dns.c File Reference

Data Structures
struct	dns_hdr
struct	dns_query
struct	dns_answer
struct	dns_table_entry
Functions
void	dns_init ()
void	dns_setserver (u8_t numdns, struct ip_addr *dnsserver)
struct ip_addr	dns_getserver (u8_t numdns)
void	dns_tmr (void)
err_t	dns_gethostbyname (const char *hostname, struct ip_addr *addr, dns_found_callback found, void *callback_arg)

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Detailed Description

DNS - host name to IP address resolver.

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Function Documentation

err_t dns_gethostbyname	(	const char *	hostname,
		struct ip_addr *	addr,
		dns_found_callback	found,
		void *	callback_arg
	)

Resolve a hostname (string) into an IP address. NON-BLOCKING callback version for use with raw API!!!

Returns immediately with one of err_t return codes:

• ERR_OK if hostname is a valid IP address string or the host name is already in the local names table.
• ERR_INPROGRESS enqueue a request to be sent to the DNS server for resolution if no errors are present.

Parameters:

	hostname	the hostname that is to be queried
	addr	pointer to a struct ip_addr where to store the address if it is already cached in the dns_table (only valid if ERR_OK is returned!)
	found	a callback function to be called on success, failure or timeout (only if ERR_INPROGRESS is returned!)
	callback_arg	argument to pass to the callback function

Returns:

a err_t return code.

struct ip_addr dns_getserver

(

u8_t

numdns

)

[read]

Obtain one of the currently configured DNS server.

Parameters:

numdns

the index of the DNS server

Returns:

IP address of the indexed DNS server or "ip_addr_any" if the DNS server has not been configured.

void dns_init

(

void

)

Initialize the resolver: set up the UDP pcb and configure the default server (DNS_SERVER_ADDRESS).

void dns_setserver	(	u8_t	numdns,
		struct ip_addr *	dnsserver
	)

Initialize one of the DNS servers.

Parameters:

	numdns	the index of the DNS server to set must be < DNS_MAX_SERVERS
	dnsserver	IP address of the DNS server to set

void dns_tmr

(

void

)

The DNS resolver client timer - handle retries and timeouts and should be called every DNS_TMR_INTERVAL milliseconds (every second by default).

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