Run-time Configuration

All µC/DNSc require a run-time configuration that must be passed during the initialization. DNS run-time configuration template files are provided (see µC/DNSc Directories and Files). The run-time configuration template file (dns-c_cfg.* ) should be copied into application folder and modified following your requirements.

Micrium provides sample configuration code free of charge; however, most sample code will likely require modification depending on the combination feature requirements and memory limitation.

Structure Fields

µC/DNSc run-time configuration is based on a structure that contains different configuration sections with many parameter settings. This section describes the run-time configuration settings, and should provide you an in-depth understanding of all parameters configuration. You will also discover which settings to modify in order to enhance the functionalities and the performances. Refer to the configuration field description section for further details.

DNSc Run-time Configuration Structure

const  DNSc_CFG  DNSc_Cfg = {
    /* ---------------- MEMORY ALLOCATION ---------------- */
    DEF_NULL,                       /* .MemSegPtr          */
 
    /* ----------------- DEFAULT SERVER ------------------ */
   "8.8.8.8",                       /* .ServerDfltPtr      */
 
    /* --------------- CACHE CONFIGURATION --------------- */
    255,                            /* .HostNameLenMax     */
    2,                              /* .CacheEntriesMaxNbr */
    1,                              /* .AddrIPv4MaxPerHost */
    1,                              /* .AddrIPv6MaxPerHost */
 
    /* -------------- REQUEST CONFIGURATION -------------- */
    DNSc_DFLT_TASK_DLY_MS,          /* .TaskDly_ms         */
    DNSc_DFLT_REQ_RETRY_NBR_MAX,    /* .ReqRetryNbrMax     */
    DNSc_DFLT_REQ_RETRY_TIMEOUT_MS, /* .ReqRetryTimeout_ms */
};

Memory allocation configuration

Structure Field

Type

Description

Possible Values

MemSegPtr

MEM_SEG

It is possible allocate all the memory used by the DNS client in a specific memory location by setting a memory segment in the configuration

DEF_NULL to allocate the memory from the HEAP

Pointer to a memory segment to allocate from (see µC/LIB - Memory Segments)

Default DNS server configuration

Structure Field	Type	Description	Possible Values
ServerDfltPtr	CPU_CHAR	The default server used by the DNS client.	Pointer to a string that contains the IP address.

Cache configuration

Structure Field	Type	Description	Possible Values
HostNameLenMax	CPU_INT16U	Maximum host name length that can be requested.	MUST be >= 2
CacheEntriesMaxNbr	CPU_INT08U	Number of entries the cache can contains.	MUST be >= 1
AddrIPv4MaxPerHost	CPU_INT08U	Maximum number of IPv4 addresses that can be stored by a host in the cache. Only valid if IPv4 is enabled (see Network Stack Configuration)	MUST be >= 0
AddrIPv6MaxPerHost	CPU_INT08U	Maximum number of IPv6 addresses that can be stored by a host in the cache. Only valid if IPv4 is enabled (see Network Stack Configuration)	MUST be >= 0

Request configuration

Structure Field

Type

Description

Possible Values

TaskDly_ms

CPU_INT08U

Configure task delay in integer milliseconds

When asynchronous mode is enabled the task can be periodically to allow other task with lower priority to run.

Default value: [DNSc_DFLT_TASK_DLY_MS] = 50ms

MUST be >= 1

ReqRetryNbrMax

CPU_INT08U

Configure maximum of request resolution retry.

Default value: [DNSc_DFLT_REQ_RETRY_NBR_MAX] = 2

MUST be >= 1

ReqRetryTimeout_ms

CPU_INT16U

Configure timeout before a request resolution retry

Default value: [DNSc_DFLT_REQ_RETRY_TIMEOUT_MS] = 1000ms

MUST be >= 100