initial work on a wifi/http configuration module

components/wifi-manager/dns_server.h

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+/*
+Copyright (c) 2019 Tony Pottier
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+@file dns_server.h
+@author Tony Pottier
+@brief Defines an extremly basic DNS server for captive portal functionality.
+
+Contains the freeRTOS task for the DNS server that processes the requests.
+
+@see https://idyl.io
+@see https://github.com/tonyp7/esp32-wifi-manager
+@see http://www.zytrax.com/books/dns/ch15
+*/
+
+#ifndef MAIN_DNS_SERVER_H_
+#define MAIN_DNS_SERVER_H_
+#include <esp_system.h>
+#include <stdbool.h>
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/** 12 byte header, 64 byte domain name, 4 byte qtype/qclass. This NOT compliant with the RFC, but it's good enough for a captive portal
+ * if a DNS query is too big it just wont be processed. */
+#define	DNS_QUERY_MAX_SIZE 80
+
+/** Query + 2 byte ptr, 2 byte type, 2 byte class, 4 byte TTL, 2 byte len, 4 byte data */
+#define	DNS_ANSWER_MAX_SIZE (DNS_QUERY_MAX_SIZE+16)
+
+
+/**
+ * @brief RCODE values used in a DNS header message
+ */
+typedef enum dns_reply_code_t {
+	DNS_REPLY_CODE_NO_ERROR = 0,
+	DNS_REPLY_CODE_FORM_ERROR = 1,
+	DNS_REPLY_CODE_SERVER_FAILURE = 2,
+	DNS_REPLY_CODE_NON_EXISTANT_DOMAIN = 3,
+	DNS_REPLY_CODE_NOT_IMPLEMENTED = 4,
+	DNS_REPLY_CODE_REFUSED = 5,
+	DNS_REPLY_CODE_YXDOMAIN = 6,
+	DNS_REPLY_CODE_YXRRSET = 7,
+	DNS_REPLY_CODE_NXRRSET = 8
+}dns_reply_code_t;
+
+
+
+/**
+ * @brief OPCODE values used in a DNS header message
+ */
+typedef enum dns_opcode_code_t {
+	DNS_OPCODE_QUERY = 0,
+	DNS_OPCODE_IQUERY = 1,
+	DNS_OPCODE_STATUS = 2
+}dns_opcode_code_t;
+
+
+
+/**
+ * @brief Represents a 12 byte DNS header.
+ * __packed__ is needed to prevent potential unwanted memory alignments
+ */
+typedef struct __attribute__((__packed__)) dns_header_t{
+  uint16_t ID;         // identification number
+  uint8_t RD : 1;      // recursion desired
+  uint8_t TC : 1;      // truncated message
+  uint8_t AA : 1;      // authoritive answer
+  uint8_t OPCode : 4;  // message_type
+  uint8_t QR : 1;      // query/response flag
+  uint8_t RCode : 4;   // response code
+  uint8_t Z : 3;       // its z! reserved
+  uint8_t RA : 1;      // recursion available
+  uint16_t QDCount;    // number of question entries
+  uint16_t ANCount;    // number of answer entries
+  uint16_t NSCount;    // number of authority entries
+  uint16_t ARCount;    // number of resource entries
+}dns_header_t;
+
+
+
+typedef enum dns_answer_type_t {
+	DNS_ANSWER_TYPE_A = 1,
+	DNS_ANSWER_TYPE_NS = 2,
+	DNS_ANSWER_TYPE_CNAME = 5,
+	DNS_ANSWER_TYPE_SOA = 6,
+	DNS_ANSWER_TYPE_WKS = 11,
+	DNS_ANSWER_TYPE_PTR = 12,
+	DNS_ANSWER_TYPE_MX = 15,
+	DNS_ANSWER_TYPE_SRV = 33,
+	DNS_ANSWER_TYPE_AAAA = 28
+}dns_answer_type_t;
+
+typedef enum dns_answer_class_t {
+	DNS_ANSWER_CLASS_IN = 1
+}dns_answer_class_t;
+
+
+
+typedef struct __attribute__((__packed__)) dns_answer_t{
+	uint16_t NAME;	/* for the sake of simplicity only 16 bit pointers are supported */
+	uint16_t TYPE; /* Unsigned 16 bit value. The resource record types - determines the content of the RDATA field. */
+	uint16_t CLASS; /* Class of response. */
+	uint32_t TTL; /* The time in seconds that the record may be cached. A value of 0 indicates the record should not be cached. */
+	uint16_t RDLENGTH; /* Unsigned 16-bit value that defines the length in bytes of the RDATA record. */
+	uint32_t RDATA; /* For the sake of simplicity only ipv4 is supported, and as such it's a unsigned 32 bit */
+}dns_answer_t;
+
+void dns_server(void *pvParameters);
+void dns_server_start();
+void dns_server_stop();
+
+
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif /* MAIN_DNS_SERVER_H_ */