(_nss_dns_getcanonname_r): Don't use CNAME records, we better follow the chain of...

diff --git a/resolv/nss_dns/dns-canon.c b/resolv/nss_dns/dns-canon.c
index e5b38f5..ae3f40b 100644 (file)
--- a/resolv/nss_dns/dns-canon.c
+++ b/resolv/nss_dns/dns-canon.c
@@ -53,81 +53,97 @@ _nss_dns_getcanonname_r (const char *name, char *buffer, size_t buflen,
     unsigned char *ptr;
   } ansp = { .ptr = buf };
   enum nss_status status;
+  int qtypes[] = { ns_t_a, ns_t_aaaa };
+#define nqtypes (sizeof (qtypes) / sizeof (qtypes[0]))
 
-  int r = __libc_res_nquery (&_res, name, ns_c_in, ns_t_cname,
-                            buf, sizeof (buf), &ansp.ptr);
-  if (r > 0)
+  for (int i = 0; i < nqtypes; ++i)
     {
-      /* 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)
+      int r = __libc_res_nquery (&_res, name, ns_c_in, qtypes[i],
+                                buf, sizeof (buf), &ansp.ptr);
+      if (r > 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;
+         /* 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))
+           continue;
+
+         /* Number of answers.   */
+         unsigned int ancount = ntohs (ansp.buf->hdr.ancount);
+
+         /* 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)
+           {
+           unavail:
+             status = NSS_STATUS_UNAVAIL;
+             break;
+           }
+
+         /* Skip over the name and the two 16-bit values containing type
+            and class.  */
+         ptr += s + 2 * sizeof (uint16_t);
+
+         while (ancount-- > 0)
+           {
+             /* Now the reply.  First again the name from the query,
+                then type, class, TTL, and the length of the RDATA.
+                We remember the name start.  */
+             unsigned char *namestart = ptr;
+             s = __dn_skipname (ptr, endptr);
+             if (s < 0)
+               goto unavail;
+
+             ptr += s;
+
+             /* Check whether type and class match.  */
+             unsigned int type = ntohs (*(uint16_t *) ptr);
+             if (type == qtypes[i])
+               {
+                 /* We found the record.  */
+                 s = __dn_expand (ansp.buf->buf, endptr, namestart,
+                                  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;
+                   }
+
+                 goto out;
+               }
+
+             if (type != ns_t_cname)
+               goto unavail;
+
+             ptr += sizeof (uint16_t);
+             if (*(uint16_t *) ptr != htons (ns_c_in))
+               goto unavail;
+
+             /* Also skip over the TTL.  */
+             ptr += sizeof (uint16_t) + sizeof (uint32_t);
+
+             /* Skip over the data length and data.  */
+             ptr += sizeof (uint16_t) + ntohs (*(uint16_t *) ptr);
+           }
        }
     }
-  else if (h_errno == TRY_AGAIN)
-    {
-    again:
-      status = NSS_STATUS_TRYAGAIN;
-      *errnop = errno;
-    }
-  else
-    {
-    unavail:
-      status = NSS_STATUS_UNAVAIL;
-      *errnop = errno;
-    }
+
+ out:
   *h_errnop = h_errno;
 
   if (ansp.ptr != buf)