squeezelite-esp32/components/wifi-manager/dns_server.h

/*
Copyright (c) 2019 Tony Pottier

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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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@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_ */