1 files changed, 137 insertions, 0 deletions
diff --git a/resolv/nss_dns/dns-canon.c b/resolv/nss_dns/dns-canon.c
new file mode 100644
index 0000000000..e5b38f5e7c
--- /dev/null
+++ b/resolv/nss_dns/dns-canon.c
@@ -0,0 +1,137 @@
+/* Copyright (C) 2004 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ulrich Drepper <drepper@redhat.com>, 2004.
+
+   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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <errno.h>
+#include <netdb.h>
+#include <resolv.h>
+#include <stdlib.h>
+#include <arpa/nameser.h>
+#include <nsswitch.h>
+
+
+#if PACKETSZ > 65536
+# define MAXPACKET	PACKETSZ
+#else
+# define MAXPACKET	65536
+#endif
+
+
+/* We need this time later.  */
+typedef union querybuf
+{
+  HEADER hdr;
+  unsigned char buf[MAXPACKET];
+} querybuf;
+
+
+enum nss_status
+_nss_dns_getcanonname_r (const char *name, char *buffer, size_t buflen,
+			 char **result,int *errnop, int *h_errnop)
+{
+  /* Just an alibi buffer, res_nquery will allocate a real buffer for
+     us.  */
+  unsigned char buf[20];
+  union
+  {
+    querybuf *buf;
+    unsigned char *ptr;
+  } ansp = { .ptr = buf };
+  enum nss_status status;
+
+  int r = __libc_res_nquery (&_res, name, ns_c_in, ns_t_cname,
+			     buf, sizeof (buf), &ansp.ptr);
+  if (r > 0)
+    {
+      /* We need to decode the response.  Just one question record.
+	 And if we got no answers we bail out, too.  */
+      if (ansp.buf->hdr.qdcount != htons (1)
+	  || ansp.buf->hdr.ancount == 0)
+	goto unavail;
+
+      /* Beginning and end of the buffer with query, answer, and the
+	 rest.  */
+      unsigned char *ptr = &ansp.buf->buf[sizeof (HEADER)];
+      unsigned char *endptr = ansp.ptr + r;
+
+      /* Skip over the query.  This is the name, type, and class.  */
+      int s = __dn_skipname (ptr, endptr);
+      if (s < 0)
+	goto unavail;
+
+      /* Skip over the name and the two 16-bit values containing type
+	 and class.  */
+      ptr += s + 2 * sizeof (uint16_t);
+
+      /* Now the reply.  First again the name from the query, then
+	 type, class, TTL, and the length of the RDATA.  */
+      s = __dn_skipname (ptr, endptr);
+      if (s < 0)
+	goto unavail;
+
+      ptr += s;
+
+      /* Check whether type and class match.  */
+      if (*(uint16_t *) ptr != htons (ns_t_cname))
+	goto unavail;
+
+      ptr += sizeof (uint16_t);
+      if (*(uint16_t *) ptr != htons (ns_c_in))
+	goto unavail;
+
+      /* Also skip over the TTL and rdata length.  */
+      ptr += sizeof (uint16_t) + sizeof (uint32_t) + sizeof (int16_t);
+
+      /* Now the name we are looking for.  */
+      s = __dn_expand (ansp.buf->buf, endptr, ptr, buffer, buflen);
+      if (s < 0)
+	{
+	  if (errno != EMSGSIZE)
+	    goto unavail;
+
+	  /* The buffer is too small.  */
+	  *errnop = ERANGE;
+	  status = NSS_STATUS_TRYAGAIN;
+	  h_errno = NETDB_INTERNAL;
+	}
+      else
+	{
+	  /* Success.  */
+	  *result = buffer;
+	  status = NSS_STATUS_SUCCESS;
+	}
+    }
+  else if (h_errno == TRY_AGAIN)
+    {
+    again:
+      status = NSS_STATUS_TRYAGAIN;
+      *errnop = errno;
+    }
+  else
+    {
+    unavail:
+      status = NSS_STATUS_UNAVAIL;
+      *errnop = errno;
+    }
+  *h_errnop = h_errno;
+
+  if (ansp.ptr != buf)
+    free (ansp.ptr);
+
+  return status;
+}