name = (char *) qname;
+  for (int unique = 0; unique < cnames; ++unique)
+    {
+      resolv_response_open_record (b, previous_name, qclass, T_CNAME, 60);
+      char *new_name = xasprintf ("%d.alias.example", unique);
+      resolv_response_add_name (b, new_name);
+      resolv_response_close_record (b);
+
+      maybe_insert_sig (b, qname);
+
+      if (previous_name != qname)
+        free (previous_name);
+      previous_name = new_name;
+    }
+
+  for (int unique = 0; unique < addresses; ++unique)
+    {
+      resolv_response_open_record (b, previous_name, qclass, qtype, 60);
+
+      if (qtype == T_A)
+        {
+          char ipv4[4] = {192, 0, 2, 1 + unique};
+          resolv_response_add_data (b, &ipv4, sizeof (ipv4));
+        }
+      else if (qtype == T_AAAA)
+        {
+          char ipv6[16] =
+            {
+              0x20, 0x01, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+              1 + unique
+            };
+          resolv_response_add_data (b, &ipv6, sizeof (ipv6));
+        }
+      resolv_response_close_record (b);
+    }
+
+  if (previous_name != qname)
+    free (previous_name);
+}
+
+static char *
+make_qname (bool do_search, int cnames, int addresses)
+{
+  return xasprintf ("a%d-c%d%s",
+                    addresses, cnames, do_search ? "" : ".example.net");
+}
+
+static void
+check_cnames_failure (int af, bool do_search, int cnames, int addresses)
+{
+  char *qname = make_qname (do_search, cnames, addresses);
+
+  struct hostent *e;
+  if (af == AF_UNSPEC)
+    e = gethostbyname (qname);
+  else
+    e = gethostbyname2 (qname, af);
+
+  if (addresses == 0)
+    check_hostent (qname, e, "error: NO_RECOVERY\n");
+  else
+    check_hostent (qname, e, "error: HOST_NOT_FOUND\n");
+
+  free (qname);
+}
+
+static void
+check (int af, bool do_search, int cnames, int addresses)
+{
+  char *qname = make_qname (do_search, cnames, addresses);
+  char *fqdn = make_qname (false, cnames, addresses);
+
+  struct hostent *e;
+  if (af == AF_UNSPEC)
+    e = gethostbyname (qname);
+  else
+    e = gethostbyname2 (qname, af);
+  if (e == NULL)
+    FAIL_EXIT1 ("unexpected failure for %d, %d, %d", af, cnames, addresses);
+
+  if (af == AF_UNSPEC || af == AF_INET)
+    {
+      TEST_COMPARE (e->h_addrtype, AF_INET);
+      TEST_COMPARE (e->h_length, 4);
+    }
+  else
+    {
+      TEST_COMPARE (e->h_addrtype, AF_INET6);
+      TEST_COMPARE (e->h_length, 16);
+    }
+
+  for (int i = 0; i < addresses; ++i)
+    {
+      char ipv4[4] = {192, 0, 2, 1 + i};
+      char ipv6[16] =
+        { 0x20, 0x01, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 + i };
+      char *expected = e->h_addrtype == AF_INET ? ipv4 : ipv6;
+      TEST_COMPARE_BLOB (e->h_addr_list[i], e->h_length,
+                         expected, e->h_length);
+    }
+  TEST_VERIFY (e->h_addr_list[addresses] == NULL);
+
+
+  if (cnames == 0)
+    {
+      /* QNAME is fully qualified.  */
+      TEST_COMPARE_STRING (e->h_name, fqdn);
+      TEST_VERIFY (e->h_aliases[0] == NULL);
+    }
+  else
+   {
+     /* Fully-qualified QNAME is demoted to an aliases.  */
+     TEST_COMPARE_STRING (e->h_aliases[0], fqdn);
+
+     for (int i = 1; i <= cnames; ++i)
+       {
+         char *expected = xasprintf ("%d.alias.example", i - 1);
+         if (i == cnames)
+           TEST_COMPARE_STRING (e->h_name, expected);
+         else
+           TEST_COMPARE_STRING (e->h_aliases[i], expected);
+         free (expected);
+       }
+     TEST_VERIFY (e->h_aliases[cnames] == NULL);
+   }
+
+  free (fqdn);
+  free (qname);
+}
+
+static int
+do_test (void)
+{
+  struct resolv_test *obj = resolv_test_start
+    ((struct resolv_redirect_config)
+     {
+       .response_callback = response,
+       .search = { "example.net", "example.com" },
+     });
+
+  static const int families[] = { AF_UNSPEC, AF_INET, AF_INET6 };
+
+  for (int do_insert_sig = 0; do_insert_sig < 2; ++do_insert_sig)
+    {
+      insert_sig = do_insert_sig;
+
+      /* If do_search is true, a bare host name (for example, a1-c1)
+         is used.  This exercises search path processing and FQDN
+         qualification.  */
+      for (int do_search = 0; do_search < 2; ++do_search)
+        for (const int *paf = families; paf != array_end (families); ++paf)
+          {
+            for (int cnames = 0; cnames <= 100; ++cnames)
+              {
+                check_cnames_failure (*paf, do_search, cnames, 0);
+                /* Now with NXDOMAIN responses.  */
+                check_cnames_failure (*paf, do_search, cnames, 255);
+              }
+
+            for (int cnames = 0; cnames <= 10; ++cnames)
+              for (int addresses = 1; addresses <= 10; ++addresses)
+                check (*paf, do_search, cnames, addresses);
+
+            /* The current implementation is limited to 47 aliases.
+               Addresses do not have such a limit.  */
+            check (*paf, do_search, 47, 60);
+          }
+    }
+
+  resolv_test_end (obj);
+
+  return 0;
+}
+
+#include <support/test-driver.c>