dns: make the dns name resolver a plugin

Type: refactor
Signed-off-by: Dave Barach <dave@barachs.net>
Change-Id: I823c2cd307a4613653a2d20f564dda062d4da31b

1 files changed, 381 insertions, 0 deletions

diff --git a/src/plugins/dns/resolver_process.c b/src/plugins/dns/resolver_process.c
new file mode 100644
index 00000000000..802da53cec5
--- /dev/null
+++ b/src/plugins/dns/resolver_process.c
@@ -0,0 +1,381 @@
+/*
+ * Copyright (c) 2017 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <dns/dns.h>
+#include <vlibapi/api.h>
+#include <vlibmemory/api.h>
+
+#include <vlib/vlib.h>
+#include <vnet/vnet.h>
+
+/* define message IDs */
+#include <dns/dns_msg_enum.h>
+
+#define vl_typedefs		/* define message structures */
+#include <dns/dns_all_api_h.h>
+#undef vl_typedefs
+
+#define vl_endianfun		/* define message structures */
+#include <dns/dns_all_api_h.h>
+#undef vl_endianfun
+
+/* instantiate all the print functions we know about */
+#define vl_print(handle, ...) vlib_cli_output (handle, __VA_ARGS__)
+#define vl_printfun
+#include <dns/dns_all_api_h.h>
+#undef vl_printfun
+
+#include <vlibapi/api_helper_macros.h>
+
+int
+vnet_dns_response_to_reply (u8 * response,
+			    vl_api_dns_resolve_name_reply_t * rmp,
+			    u32 * min_ttlp);
+int
+vnet_dns_response_to_name (u8 * response,
+			   vl_api_dns_resolve_ip_reply_t * rmp,
+			   u32 * min_ttlp);
+
+static void
+resolve_event (dns_main_t * dm, f64 now, u8 * reply)
+{
+  vlib_main_t *vm = dm->vlib_main;
+  dns_pending_request_t *pr;
+  dns_header_t *d;
+  u32 pool_index;
+  dns_cache_entry_t *ep;
+  u32 min_ttl;
+  u16 flags;
+  u16 rcode;
+  int i;
+  int entry_was_valid;
+  int remove_count;
+  int rv = 0;
+
+  d = (dns_header_t *) reply;
+  flags = clib_net_to_host_u16 (d->flags);
+  rcode = flags & DNS_RCODE_MASK;
+
+  /* $$$ u16 limits cache to 65K entries, fix later multiple dst ports */
+  pool_index = clib_net_to_host_u16 (d->id);
+  dns_cache_lock (dm);
+
+  if (pool_is_free_index (dm->entries, pool_index))
+    {
+      vec_free (reply);
+      if (0)
+	clib_warning ("pool index %d is free", pool_index);
+      vlib_node_increment_counter (vm, dns46_reply_node.index,
+				   DNS46_REPLY_ERROR_NO_ELT, 1);
+      dns_cache_unlock (dm);
+      return;
+    }
+
+  ep = pool_elt_at_index (dm->entries, pool_index);
+
+  if (ep->dns_response)
+    vec_free (ep->dns_response);
+
+  /* Handle [sic] recursion AKA CNAME indirection */
+  rv = vnet_dns_cname_indirection_nolock (dm, pool_index, reply);
+
+  /* CNAME found, further resolution pending, we're done here */
+  if (rv > 0)
+    {
+      dns_cache_unlock (dm);
+      return;
+    }
+  /* Server backfire: refused to answer, or sent zero replies */
+  if (rv < 0)
+    {
+      /* Try a different server */
+      if (ep->server_af /* ip6 */ )
+	{
+	  if (0)
+	    clib_warning ("Server %U failed to resolve '%s'",
+			  format_ip6_address,
+			  dm->ip6_name_servers + ep->server_rotor, ep->name);
+	  /* Any more servers to try? */
+	  if (ep->server_fails > 1 || vec_len (dm->ip6_name_servers) <= 1)
+	    {
+	      /* No, tell the client to go away */
+	      goto reply;
+	    }
+	  ep->retry_count = 0;
+	  ep->server_rotor++;
+	  ep->server_fails++;
+	  if (ep->server_rotor >= vec_len (dm->ip6_name_servers))
+	    ep->server_rotor = 0;
+	  if (0)
+	    clib_warning ("Try server %U", format_ip6_address,
+			  dm->ip6_name_servers + ep->server_rotor);
+	  vnet_dns_send_dns6_request
+	    (dm, ep, dm->ip6_name_servers + ep->server_rotor);
+	}
+      else
+	{
+	  if (0)
+	    clib_warning ("Server %U failed to resolve '%s'",
+			  format_ip4_address,
+			  dm->ip4_name_servers + ep->server_rotor, ep->name);
+
+	  if (ep->server_fails > 1 || vec_len (dm->ip4_name_servers) <= 1)
+	    {
+	      /* No, tell the client to go away */
+	      goto reply;
+	    }
+	  ep->retry_count = 0;
+	  ep->server_rotor++;
+	  ep->server_fails++;
+	  if (ep->server_rotor >= vec_len (dm->ip4_name_servers))
+	    ep->server_rotor = 0;
+	  if (0)
+	    clib_warning ("Try server %U", format_ip4_address,
+			  dm->ip4_name_servers + ep->server_rotor);
+	  vnet_dns_send_dns4_request
+	    (dm, ep, dm->ip4_name_servers + ep->server_rotor);
+	}
+      dns_cache_unlock (dm);
+      return;
+    }
+
+reply:
+  /* Save the response */
+  ep->dns_response = reply;
+
+  /*
+   * Pick a sensible default cache entry expiration time.
+   * We don't play the 10-second timeout game.
+   */
+  ep->expiration_time = now + 600.0;
+
+  if (0)
+    clib_warning ("resolving '%s', was %s valid",
+		  ep->name, (ep->flags & DNS_CACHE_ENTRY_FLAG_VALID) ?
+		  "already" : "not");
+  /*
+   * The world is a mess. A single DNS request sent to e.g. 8.8.8.8
+   * may yield multiple, subtly different responses - all with the same
+   * DNS protocol-level ID.
+   *
+   * Last response wins in terms of what ends up in the cache.
+   * First response wins in terms of the response sent to the client.
+   */
+
+  /* Strong hint that we may not find a pending resolution entry */
+  entry_was_valid = (ep->flags & DNS_CACHE_ENTRY_FLAG_VALID) ? 1 : 0;
+
+  if (vec_len (ep->dns_response))
+    ep->flags |= DNS_CACHE_ENTRY_FLAG_VALID;
+
+  /* Most likely, send 1 message */
+  for (i = 0; i < vec_len (ep->pending_requests); i++)
+    {
+      vl_api_registration_t *regp;
+
+      pr = vec_elt_at_index (ep->pending_requests, i);
+
+      switch (pr->request_type)
+	{
+	case DNS_API_PENDING_NAME_TO_IP:
+	  {
+	    vl_api_dns_resolve_name_reply_t *rmp;
+	    regp = vl_api_client_index_to_registration (pr->client_index);
+	    if (regp == 0)
+	      continue;
+
+	    rmp = vl_msg_api_alloc (sizeof (*rmp));
+	    rmp->_vl_msg_id =
+	      clib_host_to_net_u16 (VL_API_DNS_RESOLVE_NAME_REPLY
+				    + dm->msg_id_base);
+	    rmp->context = pr->client_context;
+	    min_ttl = ~0;
+	    rv = vnet_dns_response_to_reply (ep->dns_response, rmp, &min_ttl);
+	    if (min_ttl != ~0)
+	      ep->expiration_time = now + min_ttl;
+	    rmp->retval = clib_host_to_net_u32 (rv);
+	    vl_api_send_msg (regp, (u8 *) rmp);
+	  }
+	  break;
+
+	case DNS_API_PENDING_IP_TO_NAME:
+	  {
+	    vl_api_dns_resolve_ip_reply_t *rmp;
+
+	    regp = vl_api_client_index_to_registration (pr->client_index);
+	    if (regp == 0)
+	      continue;
+
+	    rmp = vl_msg_api_alloc (sizeof (*rmp));
+	    rmp->_vl_msg_id =
+	      clib_host_to_net_u16 (VL_API_DNS_RESOLVE_IP_REPLY
+				    + dm->msg_id_base);
+	    rmp->context = pr->client_context;
+	    min_ttl = ~0;
+	    rv = vnet_dns_response_to_name (ep->dns_response, rmp, &min_ttl);
+	    if (min_ttl != ~0)
+	      ep->expiration_time = now + min_ttl;
+	    rmp->retval = clib_host_to_net_u32 (rv);
+	    vl_api_send_msg (regp, (u8 *) rmp);
+	  }
+	  break;
+
+	case DNS_PEER_PENDING_IP_TO_NAME:
+	case DNS_PEER_PENDING_NAME_TO_IP:
+	  if (pr->is_ip6)
+	    vnet_send_dns6_reply (dm, pr, ep, 0 /* allocate a buffer */ );
+	  else
+	    vnet_send_dns4_reply (dm, pr, ep, 0 /* allocate a buffer */ );
+	  break;
+	default:
+	  clib_warning ("request type %d unknown", pr->request_type);
+	  break;
+	}
+    }
+  vec_free (ep->pending_requests);
+
+  remove_count = 0;
+  for (i = 0; i < vec_len (dm->unresolved_entries); i++)
+    {
+      if (dm->unresolved_entries[i] == pool_index)
+	{
+	  vec_delete (dm->unresolved_entries, 1, i);
+	  remove_count++;
+	  i--;
+	}
+    }
+  /* See multiple response comment above... */
+  if (remove_count == 0)
+    {
+      u32 error_code = entry_was_valid ? DNS46_REPLY_ERROR_MULTIPLE_REPLY :
+	DNS46_REPLY_ERROR_NO_UNRESOLVED_ENTRY;
+
+      vlib_node_increment_counter (vm, dns46_reply_node.index, error_code, 1);
+      dns_cache_unlock (dm);
+      return;
+    }
+
+  /* Deal with bogus names, server issues, etc. */
+  switch (rcode)
+    {
+    default:
+    case DNS_RCODE_NO_ERROR:
+      break;
+
+    case DNS_RCODE_SERVER_FAILURE:
+    case DNS_RCODE_NOT_IMPLEMENTED:
+    case DNS_RCODE_REFUSED:
+      if (ep->server_af == 0)
+	clib_warning ("name server %U can't resolve '%s'",
+		      format_ip4_address,
+		      dm->ip4_name_servers + ep->server_rotor, ep->name);
+      else
+	clib_warning ("name server %U can't resolve '%s'",
+		      format_ip6_address,
+		      dm->ip6_name_servers + ep->server_rotor, ep->name);
+      /* FALLTHROUGH */
+    case DNS_RCODE_NAME_ERROR:
+    case DNS_RCODE_FORMAT_ERROR:
+      /* remove trash from the cache... */
+      vnet_dns_delete_entry_by_index_nolock (dm, ep - dm->entries);
+      break;
+    }
+
+
+  dns_cache_unlock (dm);
+  return;
+}
+
+static void
+retry_scan (dns_main_t * dm, f64 now)
+{
+  int i;
+  dns_cache_entry_t *ep;
+
+  for (i = 0; i < vec_len (dm->unresolved_entries); i++)
+    {
+      dns_cache_lock (dm);
+      ep = pool_elt_at_index (dm->entries, dm->unresolved_entries[i]);
+
+      ASSERT ((ep->flags & DNS_CACHE_ENTRY_FLAG_VALID) == 0);
+      vnet_send_dns_request (dm, ep);
+      dns_cache_unlock (dm);
+    }
+}
+
+static uword
+dns_resolver_process (vlib_main_t * vm,
+		      vlib_node_runtime_t * rt, vlib_frame_t * f)
+{
+  dns_main_t *dm = &dns_main;
+  f64 now;
+  f64 timeout = 1000.0;
+  uword *event_data = 0;
+  uword event_type;
+  int i;
+
+  while (1)
+    {
+      vlib_process_wait_for_event_or_clock (vm, timeout);
+
+      now = vlib_time_now (vm);
+
+      event_type = vlib_process_get_events (vm, (uword **) & event_data);
+
+      switch (event_type)
+	{
+	  /* Send one of these when a resolution is pending */
+	case DNS_RESOLVER_EVENT_PENDING:
+	  timeout = 2.0;
+	  break;
+
+	case DNS_RESOLVER_EVENT_RESOLVED:
+	  for (i = 0; i < vec_len (event_data); i++)
+	    resolve_event (dm, now, (u8 *) event_data[i]);
+	  break;
+
+	case ~0:		/* timeout */
+	  retry_scan (dm, now);
+	  break;
+	}
+      vec_reset_length (event_data);
+
+      /* No work? Back to slow timeout mode... */
+      if (vec_len (dm->unresolved_entries) == 0)
+	timeout = 1000.0;
+    }
+  return 0;			/* or not */
+}
+
+void
+vnet_dns_create_resolver_process (dns_main_t * dm)
+{
+  /* Already created the resolver process? */
+  if (dm->resolver_process_node_index > 0)
+    return;
+
+  /* No, create it now and make a note of the node index */
+  dm->resolver_process_node_index = vlib_process_create
+    (dm->vlib_main, "dns-resolver-process",
+     dns_resolver_process, 16 /* log2_n_stack_bytes */ );
+}
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */