VPP-1027: DNS name resolver

This patch is a plausible first-cut, suitable for initial testing by
vcl (host stack client library).

Main features;
- recursive name resolution
- multiple ip4/ip6 name servers
- cache size limit enforcement
  - currently limited to 65K
- ttl / aging
- static mapping support
- show / clear / debug CLI commands

Binary APIs provided for the following:
- add/delete name servers
- enable/disable the name cache
- resolve a name

To Do list:
- Respond to ip4/ip6 client DNS requests (vs. binary API requests)
- Perf / scale tuning
  - map pending transaction ids to pool indices, so the cache
    can (greatly) exceed 65K entries
- Security improvements
  - Use unpredictable dns transaction IDs, related to previous item
  - Make sure that response-packet src ip addresses match the server
- Add binary APIs
  - deliver raw response data to clients
  - control recursive name resolution
- Documentation

Change-Id: I48c373d5c05d7108ccd814d4055caf8c75ca10b7
Signed-off-by: Dave Barach <dave@barachs.net>

1 files changed, 149 insertions, 0 deletions

diff --git a/src/vnet/dns/dns.h b/src/vnet/dns/dns.h
new file mode 100644
index 00000000000..5da26156f6c
--- /dev/null
+++ b/src/vnet/dns/dns.h
@@ -0,0 +1,149 @@
+/*
+ * 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.
+ */
+
+#ifndef included_dns_h
+#define included_dns_h
+
+#include <vppinfra/time.h>
+#include <vppinfra/cache.h>
+#include <vppinfra/error.h>
+
+#include <vppinfra/hash.h>
+#include <vnet/dns/dns_packet.h>
+#include <vnet/ip/ip.h>
+
+typedef struct
+{
+  /** flags */
+  volatile u8 flags;
+
+  /** The name in "normal human being" notation, e.g. www.foobar.com */
+  u8 *name;
+
+  /** Expiration time */
+  f64 expiration_time;
+
+  /** Cached dns request, for sending retries */
+  u8 *dns_request;
+
+  /** Retry parameters */
+  int retry_count;
+  int server_rotor;
+  int server_af;
+  f64 retry_timer;
+
+  /** Cached dns response */
+  u8 *dns_response;
+
+  /** Clients awaiting responses */
+  u32 *api_clients_to_notify;
+  u32 *api_client_contexts;
+  ip4_address_t *ip4_peers_to_notify;
+  ip6_address_t *ip6_peers_to_notify;
+} dns_cache_entry_t;
+
+#define DNS_CACHE_ENTRY_FLAG_VALID	(1<<0) /**< we have Actual Data */
+#define DNS_CACHE_ENTRY_FLAG_STATIC	(1<<1) /**< static entry */
+
+#define DNS_RETRIES_PER_SERVER 3
+
+#define DNS_RESOLVER_EVENT_RESOLVED	1
+#define DNS_RESOLVER_EVENT_PENDING	2
+
+
+typedef struct
+{
+  /** Pool of cache entries */
+  dns_cache_entry_t *entries;
+
+  /** Pool indices of unresolved entries */
+  u32 *unresolved_entries;
+
+  /** Find cached record by name */
+  uword *cache_entry_by_name;
+  uword *cache_lock;
+
+  /** enable / disable flag */
+  int is_enabled;
+
+  /** upstream name servers, e.g. 8.8.8.8 */
+  ip4_address_t *ip4_name_servers;
+  ip6_address_t *ip6_name_servers;
+
+  /** config parameters */
+  u32 name_cache_size;
+  u32 max_ttl_in_seconds;
+  u32 random_seed;
+
+  /* convenience */
+  vlib_main_t *vlib_main;
+  vnet_main_t *vnet_main;
+} dns_main_t;
+
+extern dns_main_t dns_main;
+
+extern vlib_node_registration_t dns46_reply_node;
+extern vlib_node_registration_t dns_resolver_node;
+
+#define foreach_dns46_reply_error                       \
+_(PROCESSED, "DNS reply pkts processed")                \
+_(NO_ELT, "No DNS pool element")                        \
+_(FORMAT_ERROR, "DNS format errors")                    \
+_(TEST_DROP, "DNS reply pkt dropped for test purposes")
+
+typedef enum
+{
+#define _(sym,str) DNS46_REPLY_ERROR_##sym,
+  foreach_dns46_reply_error
+#undef _
+    DNS46_REPLY_N_ERROR,
+} dns46_reply_error_t;
+
+void vnet_send_dns_request (dns_main_t * dm, dns_cache_entry_t * ep);
+int vnet_dns_cname_indirection_nolock (dns_main_t * dm,
+				       dns_cache_entry_t * ep, u8 * reply);
+int vnet_dns_delete_entry_by_index_nolock (dns_main_t * dm, u32 index);
+
+format_function_t format_dns_reply;
+
+static inline void
+dns_cache_lock (dns_main_t * dm)
+{
+  if (dm->cache_lock)
+    {
+      while (__sync_lock_test_and_set (dm->cache_lock, 1))
+	;
+    }
+}
+
+static inline void
+dns_cache_unlock (dns_main_t * dm)
+{
+  if (dm->cache_lock)
+    {
+      CLIB_MEMORY_BARRIER ();
+      *dm->cache_lock = 0;
+    }
+}
+
+#endif /* included_dns_h */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */