sunrpc: Always obtain AF_INET addresses from NSS [BZ #20964]

The new __libc_rpc_gethostbyname function calls gethostbyname2_r
with an AF_INET argument and is therefore not affected by the
RES_USE_INET6 flag.

Validated with the following test program, with and without
RES_OPTIONS=inet6, against a NFS server.  (Link with -lrpcsvc.)

#include <rpc/clnt.h>
#include <rpcsvc/mount.h>
#include <stdio.h>
#include <string.h>

static void
usage (char **argv)
{
  printf ("usage:\n"
          "  %1$s HOST getrpcport\n"
          "  %1$s HOST callrpc\n"
          "  %1$s HOST clnt_create\n",
          argv[0]);
}

static void
dump_exports (struct exportnode *exports)
{
  while (exports != NULL)
    {
      printf ("%s\n", exports->ex_dir);
      exports = exports->ex_next;
    }
}

int
main (int argc, char **argv)
{
  if (argc != 3)
    {
      usage (argv);
      return 1;
    }

  const char *host = argv[1];
  const char *command = argv[2];

  if (strcmp (command, "getrpcport") == 0)
    {
      int port = getrpcport (host, MOUNTPROG, MOUNTVERS, IPPROTO_UDP);
      printf ("getrpcport: %d\n", port);
    }
  else if (strcmp (command, "callrpc") == 0)
    {
      struct exportnode *exports = NULL;
      int ret = callrpc (host, MOUNTPROG, MOUNTVERS, MOUNTPROC_EXPORT,
                         (xdrproc_t) xdr_void, NULL,
                         (xdrproc_t) xdr_exports, (char *)&exports);
      if (ret != 0)
        {
          clnt_perrno (ret);
          puts ("");
          return 1;
        }
      dump_exports (exports);
    }
  else if (strcmp (command, "clnt_create") == 0)
    {
      CLIENT *client = clnt_create
        (host, MOUNTPROG, MOUNTVERS, "udp");
      if (client == NULL)
        {
          printf ("error: clnt_create failed\n");
          return 1;
        }
      struct exportnode *exports = NULL;
      int ret = CLNT_CALL (client, MOUNTPROC_EXPORT,
                           (xdrproc_t) xdr_void, NULL,
                           (xdrproc_t) xdr_exports, (char *)&exports,
                           ((struct timeval) {15, 0}));
      if (ret != 0)
        {
          clnt_perrno (ret);
          puts ("");
          return 1;
        }
      dump_exports (exports);
    }
  else
    {
      usage (argv);
      return 1;
    }

  return 0;
}

1 files changed, 73 insertions, 0 deletions

diff --git a/sunrpc/rpc_gethostbyname.c b/sunrpc/rpc_gethostbyname.c
new file mode 100644
index 0000000000..a2ee960482
--- /dev/null
+++ b/sunrpc/rpc_gethostbyname.c
@@ -0,0 +1,73 @@
+/* IPv4-only variant of gethostbyname.
+   Copyright (C) 2016 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; see the file COPYING.LIB.  If
+   not, see <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <netdb.h>
+#include <rpc/rpc.h>
+#include <scratch_buffer.h>
+#include <string.h>
+
+int
+__libc_rpc_gethostbyname (const char *host, struct sockaddr_in *addr)
+{
+  struct hostent hostbuf;
+  struct hostent *hp = NULL;
+  int herr;
+  struct scratch_buffer tmpbuf;
+  scratch_buffer_init (&tmpbuf);
+
+  while (__gethostbyname2_r (host, AF_INET,
+                             &hostbuf, tmpbuf.data, tmpbuf.length, &hp,
+                             &herr) != 0
+         || hp == NULL)
+    if (herr != NETDB_INTERNAL || errno != ERANGE)
+      {
+        struct rpc_createerr *ce = &get_rpc_createerr ();
+        ce->cf_stat = RPC_UNKNOWNHOST;
+        scratch_buffer_free (&tmpbuf);
+        return -1;
+      }
+    else
+      {
+        if (!scratch_buffer_grow (&tmpbuf))
+          {
+            /* If memory allocation failed, allocating the RPC error
+               structure might could as well, so this could lead to a
+               crash.  */
+            struct rpc_createerr *ce = &get_rpc_createerr ();
+            ce->cf_stat = RPC_SYSTEMERROR;
+            ce->cf_error.re_errno = ENOMEM;
+            return -1;
+          }
+      }
+
+  if (hp->h_addrtype != AF_INET || hp->h_length != sizeof (addr->sin_addr))
+    {
+      struct rpc_createerr *ce = &get_rpc_createerr ();
+      ce->cf_stat = RPC_SYSTEMERROR;
+      ce->cf_error.re_errno = EAFNOSUPPORT;
+      scratch_buffer_free (&tmpbuf);
+      return -1;
+    }
+
+  addr->sin_family = AF_INET;
+  addr->sin_port = htons (0);
+  memcpy (&addr->sin_addr, hp->h_addr, sizeof (addr->sin_addr));
+  scratch_buffer_free (&tmpbuf);
+  return 0;
+}