DNSc_GetHost

Converts the string representation of a host name to its corresponding IP address using DNS service.

Files

dns-c.h/dns-c.c

Prototype

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_name	Pointer 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_addrs	Pointer 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_err	Pointer 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.