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, 154 insertions, 0 deletions

diff --git a/src/vnet/dns/dns_packet.h b/src/vnet/dns/dns_packet.h
new file mode 100644
index 00000000000..e0ea8fe2706
--- /dev/null
+++ b/src/vnet/dns/dns_packet.h
@@ -0,0 +1,154 @@
+/*
+ * Copyright (c) 2015 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_packet_h
+#define included_dns_packet_h
+
+/**
+ * DNS packet header format
+ */
+
+/* *INDENT-OFF* */
+typedef CLIB_PACKED (struct {
+  u16 id;                       /**< transaction ID */
+  u16 flags;                    /**< flags  */
+  u16 qdcount;                  /**< number of questions */
+  u16 anscount;                 /**< number of answers */
+  u16 nscount;                  /**< number of name servers */
+  u16 arcount;                  /**< number of additional records */
+}) dns_header_t;
+/* *INDENT-ON* */
+
+#define DNS_RCODE_MASK (0xf)
+#define DNS_RCODE_NO_ERROR 0
+#define DNS_RCODE_FORMAT_ERROR 1
+#define DNS_RCODE_SERVER_FAILURE 2
+#define DNS_RCODE_NAME_ERROR 3
+#define DNS_RCODE_NOT_IMPLEMENTED 4
+#define DNS_RCODE_REFUSED 5
+
+#define DNS_RA (1<<7)		/**< recursion available */
+#define DNS_RD (1<<8)		/**< recursion desired */
+#define DNS_TC (1<<9)	       /**< truncation  */
+#define DNS_AA (1<<10)		/**< authoritative answer  */
+#define DNS_OPCODE_MASK (0xf<<11) /**< opcode mask */
+#define DNS_OPCODE_QUERY (0<<11)  /**< standard query */
+#define DNS_OPCODE_IQUERY (1<<11) /**< inverse query (deprecated) */
+#define DNS_OPCODE_STATUS (2<<11) /**< server status  */
+#define DNS_QR (1<<15)		/**< query=0, response=1  */
+
+
+/*
+ * Note: in DNS-land, www.foobar.com is encoded as three "labels,"
+ * each of which amount to a 1 octet length followed by up to 63
+ * octets of name. Don't forget to add a "null root label" after the last
+ * real one, or the poor slob trying to parse the name will have
+ * no chance whatsoever.
+ *
+ * All RRs have the same top level format shown below:
+ *
+ *                                    1  1  1  1  1  1
+ *      0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+ *    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *    |                                               |
+ *    /                                               /
+ *    /                      NAME                     /
+ *    |                                               |
+ *    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *    |                      TYPE                     |
+ *    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *    |                     CLASS                     |
+ *    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *    |                      TTL                      |
+ *    |                                               |
+ *    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *    |                   RDLENGTH                    |
+ *    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
+ *    /                     RDATA                     /
+ *    /                                               /
+ *    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *
+ *
+ *  DNS "questions" have the following format:
+ *
+ *                                     1  1  1  1  1  1
+ *       0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+ *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *     |                                               |
+ *     /                     QNAME                     /
+ *     /                                               /
+ *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *     |                     QTYPE                     |
+ *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ *     |                     QCLASS                    |
+ *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ */
+
+/**
+ * DNS "question" fixed header.
+ */
+/* *INDENT-OFF* */
+typedef CLIB_PACKED (struct {
+  u16 type;	/**< record type requested */
+  u16 class;	/**< class, 1 = internet */
+}) dns_query_t;
+/* *INDENT-ON* */
+
+/**
+ * DNS RR fixed header.
+ */
+/* *INDENT-OFF* */
+typedef CLIB_PACKED (struct {
+  u16 type;	/**< record type */
+  u16 class;	/**< class, 1 = internet */
+  u32 ttl;	/**< time to live, in seconds */
+  u16 rdlength;
+  /**< length of r */
+  u8 rdata[0];
+}) dns_rr_t;
+/* *INDENT-ON* */
+
+/*
+ * There are quite a number of DNS record types
+ * Feel free to add as needed
+ */
+#define foreach_dns_type                        \
+_(A, 1) 	/**< ip4 host address */        \
+_(AAAA, 28)     /**< ip6 host address */        \
+_(ALL, 255)     /**< all available data */      \
+_(TEXT, 16)     /**< a text string */           \
+_(NAMESERVER, 2) /**< a nameserver */           \
+_(CNAME, 5)      /**< a CNAME (alias) */	\
+_(MAIL_EXCHANGE, 15) /**< a mail exchange  */
+
+typedef enum
+{
+#define _(name,value) DNS_TYPE_##name = value,
+  foreach_dns_type
+#undef _
+} dns_type_t;
+
+#define DNS_CLASS_IN	1	/**< The Internet */
+
+
+#endif /* included_dns_packet_h */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */