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Anchor10439521043952 DNSc_GetHostByName() Anchor10444111044411Converts the string representation of a host name to its corresponding IP address using DNS service. Anchor10444511044451

Files

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dns-c.h/dns-c.c

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Prototype

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NET_IP_ADDR dns_ip;   dns_ip = DNSc_GetHostByName("www.micrium.com");tr NET_IP_ADDR DNSc_GetHostByName (CPU_CHAR *host_name);
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cpp
DNSc_STATUS  DNSc_GetHost(const  CPU_CHAR       *p_host_name,
                                 CPU_CHAR       *p_res_host_name,
                                 CPU_INT32U      res_hostname_len,
                                 DNSc_ADDR_OBJ  *p_addrs,
                                 CPU_INT08U     *p_addr_nbr,
                                 DNSc_FLAGS      flags,
                                 DNSc_REQ_CFG   *p_cfg,
                                 DNSc_ERR       *p_err)
p_host_namePointer to a string that contains the host name.
p_res_host_name

Pointer to a string that will receive the host name resulting from a reverse lookup OR the canonical name resulting from a forward lookup with the DNSc_FLAG_CANON set.
This argument should be left DEF_NULL if a simple forward DNS request is desired.

res_hostname_len

String length of p_res_host_name. This argument should evaluate to 0 if a simple forward DNS request is desired (with DNSc_FLAG_CANON cleared).

p_addrsPointer to arrays that will receive the IP address(es) from this function.
p_addr_nbr

Pointer to a variable that:

(1) Indicates how many addresses can fit into the addresses array pointed by the 'p_addrs' argument.

and

(2) Will receive the number of address(es) copied into the addresses array.

flags

DNS client flag:

DNSc_FLAG_NONE - By default this function is blocking.
DNSc_FLAG_NO_BLOCK - Don't block (only possible if DNSc's task is enabled).
DNSc_FLAG_FORCE_CACHE - Take host from the cache, don't send new DNS request.
DNSc_FLAG_FORCE_RENEW - Force DNS request, remove existing entry in the cache.
DNSc_FLAG_FORCE_RESOLUTION - Force DNS to resolve given host name.
DNSc_FLAG_IPv4_ONLY - Return only IPv4 address(es) (A type).
DNSc_FLAG_IPv6_ONLY - Return only IPv6 address(es) (AAAA type).
DNSc_FLAG_REVERSE_LOOKUP - Issue a reverse DNS lookup for an IP address (PTR type).
DNSc_FLAG_CANON - Process canonical name if present in DNS answers.

p_cfg

Pointer to a request configuration. Should be used to override the default DNS configuration's values for DNS server, request timeout, etc. per request.

Must be set to DEF_NULL to use default configuration.

p_errPointer to variable that will receive the return error code from this function.


Arguments

Returned Values

Resolution status:

DNSc_STATUS_PENDING  Host resolution is pending, call again to see the status. (Processed by DNSc's task)
DNSc_STATUS_RESOLVED Host is resolved.
DNSc_STATUS_FAILED   Host resolution has failed.

Required Configuration

None.

Notes / Warnings

(1) If this function successfully resolves a reverse lookup, the host's address information is added to the cache just as it would be for a forward lookup.

(2) If a forward request is successfully resolved and a reverse request is issued for the same host name, the same host cache entry will be used and the

     reverse name will be updated internally.

(3) DNSc_FLAG_REVERSE_LOOKUP and DNSc_FLAG_CANON flags cannot not be set simultaneously.

(4) DNSc_FLAG_FORCE_CACHE and DNSc_FLAG_FORCE_RENEW flags cannot be set simultaneously.

(5) DNSc_FLAG_UPDATE_PREF and DNSc_FLAG_RESET_REQ flags are meant for internal use and should never be set.

Example Usage

See Sample Application.