dns.h File Reference

#include "kernel.h"

Data Structures
struct	ResourceRecord
struct	dns_header
struct	dns_request_t
struct	resource_record
struct	dns_result_t

Macros
#define	DN_COMP_BITMASK   0xC000
#define	ERROR_MASK   0x10000
#define	FLAGS_MASK_RD   0x01 /* Recursive */
#define	FLAGS_MASK_TC   0x02
#define	FLAGS_MASK_AA   0x04 /* Authoritative */
#define	FLAGS_MASK_OPCODE   0x78
#define	FLAGS_MASK_QR   0x80
#define	FLAGS_MASK_RCODE   0x0F /* Request */
#define	FLAGS_MASK_Z   0x70
#define	FLAGS_MASK_RA   0x80
#define	DNS_DST_PORT   53

Typedefs
typedef void(*	dns_reply_callback_a) (uint32_t result, const char *hostname, uint16_t reply_id)
typedef void(*	dns_reply_callback_aaaa) (uint8_t *result, const char *hostname, uint16_t reply_id)
typedef void(*	dns_reply_callback_ptr) (const char *const result, const uint32_t ip, uint16_t reply_id)

Enumerations
enum	query_type_t {   DNS_QUERY_NONE = 0 , DNS_QUERY_A = 1 , DNS_QUERY_CNAME = 5 , DNS_QUERY_PTR = 12 ,   DNS_QUERY_AAAA = 28 , DNS_QUERY_PTR4 = 0xFFFD , DNS_QUERY_PTR6 = 0xFFFE }

Functions
struct dns_header	__attribute__ ((packed)) dns_header_t
uint32_t	dns_lookup_host (uint32_t resolver_ip, const char *hostname, uint32_t timeout)
	Look up an IPV4 hostname to IP address, with timeout. More...
uint16_t	dns_lookup_host_async (uint32_t resolver_ip, const char *hostname, uint32_t timeout, dns_reply_callback_a callback)
	Look up an IPV4 hostname to IP address, with timeout. More...
void	init_dns ()
	Initialise DNS protocol. This binds a UDP port for use with replies. More...

Variables
uint16_t	id
uint8_t	flags1
uint8_t	flags2
uint16_t	qdcount
uint16_t	ancount
uint16_t	nscount
uint16_t	arcount
uint8_t	payload [512]
uint16_t	type
uint16_t	rr_class
uint32_t	ttl
uint16_t	rdlength
struct dns_result_t	__attribute__

Detailed Description

Author

Craig Edwards (craig.nosp@m.edwa.nosp@m.rds@b.nosp@m.rain.nosp@m.box.c.nosp@m.c)

Copyright

Copyright (c) 2012-2023

Macro Definition Documentation

DN_COMP_BITMASK

#define DN_COMP_BITMASK   0xC000

DNS_DST_PORT

#define DNS_DST_PORT   53

ERROR_MASK

#define ERROR_MASK   0x10000

FLAGS_MASK_AA

#define FLAGS_MASK_AA   0x04 /* Authoritative */

FLAGS_MASK_OPCODE

#define FLAGS_MASK_OPCODE   0x78

FLAGS_MASK_QR

#define FLAGS_MASK_QR   0x80

FLAGS_MASK_RA

#define FLAGS_MASK_RA   0x80

FLAGS_MASK_RCODE

#define FLAGS_MASK_RCODE   0x0F /* Request */

FLAGS_MASK_RD

#define FLAGS_MASK_RD   0x01 /* Recursive */

FLAGS_MASK_TC

#define FLAGS_MASK_TC   0x02

FLAGS_MASK_Z

#define FLAGS_MASK_Z   0x70

Typedef Documentation

dns_reply_callback_a

typedef void(* dns_reply_callback_a) (uint32_t result, const char *hostname, uint16_t reply_id)

dns_reply_callback_aaaa

typedef void(* dns_reply_callback_aaaa) (uint8_t *result, const char *hostname, uint16_t reply_id)

dns_reply_callback_ptr

typedef void(* dns_reply_callback_ptr) (const char *const result, const uint32_t ip, uint16_t reply_id)

Enumeration Type Documentation

query_type_t

enum query_type_t

Enumerator
DNS_QUERY_NONE	Uninitialized Query
DNS_QUERY_A	'A' record: an ipv4 address
DNS_QUERY_CNAME	'CNAME' record: An alias
DNS_QUERY_PTR	'PTR' record: a hostname
DNS_QUERY_AAAA	'AAAA' record: an ipv6 address
DNS_QUERY_PTR4	Force 'PTR' to use IPV4 scemantics
DNS_QUERY_PTR6	Force 'PTR' to use IPV6 scemantics

Function Documentation

__attribute__()

struct dns_header __attribute__

(

(packed)

)

Represents a dns request/reply header, and its payload as opaque data.

dns_lookup_host()

uint32_t dns_lookup_host	(	uint32_t	resolver_ip,
		const char *	hostname,
		uint32_t	timeout
	)

Look up an IPV4 hostname to IP address, with timeout.

Note

This function is synchronous! It will block until a suitable DNS request has been obtained from the DNS server you specify, or a timeout is reached.

Parameters

resolver_ip	The IP of the resolver to use, in network byte order
hostname	Host address to resolve
timeout	Timeout in seconds

Returns

uint32_t Resolved IP address. On error or timeout, the return value is 0, which translates to 0.0.0.0.

dns_lookup_host_async()

uint16_t dns_lookup_host_async	(	uint32_t	resolver_ip,
		const char *	hostname,
		uint32_t	timeout,
		dns_reply_callback_a	callback
	)

Look up an IPV4 hostname to IP address, with timeout.

Note

This function is asynchronous. It will return the ID of the request, and will call the callback once the request has completed.

Parameters

resolver_ip	The IP of the resolver to use, in network byte order
hostname	Host address to resolve
timeout	Timeout in seconds
dns_reply_callback_a	Callback to receive the resolved IP address. If an error occured during resolution, the received IP address will be 0, which is a representation of 0.0.0.0.

Returns

uint16_t Request ID that was submitted, or 0 on error

init_dns()

void init_dns

(

)

Initialise DNS protocol. This binds a UDP port for use with replies.

Variable Documentation

__attribute__

struct dns_result_t __attribute__

ancount

uint16_t ancount

arcount

uint16_t arcount

flags1

uint8_t flags1

flags2

uint8_t flags2

id

uint16_t id

nscount

uint16_t nscount

payload

uint8_t payload[512]

qdcount

uint16_t qdcount

rdlength

uint16_t rdlength

rr_class

uint16_t rr_class

ttl

uint32_t ttl

type

uint8_t type